WO2025176518A1

WO2025176518A1 - Producing sustainable caprolactam

Info

Publication number: WO2025176518A1
Application number: PCT/EP2025/053617
Authority: WO
Inventors: Simon Winfried RAUCH; Marcel Schmitt; Yong Liu; Katharina HOELD
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2024-02-22
Filing date: 2025-02-12
Publication date: 2025-08-28
Anticipated expiration: 2026-08-22

Abstract

A process and a system to produce caprolactam based on carbon oxides and hydrogen is provided.

Description

Producing Sustainable Caprolactam

Field of the Invention

This invention relates to a process and a system to produce caprolactam based on carbon oxides and hydrogen. In addition, the invention relates to caprolactam intermediates, to caprolactam, and to polycaprolactam that can be obtained by such process as well as to the traceability of the hydrogen used therein.

Background of the Invention

Caprolactam (more precisely s-caprolactam, i.e. , azepan-2-one) is an industrially important cyclic amide, especially as it is the monomer from which the polymer polycaprolactam (poly(azepan-2-one), also known as Nylon-6, Perlon, or polyamide-6) can be formed. Commercial syntheses of caprolactam are described, for instance, in J. Tinge et al., Ullmann's Encyclopedia of Industrial Chemistry, 2018, Chapter “Caprolactam”, and the references cited therein. They start from benzene, which is mainly obtained by separation, mainly distillation, of BTX (benzene, toluene, xylenes) streams that result from fossil-based petrochemical processes like catalytic reforming or steam cracking of aliphatic hydrocarbons. Benzene is converted into cyclohexanone via different routes: hydrogenation to cyclohexane and subsequent oxidation; partial hydrogenation to cyclohexene and subsequent hydration to cyclohexanol followed by dehydrogenation, or oxidation to phenol and subsequent hydrogenation. Cyclohexanone may be reacted to cyclohexanone oxime via different routes, e.g., with hydroxylammonium sulfate, with nitric acid and hydrogen, or with ammonia and hydrogen peroxide. Alternatively, cyclohexanone oxime may be formed from benzene by hydrogenation to cyclohexane and subsequent photonitrosation. Caprolactam is obtained from cyclohexanone oxime via Beckmann rearrangement. Thus, just like the benzene, on which they are based, conventional caprolactam and polycaprolactam are normally of fossil origin.

Summary of the Invention

In a first aspect, the present invention relates to a process for producing caprolactam, the process comprising the steps

A) providing syngas;

B) subjecting said syngas to a Fischer-Tropsch process to obtain a hydrocarbon stream and subjecting said hydrocarbon stream to at least one refining step to obtain an aliphatic hydrocarbon stream comprising naphtha;

C) subjecting said aliphatic hydrocarbon stream comprising naphtha to an aromatization step to obtain at least one hydrocarbon stream comprising benzene and separating benzene from said at least one hydrocarbon stream comprising benzene;

D) converting said benzene to cyclohexanone oxime; and

E) converting said cyclohexanone oxime to caprolactam.

In a second aspect, the invention relates to a compound or compound mixture selected from the group consisting of: an aliphatic hydrocarbon stream comprising naphtha obtainable by steps A) to B) according to the invention; benzene obtainable by process steps A) to C) according to the invention; an intermediate selected from the group consisting of cyclohexane, cyclohexene, phenol, cyclohexanol, and cyclohexanone obtainable by process steps A) to D) according to the invention; cyclohexanone oxime obtainable by process steps A) to D) according to the invention; caprolactam obtainable by process steps A) to E) according to the invention; and polycaprolactam obtainable by process steps A) to F) according to the invention.

In a third aspect, the invention relates to a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized in that at least 5 %, preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, more preferably at least 95 %, most preferably all of their carbon atoms originate from carbon dioxide and/or are bio-based.

In a fourth aspect, the invention relates to a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized by a deuterium content of < 100 ppm, based on the total hydrogen content, and/or by a deuterium content being lower than the deuterium content in a corresponding compound or compound mixture of fossil origin; and/or characterized by a 613C value of more than -15 %o and/or by a 613C value being higher than the 613C value in a corresponding compound or compound mixture of fossil origin; and/or characterized by a A14C value of more than -900 %o and/or by a A14C value being higher than the A14C value in a corresponding compound or compound mixture of fossil origin.

In a fifth aspect, the invention relates to a system for producing caprolactam, the system comprising the units

I) a syngas production unit, optionally comprising a hydrogen production subunit;

II) a Fischer-Tropsch unit;

III) a benzene production unit, optionally comprising a carbon capture subunit; and

IV) a caprolactam production unit.

In a sixth aspect, the invention relates to the use of the system according to the fifth aspect of the invention for the process according to the first aspect of the invention.

In a seventh aspect, the invention relates to a process for tracing the origin of hydrogen bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising the steps

P) providing a test sample of said compound or compound mixture and optionally providing a reference sample of said compound or compound mixture produced with hydrogen of fossil origin;

Q) determining the deuterium content in said test sample and optionally determining the deuterium content in said reference sample; and

R) establishing whether said deuterium content in the test sample does not exceed 100 ppm and/or optionally whether said deuterium content in the test sample is lower than said deuterium content in the reference sample.

In an eighth aspect, the invention relates to a process for tracing the origin of carbon bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising the steps

S) providing a test sample of said compound or compound mixture and optionally providing a reference sample of said compound or compound mixture produced with carbon of fossil origin;

T) determining the 613C value and/or A14C value in said test sample and optionally determining the 6130 value and/or A14C value in said reference sample; and one or more of steps U), If), and U*)

U) establishing whether said 613C value in the test sample exceeds -15 %o and/or optionally whether said 6130 value in the test sample is higher than said 613C value in the reference sample; and/or establishing whether said A14C value in the test sample exceeds -900 %o and/or optionally whether said A14C value in the test sample is higher than said A14C value in the reference sample;

U') establishing whether said 613C value in the test sample is less than -10 %o and whether said A14C value in the test sample exceeds -900 %o;

U*) establishing whether said 613C value in the test sample exceeds -12 %o and whether said A14C value in the test sample exceeds -900 %o and/or optionally whether said A14C value in the test sample is higher than said A14C value in the reference sample.

Further aspects of the present invention will become apparent to the person skilled in the art directly from the foregoing and following description.

General Terms and Definitions

The terms "comprise(s)”, "comprising” etc. are inclusive of and may, in a preferred embodiment, be replaced by the terms "consist(s) of’, "consisting of’ etc.

The term “at least a part of’ refers to a fraction that is nonzero. It includes any fractions larger than 0 %, e.g., at least 1 ppb, at least 1 ppm, at least 1 %o, at least 1 %, at least 5 %, at least 10 %, at least 20 %, at least 30 %, at least 40 %, at least 50 %, at least 60 %, at least 70 %, at least 80 %, at least 90 %, and 100 %. Said fraction may be determined, calculated, or evaluated on the basis of a certain observation period, e.g., on an hourly, daily, weekly, monthly, or annual basis, or on the basis of a production cycle or batch manufacturing.

Whenever a sequence of process steps is described herein, in which the product of a previous step ("the intermediate”) is used as a starting material for a subsequent process ("the process") to produce and/or separate a subsequent product ("the product”), expressions such as "converting the intermediate to the product” or "subjecting the intermediate to the process” shall include the expressions “converting at least a part of the intermediate to the product” or “subjecting at least a part of the intermediate to the process".

The term “about” preferably designates an approximate value with a deviation of ± 10 %.

The term “sustainable”, as used herein, mainly refers to environmental sustainability. It relates to practices, actions, and attributes suited to maintain and preserve the health and balance of natural ecosystems and resources over the long term such that their capacities to regenerate are not exceeded, e.g., by minimizing resource depletion, pollution, waste production, and greenhouse gas emissions. When referring to resources and energy sources, the term "sustainable” includes the terms renewable (e.g., derived from biomass) and non-fossil (e.g., not derived from natural gas, oil, coal etc.).

Bio-oil designates a liquid compound mixture that is manufactured from biomass and that mainly comprises highly oxygenated compounds (e.g., glycerides, esters, carboxylic acids, phenols, alcohols, ketones, aldehydes, furans, and sugars) and water, while its exact composition depends on the biomass feedstocks and the processing steps applied. The term bio-oil includes in particular vegetable oils like rapeseed oil, sunflower oil, soybean oil, corn oil, and palm oil, waste cooking oil, tall oil, animal fats, and oils obtained by thermochemical conversion of biomass, e.g., biomass- derived pyrolysis or hydrothermal liquefaction oils

Biomass is biological material derived from living, or recently living organisms. In particular, the term biomass comprises plants or parts thereof like crops, wood, or residues thereof, marine organisms like algae, and bio waste such as organic food waste, e.g., animal fat from meat industry waste, fish fat from fish processing waste, or used cooking oil.

Brief Description of the Drawings

FIG 1 : Flow diagram showing a process to produce (poly)caprolactam starting from hydrogen and carbon dioxide

FIG 2: Flow diagram showing a process to produce (poly)caprolactam starting from hydrogen and carbon dioxide, including hydrogen recycling and carbon capture and utilization (CCU)

FIG 3: Flow diagram showing a process to produce (poly)caprolactam starting from hydrogen, carbon dioxide, and nitrogen

FIG 4: Flow diagram showing a process to produce (poly)caprolactam starting from water and carbon dioxide

FIG 5: System to perform the process of FIG 1

FIG 6: System to perform the process of FIG 2

FIG 7: System to perform the process of FIG 3

FIG 8: System to perform the process of FIG 4 Legend for FIGs 1-8:

1 : hydrogen; 2: carbon dioxide; 3: syngas; 4: naphtha; 5: benzene; 6: cyclohexanone oxime; 7: caprolactam; 8: polycaprolactam; 9: nitrogen; 10: oximation agent; 11 : water; 13: oxygen; 14: air;

20: rWGS reaction; 21 : Fischer-Tropsch process and refining step(s); 22: cracking process and separation; 23: cyclohexanone oxime production; 24: Beckmann rearrangement; 25: polymerization; 26: oximation agent production; 27: water electrolysis;

101 : water electrolysis subunit; 102: rWGS subunit; 103: Fischer-Tropsch unit; 104: cracking subunit and separation subunit(s); 105: caprolactam production unit; 106: polycaprolactam production unit; 107: carbon capture subunit; 108: air separation unit; 109: oximation agent production subunit

Detailed Description of the Invention

The present invention provides a process and a system for producing sustainable caprolactam based on carbon oxides and hydrogen.

Conventionally produced caprolactam is typically associated with a rather large product carbon footprint (PCF). Main contributors to this high carbon intensity are the origin of benzene (mainly from fossil resources, namely naphtha) that is used as a raw material, the origin of hydrogen (mainly by steam reforming of natural gas) that is required in different steps of the overall process, as well as the sources of energy that needs to be provided to the process. However, in view of the finite availability of fossil resources and the urgency to reduce net carbon dioxide emissions to the atmosphere, there is a high need to replace fossil carbon and energy sources by sustainable alternatives. Thus, the production of organic compounds from more sustainable, non-fossil resources like biomass and carbon dioxide and by using more sustainable, non-fossil energy sources has been attracting increasing interest. This applies also to caprolactam and downstream products thereof like polycaprolactam Such products with improved sustainability reduce the demand of fossil carbon resources for material and energetic use and may thus exhibit a reduced PCF.

It is described herein that Fischer-Tropsch processes may be used to obtain sustainable hydrocarbons from sustainably produced syngas (a mixture of carbon monoxide, carbon dioxide, and hydrogen), e.g., sustainable naphtha for fuel and chemical applications. Said naphtha may be employed in cracking or catalytic reforming processes to yield sustainable benzene which may form the basis for sustainable caprolactam. Finally, sustainable, commercially important polymers like polycaprolactam may be manufactured from said caprolactam.

When it comes to their carbon contents, all these syngas-derived compounds may thus be fully based on sustainable sources. For instance, in case of syngas obtained from reverse water-gas shift reaction, all the carbon atoms originate from carbon dioxide, i.e., as the case may be, a reduction of net carbon dioxide emissions is achieved or maybe even net negative carbon dioxide emissions. Similarly, the use of biomass-derived syngas, e.g., obtained from gasification of biomass or reforming of biogas, may provide (poly)caprolactam with fully bio-based carbon content. Along the same lines, if sustainable syngas as described hereinbefore is used in admixture with syngas of other sources, e.g., recycling based or fossil-based, the carbon dioxide-based or bio-based carbon contents may be adjusted as needed, e.g., to desired target values to meet customer specifications, market demands, or regulatory requirements. In addition, hydrogen is used in the processes of the present invention, e.g., as a raw material for the reverse water- gas shift reaction, as a component to adjust the composition of syngas, as a starting material to produce ammonia (as described hereinafter), or as a reactant for the hydrogenation of benzene. Thus, the carbon footprint of the hydrogen used is also important for the carbon footprint of the products obtained therefrom like caprolactam. To reduce said carbon footprint, the present invention proposes the production of hydrogen from sustainable syngas, optionally followed by water-gas shift reaction and hydrogen separation. In particular, syngas from biomass-derived or waste-derived feedstocks like biogas, biomass, and waste may help reduce the carbon intensity of hydrogen production and spare fossil resources. Also, using waste, for instance caprolactam-based waste, e.g., waste based on polycaprolactam or products derived therefrom or containing the same, as a source of syngas via gasification allows to close the recycling loop, thus providing a step towards circular economy.

Advantageously, carbon dioxide that is co-produced in syngas-producing processes or in the water-gas shift reaction is captured to avoid greenhouse gas emissions. Said captured carbon dioxide may even be used as raw material for chemical processes, e.g., for the carbon dioxide-based Fischer-Tropsch process described herein. Carbon dioxide emissions may also be avoided according to the invention by generating hydrogen via hydrocarbon pyrolysis which coproduces solid carbon instead of carbon dioxide; thus, if based on biomass-derived feedstocks, hydrocarbon pyrolysis may even provide net-negative carbon dioxide emissions. Also, the present invention proposes the use of sustainable energy sources for obtaining hydrogen via water electrolysis or chlor-alkali electrolysis. Thus, no fossil carbon sources are required as energy sources or raw material for obtaining hydrogen. In addition, it is known (see, e.g., WO 03/049748 A1; K. Harada et al., Int. J. Hydrogen Energy 2020, 45, pp. 31389-31395; H. Sato et al., Int. J. Hydrogen Energy 2021 , 46, pp. 33689-33695) that water electrolysis delivers hydrogen with a deuterium content that is lower than in the water from which it is generated, and that is also lower than in hydrogen from fossil resources (like steam reforming of natural gas). Thus, using said hydrogen in the processes described herein, in particular if the Fischer-Tropsch process starts from carbon dioxide and hydrogen, results in products with reduced deuterium content in comparison to their analogues generated with hydrogen from other, e g., fossil, sources. Thus, the present invention allows to use the deuterium content as a marker for determining whether products described herein were produced from carbon dioxide and hydrogen from water electrolysis. Further, to enable Fischer-Tropsch processes, the covalent bond of the hydrogen molecule needs to be broken. Since the dissociation energy of protonated hydrogen (H-H) is lower than the one of (partially) deuterated hydrogen (H-D, D-D), it is reasonable to assume a better energy efficiency when hydrogen of lower deuterium content is used. Thus, if hydrogen originating from water electrolysis is employed, the process according to the invention may consume less energy or release more energy, respectively, than an analogous process with hydrogen of different origins, e.g., of fossil origin, such that not only the carbon intensity, but also the energy efficiency of the process according to the invention may be advantageous.

However, beyond the origin of the carbon and hydrogen atoms, it must be borne in mind that producing caprolactam also requires a nitrogen source. Nitrogen is introduced into caprolactam typically via a hydroxylamine species as an oximation agent, obtained from ammonia, nitrogen oxides or nitrates, or - in a commercially less important photoni- trosation process- via nitrous gases, obtained from combustion of ammonia. Thus, ammonia is the key nitrogen source for caprolactam. To further reduce the carbon intensity of caprolactam, the carbon intensity of the production process for ammonia from nitrogen and hydrogen should therefore be taken into account. The present invention proposes the use of sustainably energy sources for generating ammonia, in particular for obtaining nitrogen via cryogenic air separation and for generating hydrogen via water electrolysis or chlor-alkali electrolysis. Also, the other above-mentioned sustainable processes for obtaining hydrogen may be used. Thus, the process of the invention allows to make use of ammonia with improved sustainability to produce caprolactam.

The processes of the present invention are further beneficial as they deliver hydrocarbons, in particular naphtha, that are virtually free of aromatics, sulfur-containing compounds, and nitrogen-containing compounds. In comparison to naphtha of fossil origin, which may well contain said components and impurities, the higher purity of Fischer-Tropsch- derived naphtha as described herein may prove advantageous when used as a feedstock for steam cracking: A reduced aromatics content typically results in a lower coking tendency and less fouling. Sulfur-containing compounds may cause detrimental effects like catalyst poisoning, corrosion, fouling. In addition, sulfur oxide emissions and undesired sulfur-containing steam cracking by-products may be formed. Similarly, nitrogen-containing compounds may lead to catalyst poisoning and undesired nitrogen oxide emissions. Thus, the use of highly pure Fischer-Tropsch-derived naphtha allows to perform steam cracking with excellent overall performance, especially in terms of high efficiency, profitability, and product quality, without increasing maintenance requirements or adding additional purification steps.

Thus, in a first aspect, the present invention provides a process for producing caprolactam, the process comprising the steps

A) providing syngas;

D) converting said benzene to cyclohexanone oxime; and

E) converting said cyclohexanone oxime to caprolactam.

Preferred Embodiments

1.1) The process according to the first aspect of the invention.

The process according to the invention starts with providing syngas which is a mixture of hydrogen and carbon oxides, mainly carbon monoxide. Syngas production is typically accomplished by steam reforming, autothermal catalytic reforming, dry reforming, or partial oxidation of gaseous and liquid feedstocks or by gasification of solid feedstocks. For instance, in steam reforming, hydrocarbons are converted with steam in the presence of a catalyst under high temperature and high-pressure conditions, whereas in partial oxidation, hydrocarbons are reacted with sub-stoichiometric amounts of oxygen. In dry reforming, methane and carbon dioxide are converted in an endothermic reaction in the presence of a catalyst. In any case, syngas, a mixture consisting primarily of hydrogen, carbon monoxide, and relatively small amounts of carbon dioxide, is obtained. A subsequent water-gas shift (WGS) reaction allows to adjust the hydrogen to carbon monoxide ratio in said syngas, where needed; a similar result may be achieved by adding hydrogen amounts obtained from external sources, i.e., from processes other than those to produce said syngas. Syngas may also be obtained via reverse WGS (rWGS) reaction using carbon dioxide and hydrogen as input materials. Said processes to produce syngas are described for example in H. Hiller et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Gas Production, 1. Introduction", R. Reimert et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Gas Production, 2. Processes”, and the references cited therein. Dry reforming is reviewed for example by D. Pakhare et al., Chem. Soo. Rev. 2014, 43, 7813-7837, Z. Alipour et al. Chem. Eng. J. 2023, 452, 139416, and the references cited therein. rWGS reactions are described in Y. A. Daza et al., RSC Adv. 2016, 6, 49675-49691, and the references cited therein.

Traditionally, mainly fossil resources like natural gas, naphtha, heavy vacuum residues, and coal have been used for the generation of syngas. Nowadays, in view of the finite availability of fossil resources and the urgency to reduce net carbon dioxide emissions, there is a high need to replace fossil carbon resources by sustainable, preferably renewable, carbon resources. Thus, non-fossil, sustainable sources of syngas have been attracting increasing interest. In particular, steam reforming or dry reforming of biogas, gasification of biomass or waste, and reverse water gas shift reaction of carbon dioxide and hydrogen to obtain syngas are contemplated within the scope of this disclosure as sustainable syngas sources:

Biogas, a mixture of mainly methane and carbon dioxide, may be obtained by anaerobic digestion of organic matter. As used herein, the term “biogas” includes pretreated and upgraded biogas. In the pretreatment step, water vapor as well as hydrogen sulfide, if present, are removed to obtain pretreated biogas. In the upgrading step, carbon dioxide is removed by absorption in water, by amines, by membranes, or the application of pressure swing adsorption to obtain upgraded biogas which is almost pure methane (bio-methane). Details on said biogas-related processes are described for example in E.-J. Nyns et al., Ullmann's Encyclopedia of Industrial Chemistry, 2014, Chapter “Biogas”, and the references cited therein.

Gasification of solid feedstocks like biomass or waste involves heating the feedstock to high temperatures in the presence of limited supplies of oxygen or steam. The conversion proceeds via thermal decomposition and subsequent heterogeneous reaction of the solid residue with reactive gases like oxygen, steam, carbon dioxide, or hydrogen. Solid biomass feedstocks suitable for gasification include wood or residues thereof, (energy) crops or residues thereof, agricultural waste, and sewage sludge. Solid waste feedstocks suitable for gasification include municipal waste, hazardous waste, industrial waste, mixed plastic waste, caprolactam-based waste, or end-of-life tires.

Carbon dioxide may be employed as a feedstock for syngas production via dry reforming of biogas, preferably methane, or via reverse water-gas shift (rWGS) with hydrogen. Carbon dioxide may be captured from the atmosphere (direct air capture, DAC), from the ocean (direct ocean capture, DOC; indirect ocean capture, IOC), or from industrial point sources of carbon dioxide emissions (via pre-combustion capture, oxyfuel combustion, or post-combustion capture routes). Such industrial point sources include power plants based on combustion of organic material like coal, natural gas, oil, waste (municipal waste, hazardous waste, industrial waste, mixed plastic waste, caprolactam-based waste, end-of-life tires), or biomass (wood or residues thereof, (energy) crops or residues thereof, agricultural waste, sewage sludge) and industrial facilities like plants for cement production, steel manufacturing, chemical manufacturing, biogas production and processing, and refineries. In the area of chemical manufacturing, steam crackers, steam reformers (especially to produce hydrogen), partial oxidation plants (e.g., to obtain ethylene oxide, acetylene, or syngas), and facilities for the hydrotreatment of bio-oils or waste-derived pyrolysis oils are among the main facilities that emit significant amounts of carbon dioxide. Preferably, the carbon dioxide used in the processes according to the present invention, is obtained from sustainable sources, more preferably from renewable sources, e.g., from biomass. Processes for capturing carbon dioxide are described for examples in S. Topham et al., Ullmann's Encyclopedia of Industrial Chemistry, 2014, Chapter “Carbon dioxide”, and the references cited therein.

The hydrogen used for the processes according to the present invention, e.g., for the above-mentioned rWGS reaction or for the below-mentioned production of ammonia, may be obtained according to processes known in the art. In particular, steam reforming or other syngas-producing processes (especially if followed by a water-gas shift reaction and hydrogen separation) and pyrolysis of hydrocarbons, e.g., of natural gas, biogas, or other light hydrocarbons, as well as water electrolysis and chlor-alkali electrolysis may provide substantial amounts of hydrogen. In addition, cracking processes like steam cracking of hydrocarbons as described below may deliver hydrogen. Hydrogen may also be used for adjusting the H2:CO ratio of syngas obtained by the processes described herein.

In hydrocarbon pyrolysis (also referred to as “hydrocarbon decomposition"), light hydrocarbons, in particular methane (“methane pyrolysis”), e.g., in the form of natural gas or biogas, is decomposed without the involvement of oxygen into hydrogen and solid, high-purity carbon (e.g., as carbon black, carbon powder, or granular carbon). In contrast to reforming, however, no gaseous carbon dioxide is produced, but solid carbon is formed as a by-product, which has a positive effect on economic efficiency and ecologic impact Further, compared to water electrolysis, methane pyrolysis requires significantly less energy. Therefore, methane pyrolysis is considered a promising sustainable technology for future hydrogen production.

Hydrocarbon pyrolysis may be carried out in different ways known to the one skilled in the art (Muradov et al., International Journal Hydrogen Energy 2008, 33, 6804-6839; Abbas et al., International Journal Hydrogen Energy 2010, 35, 1160-1190); Dagle et al.: An Overview of Natural Gas Conversion Technologies for Co-Production of Hydrogen and Value-Added Solid Carbon Products, Report by Argonne National Laboratory and Pacific Northwest National Laboratory (ANL-17/11, PNNL-26726, November 2017): catalytically or thermally, and with heat input via plasma, microwave, heated carrier gas, resistance heating, induction, liquid metal processes, or autothermally, in particular via plasma pyrolysis (WO 2015/116797, WO 2015/116800), metal melting/metal salt melting (WO 2020/161192, WO 2021/183959), moving bed process (US 2982622, WO 2019/145279, WO 2020/200522, WO 2023/057242), (fluidized bed) catalytic process (WO 2011/029144, WO 2016/154666), or partial/pulsed combustion (WO 2020/118417 and US 2022/0185664), the moving bed process being particularly advantageous due to its high efficiency, heat integration, flexibility, and favorable product carbon footprint. These processes differ i.a. in the form of the energy used (thermal, electrical, etc.), the process conditions (temperature, pressure, etc.), the catalysts, and/or auxiliary materials used. The pyrolysis process is preferably heated electrically, even more preferably by resistive heating (Joule heating) of the substrate material (US 2982622, WO 2019/145279, and WO 2020/200522).

The solid carbon type generated in the methane decomposition depends on the reaction conditions, reactor, and heating technology. Examples are carbon black from plasma processes carbon powder from liquid metal processes granular carbon from thermal decomposition in fixed, moving, or fluidized bed reactors.

The processing and separation of solid carbon depends on the chosen pyrolysis technology and is known by the person skilled in the art. For example, in a plasma pyrolysis process, the solid carbon in the form of carbon black is discharged from the reactor with the gas and then separated, e.g., by a cyclone. The solid carbon might be post-treated, e.g., agglomerated. Depending on the process and the metals used, in molten metal pyrolysis, the carbon floats on the melt and is skimmed off or leaves the reactor together with the gas stream and is then separated, e.g., by a filter or cyclone. In addition, a purification step to remove residual metal from the carbon could be required e.g., washing or evaporation. In the catalytic pyrolysis technology and in the fixed and moving bed technology, the solid carbon is deposited on the surface of the catalyst and/or support and taken off the reactor via the catalyst and/or support.

Thus, solid carbon may be separated by a cyclone or a filter and may be post-treated, e.g., to achieve agglomeration; further, the carbon may be purified by washing and/or evaporation techniques to remove, for instance, residual metal contamination. The resulting gas stream comprising hydrogen may be finally purified by a pressure swing adsorption process to remove remaining impurities like hydrogen sulfide, carbon oxides, hydrocarbons, and inert gases like nitrogen, to yield purified hydrogen.

Electrolysis of water is an environmentally friendly method to produce hydrogen because it uses H2O as a sustainable resource and produces only pure oxygen as by-product. Additionally, water electrolysis utilizes direct current (DC), preferably from sustainable energy sources, for example solar, wind, hydropower, and biomass. It is observed that by electrolysis of water, the deuterium atom content of the hydrogen is lower than in the hydrogen generated petrochem- ically, for example as contained in synthesis gas, in general 100 ppm, preferably in general 90 ppm, more preferably from 20 to 80 ppm, for example from 30 to 75 ppm. The deuterium atom content in electrolytically produced hydrogen may be as low as 10 ppm. The deuterium is mainly present in the form of D-H rather than D2.

Generally, any water source can be used in the water electrolysis. However, since the hydrogen has a deuterium content (i.e., a molar share of deuterium) below 100 ppm, it is preferable to use water having a deuterium content (i.e., a molar share of deuterium) below 160 ppm, based on the total hydrogen content.

Vienna Standard Mean Ocean Water (VSMOW) is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. Despite the somewhat misleading phrase "ocean water", VSMOW refers to pure water (H2O) and does not include any salt or other substances usually found in seawater. VSMOW serves as a reference standard for comparing hydrogen and oxygen isotope ratios, mostly in water samples. Very pure, distilled VSMOW water is also used for making high accuracy measurement of water’s physical properties and for defining laboratory standards since it is considered to be representative of "average ocean water”, in effect representing the water content of Earth. The isotopic composition of VSMOW water is specified as ratios of the molar abundance of the rare isotope in question divided by that of its most common isotope and is expressed as parts per million (ppm). The isotopic ratios of VSMOW water are defined as follows:

2H / 1 H = 155.76 ± 0.1 ppm (a ratio of 1 part per approximately 6420 parts)

3H / 1 H = 1.85 ± 0.36 * 10 ¹¹ ppm (a ratio of 1 part per approximately 5.41 * 10¹⁶ parts, ignored for physical properties- related work)

(see: https://en-academic.com/dic.nsf/enwiki/753132)

One suitable water electrolysis process is alkaline water electrolysis. Hydrogen production by alkaline water electrolysis is a well-established technology up to the megawatt range for a commercial level. In alkaline water electrolysis initially at the cathode side two water molecules of alkaline solution (KOH/NaOH) are reduced to one molecule of hydrogen (H2) and two hydroxyl ions (OH-). The produced H2 emanates from the cathode surface in gaseous form and the hydroxyl ions (OH-) migrate under the influence of the electrical field between anode and cathode through the porous diaphragm to the anode, where they are discharged to half a molecule of oxygen (O2) and one molecule of water (H2O). Alkaline electrolysis operates at lower temperatures such as 30-80°C with alkaline aqueous solution (KOH/NaOH) as the electrolyte, the concentration of the electrolyte being about 20% to 30 %. The diaphragm in the middle of the electrolysis cell separates the cathode and anode and also separates the produced gases from their respective electrodes, avoiding the mixing of the produced gases. However, alkaline electrolysis has negative aspects such as limited current densities (below 400 mA/cm²), low operating pressure and low energy efficiency.

Polymer electrolyte membrane (PEM) water electrolysis was developed to overcome the drawbacks of alkaline water electrolysis. Variants of PEM water electrolysis are proton exchange membrane water electrolysis (PEMWE) and anion exchange membrane water electrolysis (AEMWE) PEM water electrolysis technology is similar to the PEM fuel cell technology, where solid polysulfonated membranes (Nation®, fumapem®) are used as an electrolyte (proton conductor). These proton exchange membranes have many advantages such as low gas permeability, high proton conductivity (0 1 ± 0.02 S cm^-1), low thickness (20-300 pirn), and allow high-pressure operation. In terms of sustainability and environmental impact, PEM water electrolysis is one of the most favorable methods for conversion of sustainable energy to highly pure hydrogen. PEM water electrolysis has great advantages such as compact design, high current density (above 2 A cm^-2), high efficiency, fast response, operation at low temperatures (20-80°C) and production of ultrapure hydrogen. The state-of-the-art electrocatalysts for PEM water electrolysis are highly active noble metals such as Pt/Pd for the hydrogen evolution reaction (HER) at the cathode and IrC /RuCh for the oxygen evolution reaction (OER) at the anode.

One of the largest advantages of PEM water electrolysis is its ability to operate at high current densities. This can result in reduced operational costs, especially for systems coupled with very dynamic energy sources such as wind and solar power, where sudden spikes in energy output would otherwise result in uncaptured energy. The polymer electrolyte allows the PEM water electrolyzer to operate with a very thin membrane (ca. 100-200 pm) while still allowing high operation pressure, resulting in low ohmic losses, primarily caused by the conduction of protons across the membrane (0.1 S/cm), and a compressed hydrogen output. The PEM water electrolyzer utilizes a solid polymer electrolyte (SPE) to conduct protons from the anode to the cathode while insulating the electrodes electrically. Under standard conditions the enthalpy required for the formation of water is 285.9 kJ/mol. One portion of the required energy for a sustained electrolysis reaction is supplied by thermal energy and the remainder is supplied through electrical energy.

PEMs can be made from either pure polymer membranes or from composite membranes, where other materials are embedded in a polymer matrix. One of the most common and commercially available PEM materials is the fluoropolymer PFSA, or Nation®, a DuPont product. While Nation® is an ionomer with a perfluorinated backbone like Teflon, there are many other structural motifs used to make ionomers for proton-exchange membranes. Many use polyaromatic polymers, while others use partially fluorinated polymers.

An overview of hydrogen production by PEM water electrolysis is given in S. Kumar and V. Himabindu, Material Science for Energy Technologies 2 (2019), pp. 4442 -4454. An overview of hydrogen production by anion exchange membrane water electrolysis is given in H. A. Miller et al., Sustainable Energy Fuels, 2020, 4, pp. 2114 - 2133.

In PEM water electrolysis, deuterium in the evolving hydrogen gas can easily be depleted by a factor of from 2 to 5 with regard to the feed water. Depending on the electrolysis conditions (water flow, current density), even higher depletion factors are possible. Since the average deuterium content of water is about 150 ppm, based on the total hydrogen content, hydrogen as preferably used herein may have a deuterium content of from 30 to 75 ppm, based on the total hydrogen content, or even lower.

Hydrogen may be furthermore obtained by the chlor-alkali electrolysis process which is known to the one of skill in the art. The process is for example described in P. Schmittinger et al., Ullmann's Encyclopedia of Industrial Chemistry, 2011, Chapter “Chlorine”, pp. 538-595, and the references cited therein.

Also, cracking process like steam cracking of hydrocarbons (see step C) below) may be used to obtain at least a part of the hydrogen amounts required Thus, advantageously, the same technical process may be used for the aromatization in step C) and the provision of hydrogen in step A).

Within the present invention, the production of hydrogen is preferably not associated with carbon dioxide emissions from fossil sources. Thus, preferred processes are steam reforming, steam cracking, and other syngas-producing processes in which carbon dioxide formed as a by-product or by combustion is captured and sequestered (carbon capture and storage, CCS) or used as a chemical raw material (carbon capture and utilization, CCU) and is thus not released to the atmosphere. Further preferred processes are steam reforming and other syngas-producing processes based on renewable resources like biogas or other biomass-derived light hydrocarbons. Even more preferred processes are those with net-negative carbon dioxide emissions, e.g., steam reforming, steam cracking, and other syngas-producing processes based on renewable resources and combined with CCS or CCU, or hydrocarbon pyrolysis based on renewable resources like biogas or other biomass-derived light hydrocarbons.

Other preferred processes for the production of hydrogen are electrolysis of water and chlor-alkali electrolysis in which at least a part of the needed electrical power is generated from non-fossil, renewable sources. The term “at least in part” means that another part of the electrical power can still be produced from fossil fuels (preferably from natural gas, since combustion of natural gas causes much lower carbon dioxide emission per Megajoule of electrical energy produced than combustion of coal). However, the portion of electrical energy produced from fossil fuels should be as low as possible, preferably 50%, more preferably 30%, most preferably 20%, further most preferably 10%, ideally < 1 %.

Various methods for certification and tracking of the “energy source mix” have been set up based on local legislations, e.g., Guarantees of Origin (GOs: Europe), Renewable Electricity Certificates (RECs: USA, Canada), or international RECs (l-RECs: China, India, Brazil, Mexico, Indonesia, South Africa, etc.). Certificates such as “Non-Fossil Certificate Contracts” are common practice for tracking the ratio of non-fossil energy used in industrial processes and related products (e.g., https://www.ekoenergy.org/ecolabel/criteria/tracking/)

Preferably, the electrical power is generated at least in part, preferably exclusively, from sustainable resources, preferably wind energy, solar energy (thermal, photovoltaic, and concentrated solar energy), hydropower (tidal power, wave power, hydroelectric dams, in-river-hydrokinetics), geothermal energy, ambient or industrial heat captured by heat pumps, bioenergy (biofuel, biomass), the renewable part of waste energy sources, or nuclear energy (fission).

Preferred Embodiments

1.2) The process according to any of the preceding embodiments, wherein in step A) said syngas comprises carbon monoxide and hydrogen and wherein at least a part of said carbon monoxide and/or at least a part of said hydrogen originates from sustainable sources.

1.3) The process according to any of the preceding embodiments, wherein step A) comprises producing syngas, optionally followed by WGS reaction and/or addition of hydrogen from external sources.

1.4) The process according to any of the preceding embodiments, wherein in step A), at least a part of said syngas originates from steam reforming, autothermal catalytic reforming, or partial oxidation of gaseous and/or liquid feedstocks.

1 5) The process according to any of the preceding embodiments, wherein in step A), at least a part of said syngas originates from dry reforming of gaseous feedstocks and carbon dioxide

1 6) The process according to any of embodiments 1 4 to 1.5, wherein in step A), said gaseous and/or liquid feedstocks comprise biogas, preferably bio-methane, and/or biomass-derived light hydrocarbons.

1.7) The process according to any of the preceding embodiments, wherein in step A), at least a part of said syngas originates from gasification of solid feedstocks.

1.8) The process according to embodiment 1 .7, wherein in step A), said solid feedstocks comprise biomass, preferably selected from the group consisting of wood or residues thereof, crops or residues thereof, agricultural waste, and sewage sludge, and/or waste, preferably selected from the group consisting of municipal waste, hazardous waste, industrial waste, mixed plastic waste, caprolactam-based waste, and end-of-life tires.

1.9) The process according to any of the preceding embodiments, wherein in step A), at least a part of said syngas originates from rWGS reaction of carbon dioxide and hydrogen.

1.10) The process according to embodiment 1.9, wherein in step A), at least a part of said carbon dioxide is obtained via DAG, DOC, and/or IOC.

1.11) The process according to any of embodiments 1.9 to 1.10, wherein in step A) at least a part of said carbon dioxide is obtained via carbon capture from industrial point sources. 1.12) The process according to embodiment 1.11 , wherein in step A), said industrial point sources are selected from the group consisting of combustion power plants, cement production facilities, steel manufacturing facilities, chemical manufacturing facilities, biogas production and processing facilities, and/or refineries, preferably from the group consisting of power plants for the combustion of waste and/or biomass, steam crackers, steam reformers, partial oxidation plants, and facilities for the hydrotreatment of bio-oils or waste-derived pyrolysis oils.

1.13) The process according to any of embodiments 1.9 to 1.12, wherein in step A), at least a part of said carbon dioxide originates from biomass.

1.14) The process according to any of embodiments 1.2 to 1.13, wherein in step A), at least a part of said hydrogen originates from syngas production processes selected from the group consisting of steam reforming, autothermal catalytic reforming, and partial oxidation of gaseous and/or liquid feedstocks, dry reforming of gaseous feedstocks and carbon dioxide, and gasification of solid feedstocks, said processes being optionally followed by a WGS reaction and/or hydrogen separation.

1.15) The process according to embodiment 1.14, wherein in step A), said gaseous and/or liquid feedstocks comprise biogas, preferably bio-methane, and/or biomass-derived light hydrocarbons, and said solid feedstocks comprise biomass, preferably selected from the group consisting of wood or residues thereof, crops or residues thereof, agricultural waste, and sewage sludge, and/or waste, preferably selected from the group consisting of municipal waste, hazardous waste, industrial waste, mixed plastic waste, caprolactam- based waste, and end-of-life tires.

1.16) The process according to any of embodiments 1.2 to 1.15, wherein in step A), said hydrogen originates from syngas production processes the carbon dioxide emissions of which are captured and stored and/or utilized.

1 17) The process according to any of embodiments 1.2 to 1.16, wherein in step A), at least a part of said hydrogen originates from pyrolysis of hydrocarbons, preferably selected from the group consisting of natural gas, biogas, and other light hydrocarbons, more preferably selected from the group consisting of biogas, bio-methane, and biomass-derived light hydrocarbons, and/or at least a part of said hydrogen originates from steam cracking of hydrocarbons.

1.18) The process according to any of embodiments 1.2 to 1.17, wherein in step A), at least a part of said hydrogen originates from water electrolysis, preferably from PEM water electrolysis.

1.19) The process according to any of embodiments 1.2 to 1.18, wherein in step A), at least a part of said hydrogen originates from chlor-alkali electrolysis.

1.20) The process according to any of embodiments 1.17 to 1.19, wherein in step A), electrical power is used for said hydrocarbon pyrolysis, water electrolysis, and/or chlor-alkali electrolysis and the fraction of said electrical power that originates from fossil energy sources is 50%, preferably 30%, more preferably 20%, even more preferably 10%, most preferably < 1 %.

1.21) The process according to any of embodiments 1.17 to 1.20, wherein in step A), electrical power is used for said hydrocarbon pyrolysis, water electrolysis, and/or chlor-alkali electrolysis and at least a part, preferably all, of said electrical power originates from non-fossil energy sources, preferably selected from the group consisting of wind energy, solar energy, hydropower, geothermal energy, ambient or industrial heat captured by heat pumps, bioenergy (biofuel, biomass), the renewable part of waste energy sources, or nuclear energy.

Fischer-Tropsch synthesis refers to the catalytic process of manufacturing mainly liquid hydrocarbons from syngas. The produced hydrocarbons comprise alkanes and alkenes and, depending on the process conditions (e.g., temperature and catalyst), range from substitute natural gas over gasoline (boiling range of approx. 50-180 °C) and diesel oil (boiling rage of approx. 180-320 °C) to waxes. Refining of this raw product spectrum delivers commercially attractive fractions like liquefied petroleum gases (LPG), gasoline, diesel fuels, or olefins for petrochemical use. Refining may include typical fractionation techniques to separate the obtained raw products like distillation as well as process steps to further modify the chemical composition of the obtained raw products, like cracking and isomerization, in particular hydrocracking and hydroisomerization, and combinations thereof.

Fischer-Tropsch (FT) processes may be carried out as low-temperature (LTFT) and high-temperature (HTFT) processes. In LTFT processes, typically temperatures of 220-250 °C and iron- or cobalt-based catalysts are employed to obtain higher amounts of diesel and wax fractions. In HTFT processes, typically temperatures of 330-350 °C and ironbased catalysts are used to increase the yields of light olefin and gasoline fractions. Also, ruthenium-based catalysts have proven to be active in FT processes.

Details on FT products and FT processes are disclosed for example in T. Kaneko et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Coal Liquefaction”, A. Yu. Krylova, Solid Fuel Chemistry 2014, 48, 22-35, T. Lin et al, ACS Catal. 2022, 12, 12092-12112, and the references cited therein.

Of importance, hydrocarbons to be regarded as naphtha fractions may be generated by FT processes: For instance, they may be obtained by distillation of FT raw products, preferably from FT processes designed to increase the yields of hydrocarbons with up to about 12 carbon atoms. In addition, naphtha may be produced by refining treatment of heavier hydrocarbons and waxes from FT processes, in particular by hydrocracking and optionally hydroisomerization, e.g., in the presence of catalysts like zeolites, for instance, HZSM-5.

Preferred Embodiments

1.22) The process according to any of the preceding embodiments, wherein in step B), said Fischer-Tropsch process is carried out in the presence of a catalyst, preferably in the presence of an iron, cobalt, or ruthenium catalyst.

1.23) The process according to any of the preceding embodiments, wherein in step B), said at least one refining step comprises at least one distillation step.

1.24) The process according to any of the preceding embodiments, wherein in step B), said Fischer-Tropsch process is carried out as high-temperature Fischer-Tropsch process and said at least one refining step comprises at least one distillation step.

1.25) The process according to any of the preceding embodiments, wherein in step B), said Fischer-Tropsch process is carried out as low-temperature Fischer-Tropsch process and said at least one refining step comprises a hydrocracking and/or hydroisomerization step, preferably in the presence of a zeolite catalyst. In step C), benzene is obtained from an aliphatic hydrocarbon stream, in particular from naphtha, by aromatization and subsequent separation. The aromatization step may be accomplished as a part of a cracking process, in particular of (fluid) catalytic cracking, thermal cracking, and steam cracking. The main reaction products obtained from such cracking processes, in particular of steam cracking, comprise C2-4-olefins (ethylene, propylene, butylene isomers, butadiene), Cg-s-aromatics (benzene, toluene, xylene isomers, and ethyl benzene), and pyrolysis gasoline (a complex mixture of various hydrocarbons comprising further amounts of Ce-s-aromatics, especially benzene). Steam cracking also delivers certain amounts of Cu-alkanes and hydrogen. Alternatively, aromatization may be achieved by catalytic reforming. Said cracking and reforming processes are known in the art and for example described in G. Alfke, Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Oil Refining”, pp. 216-245, in H. Zimmermann et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Ethylene”, pp. 469-494, in H. 0. Folkins, Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Benzene”, pp. 240-251, and the references cited therein.

Said cracking and reforming processes will typically deliver product streams comprising various hydrocarbons. The utilization of common fractionation, separation, and purification techniques, especially of extraction and distillation steps, allows to obtain hydrocarbon streams comprising Ce-s-aromatics, in particular hydrocarbon streams comprising benzene, and to isolate benzene from said hydrocarbon streams. Fractionation, separation, and purification processes to isolate benzene may include adsorption, absorption, solvent extraction, distillation, and extractive distillation steps as well as combinations thereof and are for example described in H. O. Folkins, Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Benzene”, pp. 242-260, in H. Zimmermann et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Ethylene", pp. 469-515, and in the references cited therein.

In particular steam cracking processes typically emit large amounts of carbon dioxide because the required high temperatures are achieved by combustion of natural gas. Preferably, said carbon dioxide emissions are captured, preferably via post-combustion capture with chemical absorbent agents such as alkanolamines, to reduce the amount of greenhouse gas emissions; even more preferably, said captured carbon dioxide is used as a chemical raw material, e.g., to produce syngas by reaction with hydrogen (rWGS) as described herein for step A).

Steam cracking also delivers relevant amounts of hydrogen. Preferably, at least a part of said hydrogen is used in the processes according to the invention, e.g., in step A) to produce syngas by reaction with carbon dioxide (rWGS) or to adjust the carbon monoxide to hydrogen ratio in syngas or in step D) (described hereinafter) to hydrogenate benzene or to produce ammonia by reaction with nitrogen (Haber-Bosch process).

It is contemplated within the present invention that an aliphatic hydrocarbon stream comprising naphtha obtained by the process steps A) to B) as described hereinbefore is used as a starting material for the formation of benzene. However, not necessarily all of said aliphatic hydrocarbon stream comprising naphtha needs to be employed for said conversion, but parts of it may be used for other purposes. On the other hand, process steps A) to B) do not have to be the only source of the aliphatic hydrocarbon stream comprising naphtha to be converted to benzene, i.e., the aliphatic hydrocarbon stream comprising naphtha of process steps A) to B) may be complemented for the purpose of conversion to benzene with one or more aliphatic hydrocarbon streams comprising naphtha originating from other, preferably sustainable, renewable, and/or non-fossil, sources. For instance, a portion of the aliphatic hydrocarbon stream comprising naphtha used for conversion to benzene may be manufactured by methods and/or obtained from feedstocks other than those described by steps A) to B). Said portion of the aliphatic hydrocarbon stream comprising naphtha may be obtained, for example, from Fischer-Tropsch synthesis starting with syngas of fossil origin, from refining of hydrocarbon streams of fossil origin, or from hydrotreatment of bio-oils. Said portion may also comprise mixtures of aliphatic hydrocarbon streams comprising naphtha from various sources.

Preferred Embodiments

1.26) The process according to any of the preceding embodiments, wherein in step C) said aliphatic hydrocarbon stream comprising naphtha, i.e., the aliphatic hydrocarbon stream comprising naphtha originating from the process according to steps A) to B), is employed in admixture with at least one aliphatic hydrocarbon stream comprising naphtha originating from other sources.

1.27) The process according to embodiment 1 .26, wherein in step C) the fraction of the aliphatic hydrocarbon stream comprising naphtha originating from the process according to steps A) to B) in the admixture is at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said aliphatic hydrocarbon stream comprising naphtha.

1.28) The process according to any of the preceding embodiments, wherein in step C), at least a part of said aliphatic hydrocarbon stream comprising naphtha originates from sustainable and/or non-fossil sources, preferably at least 2 5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said aliphatic hydrocarbon stream comprising naphtha.

1.29) The process according to any of the preceding embodiments, wherein in step C), at least a part of said aliphatic hydrocarbon stream comprising naphtha obtained in step B) is used, preferably at least 25 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of the aliphatic hydrocarbon stream comprising naphtha obtained in step B).

1.30) The process according to any of the preceding embodiments, wherein in step C), the aromatization step is part of a cracking process, preferably selected from the group consisting of catalytic cracking, fluid catalytic cracking, thermal cracking, and steam cracking processes, more preferably selected from the group consisting of fluid catalytic cracking and steam cracking processes.

1.31) The process according to any of embodiments 1.26 to 1.29, wherein in step C), the aromatization step is part of a catalytic reforming process.

1.32) The process according to any of the preceding embodiments, wherein at least a part of the carbon dioxide emitted in the course of the aromatization step according to step C), preferably from a steam cracker furnace, is captured and preferably at least a part of said captured carbon dioxide is used in step A) to provide syngas by reaction with hydrogen in a rWGS reaction.

1.33) The process according to any of the preceding embodiments, wherein at least a part of the hydrogen produced in the course of the aromatization step according to step C), preferably during steam cracking, is used in step A) to provide syngas by reaction with carbon dioxide in a rWGS reaction and/or in step A) to adjust the carbon monoxide to hydrogen ratio in the syngas and/or in step D) for the hydrogenation of benzene and/or in step D) to provide ammonia by reaction with nitrogen.

1.34) The process according to any of the preceding embodiments, wherein in step C), separating benzene comprises fractionation, separation, and purification processes, preferably selected from the group consisting of adsorption, absorption, solvent extraction, distillation, and extractive distillation steps as well as combinations thereof, more preferably selected from the group of solvent extraction, distillation, and extractive distillation steps as well as combinations thereof.

In step D) of the process according to the present invention, the benzene obtained in step C) is converted to cyclohexanone oxime. Different approaches may be pursued to achieve this conversion.

First, benzene may be reduced to cyclohexane. To this end, benzene is contacted with hydrogen in the presence of a first heterogeneous catalyst to effectuate a hydrogenation reaction whereby cyclohexane is formed. Suitable catalysts comprise nickel, platinum, or palladium on a support such as alumina, or a Raney nickel catalyst. The process temperature is about 300 °C or less at a pressure of about 20 MPa to about 30 MPa. Further details are for example disclosed in M. L. Campbell, Ullmann's Encyclopedia of Industrial Chemistry, 2011 , Chapter “Cyclohexane”, pp. 44-46, and the references cited therein.

Said cyclohexane may be used in admixture with cyclohexane originating from other sources than from steps A) to D) Said cyclohexane may be converted to cyclohexanone oxime, obtained in the form of its dihydrochloride in the presence of excess hydrogen chloride, by photonitrosation of cyclohexane with nitrosyl chloride. Said photooximation process is for example disclosed in J. Tinge et al., Ullmann's Encyclopedia of Industrial Chemistry, 2018, Chapter “Caprolactam”, pp. 16-17, and the references cited therein.

According to a different route, the obtained cyclohexane is oxidized in the presence of oxygen and, optionally, a second heterogeneous catalyst, whereby cyclohexanone is formed. Cyclohexanone can be manufactured from cyclohexane forexample by liquid-phase oxidation in the presence of air in an uncatalyzed or catalyzed reaction (e.g., cobalt catalyst as second heterogeneous catalyst) at a temperature in the range of about 140 °C to about 180 °C and a pressure in the range of 0.8 MPa to about 2 MPa. Cyclohexanone can also be manufactured from cyclohexane in the presence of anhydrous (meta-)boric acid. Cyclohexanol is produced by such processes as a side product. Such mixtures comprising cyclohexanone and cyclohexanol are also known as “KA oil” (“ketone-alcohol oil”) and “AnoIon”. Suitable manufacturing processes for cyclohexanone from cyclohexane such as the above discussed ones are for example disclosed in M. T. Musser, Ullmann's Encyclopedia of Industrial Chemistry, 2011, Chapter “Cyclohexanol and Cyclohexanone”, pp. 51-52, and the references cited therein. Alternatively, benzene may be reduced selectively to cyclohexene. Cyclohexene may be converted to cyclohexanone by hydration to cyclohexanol in the presence of a heterogeneous catalyst followed by dehydrogenation to cyclohexanone at 400-450 °C without catalyst or in the presence of a catalyst under milder conditions. Details on the production of cyclohexene from benzene and its conversion to cyclohexanone are for example disclosed in M. T. Musser, Ullmann's Encyclopedia of Industrial Chemistry, 2011, Chapter “Cyclohexanol and Cyclohexanone”, pp. 52-54, and the references cited therein.

According to a further alternative pathway from benzene to cyclohexanone, benzene is first oxidized to phenol. Processes to achieve this conversion are for example described in M. Weber et al., Ullmann's Encyclopedia of Industrial Chemistry, 2020, Chapter ''Phenol'', pp. 11-13, and the references cited therein. Cyclohexanone can be obtained from phenol by hydrogenation in the vapor phase in the presence of noble metal catalysts. Details on this process can be found in M. T. Musser, Ullmann's Encyclopedia of Industrial Chemistry, 2011 , Chapter ''Cyclohexanol and Cyclohexanone”, pp. 50-51 , and the references cited therein.

For the conversion of cyclohexanone to cyclohexanone oxime, different oximation routes with different oximation agents are available: In the Raschig process and in similar processes, oximation of cyclohexanone occurs with hydroxylammonium sulfate wherein the freed sulfuric acid is neutralized with aqueous ammonia. In the hydroxylamine phosphate oxime process, nitrate ions or nitrogen oxides are selectively hydrogenated with hydrogen gas in the presence of a catalyst in a phosphoric acid buffer solution to form hydroxylammonium dihydrogenphosphate; contacted with said hydroxylamine species, cyclohexanone is converted to cyclohexanone oxime. In the ammoximation process, cyclohexanone is reacted with ammonia and hydrogen peroxide in the presence of a catalyst to yield cyclohexanone oxime. Details on the conversion of cyclohexanone to cyclohexanone oxime can be found for example in J. Tinge et al., Ullmann's Encyclopedia of Industrial Chemistry, 2018, Chapter “Caprolactam”, pp. 2-11 , and the references cited therein.

Methods to produce hydroxylamine and salts thereof are known in the art and described for example in J. Ritz et al., Ullmann's Encyclopedia of Industrial Chemistry, 2012, Chapter “Hydroxylamine”, J. Tinge et al., Ullmann's Encyclopedia of Industrial Chemistry, 2018, Chapter “Caprolactam”, and the references cited therein. All of these processes make use of hydrogen, for the manufacture of ammonia (from nitrogen and hydrogen according to the well-known Haber-Bosch process) and/or, if nitrogen oxides or nitrates are used, for the hydrogenation of the same (e.g., catalytic hydrogenation of nitric oxide or catalytic hydrogenation of nitrates). Of note, also said nitrogen oxides or nitrates are often derived from ammonia, i.e., from nitrogen and hydrogen as raw materials. Still, the predominant production routes of hydrogen are based on fossil fuels, mainly on steam reforming of natural gas (above all methane) and other light hydrocarbons. However, the petrochemical steam reforming process has its negative impacts regarding its carbon footprint including the consumption of a lot of fossil-based natural resources and energy. Thus, the production of sufficient amounts of hydrogen may represent a challenge where fossil resources and energies should be avoided for sustainability reasons. Thus, the hydrogen needed to produce hydroxylamine and derivatives thereof as used in the processes according to the invention is preferably obtained from sustainable sources. In particular, it may be obtained as described for step A) of this invention, e.g., via water electrolysis or chlor-alkali electrolysis powered by sustainable energy sources, via hydrocarbon pyrolysis based on renewable resources, or via steam reforming and other syngasproducing processes based on renewable resources and combined with CCS or CCU.

Similarly, the nitrogen needed for the synthesis of ammonia is preferably obtained by (cryogenic) air separation that is powered by electricity at least in part generated from sustainable resources, as described for step A).

It is contemplated within the present invention that benzene obtained by the process steps A) to C) as described hereinbefore is used as a starting material for the formation of cyclohexanone oxime. However, not necessarily all of said benzene needs to be employed for said conversion, but parts of it may be used for other purposes. On the other hand, process steps A) to C) do not have to be the only source of the benzene to be converted to cyclohexanone oxime, i.e., benzene of process steps A) to C) may be complemented for the purpose of conversion to cyclohexanone oxime with benzene originating from other, preferably sustainable and/or non-fossil, sources. For instance, a portion of the benzene used for conversion to cyclohexanone oxime may be manufactured by methods and/or from feedstocks other than those described by steps A) to C). Said portion of benzene may be obtained, for example, from a hydrocarbon stream of fossil origin. Said portion may also comprise mixtures of benzene from various sources.

Preferred Embodiments

1.35) The process according to any of the preceding embodiments, wherein in step D) said benzene, i.e., the benzene originating from the process according to steps A) to C), is employed in admixture with benzene originating from other sources.

1.36) The process according to embodiment 1.35, wherein in step D) the fraction of benzene originating from the process according to steps A) to C) in the admixture is at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said benzene.

1.37) The process according to any of the preceding embodiments, wherein in step D), at least a part of said benzene originates from sustainable and/or non-fossil sources, preferably at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said benzene.

1.38) The process according to any of the preceding embodiments, wherein in step D), at least a part of said benzene obtained in step C) is used, preferably at least 25 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of the benzene obtained in step C).

1.39) The process according to any of the preceding embodiments, wherein step D) comprises the substeps

D1 a) subjecting said benzene to hydrogenation to obtain cyclohexane; D2a) subjecting said cyclohexane to oxidation to obtain cyclohexanone; and

D3) subjecting said cyclohexanone to oximation to obtain cyclohexanone oxime.

1.40) The process according to embodiment 1.39, wherein in step D2a) oxidation is effected in the presence of oxygen and, optionally, a second heterogeneous catalyst, and wherein preferably said oxygen originates from water electrolysis, more preferably from water electrolysis powered by sustainable energy sources.

1.41) The process according to any of embodiments 1.1 to 1.38, wherein step D) comprises the substeps

D1 b) subjecting said benzene to hydrogenation to obtain cyclohexene;

D2b) subjecting said cyclohexene to hydration to obtain cyclohexanol and subjecting said cyclohexanol to dehydrogenation to obtain cyclohexanone; and D3) subjecting said cyclohexanone to oximation to obtain cyclohexanone oxime.

1.42) The process according to any of embodiments 1.1 to 1.38, wherein step D) comprises the substeps

D1c) subjecting said benzene to oxidation to obtain phenol;

D2c) subjecting said phenol to hydrogenation to obtain cyclohexanone; and

D3) subjecting said cyclohexanone to oximation to obtain cyclohexanone oxime.

1.43) The process according to any of embodiments 1.1 to 1.38, wherein step D) comprises the substeps

D1 a) subjecting said benzene to hydrogenation to obtain cyclohexane; and

D2d) subjecting said cyclohexane to photonitrosation to obtain cyclohexanone oxime.

1.44) The process according to any of embodiments 1.39 to 1.42, wherein in step D3) oximation is effectuated by reaction with hydroxylammonium sulfate, and wherein hydrogen and/or nitrogen are used in the process for obtaining said hydroxylammonium sulfate.

1 45) The process according to any of embodiments 1.39 to 1.42, wherein in step D3) oximation is effectuated by reaction with hydroxylammonium dihydrogenphosphate, and wherein hydrogen and/or nitrogen are used in the process for obtaining said hydroxylammonium dihydrogenphosphate.

1 46) The process according to any of embodiments 1.39 to 1.42, wherein in step D3) oximation is effectuated by reaction with ammonia and hydrogen peroxide, and wherein hydrogen and nitrogen are used in the process for obtaining said ammonia.

1.47) The process according to any of embodiments 1.39 to 1 .40 and 1.43 to 1.46, wherein in step D2a) or D2d) said cyclohexane, i.e., the cyclohexane originating from the process according to steps A) to D1 a), is employed in admixture with cyclohexane originating from other sources.

1.48) The process according to any of embodiments 1 .39 to 1 .40 and 1 .43 to 1.47, wherein in step D2a) or D2d) the fraction of cyclohexane originating from the process according to steps A) to D1 a) in the admixture is at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said cyclohexane.

1.49) The process according to any of embodiments 1.39 to 1.40 and 1.43 to 1.48, wherein in step D2a) or D2d), at least a part of said cyclohexane originates from sustainable and/or non-fossil sources, preferably at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said cyclohexane.

1.50) The process according to any of embodiments 1.39 to 1.40 and 1.43 to 1.49, wherein in step D2a) or D2d), at least a part of said cyclohexane obtained in step D1 a) is used, preferably at least 25 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of the cyclohexane obtained in step D1a).

1.51) The process according to any of embodiments 1.39 to 1.50, wherein in steps D1a), D1 b), D2c), and/or D3), hydrogen is used and at least a part of said hydrogen originates from syngas production processes selected from the group consisting of steam reforming, autothermal catalytic reforming, and partial oxidation of gaseous and/or liquid feedstocks, dry reforming of gaseous feedstocks and carbon dioxide, and gasification of solid feedstocks, said processes being optionally followed by a WGS reaction and/or hydrogen separation.

1.52) The process according to embodiment 1.51, wherein in steps D1a), D1b), D2c), and/or D3), said gaseous and/or liquid feedstocks comprise biogas, preferably bio-methane, and/or biomass-derived light hydrocarbons, and said solid feedstocks comprise biomass, preferably selected from the group consisting of wood or residues thereof, crops or residues thereof, agricultural waste, and sewage sludge, and/or waste, preferably selected from the group consisting of municipal waste, hazardous waste, industrial waste, mixed plastic waste, caprolactam- based waste, and end-of-life tires.

1.53) The process according to any of embodiments 1.51 to 1.52, wherein in steps D1 a), D1 b), D2c), and/or D3), said hydrogen originates from syngas production processes the carbon dioxide emissions of which are captured and stored and/or utilized.

1 54) The process according to any of embodiments 1.39 to 1.53, wherein in steps D1a), D1 b), D2c), and/or D3), hydrogen is used and at least a part of said hydrogen originates from pyrolysis of hydrocarbons, preferably selected from the group consisting of natural gas, biogas, and other light hydrocarbons, more preferably selected from the group consisting of biogas, bio-methane, and biomass-derived light hydrocarbons.

1.55) The process according to any of embodiments 1.39 to 1.54, wherein in steps D1a), D1 b), D2c), and/or D3), hydrogen is used and at least a part of said hydrogen originates from water electrolysis and/or chlor-alkali electrolysis using electrical power, preferably from PEM water electrolysis.

1.56) The process according to any of embodiments 1.44 to 1.55, wherein in step D3), at least a part of said nitrogen originates from cryogenic air separation using electrical power.

1.57) The process according to any of embodiments 1.55. to 1.56, wherein in step D3), the fraction of said electrical power that originates from fossil energy sources is 50%, preferably 30%, more preferably 20%, even more preferably 10%, most preferably < 1 %.

1.58) The process according to any of embodiments 1.55. to 1.57, wherein in step D3), at least a part, preferably all, of said electrical power originates from non-fossil energy sources, preferably selected from the group consisting of wind energy, solar energy, hydropower, geothermal energy, ambient or industrial heat captured by heat pumps, bioenergy (biofuel, biomass), the renewable part of waste energy sources, or nuclear energy.

Caprolactam is formed from cyclohexanone oxime and the dihydrochloride thereof, respectively, by a Beckmann rearrangement reaction which can be carried out in the liquid phase or in the gas phase in the presence of a catalyst. Manufacturing methods for caprolactam from cyclohexanone oxime are for example disclosed in J. Tinge et al., Ullmann's Encyclopedia of Industrial Chemistry, 2018, Chapter "Caprolactam”, pp. 11-14, and the references cited therein. In liquid phase for example, fuming sulfuric acid or oleum is used as a catalyst followed by a neutralization reaction with ammonia or ammonia water and separation of the caprolactam which is then purified in additional process steps.

It is contemplated within the present invention that cyclohexanone oxime obtained by the process steps A) to D) as described hereinbefore is used as a starting material for the formation of caprolactam. However, not necessarily all of said cyclohexanone oxime needs to be employed for said conversion, but parts of it may be used for other purposes. On the other hand, process steps A) to D) do not have to be the only source of the cyclohexanone oxime to be converted to caprolactam, i.e., cyclohexanone oxime of process steps A) to D) may be complemented for the purpose of conversion to caprolactam with cyclohexanone oxime originating from other, preferably sustainable and/or non-fossil, sources. For instance, a portion of the cyclohexanone oxime used for conversion to caprolactam may be manufactured by methods and/or from feedstocks other than those described by steps A) to D). Said portion of cyclohexanone oxime may be obtained, for example, from benzene of fossil origin. Said portion may also comprise mixtures of cyclohexanone oxime from various sources

Preferred Embodiments

1 59) The process according to any of the preceding embodiments, wherein in step E) said cyclohexanone oxime, i.e., the cyclohexanone oxime originating from the process according to steps A) to D), is employed in admixture with cyclohexanone oxime originating from other sources.

1.60) The process according to embodiment 1.59, wherein in step E) the fraction of cyclohexanone oxime originating from the process according to steps A) to D) in the admixture is at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said cyclohexanone oxime.

1.61) The process according to any of the preceding embodiments, wherein in step E), at least a part of said cyclohexanone oxime originates from sustainable and/or non-fossil sources, preferably at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said cyclohexanone oxime.

1.62) The process according to any of the preceding embodiments, wherein in step E), at least a part of said cyclohexanone oxime obtained in step D) is used, preferably at least 25 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of the cyclohexanone oxime obtained in step D).

Further steps:

Optionally, caprolactam can be further converted to polycaprolactam, which may be achieved via hydrolytic polymerization of molten caprolactam in the presence of water. Such hydrolytic polymerization can be carried out for example as a continuous process in so-called "VK tube” reactors. Remaining nonpolymerized fractions (monomer and oligomers) may be removed from the polymer by extraction techniques like liquid extraction, vacuum extraction, and supercritical fluid extraction. Methods for manufacturing polycaprolactam from caprolactam are for example described in B. Herzog et al., Ullmann's Encyclopedia of Industrial Chemistry, 2020, Chapter “Polyamides”, pp. 22-28 and the references cited therein.

It is contemplated within the present invention that caprolactam obtained by the process steps A) to E) as described hereinbefore is used as a starting material for the polymerization to polycaprolactam. However, not necessarily all of said caprolactam needs to be employed for said polymerization, but parts of it may be used for other purposes. On the other hand, process steps A) to E) do not have to be the only source of the caprolactam to be polymerized, i.e., caprolactam of process steps A) to E) may be complemented for the purpose of polymerization with caprolactam originating from other, preferably sustainable and/or non-fossil, sources. For instance, a portion of the caprolactam used for polymerization may be manufactured by methods and/or from feedstocks other than those described by steps A) to E). Said portion of caprolactam may be obtained, for example, from benzene of fossil origin or via depolymerization of polycaprolactam-containing plastic waste. Such methods are for example disclosed in WO 96/18612 A1 , EP 568882 A1 and EP 1975156 A1. Said portion may also comprise mixtures of caprolactam from various sources, in particular from the two aforementioned ones.

Preferred Embodiments

1.63) The process according to any of the preceding embodiments, the process further comprising step F)

F) subjecting said caprolactam to polymerization to obtain polycaprolactam.

1.64) The process according to embodiment 1.63, wherein step F) comprises the purification of polycaprolactam, in particular the removal of nonpolymerized fractions by extraction.

1.65) The process according to any of embodiments 1.63 to 1.64, wherein in step F) said caprolactam, i.e., the caprolactam originating from the process according to steps A) to E), is employed in admixture with caprolactam originating from other sources.

1.66) The process according to embodiment 1.65, wherein in step F) the fraction of caprolactam originating from the process according to steps A) to E) in the admixture is at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said caprolactam.

1.67) The process according to any of embodiments 1 .63 to 1 .66, wherein in step F), at least a part of said caprolactam originates from sustainable and/or non-fossil sources, preferably at least 2.5 %, more preferably at least 5 %, more preferably at least 7.5 %, more preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of said caprolactam.

1.68) The process according to any of embodiments 1.63 to 1.67, the process further comprising step F), wherein in step F), at least a part of said caprolactam obtained in step E) is used, preferably at least 25 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, most preferably all of the caprolactam obtained in step E).

Further embodiments of the first aspect of the invention are described by the combination of any and each of the above definitions and embodiments with one another, in particular by way of FIGs 1-4.

FIG 1 depicts a process to produce (poly)caprolactam (7, 8): Hydrogen (1), preferably obtained from electrolysis driven by sustainably generated electrical power, and carbon dioxide (2), preferably of biogenic origin, are converted to syngas (3) in a rWGS reaction (20). A Fischer-Tropsch process, including subsequent refining, (21) delivers naphtha (4) from said syngas (3). Naphtha (4) is used as a feedstock for a cracking process, preferably a steam cracking process, (with subsequent product separation) (22) which yields benzene (5). Said benzene (5) is converted to cyclohexanone oxime (6) in a cyclohexanone oxime production (23) according to one of the pathways described herein. Caprolactam (7) is formed from cyclohexanone oxime (6) via Beckmann rearrangement (24) and may optionally be further polymerized (25) to polycaprolactam (8).

FIG 2 depicts another process to produce (poly)caprolactam (7, 8): The process of FIG 2 differs from the one depicted in FIG 1 by the fact that hydrogen that is formed during the cracking process (22) is fed back as a starting material (1) to the rWGS reaction (20). Similarly, carbon dioxide that is emitted by heating the cracking process is captured and used as a starting material (2) in the rWGS reaction (20).

FIG 3 depicts another process to produce (poly)caprolactam (7, 8): The process of FIG 3 differs from the one depicted in FIG 1 by the fact that hydrogen (1) and nitrogen (9), preferably obtained by cryogenic air separation, are used to produce the oximation agent (10) that is employed in the conversion (23) of benzene (5) to cyclohexanone oxime (6). Of note, the process of FIG 3 may optionally comprise the additional elements and features of the process of FIG 2. FIG 4 depicts another process to produce (poly)caprolactam (7, 8): The process of FIG 4 differs from the one depicted in FIG 1 by the fact that hydrogen (1) and oxygen (12) are obtained by electrolysis (27), preferably using electricity of sustainable origin, of water (11) and are used in the conversion (23) of benzene (5) to cyclohexane oxime (6), e.g., for hydrogenation and oxidation steps, respectively. Of note, the process of FIG 3 may optionally comprise the additional elements and features of the process of FIG 2.

The different embodiments described herein for the first aspect of the invention apply equally to the further aspects of the invention.

In further aspects, the invention relates to the products obtained by carrying out the processes described herein:

The process steps A) to F) as described for the first aspect of the invention may provide precursors, downstream products, and by-products of the caprolactam production process. The present invention also relates to such compounds and compound mixtures.

In particular, steps A) to B) may deliver compound mixtures selected from a hydrocarbon stream and an aliphatic hydrocarbon stream comprising naphtha, as described hereinbefore.

Process steps A) to C), especially when step C) comprises steam cracking, may deliver C24-olefins (ethylene, propylene, butylene isomers, butadiene), Ce-s-aromatics (benzene, toluene, xylene isomers, and ethyl benzene), pyrolysis gasoline (a complex mixture of various hydrocarbons comprising further amounts of Ca-s-aromatics, especially benzene), Ci-4-alkanes, and hydrogen.

Process steps A) to D) may provide cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, and cyclohexanone oxime.

Process steps A) to E) provides caprolactam.

Process steps A) to F) provides polycaprolactam.

Said process steps A) to F) may be according to any of the embodiments described for the first aspect of the invention.

As described for the first aspect of the invention, the process according to the invention allows for the carbon atoms in the production process of caprolactam and polycaprolactam to originate fully or in part from carbon dioxide or from biomass and biogas, respectively. Thus, the carbon contents of any of the precursors, downstream products, by-products of the caprolactam production process, and the compounds and compound mixtures mentioned above for the second aspect of the invention may be fully carbon dioxide-based and/or bio-based. Depending on the availabilities of different carbon sources and the demands and requirements to be met, the skilled person will find no difficulty in creating mixtures of different carbon sources such that desired target values regarding carbon dioxide-based and/or bio-based carbon contents are achieved.

Of note, the content of carbon atoms originating from biomass as used herein is preferably determined via measurement of the ¹⁴C mole fraction, more preferably according to DIN EN 16640:2017-08

The compound and compound mixtures according to the third aspect of the invention may in addition be characterized by the features described for the second aspect of the invention.

In a fourth aspect, the invention relates to a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized by a deuterium content of < 100 ppm, based on the total hydrogen content, and/or by a deuterium content being lower than the deuterium content in a corresponding compound or compound mixture of fossil origin; and/or characterized by a 613C value of more than -15 %o and/or by a 513C value being higher than the 613C value in a corresponding compound or compound mixture of fossil origin; and/or characterized by a A14C value of more than -900 %o and/or by a A14C value being higher than the A14C value in a corresponding compound or compound mixture of fossil origin.

As described for the first aspect of the invention, different carbonaceous feedstocks (e.g., solid, liquid, CO2) of different origins (fossil, biogenic, atmospheric/hydrospheric) as well as mixtures thereof may be used to provide syngas. It is known that said different origins are associated with different carbon isotopic patterns (see, e.g., H. Graven et al., Global Biogeochem Cycles 2020; 34(11):e2019GB006170; doi: 10.1029/2019GB006170).

There are three naturally occurring carbon isotopes on Earth: carbon-12 (12C), carbon-13 (13C), and carbon-14 (14C). Carbon-12 and carbon-13 are both stable, while carbon-14 is unstable and has a half-life of approximately 5730 years. Carbon-14 decays into nitrogen-14 (14N) through beta decay. The primary natural source of carbon-14 on Earth is cosmic ray action on nitrogen in the atmosphere. While fossil carbon sources are essentially devoid of 14C, it is found in trace amounts in the atmosphere, hydrosphere, and biosphere (thus being useful as a tracer for “biogenic carbon" in contrast to fossil carbon).

The natural isotopic abundance of 12C is about 98.9%, based on the total carbon content. The natural isotopic abundance of 13C is about 1.1 %. The 13C/12C isotopic ratio of chemical compounds is given relative to an international standard, the Vienna-Pee-Dee-Belemnite-Standard (V-PDB). The 13C/12C isotopic ratio is given as 613C value in the unit %o. The standard per definition has a 513C value of 0 %o. Substances with a higher 13C content than the standard have positive 513C values, substances with a lower 13C content than the standard have negative 513C values.

The natural isotopic abundance of 14C is about 1 part per trillion (ppt). The 14C/12C isotopic ratio of chemical compounds is given relative to an international standard, the Oxalic Acid I standard (NIST SRM 4990B). The 140/120 isotopic ratio is expressed as A14C value in the unit %o. The standard per definition has a A14C value of 0 %o. Substances with a higher 14C content than the standard have positive A14C values, while substances with a lower 140 content than the standard have negative A14C values.

The isotopic patterns of carbon-containing molecules reflect the isotopic patterns of the feedstocks they are produced from. Thus, the process according to the first aspect of the invention allows to obtain precursors, intermediates, downstream products, by-products of the caprolactam production process, and the compounds and compound mixtures mentioned above for the second aspect of the invention with particular 13C and 14C isotopic patterns.

Fossil-based carbon-containing molecules in general exhibit, depending on the feedstock, 513C values approximately ranging from -50 %o to -15 %o (e.g., from -44 %o to -19 %o) and A14C values of less than - 800 %o (preferably of less than 900 %o, e.g., approximately -1000 %o).

Biogenic carbon-containing molecules in general exhibit, depending on the feedstock, 513C values approximately ranging from -30 %o to -10 %o (e.g., from -29 %o to -12 %o) and A14C values approximately ranging from -200 %o to +200 %o (e.g., from -150 %o to +150 %o).

Carbon-containing molecules derived from CO2 from the atmosphere in general exhibit, depending i a. on the time point of DAC), 513C values approximately ranging from -11 %o to -6 %o (e.g , from -10 %o to -7 %o, in particular from - 9 5 %o to -8.0 %o,) and A14C values approximately ranging from -100 %o to +20 %o (e.g., from -80 %o to +15 %o).

Carbon-containing molecules derived from CO2 from the ocean in general exhibit, depending i.a. on the time point of DOC or IOC), 513C values approximately ranging from -3 %o to +4 %o (e.g., from -2 %o to +2 %o, in particular from -0.6 %o to +2 %o,) and A14C values approximately ranging from -50 %o to +20 %o (e.g., from -30 %o to +10 %o, in particular from -5 %o to +10 %o) for the shallow ocean and approximately ranging from -300 %oto -50 %o (e.g., from -250 %o to -100 %o) for the deep ocean.

Consequently, the compounds and compound mixtures described herein, in particular selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, may be qualified as at least in part non-fossil in case they are characterized by a 513C value of more than -15 %o, preferably of more than -11 %o, and/or a by A14C value of more than -1000 %o, preferably of more than -900 %o, more preferably of more than -800 %o, more preferably of more than - 500 %o.

They may be qualified as at least in part biogenic in case they are characterized by a 513C value of less than -10 %o, preferably of less than -11 %o , more preferably in the range from -29 %o to -12 %o, and by a A14C value of more than - 900 %o, preferably of more than -800 %o, more preferably of more than - 500 %o. They may be qualified as derived at least in part from CO2 captured from the atmosphere and/or the ocean in case they are characterized by a 613C value of more than -12 %o, preferably of more than -11 %o , more preferably of more than -10 %o, and by a A14C value of more than - 900 %o, preferably of more than -800 %o, more preferably of more than - 500 %o.

The one of skill in the art will be familiar with test methods and procedures to determine the 13C and 14C contents in the precursors, intermediates, downstream products, by-products of the caprolactam production process, and in the compounds and compound mixtures mentioned above. For instance, the carbon isotope contents are preferably determined according to the methods described below.

14C contents can be measured using gas proportional counting, liquid scintillation counting, and accelerator mass spectrometry (AMS). The latter approach is the most sensitive of the three and may also be used for 13C content determination.

14C/12C and 13C/12C isotopic ratios may for example be measured according to ASTM 6866-22 in which two analysis methods are disclosed: accelerator mass spectrometry (AMS) along with isotope ratio mass spectrometry (IRMS) (denoted "Method B” in ASTM D6866-22) or liquid scintillation counters (LSC) using sample carbon that has been converted to benzene (denoted "Method C” in ASTM D6866-22) wherein the maximum total error for both methods is +/- 3 %.

In both methods disclosed in ASTM 6866-22, the 140/120 or 14C/13C isotope ratio is determined relative to a carbonbased modern reference material such as NIST Standard Reference Material (SRM) 4990C. The 14C content can be directly calculated from the measured values obtained by Method B (chapter 9 5) and C (chapter 134). Method B is described in detail in chapters 6 to 9 and Method C is described in detail in chapters 10 to 13 of ASTM D6866-22.

The 14C content can also be determined according to DIN EN 16785-1 by following the guidelines for “Group 1 products” disclosed in this norm and according to CEN/TS 16640. The uncertainty for the measurement method disclosed in DIN EN 16785-1 is +/- 3 % of the measured value for the biobased-carbon content. The biogenic carbon content is then calculated with formula C.1 in Annex C of DIN EN 16785-1 for the total mass of the sample.

The 14C content can also be determined using the method and device disclosed in KR 10-2022-0058093 A. Modifications and adaptions of the methods and devices described above which may be required for use in the system and processes according to the present invention can be made by a skilled person.

As described for the first aspect of the invention, water electrolysis results in a depletion of deuterium in the produced hydrogen. If such hydrogen is used in step A) to provide syngas by reaction with carbon dioxide (rWGS) or to adjust the carbon monoxide to hydrogen ratio in syngas or in step D) to hydrogenate benzene, said depletion of deuterium will be detectable along the production chain of caprolactam and polycaprolactam. Thus, the process according to the first aspect of the invention allows to obtain deuterium-depleted precursors, downstream products, by-products of the caprolactam production process, and the compounds and compound mixtures mentioned above for the second aspect of the invention. The one of skill in the art will be familiar with test methods and procedures to determine the deuterium content in hydrogen, the precursors, downstream products, by-products of the caprolactam production process, and of the compounds and compound mixtures mentioned above. For instance, the deuterium content is preferably determined according to the methods described below.

In particular, a method suitable for determining the deuterium content in said compounds and compound mixtures comprises the steps:

I) combusting a sample of the compounds and/or compound mixtures and thereby forming a combustion gas comprising water; ii) separating the water from the combustion gas formed in step I); and iii) determining the deuterium content in the water separated from the combustion gas in step ii).

For instance, the following method descriptions are suited for determination of the molar share of deuterium based on the total hydrogen content (deuterium content) of gas and liquid samples. The isotopic H/D-share analysis is based on mass spectrometry or NMR spectroscopy. Three different methods can be used: method A for gas samples, method B for liquid samples, and method C can be used for any sample soluble in suitable solvents for NMR spectroscopy.

For the determination of the “D content in gas and liquid samples” it is of crucial importance not to contaminate the samples e.g., with ambient humidity or other ambient components containing hydrogen or deuterium. Therefore gastight materials and sealings must be used with clean sample containers to avoid any cross-contamination. Therefore, before filling and sealing a sample container it must be flushed at least 20 times the sample container volume with the gas or liquid stream to be analyzed. The same is valid for the experimental setup of the gas sampler and mass spectrometer. Utmost care must be taken to avoid cross-contamination e.g., via condensation of humidity. The analytical setup from sampling to mass spectrometry is validated with known reference samples.

Method A) Gas samples

Total deuterium from HD and D2 in hydrogen gas samples can be determined via ultra-high resolution quadrupole mass spectrometry using a Hiden DLS-20 (Hiden Analytical Ltd., Warrington, Cheshire, UK) analyzer setup. The general method setup is described in C.C. Klepper, T.M. Biewer, U. Kruezi, S. Vartanian, D. Douai, D.L. Hillis, C. Marcus, Extending helium partial pressure measurement technology to JET DTE2 and ITER; Rev. Sci. Instrum., 87 (11) (2016); doi: 10.1063/1.4963713. For the hydrogen gas samples, the threshold ionization mass spectrometry mode (TIMS) can be used as described in S. Davies, J.A. Rees, D.L. Seymour; Threshold ionization mass spectrometry (TIMS); A complementary quantitative technique to conventional mass resolved mass spectrometry; Vacuum, 101 (2014), pp. 416-422; doi: 10.1016/j.vacuum.2013.06.004. Sensitivity is +/-1 ppm.

Method B) Liquid samples

Analysis of liquid samples can be executed via isotope ratio monitoring gas chromatography/mass spectrometry (IRMS). Therefore, a DELTA V PLUS CF-IRMS mass spectrometer can be used. This mass spectrometer with magnetic sector with continuous flux DELTA V PLUS CF-IRMS can be used to measure the isotopic ratio of ²H/¹H. Measurement of D/H in a continuous He-flow mode needs the complete removal of low energy 4 He⁺ ions from the HD⁺ ion beam at m/z 3). The method is described in RAPID COMMUNICATIONS IN MASS SPECTROMETRY Rapid Commun. Mass Spectrom. 13, 1226-1230 (1999), W.A. Brandt et al. Sensitivity is within +1-3 ppm. Method C) Analysis of hydrogen isotope ratios

Analysis of isotope ratios in starting materials, intermediates, and products can be furthermore executed via SNIF- NMR related methods (“site-specific natural isotope fractionation studied by nuclear magnetic resonance”) using high resolution ²H-NMR (Bruker Avance NEO 600 MHz NMR Spectrometer and Bruker Avance III HD 700 MHz NMR Spectrometer both equipped with TCI probes).

Principles of this technology are described in Gerard J. Martin, Serge Akoka, and Maryvonne L. Martin; SNIF-NMR Part 1 : Principles; in Graham A. Webb (ed.), Modern Magnetic Resonance, Springer (2008) pp 1651-1658 as well as Maryvonne Martin, Benli Zhang, and Gerard J. Martin; SNIF-NMR Part 2: Isotope Ratios as Tracers of Chemical and Biochemical Mechanistic Pathways; in Graham A. Webb (ed.), Modern Magnetic Resonance, Springer (2008) pp 1659-1667 and Gerard J. Martin, Maryvonne L. Martin and Gerald Remaud; SNIF-NMR Part 3: From Mechanistic Affiliation to Origin Inference; in Graham A. Webb (ed.), Modern Magnetic Resonance, Springer (2008) pp 1669-1680.

The compound and compound mixtures according to the fourth aspect of the invention may in addition be characterized by the features described for the second and/or third aspect of the invention.

Preferred Embodiments

4.1) The compound or compound mixture according to the fourth aspect of the invention.

4.2) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a 613C value of more than -15 %o, preferably of more than -11 %o.

43) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a 613C value being higher than the 613C value in a corresponding compound or compound mixture of fossil origin.

44) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a A14C value of more than -900 %o, preferably of more than -800 %o.

4.5) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a A14C value being higher than the A14C value in a corresponding compound or compound mixture of fossil origin.

4.6) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a 613C value of less than -10 %o, preferably in the range from -29 %o to -12 %o, and by a A14C value of more than -900 %o, preferably of more than -800 %o.

4.7) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a 513C value of more than -12 %o, preferably of more than -10 %o, and by a A14C value of more than - 900 %o, preferably of more than -800 %o.

4.8) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a deuterium content of 100 ppm, based on the total hydrogen content, preferably in the range of from 10 to 95 ppm, more preferably in the range of from 15 to 90 ppm, most preferably in the range of from 20 to 80 ppm, especially in the range of from 30 to 75 ppm.

4.9) The compound or compound mixture according to any of the preceding embodiments, wherein said compound or compound mixture is characterized by a deuterium content being lower than the deuterium content in a corresponding compound or compound mixture of fossil origin.

II) a Fischer-Tropsch unit;

IV) a caprolactam production unit.

As used herein, the term system refers to an arrangement of units that allows for the exchange of material and/or energy streams between the different units. Said exchange may be accomplished by fluid connections, by pipelines, or by other means of transportation. In particular, said system may be embodied by a production plant, more specifically by an integrated production plant.

Wherever in the following description of the units of the system reference is made to certain process steps, these process steps should be understood to be according to the first aspect of the invention, including all the embodiments described therein and their combinations.

Preferred Embodiments

5 1) The system according to the fifth aspect of the invention.

52) The system according to any of the preceding embodiments, wherein the system is a production plant, preferably an integrated production plant.

Unit I)

The syngas production unit is equipped to produce and provide syngas by any of the processes, including their embodiments, described for process step A) of the first aspect of the invention.

Unit I) may be implemented as and may comprise a subunit suitable for performing steam reforming, autothermal catalytic reforming, or partial oxidation of gaseous and/or liquid feedstocks, a subunit for performing dry reforming of gaseous feedstocks and carbon dioxide, and/or a subunit for gasification of solid feedstocks to obtain syngas.

Further, unit I) may comprise a subunit for subjecting said syngas to a WGS reaction.

Unit I) may also be implemented as and may comprise a subunit suitable for performing rWGS reaction of carbon dioxide and hydrogen to generate syngas.

Thus, unit I) may comprise a hydrogen production subunit. Said hydrogen production subunit may be implemented as and may comprise a subunit suitable for performing hydrocarbon pyrolysis or a subunit suitable for performing water electrolysis or a subunit for performing chlor-alkali electrolysis. Unit I) may also comprise a biogas production subunit, optionally including a biogas upgrading subunit. Biogas may be used as a feedstock for the syngas production in said syngas production unit or as a feedstock for the hydrogen production in said hydrocarbon pyrolysis subunit.

Unit I) may further comprise a carbon dioxide production subunit, e.g., implemented as a DAC, DOC, IOC facility or another facility capable of capturing carbon dioxide from an industrial point source.

Unit I) comprises means to receive and store said gaseous, liquid, and/or solid feedstocks, as well as the reactants like steam, oxygen etc. It may also comprise means to receive and store carbon dioxide, e.g., from external sources like DAC, DOC, IOC facilities or other carbon capture subunits, especially from the carbon capture subunit of unit III), as described below. It may further comprise means to receive and store hydrogen, e.g., from unit III). Said hydrogen production subunit may comprise means to receive and store hydrocarbons for pyrolysis and water for electrolysis.

Unit I) may be fluidly connected and arranged upstream to unit II) in respect of the syngas stream; it may be fluidly connected and arranged downstream to the carbon capture subunit of unit III) in respect of the carbon dioxide stream and/or to unit III) in respect of the hydrogen stream.

Preferred Embodiments

5.3) The system according to any of the preceding embodiments, wherein unit I) comprises a steam reforming subunit, an autothermal catalytic reforming subunit, and/or a dry reforming subunit.

5.4) The system according to any of the preceding embodiments, wherein unit I) comprises a WGS subunit.

5.5) The system according to any of the preceding embodiments, wherein unit I) comprises a rWGS subunit.

5.6) The system according to any of the preceding embodiments, wherein unit I) comprises a hydrocarbon pyrolysis subunit.

57) The system according to any of the preceding embodiments, wherein unit I) comprises a water electrolysis subunit.

58) The system according to any of the preceding embodiments, wherein unit I) comprises a chlor-alkali electrolysis subunit.

5.9) The system according to any of the preceding embodiments, wherein unit I) comprises a biogas production subunit, optionally including a biogas upgrading subunit.

5.10) The system according to any of the preceding embodiments, wherein unit I) comprises a carbon dioxide production subunit, preferably selected from a DAC subunit, a DOC subunit, an IOC subunit, and/or a subunit for capturing carbon dioxide from an industrial point source.

5.11) The system according to any of the preceding embodiments, wherein unit I) is fluidly connected and arranged upstream to unit II).

5.12) The system according to any of the preceding embodiments, wherein unit I) is fluidly connected and arranged downstream to unit III). Unit II)

The Fischer-Tropsch unit is equipped to produce from syngas and to provide hydrocarbons, in particular an aliphatic hydrocarbon stream comprising naphtha, by any of the processes, including their embodiments, described for process step B) of the first aspect of the invention.

Unit II) may comprise a FT synthesis subunit for converting said syngas to hydrocarbons. Further, unit II) may comprise at least one distillation subunit for obtaining an aliphatic hydrocarbon stream comprising naphtha from the FT raw products. Said distillation subunit may comprise at least one distillation column, at least one thin film evaporator or a combination thereof. In thin-film evaporators the medium to be evaporated or the solution to be concentrated by evaporation, respectively, is applied to the evaporator area as a thin film. Thereby, a short contact time with the heating surface is feasible and thermally unstable liquids and substances, respectively, can be evaporated in such thin-film evaporators. Furthermore, thin-film evaporators can be used for separation tasks if the product accumulating as a residue has poor flow properties and/or is prone to agglutinations. Thin-film evaporation processes are based on the principle of simple distillation according to which the separating capacity of said type of evaporator is limited. Suitable thin-film evaporators are available in various designs, for example as falling-film evaporators or as rotary evaporators. Also, unit II) may comprise a refining subunit for hydrocracking and/or hydroisomerizing heavier hydrocarbons and waxes from FT processes.

Unit II) may be fluidly connected and arranged downstream to unit I) in respect of the syngas stream. It may be fluidly connected and arranged upstream to unit III) in respect of the hydrocarbon stream (i.e. , the naphtha stream).

Preferred Embodiments

5 13) The system according to any of the preceding embodiments, wherein unit II) comprises a FT synthesis subunit

5 14) The system according to any of the preceding embodiments, wherein unit II) comprises at least one distillation subunit, preferably comprising one distillation column.

5 15) The system according to any of the preceding embodiments, wherein unit II) comprises at least one refining subunit, preferably selected from a hydrocracking subunit and/or a hydroisomerization subunit.

5.16) The system according to any of the preceding embodiments, wherein unit II) is fluidly connected and arranged downstream to unit I).

5.17) The system according to any of the preceding embodiments, wherein unit II) is fluidly connected and arranged upstream to unit III).

Unit III)

The benzene production unit is equipped to produce benzene from said aliphatic hydrocarbon stream comprising naphtha and to separate it, by any of the processes, including their embodiments, described for process step C) of the first aspect of the invention.

Unit III) may comprise an aromatization subunit for obtaining benzene from said aliphatic hydrocarbon stream comprising naphtha. The aromatization subunit may be implemented as and may comprise a cracking subunit, in particular a catalytic cracking subunit, fluid catalytic cracking subunit, thermal cracking subunit, and steam cracking subunit, preferably a steam cracking subunit ("steam cracker”). Also, the aromatization subunit may be implemented as and may comprise a catalytic reforming facility.

Further, unit III) may comprise at least one separation subunit for separating benzene from the product stream obtained in the aromatization step. Said separation may be conducted in multiple steps. In particular, said separation subunits may be implemented as and may comprise extraction subunits and/or distillation subunits (e.g., with features as described for unit II) above).

Said benzene production subunit, preferably including said separation subunit, may also be equipped to produce hydrogen from said aliphatic hydrocarbon stream comprising naphtha, in particular via steam cracking, and to separate it, by any of the processes, including their embodiments, described for process step C) of the first aspect of the invention.

Unit III) may further comprise a carbon capture subunit, preferably a post-combustion carbon capture subunit, to capture carbon dioxide emitted from said aromatization subunit, in particular from said steam cracker.

Unit III) may be fluidly connected and arranged downstream to unit II) in respect of the hydrocarbon stream (i.e., the naphtha stream). It may be fluidly connected and arranged upstream to unit IV) in respect of the benzene stream and optionally in respect of the hydrogen stream.

Further, it may be fluidly connected and arranged upstream to unit I) in respect of the carbon dioxide stream and in respect of the hydrogen stream.

Preferred Embodiments

5.18) The system according to any of the preceding embodiments, wherein unit III) comprises an aromatization subunit, preferably a cracking subunit, more preferably a catalytic cracking subunit, a fluid catalytic cracking subunit, a thermal cracking subunit, or a steam cracking subunit.

5 19) The system according to any of the preceding embodiments, wherein unit III) comprises at least one separation subunit, preferably selected from the group consisting of extraction subunits and distillation subunits.

5.20) The system according to any of the preceding embodiments, wherein unit III) comprises a carbon capture subunit, preferably a post-combustion carbon capture subunit.

5.21) The system according to any of the preceding embodiments, wherein unit III) is fluidly connected and arranged downstream to unit II).

5.22) The system according to any of the preceding embodiments, wherein unit III) is fluidly connected and arranged upstream to unit IV).

5.23) The system according to any of the preceding embodiments, wherein unit III) is fluidly connected and arranged upstream to unit I).

Unit IV)

The caprolactam production unit is equipped to produce caprolactam from benzene, via any of the intermediates and by any of the processes, including their embodiments, described for process steps D) and E) of the first aspect of the invention. Thus, unit IV) may comprise a cyclohexane synthesis subunit, a cyclohexene synthesis subunit, a phenol synthesis subunit, a cyclohexanol synthesis subunit, a cyclohexanone synthesis subunit, a cyclohexanone oxime synthesis subunit, and/or a caprolactam synthesis subunit, each of them equipped to provide the respective intermediates or products according to the process steps D) and E).

Unit IV) may also comprise an oximation agent production subunit, preferably a hydroxylamine production subunit, to obtain an oximation agent, preferably a hydroxylamine species, e.g., as described in step D) above, e.g., hydroxylamine, hydroxylammonium sulfate, or hydroxylammonium dihydrogenphosphate, that may be used as a feed for the cyclohexanone oxime synthesis subunit to produce obtain cyclohexanone oxime from cyclohexanone.

Unit IV) may further comprise an ammonia production subunit to obtain ammonia from nitrogen and hydrogen.

Unit IV) may be fluidly connected and arranged downstream to unit III) in respect of the benzene stream. It may be fluidly connected and arranged upstream to unit V) in respect of the caprolactam stream.

Said cyclohexane synthesis subunit, said cyclohexene synthesis subunit, and/or said cyclohexanone synthesis subunit may be fluidly connected and arranged downstream to the hydrogen production subunit of unit I) and/or to the WGS subunit of unit I) in respect of the hydrogen stream.

Said oximation agent production subunit, preferably said hydroxylamine production subunit, and/or said ammonia production subunit may be fluidly connected and arranged downstream to the hydrogen production subunit of unit I) and/or to the WGS subunit of unit I) in respect of the hydrogen stream.

Said cyclohexanone synthesis subunit may be fluidly connected and arranged downstream to the water electrolysis subunit of unit I) in respect of the oxygen stream.

Preferred Embodiments

524) The system according to any of the preceding embodiments, wherein unit IV) comprises a cyclohexane synthesis subunit, a cyclohexanone synthesis subunit, a cyclohexanone oxime synthesis subunit, and a caprolactam synthesis subunit.

5.25) The system according to any of the preceding embodiments, wherein unit IV) comprises a cyclohexene synthesis subunit, a cyclohexanol synthesis subunit, a cyclohexanone synthesis subunit, a cyclohexanone oxime synthesis subunit, and a caprolactam synthesis subunit.

5.26) The system according to any of the preceding embodiments, wherein unit IV) comprises a phenol synthesis subunit, a cyclohexanone synthesis subunit, a cyclohexanone oxime synthesis subunit, and a caprolactam synthesis subunit.

5.27) The system according to any of the preceding embodiments, wherein unit IV) comprises a cyclohexane synthesis subunit, a cyclohexanone oxime synthesis subunit, and a caprolactam synthesis subunit.

5.28) The system according to any of the preceding embodiments, wherein unit IV) comprises an oximation agent production subunit, preferably a hydroxylamine production subunit.

5.29) The system according to any of the preceding embodiments, wherein unit IV) comprises an ammonia production subunit. 5.30) The system according to any of the preceding embodiments, wherein unit IV) is fluidly connected and arranged downstream to unit III).

5.31) The system according to any of the preceding embodiments, wherein unit IV) is fluidly connected and arranged upstream to unit V).

5.32) The system according to any of embodiments 5.24 to 5.27, wherein said cyclohexane synthesis subunit, said cyclohexene synthesis subunit, and/or said cyclohexanone synthesis subunit is fluidly connected and arranged downstream to the hydrogen production subunit of unit I) and/or to the WGS subunit of unit I).

5.33) The system according to any of embodiments 5.28 and 5.29, wherein said oximation agent production subunit, preferably said hydroxylamine production subunit, and/or said ammonia production subunit is fluidly connected and arranged downstream to the hydrogen production subunit of unit I) and/or to the WGS subunit of unit I).

5.34) The system according to any of embodiments 5.24 to 5.26, wherein said cyclohexanone synthesis subunit may be fluidly connected and arranged downstream to the water electrolysis or chlor-alkali electrolysis subunit of unit I).

Further units

The system according to the invention may comprise further units and subunits, e.g., for performing the further process steps described above for the first aspect of the invention, like polymerization of caprolactam to polycaprolactam according to step F), (cryogenic) air separation to obtain nitrogen as described in step D), or providing sustainable energy, preferably electricity, to energy-consuming process steps:

Unit V)

The polycaprolactam production unit V) is equipped to produce polycaprolactam from caprolactam according to the process step F), including its embodiments, according to the first aspect of the invention

Unit V) may comprise a subunit for polymerization of caprolactam and for purification of polycaprolactam, each of them equipped to perform step F) as described above.

Unit V) may be fluidly connected and arranged downstream to unit IV) in respect of the caprolactam stream.

Preferred Embodiments

5.35) The system according to any of the preceding embodiments, the system further comprising unit V)

V) a polycaprolactam production unit.

5.36) The system according to any of the preceding embodiments, wherein unit V) comprises a polymerization subunit and a purification subunit.

5.37) The system according to any of the preceding embodiments, wherein unit V) is fluidly connected and arranged downstream to unit IV). Unit VI)

The air separation unit VI), preferably a cryogenic air separation unit, is equipped to separate air components, in particular to deliver nitrogen, e.g., as used for the production of ammonia as described in step D) according for the first aspect of the invention.

Unit VI) may be fluidly connected and arranged upstream to the ammonia production subunit of unit IV) in respect of the nitrogen stream.

Preferred Embodiments

5.38) The system according to any of the preceding embodiments, the system further comprising unit VI)

VI) an air separation unit, preferably a cryogenic air separation unit.

5.39) The system according to any of the preceding embodiments, wherein unit VI) is fluidly connected and arranged upstream to unit IV), in particular to the ammonia production subunit thereof.

Unit VII)

The power plant VII) is equipped to provide electrical power, preferably sustainable electrical power, to the other units of the system as described above. Sustainable power sources are mentioned for step A) above.

Unit VII) may provide electrical power preferably to the hydrocarbon pyrolysis subunit or chlor-alkali electrolysis subunit of unit I) to obtain hydrogen, to the water electrolysis subunit of unit I) to obtain hydrogen and oxygen, and to the air separation unit VI) to obtain nitrogen.

Preferred Embodiments

540) The system according to any of the preceding embodiments, the system further comprising unit VII)

VII) a power plant, preferably a sustainable power plant, more preferably a power plant selected from the group consisting of wind energy plants, solar energy plants, hydropower plants, geothermal energy plants, bioenergy plants, waste incineration plants, and nuclear power plants.

5.41) The system according to any of the preceding embodiments, wherein unit VII) provide electrical power to hydrocarbon pyrolysis subunit of unit I), to the water electrolysis subunit of unit I), to the chlor-alkali electrolysis subunit of unit I), and/or to the air separation unit VI).

Further embodiments of the fifth aspect of the invention are described by the combination of any and each of the above definitions and embodiments with one another, in particular by way of FIGs 5-8.

FIG 5 depicts a system for performing the process according to FIG 1. A rWGS subunit (102) receives hydrogen (1) and carbon dioxide (2) to produce syngas (3). Said syngas (3) is fed into a Fischer-Tropsch unit (103) to obtain naphtha (4) which is used as a feedstock in a cracking subunit (104) to form and separate benzene (5). In a caprolactam production unit (105), caprolactam (7) is formed and optionally polymerized to polycaprolactam (8) in a polycaprolactam production unit (106). FIG 6 depicts a system for performing the process according to FIG 2. The system of FIG 6 differs from the one depicted in FIG 5 by the fact that the rWGS subunit (102) may receive hydrogen from the cracking subunit (104). Further, a carbon capture subunit (107) may capture carbon dioxide emitted from the cracking subunit (104) and provide it to the rWGS subunit (102).

FIG 7 depicts a system for performing the process according to FIG 3. The system of FIG 7 differs from the one depicted in FIG 5 by the fact that an air separation unit (108), preferably a cryogenic air separation unit, generates nitrogen (9) from air (13) and provides said nitrogen (9) to an oximation agent production subunit (109). Said subunit (109) furthermore receives hydrogen (1). Thus, in subunit (109), the oximation agent is produced that is utilized in the caprolactam production unit (105). Of note, the system of FIG 7 may optionally comprise the additional elements and features of the system of FIG 6.

FIG 8 depicts a system for performing the process according to FIG 4. The system of FIG 8 differs from the one depicted in FIG 5 by the fact that a water electrolysis subunit (101) receives water (11) to produce hydrogen (1) and oxygen (12). Said hydrogen (1) is provided to the rWGS subunit (102) as well as to the caprolactam production unit (105). Said oxygen (12) is provided to the caprolactam production unit (105), too. Of note, the system of FIG 8 may optionally comprise the additional elements and features of the systems of FIG 6 and 7.

As described above, the system according to the fifth aspect is suitable for carrying out the processes according to the first aspect of the invention. Thus, the embodiments described above for the first and fifth aspects apply equally to the sixth aspect of the invention.

It is to be understood that the system may be used for the processes described herein by one or more operators or entities The processes may be run sequentially or simultaneously. Also, the system may be used for continuous or batch processing.

R) establishing whether said deuterium content in the test sample does not exceed 100 ppm and/or optionally whether said deuterium content in the test sample is lower than said deuterium content in the reference sample. More specifically, the invention relates to a process for tracing the origin of hydrogen bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising steps A) and B); any further steps selected from C), D), E), and F) as necessary to obtain said compound or compound mixture; and steps P), Q), and R).

Similarly, in an eighth aspect, the invention relates to a process for tracing the origin of carbon bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising the steps

T) determining the 5130 value and/or A14C value in said test sample and optionally determining the 5130 value and/or A140 value in said reference sample; and one or more of steps U), U’), and U*)

U) establishing whether said 5130 value in the test sample exceeds -15 %o and/or optionally whether said 5130 value in the test sample is higher than said 5130 value in the reference sample; and/or establishing whether said A14C value in the test sample exceeds -900 %o and/or optionally whether said A14C value in the test sample is higher than said A14C value in the reference sample;

U') establishing whether said 513C value in the test sample is less than -10 %o and whether said A14C value in the test sample exceeds -900 %o;

More specifically, the invention relates to a process for tracing the origin of carbon bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising steps A) and B); any further steps selected from C), D), E), and F) as necessary to obtain said compound or compound mixture; steps S) and T); and one or more of steps U), U’), and LT). As described for the fourth aspect of the invention, if bio-based feedstocks are used for the provision of syngas in step A), said syngas will exhibit A14C values that are increased in comparison to the use fossil feedstocks. Likewise, if carbon dioxide from the atmosphere or the ocean is used as a feedstock for step A), increased 613C and A14C values (i.e., increased 13C and 14C contents) will be observed in the syngas and consequently along the production chain of caprolactam and polycaprolactam. Also, if deuterium-depleted hydrogen, as obtained from water electrolysis, is used in step A) to provide syngas by reaction with carbon dioxide (rWGS) or to adjust the carbon monoxide to hydrogen ratio in syngas or in step D) to hydrogenate benzene, said depletion of deuterium will be detectable along the production chain of caprolactam and polycaprolactam. Thus, the process according to the first aspect of the invention may deliver 513C-enriched, A14C-enriched, and/or deuterium-depleted precursors, downstream products, by-products of the caprolactam production process, and the compounds and compound mixtures mentioned above for the second aspect of the invention. Hence, the 13C, 14C, and deuterium contents in the aliphatic hydrocarbon stream comprising naphtha, in benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and/or polycaprolactam can be used to trace the origin of the carbon and hydrogen atoms, respectively, in said compounds or compound mixtures.

Tracing of the origin of carbon and hydrogen is, for instance, required for establishing in a reliable way that a (poly)ca- prolactam production process uses as little fossil-based resources and energy as possible. Hence, by determining the 13C, 14C, and deuterium contents of said precursors, downstream products, by-products of the caprolactam production process, and the compounds and compound mixtures, it is possible to confirm that bio-based feedstocks or CO2 from the atmosphere or the ocean were employed (net negative carbon dioxide emissions) and that hydrogen obtained from water electrolysis was used in the manufacturing process. By doing so, sustainability claims related to the products may be verified.

Thus, the processes according to the seventh and eighth aspects of the present invention can be used to trace the origin of the syngas provided in step A) and of the hydrogen provided in steps A) and/or D), e g. , the non-fossil origin from water electrolysis. In particular, the numerical limits for 13C, 14C, and deuterium (including preferred ranges) described above for the fourth aspect of the invention apply for the purposes of this tracing. For instance, a deuterium content of < 100 ppm in a test sample (hydrogen, aliphatic hydrocarbon stream comprising naphtha, benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, or polycaprolactam) is considered indicative of water electrolysis being the hydrogen origin. Alternatively, comparative determinations of the deuterium content in a test sample and in a corresponding reference sample (produced with hydrogen of fossil origin) may be indicative of water electrolysis being the origin of hydrogen in the test sample if the deuterium content in the test sample is lower than in the reference sample.

Methods and procedures to determine the 13C, 14C, and deuterium contents of hydrogen, the precursors, downstream products, by-products of the caprolactam production process, and of the compounds and compound mixtures mentioned above are known to the one of skill in the art and are described above for the fourth aspect of the invention.

Further embodiments of the different aspects of the invention are described by the combination of any and each of the above definitions and embodiments with one another. Further preferred embodiments

1. A process for producing caprolactam, the process comprising the steps

A) providing syngas;

D) converting said benzene to cyclohexanone oxime; and

E) converting said cyclohexanone oxime to caprolactam.

2. The process according to embodiment 1 , wherein in step A), at least a part of said syngas originates from reverse water-gas shift reaction of carbon dioxide and hydrogen.

3. The process according to embodiment 2, wherein in step A), at least a part of said carbon dioxide is obtained via direct air capture, direct ocean capture, indirect ocean capture, or via carbon capture from industrial point sources.

4. The process according to embodiment 2, wherein in step A), at least a part of said hydrogen originates from pyrolysis of hydrocarbons, from water electrolysis, and/or from chlor-alkali electrolysis.

5 The process according to embodiment 4, wherein in step A), electrical power is used for said hydrocarbon pyrolysis, water electrolysis, and/or chlor-alkali electrolysis and the fraction of said electrical power that originates from fossil energy sources is 50%, preferably 30%, more preferably 20%, even more preferably 10%, most preferably < 1 %.

6. The process according to any of the preceding embodiments, wherein in step C), the aromatization step is part of a cracking process, preferably of a steam cracking process.

7. The process according to embodiment 6, wherein at least a part of the carbon dioxide emitted in the course of the cracking process is captured and preferably at least a part of said captured carbon dioxide is used in step A) to provide syngas by reaction with hydrogen in a reverse water-gas shift reaction.

8. The process according to any of the preceding embodiments, wherein step D) comprises the substeps

D3) subjecting said cyclohexanone to oximation to obtain cyclohexanone oxime; or step D) comprises the substeps

D1 b) subjecting said benzene to hydrogenation to obtain cyclohexene;

D2b) subjecting said cyclohexene to hydration to obtain cyclohexanol and subjecting said cyclohexanol to dehydrogenation to obtain cyclohexanone; and

D1 c) subjecting said benzene to oxidation to obtain phenol;

D2c) subjecting said phenol to hydrogenation to obtain cyclohexanone; and

D3) subjecting said cyclohexanone to oximation to obtain cyclohexanone oxime; and wherein in step D3) oximation is effectuated by reaction with hydroxylammonium sulfate, and wherein hydrogen and/or nitrogen are used in the process for obtaining said hydroxylammonium sulfate; or wherein in step D3) oximation is effectuated by reaction with hydroxylammonium dihydrogenphosphate, and wherein hydrogen and/or nitrogen are used in the process for obtaining said hydroxylammonium dihydrogenphosphate; or wherein in step D3) oximation is effectuated by reaction with ammonia and hydrogen peroxide, and wherein hydrogen and nitrogen are used in the process for obtaining said ammonia; and wherein in steps D1 a), D1 b), D2c), and/or D3), at least a part of said hydrogen originates from pyrolysis of hydrocarbons, from water electrolysis, and/or from chlor-alkali electrolysis.

9. The process according to any of the preceding embodiments, the process further comprising step F)

F) subjecting said caprolactam to polymerization to obtain polycaprolactam.

10. A compound or compound mixture selected from the group consisting of: an aliphatic hydrocarbon stream comprising naphtha obtainable by steps A) to B) according to any of the preceding embodiments; benzene obtainable by process steps A) to C) according to any of the preceding embodiments; an intermediate selected from the group consisting of cyclohexane, cyclohexene, phenol, cyclohexanol, and cyclohexanone obtainable by process steps A) to D) according to any of the preceding embodiments; cyclohexanone oxime obtainable by process steps A) to D) according to any of the preceding embodiments; caprolactam obtainable by process steps A) to E) according to any of the preceding embodiments; and polycaprolactam obtainable by process steps A) to F) according to any of the preceding embodiments. 11. A compound or compound mixture, optionally according to embodiment 10, selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized in that at least 5 %, preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, more preferably at least 95 %, most preferably all of their carbon atoms originate from carbon dioxide and/or are bio-based.

12. A compound or compound mixture, optionally according to any of embodiments 10 and 11, selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized by a deuterium content of < 100 ppm, based on the total hydrogen content, preferably in the range of from 10 to 95 ppm, more preferably in the range of from 15 to 90 ppm, most preferably in the range of from 20 to 80 ppm, especially in the range of from 30 to 75 ppm, and/or with a deuterium content being lower than the deuterium content in a corresponding compound or compound mixture of fossil origin.

13. A system for producing caprolactam, the system comprising the units

II) a Fischer-Tropsch unit;

IV) a caprolactam production unit.

14. Use of the system according to embodiment 13 for the process according to any of embodiments 1 to 9.

15. A process for tracing the origin of hydrogen bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising the steps

Claims

1. A process for producing caprolactam, the process comprising the steps

A) providing syngas;

D) converting said benzene to cyclohexanone oxime; and

E) converting said cyclohexanone oxime to caprolactam.

2. The process according to claim 1 , wherein in step A), at least a part of said syngas originates from reverse water- gas shift reaction of carbon dioxide and hydrogen, wherein preferably at least a part of said carbon dioxide is obtained via direct air capture, direct ocean capture, indirect ocean capture, or via carbon capture from industrial point sources.

3. The process according to claim 2, wherein in step A), at least a part of said hydrogen originates from pyrolysis of hydrocarbons, from steam cracking of hydrocarbons, from water electrolysis, and/or from chlor-alkali electrolysis.

4 The process according to claim 3, wherein in step A), electrical power is used for said hydrocarbon pyrolysis, water electrolysis, and/or chlor-alkali electrolysis and the fraction of said electrical power that originates from fossil energy sources is < 50%, preferably < 30%, more preferably < 20%, even more preferably < 10%, most preferably < 1 %.

5. The process according to any of the preceding claims, wherein in step C), the aromatization step is part of a cracking process, preferably of a steam cracking process, wherein preferably at least a part of the carbon dioxide emitted in the course of the cracking process is captured and preferably at least a part of said captured carbon dioxide is used in step A) to provide syngas by reaction with hydrogen in a reverse water-gas shift reaction.

6. The process according to any of the preceding claims, wherein step D) comprises the substeps

D1 a) subjecting said benzene to hydrogenation to obtain cyclohexane;

D2a) subjecting said cyclohexane to oxidation to obtain cyclohexanone; and

D1 b) subjecting said benzene to hydrogenation to obtain cyclohexene;

D1 c) subjecting said benzene to oxidation to obtain phenol;

D2c) subjecting said phenol to hydrogenation to obtain cyclohexanone; and

7. process for producing polycaprolactam, the process comprising the process for producing caprolactam according to any of the preceding claims, the process further comprising step F)

F) subjecting said caprolactam to polymerization to obtain polycaprolactam.

8. A compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized in that at least 5 %, preferably at least 10 %, more preferably at least 20 %, more preferably at least 30 %, more preferably at least 40 %, more preferably at least 50 %, more preferably at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, more preferably at least 95 %, most preferably all of their carbon atoms originate from carbon dioxide and/or are bio-based.

9. A compound or compound mixture, optionally according to claim 8, selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized by a 613C value of more than -15 %o and/or by a 613C value being higher than the 513C value in a corresponding compound or compound mixture of fossil origin and/or characterized by a A14C value of more than -900 %o and/or by a A14C value being higher than the A14C value in a corresponding compound or compound mixture of fossil origin.

10. A compound or compound mixture, optionally according to any of claims 8 to 9, wherein said compound or compound mixture is characterized by a 513C value of less than -10 %o and by a A14C value of more than -900 %o or is characterized by a 513C value of more than -12 %o and by a A14C value of more than - 900 %o.

11. A compound or compound mixture, optionally according to any of claims 8 to 10 , selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, characterized by a deuterium content of 100 ppm, based on the total hydrogen content, and/or by a deuterium content being lower than the deuterium content in a corresponding compound or compound mixture of fossil origin.

12. A system for producing caprolactam, the system comprising the units

II) a Fischer-Tropsch unit;

IV) a caprolactam production unit.

13. Use of the system according to claim 12 for the process according to any of claims 1 to 7.

14. A process for tracing the origin of hydrogen bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising

- steps A) and B) according to any of the preceding claims;

- any further steps selected from C), D), E), and F) according to any of the preceding claims as necessary to obtain said compound or compound mixture; and

- steps P), Q), and R)

Q) determining the deuterium content in said test sample and optionally determining the deuterium content in said reference sample; R) establishing whether said deuterium content in the test sample does not exceed 100 ppm and/or optionally whether said deuterium content in the test sample is lower than said deuterium content in the reference sample.

15. A process for tracing the origin of carbon bound in a compound or compound mixture selected from the group consisting of an aliphatic hydrocarbon stream comprising naphtha, of benzene, cyclohexane, cyclohexene, phenol, cyclohexanol, cyclohexanone, cyclohexanone oxime, caprolactam, and polycaprolactam, the process comprising

- steps A) and B) according to any of the preceding claims;

- any further steps selected from C), D), E), and F) according to any of the preceding claims as necessary to obtain said compound or compound mixture;

- steps S) and T);

T) determining the 5130 value and/or A14C value in said test sample and optionally determining the 5130 value and/or A14C value in said reference sample; and

- one or more of steps U), U’), and U*).

U) establishing whether said 513C value in the test sample exceeds -15 %o and/or optionally whether said 513C value in the test sample is higher than said 513C value in the reference sample; and/or establishing whether said A14C value in the test sample exceeds -900 %o and/or optionally whether said A14C value in the test sample is higher than said A14C value in the reference sample;

U*) establishing whether said 513C value in the test sample exceeds -12 %o and whether said A14C value in the test sample exceeds -900 %o and/or optionally whether said A14C value in the test sample is higher than said A14C value in the reference sample.