WO2025068500A1

WO2025068500A1 - Process for ethene oligomerisation

Info

Publication number: WO2025068500A1
Application number: PCT/EP2024/077277
Authority: WO
Inventors: Juan Salvador MARTÍNEZ ESPÍN; Yunfei Bai; Esben Taarning
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 2023-09-29
Filing date: 2024-09-27
Publication date: 2025-04-03
Anticipated expiration: 2026-03-29

Abstract

The present invention regards a process for ethene oligomerization to produce a composition enriched in ethene oligomerization products. It also regards uses of this composition enriched in ethene oligomerization products for producing liquid hydrocarbon fuels and for producing platform chemicals. In the process oligomerization is carried out in the presence of a catalytic material comprising nickel (Ni) and a porous framework structure, the framework structure being substantially free of aluminum (Al) and comprising silicon (Si) and a further tetravalent metal (Me), and the framework structure having pores with a diameter in the range of from 0.4 to 50 nm as measured by nitrogen adsorption.

Description

PROCESS FOR ETHENE OLIGOMERISATION

FIELD

The present invention regards a process for ethene oligomerization to produce a composition enriched in ethene oligomerization products. It also concerns uses of this composition enriched in ethene oligomerization products for producing liquid hydrocarbon fuels and for producing platform chemicals.

BACKGROUND

When producing hydrocarbon fuels (C5+) from methanol and ethanol using zeolite processing, light hydrocarbons (C1-C4) are created as byproducts. Some of these byproducts, such as propylene and butenes, may be recycled and converted into valuable fuelrange hydrocarbons (C5+). However, saturated alkanes and ethene cannot be easily converted using the same zeolite processing method and are considered waste products.

One option to address this issue is to reform these light products to generate syngas and produce methanol that can be converted again. However, this process is expensive and not necessarily profitable, so the byproducts are often just burned to generate heat.

Processes have also been proposed to convert ethene into higher olefins like butenes, which are useful as platform chemicals. For example, ethene can easily be converted into hydrocarbon fuels (C5+). Currently, industrial methods for converting ethene to butene rely on various homogeneous catalyzed processes. However, there is still a need for improved procedures and catalysts for utilizing ethene.

SUMMARY OF THE INVENTION

The present inventors have developed an improved heterogeneous catalytic material suitable for ethene oligomerization. The catalytic material is useful for producing butenes, hexenes and octenes from ethene, which are useful platform chemicals. According to an aspect of the present invention, a process for ethene oligomerization is provided, wherein a first composition comprising ethene is brought into contact with a catalytic material to provide a second composition enriched in ethene oligomerization products, wherein the catalytic material comprises nickel (Ni) and a porous framework structure, the framework structure being substantially free of aluminum (Al) and comprising silicon (Si) and a further tetravalent metal (Me), and the framework structure having pores with a diameter in the range of from 0.4 to 50 nm as measured by nitrogen adsorption.

The process according to the present invention surprisingly has a reduced selectivity towards alkanes. A low selectivity towards alkanes is an advantage when using the catalyst for fuels production or for platform chemicals production, as alkanes are considered waste products. Moreover, a low number of different reaction products is formed in the process of the present invention, which is advantageous in chemicals production since it makes the purification to obtain pure product streams for chemicals production easier. Also, the process according to the present invention shows improved selectivity towards butenes and in particular it shows improved selectivity towards linear butenes which are useful platform chemicals. Using a heterogeneous catalyst instead of a homogeneous catalyst offers additional advantages in industrial settings, since handling of such are significantly easier, both when it comes to separation of reaction products and for prolonged use of the catalysts.

DRAWING

Figure 1 : Selectivity to linear butenes as a function of ethene conversion

Figure 2: Product selectivities at similar ethene conversion

Figure 3: Transmission FTIR spectra of catalytic material with CO as probe molecule

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise specified, any given percentages for gas content are % by volume.

Metal substituted zeolitic and zeotype materials are known to provide useful heterogeneous catalytic materials catalyzing a great variety of reactions. They are generally known to contain both Bronsted acidic sites and Lewis acidic sites which affect the catalytic activity of the materials by acting as electron pair acceptors thus affecting the catalytic activity of the materials.

The present inventors, seeking to develop improved methods for providing ethene oligomerization products, have now developed an improved heterogeneous catalytic material suitable for ethene oligomerization.

Catalytic material

During their work the inventors found that using a catalytic material based on a zeolitic framework structure substantially free of aluminum and substituted with a tetravalent metal (Me) and loaded with nickel, showed significant improvements over the prior art processes for producing ethene oligomerization products from ethene. In particular, they found that even small amounts of aluminum present in the framework structure affected the ethene oligomerization products obtained.

In the present context the catalytic material is understood to catalyze the conversion of ethene into ethene oligomerization products.

The catalytic material comprises a porous silica framework structure having a large surface area. The silica framework structure contains tetravalent metals in the framework. The catalytic material also comprises nickel sites which, without wishing to be bound by theory, are closely situated to the tetravalent metal sites, as ion exchanged nickel ions or as nickel oxide. The porous framework structure may also be referred to as a “porous metallo-silicate material” and the catalytic material as a “nickel loaded porous metallo- silicate material”.

In an embodiment, the molar ratio of Ni to Me is in the range of from 0.05 to 20, such as 0.3 to 3.

In an embodiment, the loading of Ni is from 0.01 to 10 wt %, such as 0.5-3.0 wt %.

Preferred catalytic materials are Ni-SnBEA, Ni-ZrBEA, Ni-HfBEA, or mixtures thereof. Porous framework structure

Without being bound by theory, it is hypothesized that by avoiding aluminum in the framework structure and replacing it with one or more tetravalent metals (Me), the resulting porous metallo-silicate framework structure is essentially free of Bronsted acidic sites but offers Lewis acidic sites which when loaded with nickel provides an improved conversion of ethene into ethene oligomerization products.

In support of this theory, the inventors successfully synthesized a porous framework structure directly from a silicon source, a tetravalent metal source, and a template, which was subsequently loaded with nickel providing an improved conversion of ethene into ethene oligomerization products.

In an embodiment the catalytic material shows no bands at wavelengths above 2200 cnv ¹ in transmission FTIR with CO as probe molecule. It is generally understood that bands at wavelengths above 2200 cm^-1 are an indicator of nickel interacting with Bronsted acidic sites in the framework structure. The results are not affected of whether the porous framework structure has been loaded with nickel. It is to be understood that "no band" means that the intensity stays at background level taking into account the variation in background. In general, this means that above 2200 cm^-1 the signal is less than 0.5% above background.

In the present context “substantially free of aluminum” is meant to refer to a porous framework structure, where the molar ratio of Si to Al in the framework structure is above 300.

The tetravalent metal (Me) is selected from the group consisting of Sn, Ti, Zr, Hf, Ge; or mixtures thereof. In an embodiment, the tetravalent metal (Me) is preferably Sn.

In an embodiment, the molar ratio of Si to Me is in the range of from 20 to 400, such as 75-150.

In an embodiment, the framework structure comprises a structure selected from any one of the microporous structures BEA, MFI, FAU, FER, MOR, MTW, the mesoporous structures MCM-41 , SBA-15, or mixtures thereof. It is known from literature that many tin-containing silicas (stannosilicates) have similar catalytic properties like Sn-Beta. For example Sn-Beta (stannosilicate, crystalline), Sn- MFI (stannosilicate, crystalline), Sn-MCM-41 (stannosilicate, amorphous ordered material) and Sn-SBA-15 (stannosilicate, amorphous ordered material) have been shown to be active catalysts for the isomerization of glucose to fructose at 80 °C, and for the conversion of dihydroxyacetone to methyl lactate in methanol at temperatures in the range of 40-120 °C. All materials were found to be able to transform sucrose to methyl lactate in methanol at 160 °C. Overall, the study showed that all four stannosilicates can catalyze the same reactions. Similarly, the same applies to other metallosilicates such as Zr-, Hf- , Ti- and Ge-silicates. For instance, Zr-MFI, Zr-MCM-41 and Zr-Beta were all active in the N-alkylation of aniline with benzyl alcohol, or Ti-MFI and Ti-Beta in the ketonization of propionic acid.

Examples of such literature are Osmundsen et al., Tin-containing silicates: structureactivity relations. Proc. R. Soc. A (2012) 468, 2000-2016; Tolborg et al., Tin-containing silicates: alkali salts improve methyl lactate yield from sugars, ChemSusChem (2015) 8, 613-617; Rojas-Buzo, et al, In-Situ-Generated Active Hf-hydride in Zeolites for the Tandem N-Alkylation of Amines with Benzyl Alcohol. ACS Catalysis. (2021) 11 , 13, 8049- 8061 ; and Yang, et al., Ketonization of propionic acid over TS-1 and Ti-Beta zeolites: Mechanism and effects of topology and hydrophobicity, J. Catal. (2024) 429, 115247.

It is generally preferred that the framework structure has pores with a diameter in the range of from 0.4 to 50 nm as measured by nitrogen adsorption. Such framework structures may be referred to as mesoporous (2-50 nm) or microporous (0.4-2 nm) framework structures.

First composition comprising ethene

The first composition comprising ethene may include other hydrocarbons in addition to ethene. The first composition may comprise primarily ethene, or may comprise a mixture of ethene and other light olefins such as propene, butenes, and higher olefins. In addition, the first composition may also contain saturated hydrocarbons such as methane, ethane, propane, butane, and higher alkanes. In an embodiment, the first composition comprises 50-99% olefins. In an embodiment, the first composition comprises primarily ethene, such as more than 90, 95, 96, 97, or 98% of ethene.

The first composition may be a stream which is continuously fed to a reaction zone comprising the catalytic material.

In an embodiment the first composition comprising ethene is produced by dehydration of ethanol. In another embodiment the first composition comprising ethene is a recycle stream from a process for making liquid hydrocarbon fuels from lighter olefins. In an embodiment the recycle stream comprises a mixture of olefins and alkanes. In an embodiment, the recycle stream comprises 50-99% olefins. The recycle stream may e.g. comprise 50% ethene, 5% butane, and 45% butene isomers. In an embodiment, the ethene of the first composition is derived from a light hydrocarbon by-product from producing liquid hydrocarbon fuels.

Generally, the first composition is a gas phase composition, but it may also be compressed into a liquid composition at sufficient pressures. In an embodiment, the first composition comprises a diluent, such as a noble gases, N2, CO2, methane, ethane, propane, butane, isobutane; or mixtures thereof.

Second composition enriched in ethene oligomerization products

The second composition enriched in ethene oligomerization products is a composition (or stream) where some or substantially all of the ethene present in the first composition has been oligomerised into higher olefins such as butenes, hexenes, and other higher olefins. The second composition enriched in ethene oligomerization products may contain a large fraction of unconverted ethene or it may be essentially depleted in ethene. The second composition may in addition comprise cracking products of the olefins formed.

In an embodiment the second composition enriched in ethene oligomerization products is obtained by dehydrating ethanol to obtain a first composition of pure ethene and oligomerising it to a second composition comprising approximately 25% ethene, 60% butene isomers, 10% hexene isomers, and 5% other higher olefins. In an embodiment, the second composition enriched in ethene oligomerization products is obtained by oligomerising a first composition comprising ethene obtained from a liquid hydrocarbon fuel synthesis process. In an embodiment, the second composition enriched in ethene oligomerization products is obtained by oligomerising a first composition comprising ethene obtained from a liquid hydrocarbon fuel synthesis process, where the first composition comprises approximately 50% ethene, 10% butane, and 40% butene, and the second composition enriched in ethene oligomerization products comprises approximately 10% ethene, 10% butane, 70% butene isomers, and 10% hexene isomers.

The ethene oligomerization process

The first composition is brought into contact with the catalytic material in a reaction zone. Generally, the process is carried out in gas phase, but it may also be carried out under pressure to be partly or entirely in liquid phase.

The process for ethene oligomerization may be conducted in a reactor having a reaction zone containing the catalytic material, where the first composition comprising ethene is converted into the second composition enriched in ethene oligomerization products. Generally the reactor has an inlet for feeding the first composition to the reaction zone and an outlet for recovering the second composition from the reaction zone.

In an embodiment the reactor is a fixed bed reactor, such as a tubular reactor containing catalyst material in the form om pellets or extrudates. In another embodiment, the reactor is an adiabatic reactor. In an embodiment the reactor is actively cooled to control the temperature.

In an embodiment the oligomerization process is operated at high pressure, such as 10 bar, 20 bar, 30 bar, 40 bar, 50 bar, or higher pressure.

In an embodiment the oligomerization process is operated at a temperature in the range of 40 °C - 400 °C.

In an embodiment the ethene oligomerization process is operated under conditions where the ethene is in a liquid state. In an embodiment, the ethene oligomerization process is operated under conditions where the ethene is in a gaseous state.

Producing liquid fuels

One process for producing liquid hydrocarbon fuels from ethene involve a first step of producing C4+ olefins from ethene, a second step of converting C4+ olefins into fuel range olefins and a third step of hydrogenating the olefins to alkanes.

The second composition produced in the ethene oligomerization process may be used for producing liquid hydrocarbon fuels. It may be used directly as feed or co-feed in a fuel synthesis process. In an embodiment the second composition enriched in oligomerization products is converted to C10-C18 olefins using an acidic catalyst comprising aluminum, and hydrogenated to C10-C18 alkanes. In an embodiment the second composition enriched in oligomerization products is co-fed with ethanol and/or methanol and converted into a fuel-range hydrocarbon product using a zeolite catalyst.

In a third embodiment the second composition enriched in oligomerization products is fractionated to a light fraction comprising ethene and a heavy fraction essentially free of ethene. In an embodiment the light fraction is recycled and combined with the first composition comprising ethene. In an embodiment the heavy fraction is processed into a fuel range hydrocarbon product using acidic catalysts.

An advantage is that less alkanes are produced than in prior art processes which means less carbon material must be discarded.

Producing Platform chemicals

The second composition produced in the ethene oligomerization process may be used for producing platform chemicals, such as butene. It may require a purification of the second composition.

An advantage in this context is that the second composition obtained according to the invention has a higher mole ratio of linear olefins to branched olefins compared to the prior art. This makes it more suitable for the production of chemicals, such as butadiene via dehydrogenation of 1- and 2- butene, or metathesis of 2-butene to propene. In these cases, branched olefins are unwanted as they will not convert into the desired products.

EXAMPLES

Example 1 : Preparation of Ni-SnBEA catalyst

30.6 g of tetraethyl orthosilicate (TEOS, Aldrich, 98%) was mixed with 33.1 g of tetraethylammonium hydroxide (TEAOH, Sigma-Aldrich, 35% in water) under stirring for 60- 120 minutes, until a homogenous solution was formed. Afterwards, 0.514 g of tin(IV) chloride pentahydrate (SnC SFW, Aldrich, 98%) was dissolved in 2 mL of demineralized water and added to the solution dropwise.

The mixture was maintained under stirring until a viscous gel formed. Subsequently, 3.1 g of hydrofluoric acid (HF, Fluka, 47-51 %) was diluted with 1.6 g of demineralized water and added to the synthesis gel, forming a brittle solid precursor. The resulting precursor was then crushed and transferred into an autoclave having a Teflon liner. The hydrothermal synthesis was conducted for 80 days at 140 °C until crystallization was achieved. The obtained material was filtered, washed with abundant water, dried at 80 °C overnight, and calcined in air at 550 °C for 6 hours using a temperature ramp of 5 °C/min to obtain SnBEA. In the final step, Ni was loaded onto the SnBEA using incipient wetness method with nickel(ll) nitrate hexahydrate (Ni(NO3)2'6H2O, Aldrich, 99%) solution to achieve specific Ni loading of 1.0 wt%. The impregnated Ni-SnBEA material was then dried at 80 °C overnight and calcined at 550 °C (temperature ramp 3 °C /min) for 6 hours to complete the synthesis of the catalytic material (Ni-SnBEA) according to the present invention having Sn as tetravalent metal (Me) and having a Ni loading 1.0 wt% and having a Si/Sn nominal ratio of 100.

Example 2: Preparation of Ni-ZrBEA catalyst

30.6 g of tetraethyl orthosilicate (TEOS, Aldrich, 98%) was mixed with 33.1 g of tetraethylammonium hydroxide (TEAOH, Sigma-Aldrich, 35% in water) under stirring for 60- 120 minutes, until a homogenous solution was formed. Afterwards, 0.473 g of zirconyl(IV) chloride octahydrate (ZrOCfe StW, Sigma-Aldrich, 98%) was dissolved in 2 mL of demineralized water and added to the solution dropwise.

The mixture was maintained under stirring until a viscous gel formed. Subsequently, 3.1 g of hydrofluoric acid (HF, Fluka, 47-51 %) was diluted with 1.6 g of demineralized water and added to the synthesis gel, forming a brittle solid precursor. The resulting precursor was then crushed and transferred into an autoclave having a Teflon liner. The hydrothermal synthesis was conducted for 80 days at 140 °C until crystallization was achieved. The obtained material was filtered, washed with abundant water, dried at 80 °C overnight, and calcined in air at 550 °C for 6 hours using a temperature ramp of 5 °C/min to obtain ZrBEA. In the final step, Ni was loaded onto the ZrBEA using incipient wetness method with nickel(ll) nitrate hexahydrate (Ni(NO3)2'6H2O, Aldrich, 99%) solution to achieve specific Ni loading 1.0 wt%. The impregnated Ni-ZrBEA precursor was then dried at 80 °C overnight and calcined at 550 °C (3 °C /min) for 6 hours to complete the synthesis of the catalytic material (Ni-ZrBEA) according to the present invention having Zr as tetravalent metal (Me) and having a Ni loading 1.0 wt% and having a Si/Zr nominal ratio of 100.

Example 3: Preparation of Ni-HfBEA catalyst

30.6 g of tetraethyl orthosilicate (TEOS, Aldrich, 98%) was mixed with 33.1 g of tetraethylammonium hydroxide (TEAOH, Sigma-Aldrich, 35% in water) under stirring for 60- 120 minutes, until a homogenous solution was formed. Afterwards, 0.470 g of haf- nium(IV) chloride (HfCL, Aldrich, 98%) was dissolved in 2 mL of demineralized water and added to the solution dropwise.

The mixture was maintained under stirring until a viscous gel formed. Subsequently, 3.1 g of hydrofluoric acid (HF, Fluka, 47-51 %) was diluted with 1.6 g of demineralized water and added to the synthesis gel, forming a brittle solid precursor. The resulting precursor was then crushed and transferred into an autoclave having a Teflon liner. The hydrothermal synthesis was conducted for 80 days at 140 °C until crystallisation was achieved. The obtained material was filtered, washed with abundant water, dried at 80 °C overnight, and calcined in air at 550 °C for 6 hours using a temperature ramp of 5 °C/min to obtain HfBEA. In the final step, Ni was loaded onto the HfBEA using incipient wetness method with nickel(ll) nitrate hexahydrate (Ni(NC>3)2-6H2O, Aldrich, 99%) solution to achieve specific Ni loading 1.0 wt%. The impregnated Ni-HfBEA precursor was then dried at 80 °C overnight and calcined at 550 °C (3 °C /min) for 6 hours to complete the synthesis of the catalytic material (Ni-HfBEA) according to the present invention having Hf as tetravalent metal (Me) and having a Ni loading 1.0 wt% and having a Si/Hf nominal ratio of 100.

Example 4 (comparative): Preparation of Ni-AIBEA catalyst

30.6 g of tetraethyl orthosilicate (TEOS, Aldrich, 98%) was mixed with 33.1 g of tetraethylammonium hydroxide (TEAOH, Sigma-Aldrich, 35% in water) under stirring for 60- 120 minutes, until a homogenous solution was formed. Afterwards, 0.236 g of alumi- num(lll) chloride hexahydrate (AICI3 6H2O, Fluka, 99%) was dissolved in 2 mL of demineralized water and added to the solution dropwise.

The mixture was maintained under stirring until a viscous gel formed. Subsequently, 3.1 g of hydrofluoric acid (HF, Fluka, 47-51 %) was diluted with 1.6 g of demineralized water and added to the synthesis gel, forming a brittle solid precursor. The resulting precursor was then crushed and transferred into an autoclave having a Teflon liner. The hydrothermal synthesis was conducted for 30 days at 140 °C until full crystallization was achieved. The obtained material was filtered, washed with abundant water, dried at 80 °C overnight, and calcined in air at 550 °C for 6 hours using a temperature ramp of 5 °C/min to obtain AIBEA. In the final step, Ni was loaded onto the AIBEA using incipient wetness method with nickel(ll) nitrate hexahydrate (Ni(NC>3)2-6H2O, Aldrich, 99%) solution to achieve specific Ni loading of 1.0 wt%. The impregnated Ni-AIBEA precursor was then dried at 80 °C overnight and calcined at 550 °C (3 °C /min) for 6 hours to complete the synthesis of the catalytic material (Ni-AIBEA) having Al as trivalent metal and having a Ni loading 1.0 wt% and having a Si/AI nominal ratio of 150.

Example 5: Transmission FTIR experiments with CO as probe molecule

Transmission FTIR experiments were carried out using a Vertex 70 spectrometer. Before the experiments, samples were prepared by pressing around 25 mg of sample powder into thin pellets, and then setting them into copper envelopes made for the test cell with KBr windows. Samples were pretreated under vacuum overnight at 450 °C with the ramp of +5 °C/min for 60 minutes, then cooled down to room temperature with the ramp of -10 °C/min. A background of the KBr windows was then measured. Subsequently, the pellets were placed into the measuring position and the samples were cooled down to liquid nitrogen temperature before measuring a reference blank spectrum. Afterwards, the probe molecule carbon monoxide (CO) was introduced into the cell up to saturation levels of the sample. Then, CO was desorbed step-wise from saturation pressure to around 1 x 10'² mbar, while spectra were taken during this process at liquid nitrogen temperatures. Spectra were recorded in the range 4000-500 cm-1 , by accumulating 128 scans at 2 cm^-1 resolution. FTIR data were analyzed using Bruker OPUS software and OriginPro 2023.

Example 6: Ethene oligomerization test

Catalytic tests were carried out in a fixed bed stainless steel reactor in a Microactivity Effi setup (PID Eng & Tech). Before each experiment, 500 mg of catalyst was pressed, crushed, and sieved to 250-425 pm grain size. The catalyst was loaded in the reactor and activated in-situ at 300 °C overnight under 1 bar of nitrogen gas (40 mL/min). The total pressure was then increased to 30 bar in inert flow (argon (Ar)) and controlled by a back-pressure regulator before running the reaction. During reaction, the partial pressures were controlled by adjusting individual flows of ethene (provided by Praxair, 3.5 grade) and inert (Ar, Praxair, 5.0) (combined flows=first composition), keeping the total pressure constant at 30 bar. The catalytic tests were run at a temperature of 250 °C to 300 °C with a total pressure of 30 bar, with an Ar flow of 20 mL/min and an ethene flow of 10 mL/min (contact time of 0.017 min g of catalyst/mL). The ethene partial pressure was maintained at 10 bar in all the tests. A small portion of the reactor effluent (second composition) was led through heated lines to an online gas chromatograph (Scion 456- GC) equipped with six columns: MolSieve 13X, HayeSep Q, HayeSep N, Rt-Stabilwax, Rt- Alumina/MAPD, and Rtx-1 ; and three detectors: one TCD and two Fl Ds. All effluent products (second composition) were analysed simultaneously, without the need to condense the heavy products. Ethene conversion and product selectivity were calculated as follows:

Where:

Xi is the product i carbon fraction

RFi is the response factor normalised on a carbon basis

Xethene is the ethene carbon fraction in the products

S/ is the selectivity to product i on a carbon basis

X is ethene conversion

Yi is the yield of product i on a carbon basis

The results are shown in figures 1 and 2. As can be seen in figure 1 , with the Lewis acidic catalysts according to the present invention (Examples 1 to 3), the selectivity to linear butenes does not decrease with ethene conversion. In contrast, the selectivity to linear butenes decreases with ethene conversion for the Bronsted acidic reference catalyst (Ni- AIBEA, Example 4).

In figure 2, the product selectivities obtained with the Lewis acidic catalysts are compared to the product selectivities obtained with the Ni-AIBEA catalyst, at similar ethene conversion. As can be seen, the Lewis acidic catalysts (Examples 1 to 3) show higher selectivity to linear butenes, while minimising the formation and reduced products (i.e. , ethane, i- butane, n-butane) and cracked products (i.e., propene, pentene). Moreover, the selectivity to olefins C2x (where x=2 or 3) is 95 % or higher with the Lewis acidic catalysts of Examples 1 to 3, compared to below 70 % with the Bronsted acidic catalyst (Ni-AIBEA) of Example 4.

In figure 3, the spectra from the transmission FTIR experiments with CO as probe molecule are shown. For each catalyst, several spectra are presented in various shadings of grey, acquired at various pressures, from saturation pressure (dark grey) to approximately 1 x 10'² mbar (light grey). It can be seen that with the catalysts of the invention described in examples 1 to 3, no bands are detected above 2200 cm^-1. The bands above 2200 cm^-1 can be assigned to Bronsted sites exchanged with Ni²⁺. The absence of these bands indicates that the catalysts of the invention from examples 1 to 3 do not have Bronsted acid sites.

Example 7: Fuels production

This example illustrates how the product sample (second composition) from Example 6 can be converted into a liquid hydrocarbon fuel. The second composition enriched in ethene oligomerization products obtained by using Ni-ZrBEA as catalyst in the process according to the invention comprises 72% ethene, 22% butene isomers (1- and 2-butene), and 6% hexene isomers (1-, 2- and 3-hexene). This mixture is subjected to fractionation and split into a light and a heavy fraction. The light fraction comprises substantially all of the ethene and minor amounts of butenes and is recycled to the process according to the invention by combining it into the first composition. The heavy fraction is essentially free of ethene and comprises about 79% butenes, 21 % hexenes, and minor amounts of higher olefins. The heavy fraction is converted into fuel-range olefins by acid catalyzed oligomerization processing, e.g. using a silica-alu- mina catalyst at 120 °C and 35 bar. The product from this step comprises 35% C4-C8 olefins, 60% C10-C18 olefins, and 5% C20+ olefins. The olefins mixture is fractionated and separated into light olefins and fuels-range olefins. The light olefins may be used for recycle to the process according to the invention by combining it into the first composition and the fuel-range olefins are hydrogenated and fractionated into naphtha, kerosene, and diesel fractions.

Claims

1 . A process for ethene oligomerization, wherein a first composition comprising ethene is brought into contact with a catalytic material to provide a second composition enriched in ethene oligomerization products, wherein the catalytic material comprises nickel (Ni) and a porous framework structure, the framework structure being substantially free of aluminum (Al) and comprising silicon (Si) and a further tetravalent metal (Me), and the framework structure having pores with a diameter in the range of from 0.4 to 50 nm as measured by nitrogen adsorption.

2. The process according to claim 1 , wherein the catalytic material shows no bands at wavelengths above 2200 cm^-1 in transmission FTIR with CO as probe molecule.

3. The process according to any one of the preceding claims, wherein the molar ratio of Si to Al in the framework structure is above 300.

4. The process according to any one of the preceding claims, wherein the tetravalent metal (Me) is selected from the group consisting of Sn, Ti, Zr, Hf, Ge; or mixtures thereof.

5. The process according to any one of the preceding claims, wherein the molar ratio of Si to Me is in the range of from 20 to 400, such as 75-150.

6. The process according to any one of the preceding claims, wherein the framework structure comprises a structure selected from any one of the microporous structures BEA, MFI, FAU, FER, MOR, MTW, the mesoporous structures MCM- 41 , SBA-15, or mixtures thereof.

7. The process according to any one of the preceding claims, wherein the molar ratio of Ni to Me is in the range of from 0.05 to 20, such as 0.3 to 3.

8. The process according to any one of the preceding claims, wherein the loading of Ni is from 0.01 to 10 wt %, such as 0.5-3.0 wt %.

9. The process according to any one of the preceding claims, wherein the ethene oligomerization products comprise C2n-olefins, where n=2, 3, or 4.

10. The process according to claim 9, wherein the C2n-olefins are selected from butene and hexene; or mixtures thereof.

11 . The process according to any one of the preceding claims, wherein the first composition is brought into contact with the catalytic material at a oligomerization temperature below 400 °C.

12. The process according to any one of the preceding claims, wherein the first composition is a gas phase composition.

13. The process according to any one of the preceding claims, wherein the first composition comprises a diluent, such as a noble gases, N2, CO2, methane, ethane, propane, butane, isobutane; or mixtures thereof.

14. The process according to any one of the preceding claims, wherein the ethene of the first composition is derived from a light hydrocarbon by-product from producing liquid hydrocarbon fuels.

15. The process according to any one of the preceding claims, wherein the catalytic material is selected from the group consisting of Ni-SnBEA, Ni-ZrBEA, Ni- HfBEA, or mixtures thereof.

16. A use of the second composition of any one of the preceding claims for producing liquid hydrocarbon fuels.

17. The use according to claim 16, wherein the second composition is combined with a third composition comprising methanol and/or ethanol for producing liquid hydrocarbon fuels.

18. A use of the second composition of any one of claims 1 to 15 for producing butene.