WO2025114973A1

WO2025114973A1 - Systems and methods for metathesis of mixed butene and butane feedstocks and recovery and recycle of reactive compounds

Info

Publication number: WO2025114973A1
Application number: PCT/IB2024/062057
Authority: WO
Inventors: Vidya Sagar GUGGILLA; Rajitha VUPPULA; Dhaneesh Varappurath Sukumaran; Batchala Shanmukha RAO; Amit Sharma
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2023-11-30
Filing date: 2024-11-30
Publication date: 2025-06-05
Anticipated expiration: 2026-05-30

Abstract

Provided here are methods that include supplying a C₄ feed stream containing inert C₄ compounds to a metathesis reactor to produce a metathesis product stream containing ethene, propene, unreacted butenes, the inert C₄ compounds, and C₅-C₆ olefins, supplying the metathesis product stream to a C₃distillation column to produce a C₂-C₃ product stream and a C₄+-rich stream containing the unreacted butenes, the inert C₄ compounds, and the C₅-C₆ olefins, and supplying the C₄+-rich stream to a C5 column to produce a C₄-C₅ recycle stream containing the unreacted butenes, the inert C₄ compounds, and C₅ olefins and a C₆ product stream containing C₆ olefins. The method further includes diverting a portion of the C₄-C₅ recycle stream to a C₄ separation zone to produce one or more inert C₄-rich streams and one or more reactive C₄-C₅-rich streams, which are recycled to the metathesis reactor with a remainder of the C₄-C₅ recycle stream.

Description

SYSTEMS AND METHODS FOR METATHESIS OF MIXED BUTENE AND BUTANE FEEDSTOCKS AND RECOVERY AND RECYCLE OF REACTIVE COMPOUNDS

Cross-Reference to Related Applications

[0001] This application claims priority to and the benefit of European Application No. EP23213231.6, filed on November 30, 2023. The contents of the referenced application are incorporated into the present application by reference.

Technical Field

[0002] The disclosure relates to the production of desired olefins from a mixed butene and butane feedstock, including recovery and recycle of reactive compounds from a metathesis reactor effluent.

Background

[0003] There is continued interest in production of light olefins, such as ethene and propene. Metathesis provides a path for production of certain olefins from certain lower value feedstocks. However, the metathesis feedstocks and/or effluent streams may include various inert compounds that negatively affect metathesis operations.

Summary

[0004] In certain systems, C4 raffinate steams of relatively low value may be valorized to meet an increasing demand for higher value products. The C4 raffinate steams can be provided from a fluid catalytic cracker (FCC), a gas/mixed/liquid steam cracker, or a methanol-to-olefins (MTO) unit. The C4 raffinate steams of certain examples primarily include butanes (e.g., C4 paraffins such as butane and 2-methylpropane), but-l-ene, but-2-enes, 2-methylprop-l-ene (e.g., isobutene), and 1,3-butadiene. However, various C4 isomers have certain similar physical properties that result in similar or very close boiling points. As such, a major challenge is identified herein as the separation of but-l-ene, but-2-enes, and butanes. In particular, separation or removal of butanes or inert C4 compounds that are present in the feedstock in a threshold range (e.g., less than 30 mole percent, from about 0.01 to 30 mole percent, from about 20 to 30 mole percent) by distillation is extremely costly and would greatly benefit from new and sustainable processes. [0005] The present disclosure addresses the use of such a mixed stream in metathesis processes with one or more separators or separation units of a C4 separation zone that is integrated downstream of a metathesis reactor. The C4 separation zone enables maximum utilization of C4 olefins within a mixed C4 feedstock that also contains inert C4 compounds, such as butane and 2- methylpropane at a total concentration in a range from 20 to 30 mole percent. For example, the C4 separation zone disclosed herein receives a C4-C5 bleed stream (e.g., at least a portion of a C4-C5 recycle stream) and produces one or more inert C4-rich streams (e.g., C4 paraffin-rich streams) and one or more reactive C4-C5-rich streams (e.g., C4-C5 olefin- rich streams). The reactive C4-C5-rich streams can thus be recycled back to the metathesis reactor for further production of desired products and high-value chemicals. It should be understood that each reactive C4-Cs-rich stream can each include one or more C4 olefins, one or more C5 olefins, or a combination thereof.

[0006] Metathesis is recognized herein as a preferred process for valorization of low value olefins, such as C4 and C5 olefins, into higher value products, such as propene and hexenes. The present disclosure provides systems and methods for valorizing certain low-value C4 product streams or raffinate streams from a steam cracker into higher value products. The present disclosure include one or more C4 separation units integrated downstream of a metathesis reactor to facilitate the recovery of reactive C4-C5 olefins for recycle to the metathesis reactor. The advancements disclosed herein may be broadly applied to various metathesis reactions, including those for C2 to C12 olefins. The present examples include metathesis processes, such as self and cross metathesis of but-l-ene and but-2-enes that are provided to a metathesis reactor. The metathesis byproducts can be processed via recycling back to the metathesis reactor to enhance desired olefin product formation. The metathesis reactor may be a fixed-bed reactor operating at low reaction temperatures and with a rhenium oxide-coated y-alumina-based catalyst (Re2O7/yAhO3), in some examples.

[0007] The disclosure herein provides several examples of systems for the production of chemicals, such as ethene, propene, and/or hexene, and methods for producing chemicals. Examples include a method for producing chemicals that includes supplying a C4 feed stream containing about 0.1-30 mole percent (mol. %) inert C4 compounds to a metathesis reactor containing a metathesis catalyst to produce a metathesis product stream containing ethene, propene, unreacted butenes, the inert C4 compounds, C5 olefins, and Ce olefins. The method further includes supplying the metathesis product stream to a C3 distillation column to produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes, the inert C4 compounds, the C5 olefins, and the Ce olefins. The method further includes supplying the C2-C3 product stream to a C2/C3 splitter to produce an ethene product stream and a propene product stream. The method further includes supplying the C4+-rich stream to a C5 column to produce a C4-C5 recycle stream containing the unreacted butenes, the inert C4 compounds, and the C5 olefins and a Ce product stream containing the Ce olefins. The method further includes diverting a portion of the C4-C5 recycle stream as a C4-C5 bleed stream to a C4 separation zone having at least one separator to produce one or more inert C4-rich streams and one or more reactive C4-Cs-rich streams. The method further includes recycling the one or more reactive C4-Cs-rich streams and a remainder of the C4-C5 recycle stream to the metathesis reactor along with the C4 feed stream.

[0008] In some examples, the at least one separator includes a flash column, and the method further includes cooling the C4-C5 bleed stream to a flash temperature threshold and supplying the C4-C5 bleed stream to the flash column to produce a C4-rich stream as the one or more inert C4-rich streams and a Cs-rich stream as the one or more reactive CT-Cs-rich streams.

[0009] In some examples, the at least one separator includes a flash column and a C4 separator that includes a dividing-wall column or a fractionator, and the method further includes cooling the C4-C5 bleed stream to a flash temperature threshold, supplying the C4-C5 bleed stream to the flash column to produce a Cs-rich stream as the one or more reactive CT-Cs-rich streams and C4-rich stream, and supplying the C4-rich stream to the C4 separator to produce a but-l-ene-rich stream and a but-2-ene-rich stream as the one or more reactive CT-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

[0010] In some examples, the at least one separator includes a C4 fractionator, and the method further includes supplying the C4-C5 bleed stream to the C4 fractionator to produce a but-l-ene-rich stream and a C5 olefin and but-2-ene-rich stream as the one or more reactive CT-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

[0011] In some examples, the C4 feed stream contains about 20-30 mol. % of the inert C4 compounds and contains at least 15 mol. % of but-l-ene. In some examples, the method further includes removing one or more contaminants from the C4 feed stream upstream of the metathesis reactor with one or more guard beds containing adsorbent. The one or more contaminants can include a sulfur compound, a salt compound, a metal, or a combination thereof. In some examples, the C4 feed stream is sourced from a steam cracker, a fluid catalytic cracker, or a methanol-to- olefins unit. In some examples, the metathesis catalyst includes a rhenium oxide-coated y-alumina- based catalyst that is non-reactive to the inert C4 compounds.

[0012] A system for producing chemicals that includes a metathesis reactor containing a metathesis catalyst and configured to receive a C4 feed stream containing about 0.1-30 mole percent (mol. %) inert C4 compounds and produce a metathesis product stream containing ethene, propene, unreacted butenes, the inert C4 compounds, C5 olefins, and Ce olefins. The system includes a C3 distillation column configured to receive the metathesis product stream and produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes, the inert C4 compounds, the C5 olefins, and the Ce olefins. The system includes a C2/C3 splitter configured to receive the C2-C3 product stream and produce an ethene product stream and a propene product stream. The system includes a Cs column configured to receive the C4+-rich stream and produce a C4-C5 recycle stream containing the unreacted butenes, the inert C4 compounds, and the C5 olefins and a Ce product stream containing the Ce olefins. The system includes a C4 separation zone having at least one separator and configured to receive a diverted portion of the C4-C5 recycle stream as a C4-C5 bleed stream and produce one or more inert C4-rich streams and one or more reactive C4-Cs-rich streams. The one or more reactive CT-Cs-rich streams and a remainder of the C4-C5 recycle stream are routed to the metathesis reactor along with the C4 feed stream to produce the metathesis product stream.

[0013] In some examples, the at least one separator includes a flash column configured to separate the C4-C5 bleed stream into a C4-rich stream as the one or more inert C4-rich streams and a Cs-rich stream as the one or more reactive CT-Cs-rich streams.

[0014] In some examples, the at least one separator includes a flash column and a C4 separator that includes a dividing-wall column or a fractionator. The flash column is configured to separate the C4-C5 bleed stream into a Cs-rich stream as the one or more reactive C4-Cs-rich streams and a C4-rich stream. Additionally, the C4 separator is configured to separate the C4-rich stream into a but-l-ene-rich stream and a but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

[0015] In some examples, the at least one separator includes a C4 fractionator configured to separate the C4-C5 bleed stream into a but-l-ene-rich stream and a C5 olefin and but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

[0016] In some examples, the C4 feed stream contains about 20-30 mol. % of the inert C4 compounds, and the inert C4 compounds include butane and 2-methylpropane. In some examples, the system further includes one or more guard beds containing adsorbent and configured to remove one or more contaminants from the C4 feed stream upstream of the metathesis reactor. In some examples, the adsorbent includes oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and the one or more contaminants include a sulfur compound, a salt compound, a metal, or a combination thereof.

[0017] Still other aspects and advantages of these examples and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Furthermore, it is to be understood that the features of the various examples described herein are not mutually exclusive and may exist in various combinations and permutations.

Brief Description of the Drawings

[0018] Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements or procedures in a method. Embodiments are illustrated by way of example and not by way of limitation in the accompanying drawings. The present disclosure can be better understood by referring to the following figures. These drawings illustrate the principles of the disclosure and no limitation of the scope of the disclosure is thereby intended. [0019] FIG. 1 is a schematic representation of a system for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a reactive Cs-rich stream, according to an example.

[0020] FIG. 2 is a schematic representation of a system for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a reactive Cs-rich stream, a but-l-ene-rich stream, and a but-2-ene-rich stream, according to an example. [0021] FIG. 3 is a schematic representation of a system for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a but-l-ene-rich stream and a combined C5 olefin and but-2-ene-rich stream, according to an example.

[0022] FIG. 4 is a schematic representation of a control system for controlling operation of the disclosed systems for improved chemical production, according to an example.

Detailed Description

[0023] So that the manner in which the features and advantages of the examples of the systems and methods disclosed herein, as well as others that will become apparent, may be understood in more detail, a more particular description of examples of systems and methods briefly summarized above may be had by reference to the following detailed description of examples thereof, in which one or more are further illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various examples of the systems and methods disclosed herein and are therefore not to be considered limiting of the scope of the systems and methods disclosed herein as it may include other effective examples as well.

[0024] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in certain embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to examples of the present disclosure, are synonymous. [0025] The term “about” refers to a range of values including the specified value, which a person of ordinary skill in the art would consider reasonably similar to the specified value. In examples, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting example, when the term “about” is used with a particular value, then “about” refers to a range extending to ±10% of the specified value, alternatively ±5% of the specified value, or alternatively ±1% of the specified value, or alternatively ±0.5% of the specified value. In examples, “about” refers to the specified value.

[0026] The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of a component in 100 grams of the material is 10 wt.% of such component. The term “enriched” or “rich” or their variations mean an amount of at least generally about 20 wt. %, and preferably about 25 wt. %, of a compound or class of compounds in a stream. The term “substantially contains” means that the mixture includes at least 60%, or even at least 70%, or even at least 80% by weight of the relevant hydrocarbon-based compounds. The term “ppmw” refers to part per million by weight. The terms “reducing,” “reduced,” or any variation thereof, when used in the claims and/or the specification includes any measurable decrease or complete removal to achieve a desired result.

[0027] As used herein, the term “Cx-C_y compounds,” in which x and y are positive integer values, refers to hydrocarbon-based compounds, each compound containing between x and y carbon atoms, x and y inclusive. For example, a C3-C5 fraction or stream refers to a mixture that substantially contains or entirely contains hydrocarbon-based compounds, each compound containing 3, 4, or 5 carbon atoms. Additionally, it may be noted that, in certain cases, a Cx-C_y fraction or stream may not include a respective compound having each of the referenced integer values. As one example, a C4-C8 fraction can be a stream that contains compounds of 4, 5, and 7 carbon atoms, without any compounds of 6 or 8 carbon atoms. As another example, a C4-C5 stream can include compounds having only 4 carbon atoms, only 5 carbon atoms, or a mixture of both.

[0028] As used herein, the term “Cx+ compounds,” in which x is a positive integer value, refers to hydrocarbon-based compounds, each compound containing at least x carbon atoms. For example, a C3+ fraction refers to a mixture that substantially contains or entirely contains hydrocarbon- based compounds, each compound containing 3 or more (e.g., 3, 4, 5, 6, and so forth) carbon atoms. As used herein, the term “Cx- compounds,” in which x is a positive integer value, refers to hydrocarbon-based compounds, each compound containing no more than x carbon atoms. For example, a C4- fraction refers to a mixture that substantially contains or entirely contains hydrocarbon- based compounds, each compound containing 4, 3, 2, or 1 carbon atoms. It may be noted that, in certain cases, a “Cx- fraction” may also include hydrogen (H2), in addition to hydrocarbons having x or fewer carbon atoms.

[0029] As used herein, the term “zone” can refer to an area including one or more units and/or one or more sub-zones. Units can include one or more reactors or reactor vessels, separators, strippers, extraction columns, fractionation columns, heaters, exchangers, pipes, pumps, valves, compressors, sensors, and controllers. Additionally, a unit, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones that contain various equipment.

[0030] As used herein, the term “inert C4-rich stream” refers to a stream rich in one or more C4 compounds that are inert or non-reactive in the presence of a metathesis catalyst of the system. For examples in which the metathesis catalyst includes a rhenium oxide-coated catalyst, the inert C4 compounds include butane and 2-methylpropane. Additionally, as used herein, the term “reactive C4-Cs-rich stream” refers to a stream rich in one or more C4 compounds, one or more C5 compounds, or a combination thereof that are reactive in the presence of a metathesis catalyst of the system. For examples in which the metathesis catalyst includes a rhenium oxide-coated catalyst, the reactive C4-C5 compounds include one or more C4 olefins, one or more C5 olefins, or a combination thereof.

[0031] The present disclosure describes various examples related to systems and methods for improved recovery of unreacted C4-C5 olefins downstream of a metathesis reactor and further utilization of the recovered products to enhance productivity and yield of the metathesis reactor, without undue increases in cost. The examples included herein perform metathesis on a C4 raffinate stream that is rich in but-l-ene, while containing non-negligible amounts of but-2-enes and butanes. The present disclosure enables recovery of maximum C4-C5 olefins within a downstream C4 separation zone and facilitates recycle of the recovered olefins to produce high value chemicals via metathesis processes.

[0032] As presently recognized, it is desired to perform metathesis reactions on relatively low value butene feedstocks to upgrade the feedstocks into more valuable and desired products. Certain examples include a C4 feedstock or raffinate stream containing /?-butenes, /?-butane, z-butane, 2- methylprop-l-ene (z-butylene, isobutene), propane, and so forth. The composition of the C4 feedstock can depend on its source, including gas, mixed, or liquid steam cracker feeds utilized after a selective hydrogenation unit (SHU), a methyl tert-butyl ether (MTBE) reactor, a but-l-ene (Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, a methanol-to-olefins unit or process, and/or an FCC downstream process. In some examples, the C4 feedstock has a composition in accordance with a C4 raffinate II stream or a C4 raffinate III stream. Sample compositions of two different C4 raffinate streams are provided in the Examples section below.

[0033] To facilitate the metathesis reactions in the metathesis reactor, a metathesis catalyst, such as a rhenium oxide-coated y-alumina-based catalyst, is provided in the metathesis reactor. The rhenium oxide-coated y-alumina-based catalyst (R^O/yAhCh) can be spherical or an extrudate. One such rhenium oxide-coated y-alumina-based catalyst has y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. Other examples include y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 3 mm in diameter and from about 4 mm to about 8 mm in length, with the rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. In certain examples, the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount ranging from about 4.8 wt.% to about 5.6 wt.%. The rhenium oxidecoated y-alumina-based catalyst can facilitate conversion of one or more of: (trans/cis (t/c)) but-2- ene with but-l-ene to propene and (t/c) pent-2-ene, but-l-ene with but-l-ene to ethene and (t/c) hex-3-ene, ethene with (t/c) but-2-ene to propene and propene, ethene with (t/c) pent-2-ene to propene and but-l-ene, but-l-ene with (t/c) pent-2-ene to propene and (t/c) hex-3 -ene, and (t/c) pent-2-ene and (t/c) pent-2-ene to (t/c) but-2-ene and (t/c) hex-3-ene in an operational metathesis reactor. In certain examples, the rhenium oxide-coated y-alumina-based catalyst can be functional for at least 300 days in the operational metathesis reactor. In certain examples, the catalyst is regenerated for greater than 50 times in the operational metathesis reactor. Based on regeneration times, the catalyst can be functional for about 1000 days or longer. These days can vary based on the weight hourly space velocity that may range from 0.6/hr to 10/hr. In certain examples, in addition or alternative to the rhenium oxide-coated y-alumina-based catalyst, the metathesis catalyst is or includes rhenium oxide that is dispersed throughout a core or interior of the y-alumina. The y-alumina particles of these rhenium oxide-dispersed y-alumina-based catalyst can be spherical or an extrudate.

[0034] Methods of preparing a rhenium oxide-coated y-alumina-based catalyst include the steps of calcining a y-alumina-based support to form a calcined y-alumina-based support at a temperature ranging from about 450 Celsius (°C) to about 550 °C and treating the calcined y-alumina-based support with an aqueous rhenium-containing mixture in a rotating drum impregnation unit to form a rhenium-coated y-alumina-based support. In certain examples, the aqueous rhenium-containing mixture is a NTBReC solution, an Al(ReO4)3 solution, or a HReCh solution. In certain examples, the impregnation unit is rotated at a speed ranging from about 15 revolutions per minute (rpm) to about 25 rpm to form a rhenium- coated y-alumina-based support. The method also includes the steps of aging the rhenium-coated y-alumina-based support to form a rhenium oxide-coated y- alumina-based catalyst after calcination, containing a rhenium oxide coating ranging from about 150 micrometers (pm) to about 250 pm in thickness, drying the rhenium-coated y-alumina-based catalyst immediately after aging, and calcining the rhenium-coated y-alumina-based catalyst at a temperature ranging from about 450 °C to about 550 °C to form rhenium oxide coated y-alumina. In certain examples, the step of aging the rhenium- coated y-alumina-based support is carried out for a time less than 5 minutes thereby to form a rhenium oxide-coated y-alumina-based catalyst after calcination. In certain examples, the step of drying the rhenium- coated y-alumina-based catalyst immediately after aging at a temperature ranges from about 140 °C to about 160 °C.

[0035] The particle size of the y-alumina-based support can range from about 1.2 millimeters (mm) to about 3 mm. For example, the diameter of a spherical or a cylindrical y-alumina-based support can range from about 1.2 mm to about 3 mm. In certain examples, the y-alumina-based support has a pore volume ranging from about 0.5 milliliter per gram (ml/g) to about 0.65 ml/g. In certain examples, the y-alumina-based support has a pore diameter ranging from about 75 Angstroms (A) to about 110 A. In certain examples, the y-alumina-based support has a total acidity ranging from about 0.58 millimole per gram (mmolNH3/g) to about 0.62 mmolNH3/g. In certain examples, the rhenium oxide-coated y-alumina-based catalyst can contain rhenium oxide in an amount ranging from about 4.8 weight percent (wt. %) to about 5.6 wt. %. The rhenium oxi decoated y-alumina-based catalyst can have a surface area ranging from about 200 square meters per gram (m²/g) to about 270 m²/g. The rhenium oxide-coated y-alumina-based catalyst can be spherical in shape or an extrudate. An extrudate can be cylindrical or lobed or of other shapes. In certain examples, the rhenium particles of the coating have a particle size ranging from about 0.3 nanometer (nm) to about 1.2 nm.

[0036] Examples include methods of preparing an activated rhenium oxide-coated y-alumina- based catalyst. One such method includes the steps of treating the rhenium oxide-coated y-alumina- based catalyst under air at a temperature from about 500 °C to about 550 °C to produce an activated rhenium oxide-coated y-alumina-based catalyst, purging nitrogen into the activated rhenium oxi decoated y-alumina-based catalyst to displace the air, and cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is carried out for about 4 hours to about 24 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is carried out for about 6 hours.

[0037] The rhenium oxide-coated y-alumina-based catalyst is used for self and cross metathesis of but-l-ene and (t/c) but-2-enes, in some examples. The rhenium oxide-coated y-alumina-based catalyst is used for self and cross metathesis of pent-2-ene, in some examples. The metathesis reactor can be operated at temperatures ranging from 35 to 100 °C, in some examples. The metathesis reactor can be operated at temperatures ranging from 50 to 100 °C, in some examples. In some examples, the operated at temperatures ranging from 50 to 500 °C. Operating pressures of the metathesis reactor can range from atmospheric pressures to pressures up to 30 bar, in some examples. The metathesis reactor can use a liquid feed, a vapor feed or a mixed phase feed. If low temperature liquid phase feed is used for metathesis reactor, the outlet product can either be liquid phase or mixed vapor-liquid phase depending on the pressure and temperature of the reactor.

[0038] The systems disclosed herein implement a metathesis reactor followed by one or more separation columns of a C4 separation zone for separating unconverted feed and products. As described herein, various systems can be implemented to increase metathesis reactor productivity and/or increase the feedstock utilization based on recovery of reactive components from downstream of a metathesis reactor and recycling of the reactive components. In some examples, the feedstock supplied to the system is a C4 raffinate stream. The composition of the C4 raffinate stream can include greater than 15 mole percent (mol. %) of but-l-ene, a non-zero amount of but- 2-enes, as well as an amount of inert C4 compounds (e.g., n-butane and/or isobutene) in a range from 20 to 30 mol. %. In some examples, the C4 raffinate stream contains less than 30 mol. % of inert C4 compounds, such as an amount in a range from 0.01-30 mol. %. To efficiently separate out the inert C4 compounds, as described below, the downstream separation zone can include a C4 flash column, a C4 flash column and a C4 separator (e.g., dividing- wall column or fractionator), or a C4 fractionator. In certain examples, the particular configuration of the downstream separation zone is selected based on the composition of the C4 raffinate stream (including inert components), the composition of the effluent stream from the reactor outlet (including unreacted feed components), the product slate requirements of the associated system, or any suitable combination of these factors. Indeed, the present systems and methods provide flexible, adaptable strategies by which inert components can be removed and unconverted feed components can be redirected for improved metathesis operations.

[0039] FIG. 1 is a schematic representation of a system 100 for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a reactive Cs-rich stream, according to an example. The system 100 of the illustrated example includes one or multiple guard beds, a metathesis reactor, a C3 column (or light distillation column or depropenizer), a C2/C3 splitter (or C2/C3 distillation column), a C5 column (or heavy distillation column or depentenizer), and a C4 flash column that separates the reactive Cs-rich stream from an inert C4-rich stream for recycle back to the metathesis reactor. In additional detail, the system 100 facilitates the pretreatment and metathesis of a C4 stream 102 containing inert compounds to produce desired olefin products, with improved reactor productivity provided by the separation and recovery of a reactive Cs-rich stream that is recycled to the metathesis reactor. As illustrated, the system 100 includes a treatment zone 104, a metathesis zone 110, an olefin separation zone 120, and a C4 separation zone 150.

[0040] In some examples, the C4 stream 102 is a C4 raffinate stream. The C4 stream 102 of certain examples contains at least 15 mol. % of but-l-ene. The C4 stream 102 of certain examples contains about 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mol. % of but-l-ene. In some examples, the C4 stream 102 is produced from a steam cracker or steam cracker furnace. In some examples, the C4 stream 102 may be sourced downstream of a steam cracker (e.g., a gas steam cracker, a liquid steam cracker, a light crude oil steam cracker, a crude oil cut steam cracker, a mixed feed steam cracker), downstream of a MTBE reactor, downstream of a Bl column, downstream of a B2 column, downstream of a butadiene hydrogenation reactor, as a C4 raffinate stream from an MTO process or reactor, or as a C4 raffinate stream from a refinery FCC process or reactor, or any combination thereof. For such examples, the composition of the C4 stream 102 may vary based on the source of the C4 stream. Additionally, certain examples of the C4 stream 102 optionally also include certain C5 compounds, such as pent-l-ene or other pentenes, in combination with the C4 compounds.

[0041] The C4 stream 102 contains a non-zero amount of inert C4 compounds, in certain examples. For example, the C4 stream 102 can contain an amount of inert C4 compounds in a range from about 20 mol. % to about 30 mol. %. In some examples, the C4 stream 102 can contain an amount of inert C4 compounds in a range from about 0.01 mol. % to about 30 mol. %. In some examples, the C4 stream 102 includes more than about 0.01, 0.5, 5, 10, 15, 20, or 25 mol. % of inert C4 compounds. In certain examples, the C4 stream 102 includes less than about 40, 35, 30, 25, 20, or 15 mol. % of inert C4 compounds. In some examples, the C4 stream 102 is a raffinate-II or raffinate-III stream having less than about 30 mol. % of inert C4 compounds. The inert C4 compounds, such as butane and 2-methylpropane, do not react within the metathesis zone 110. As such, present examples include features downstream of the metathesis zone 110 that efficiently remove one or more inert C4 compounds from the system 100, while enabling recovery of certain reactive species.

[0042] For the illustrated example, the C4 stream 102 containing inert C4 compounds is directed to the treatment zone 104 and introduced into a guard bed 106 (e.g., pretreater) to produce a pretreated C4 stream 108 having a reduced amount of one or more impurities therein. For example, the guard bed 106 can pretreat the C4 stream 102 via adsorbents that remove impurities or contaminants, such as sulfur compounds, sulfides, salt compounds, metals, oxygenates (e.g., MTBE, methoxymethane, dimethyl ether (DME), methanol), alcohols, green oil (heavy hydrocarbons), ethers, mercaptans, and/or nitrogen compounds (e.g., ammonia, amines, and nitriles). The guard bed 106 and/or treatment zone 104 can thus remove any suitable reactive compounds and/or inert compounds from the C4 stream 102 that can otherwise negatively affect operation of one or more downstream units of the system 100. Additionally, the guard bed 106 can include one or more layers of suitable adsorbents, including aluminum oxides, Ti, Zn, and/or Mg oxides, Type 13X molecular sieves, zeolites, activated carbon, and/or any combination thereof. In some examples, the treatment zone 104 includes multiple guard beds 106 therein that are implemented in series operation, in parallel operation, or a combination thereof. The multiple guard beds 106 are provided to facilitate continuous operation of the treatment zone 104, such as by enabling one or more guard beds 106 to be in operation while one or more other guard beds 106 are in standby and/or regeneration for future use. In some examples, multiple guard beds 106 are combined within a suitable vessel through which the C4 stream 102 travels. The pretreated C4 stream 108 is thus prepared and conditioned before exiting the treatment zone 104.

[0043] From the treatment zone 104, the pretreated C4 stream 108 is directed to the metathesis zone 110 and introduced into a metathesis reactor 112 in fluid communication with the guard bed 106. As such, the metathesis reactor 112 produces a metathesis product stream 114 that contains a mixture of C2-C6 olefin metathesis products. In an example, the metathesis product stream 114 contains ethene, propene, unreacted butenes, inert C4 compounds, C5 olefins, and Ce olefins. The metathesis reactor 112 can operate with any suitable liquid feed, vapor feed, or mixed phase feed. The metathesis reactor 112 can be implemented as a suitable down-flow or up-flow, fixed-bed, packed-bed, or a plug flow reactor with a metathesis catalyst. In certain examples, the metathesis catalyst can be a rhenium-based metathesis catalyst or a rhenium oxide-coated y-alumina-based catalyst. The rhenium-based metathesis catalyst enables self-metathesis and cross-metathesis of but-l-ene and but-2-enes. Additionally, the metathesis catalyst can also be implemented for selfmetathesis and cross-metathesis of pent-l-ene.

[0044] In some examples, the metathesis zone 110 includes multiple metathesis reactors 112 therein, which can be implemented in series or in parallel operation. In some examples, at least one reactor remains online while at least one other reactor is in regeneration or standby mode, preparing for subsequent operation. The number of reactors in the plant can be determined by an economic optimization between catalyst cost and capex for the reactors. In most cases, two reactors or three reactors can be used, where at least one reactor is in regeneration or standby. In some examples, the temperature of the metathesis reactor 112 is in a range from 35 °C to 100 °C, 30 °C to 100 °C, 30 °C to 90 °C, and so forth. The operating temperature of the metathesis reactor 112 can be in a range from 50 °C to 500 °C, in some examples, such as temperatures between 50 °C to 400 °C, 50 °C to 300 °C, 50 °C to 200 °C, 50 °C to 100 °C, and so forth. In some examples, the operating temperature is below 250 °C, such as below 200 °C, below 150 °C, below 100 °C, or about 50 °C. It is presently recognized that the metathesis reactors and catalysts used by other systems can demand substantially higher operating temperatures, such as temperatures greater than 250 °C, and as such, the lower operating temperatures of the disclosed metathesis reactor 112 reduce the operational cost and energy demands of the reactor compared to other systems. The operating pressures of the metathesis reactor 112 can be in a range from atmospheric pressure (0 barg) to 30 barg. Certain examples include metathesis reactions that are pressure independent, such that any pressure that is suitable for integration with upstream and downstream operations may be utilized. In some examples, the metathesis reactor 112 does not receive an ethene co-feed, which desirably avoids consumption of the higher value ethene olefin chemical feedstock to facilitate metathesis.

[0045] The metathesis catalyst is prone to gradual deactivation due to formation of intermediate species, moisture, or carbon deposition, and as such, it is desirable to operate the metathesis reactor such that a reasonable operating cycle time in a fixed bed plug flow reactor is between 1 day and 100 days, such as between 3 days and 30 days. In some examples, this is achieved by limiting the flow rate of C4 stream 102 into the metathesis reactor 112 to a weight hourly space velocity (WHSV) of between 0.1 h'¹ and 25 h’¹, such as values between 0.5 h'¹ and 10 h’¹. Regeneration of the metathesis catalyst can be performed when a metathesis reactor is in regeneration mode using nitrogen, air, enriched air, or oxygen at temperatures between 300 °C and 600 °C, such as temperatures between 300 °C and 550 °C, 350 °C and 600 °C, 350 °C and 550 °C, about 450 °C, and so forth. In some examples, the catalyst can be regenerated in-situ or online, ex-situ or offline, and/or with continuous catalyst replacement.

[0046] In the illustrated example, the metathesis product stream 114 exits the metathesis zone 110 and is directed to the olefin separation zone 120. For the illustrated example, the olefin separation zone 120 includes a C3 column 122, a C2/C3 splitter 124, and a C5 column 126. The metathesis product stream 114 is directed to the C3 column 122, which is in fluid communication with the metathesis reactor 112. The C3 column 122 separates the metathesis product stream 114 into a C2-C3 olefin stream 128 and a C4+-rich stream 130 or C4+ olefin stream. The C2-C3 olefin stream 128 contains ethene and propene, and the C4+-rich stream 130 contains the unreacted butenes, the inert C4 compounds, the C5 olefins, and the Ce olefins from the metathesis product stream 114. The C2-C3 olefin stream 128 is supplied to the C2/C3 splitter 124, which is in fluid communication with the C3 column 122. The C2/C3 splitter 124 separates ethene and propene of the C2-C3 olefin stream 128 into an ethene product stream 132 and a propene product stream 134. [0047] For the illustrated example, the C4+-rich stream 130 is directed to the C5 column 126, which is in fluid communication with the C3 column 122. The C5 column 126 separates the C4+-rich stream 130 into a CT-Cs-rich stream 136 and a Ce olefin stream 138. The Ce olefin stream 138 is output by the system 100 as a heavy product stream containing Ce internal olefins. In some examples, the Ce olefin stream 138 is provided or sold as gasoline octane boosters. In some examples, the Ce olefin stream 138 can be provided as internal olefins to produce linear internal olefins via further isomerization or utilized in a steam cracker to produce additional high value products.

[0048] The C4-Cs-rich stream 136 produced by the C5 column 126 contains the unreacted butenes, the inert C4 compounds, and the C5 olefins of the C4+-rich stream 130. As such, to address the inert C4 compounds and prevent their accumulation, the system 100 diverts a portion of the C4-Cs-rich stream 136 to the C4 separation zone 150 as a C4-C5 bleed stream 152. Generally, the fraction or percentage of the C4-Cs-rich stream 136 that is directed to the C4 separation zone 150 depends on a concentration or content of the inert C4 compounds in the feed to the metathesis reactor 112, such that a higher fraction of the C4-Cs-rich stream 136 is diverted in response to a higher concentration of inert C4 compounds. Additionally, in some examples, the amount of C5 olefins contained in the C4-Cs-rich stream 136 is dependent or based on the concentration of but- 2-enes in the feed to the metathesis reactor 112. In general, the C4 separation zone 150 separates the C4-C5 bleed stream 152 into one or more inert C4-rich streams and one or more reactive C4-Cs-rich streams. In the present example, the C4 separation zone 150 includes a C4 flash column 154 in fluid communication with the C5 column 126. The C4 flash column 154 separates the C4-C5 bleed stream 152 into a C4-rich stream 160 (e.g., an inert C4-rich stream) and a Cs-rich stream 162 (e.g., a reactive C4-C5-rich stream). In certain examples, the C4 separation zone 150 cools the C4-C5 bleed stream 152 via any suitable cooling unit or device to a flash temperature threshold, at which C4 compounds can be recovered in a gaseous or vapor phase and at which C5 olefins can be recovered (e.g., partly recovered) in a liquid phase. The C4 flash column 154 can be operated at any suitable temperature that leverages the boiling point difference between C4 compounds and C5 olefins.

[0049] Based on the separation at the flash temperature threshold, the C4-rich stream 160 includes the unreacted butenes and the inert C4 compounds and the Cs-rich stream 162 includes the C5 olefins. The C4-rich stream 160 can be removed or purged from the system 100, thus cleansing the system 100 of inert materials that may otherwise negatively affect operation. It may be appreciated that the C4-rich stream 160 may be collected to be sold as a product (e.g., liquid petroleum gas (LPG)), or subsequently subject to further purification, or it may be provided as an input stream to another system or unit of a hydrocarbon processing facility. The Cs-rich stream 162 containing the C5 olefins is thus directed to mix with a remainder of the CT-CVrich stream 136 for production of further desired olefins.

[0050] In the present example, the Cs-rich stream 162 and the remainder of the CT-CVrich stream 136 (e.g., that was not diverted to the C4 separation zone 150) are sent to the metathesis zone 110 as a recycle stream 140, thus enabling conversion of any unreacted butenes therein, C5 olefins, and/or other reactive components therein. That is, the recycle stream 140 is recycled to the metathesis zone 110 where it is combined with the pretreated C4 stream 108 before being metathesized to form the metathesis product stream 114. The Cs column 126 and the C4 flash column 154 are both in fluid communication with the metathesis reactor 112 to facilitate this recycle.

[0051] FIG. 2 is a schematic representation of a system 200 for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a reactive Cs-rich stream, a but-l-ene-rich stream, and a but-2-ene-rich stream, according to an example. The system 200 includes the treatment zone 204, the metathesis zone 210, the olefin separation zone 220, and the C4 separation zone 250, which each correspond to and include similar components as the zones discussed above with respect to FIG. 1. These components are similarly labeled, and their descriptions are not repeated in detail for improved clarity. As shown, the system 200 includes an additional separator in the C4 separation zone 250 for further recovery of reactive components to improve the operating efficiency of the system 200.

[0052] In particular, the system 200 includes a C4 separation zone 250 that is modified relative to the C4 separation zone 150 of FIG. 1. In the illustrated example, the C4 separation zone 250 further includes a C4 separator 270 that is integrated downstream of the C4 flash column 254. In some examples, unreacted butenes in the metathesis product stream 214 can be efficiently separated from inert, paraffinic components and recycled back to the metathesis zone 210. Accordingly, the metathesis product stream 214 is directed through the olefin separation zone 220 to generate the various product streams discussed above. The olefin separation zone 220 produces the C4-Cs-rich stream 236, from which the system 200 diverts a portion to the C4 separation zone 250 as a C4-C5 bleed stream 252.

[0053] As mentioned, the C4 separation zone 250 generally separates the C4-C5 bleed stream 252 into one or more inert C4-rich streams and one or more reactive CT-Cs-rich streams, thereby enabling the one or more reactive C4-Cs-rich streams to be recycled for improved product yield. Within the C4 separation zone 250, the C4 flash column 254 separates the C4-C5 bleed stream 252 into a C4-rich stream 260 and a Cs-rich stream 262 (e.g., a reactive C4-C5-rich stream) The C4-rich stream 260 includes the unreacted butenes and the inert C4 compounds and the Cs-rich stream 262 includes the C5 olefins. In the illustrated example, the C4 flash column 254 is in fluid communication with the C4 separator 270 and supplies the C4-rich stream 260 to C4 separator 270. The C4 separator 270 is any suitable separation column, unit, or complex that separates one or more reactive C4 components from one or more inert C4 components. In some examples, the C4 separator 270 is a dividing-wall column (DWC). The DWC can incorporate the operations of two distillation columns into a single column or vessel. In some examples, the C4 separator 270 is a fractionator or super fractionator. For certain examples, the super fractionator can be a two-step or three-step fractionator having one or more fractionation or distillation columns. A first fractionation column can provide a top product stream of but-l-ene and 2-methylpropane and a bottom product stream of but-2-enes and butane. Based on the concentration of inert C4 compounds and a concentration setpoint for but-l-ene and/or but-2-enes, the super fractionator can include additional distillation columns to remove the inert C4 compounds from their respective product streams. As such, the C4 separator 270 separates out C4 components having relatively close boiling points from one another, such as butanes and butenes.

[0054] The C4 separator 270 receives the C4-rich stream 260 from the C4 flash column 254 and produces a but-l-ene-rich stream 272 (e.g., a reactive C4-C5-rich stream) from a top of the C4 separator 270, a butane-rich stream 274 (e.g., an inert C4-rich stream) from a side or middle draw of the C4 separator 270, and a but-2-ene-rich stream 276 (e.g., a reactive CT-CVrich stream) from a bottom of the C4 separator 270. Indeed, the C4 separator 270 can separate the components therein based on their boiling points, of which but-2-enes are the highest and but-l-ene is the lowest. The butane-rich stream 274 can be purged from the system 200, further processed, and/or directed to a steam cracker as a recycle stream, in some examples. Accordingly, removal of the butane-rich stream 274 containing the inert C4 compounds therein desirably reduces accumulation of inert compounds within the system 200.

[0055] Based on desired or target operations of the metathesis reactor 212, one or both of the but-l-ene-rich stream 272 and but-2-ene-rich stream 276 can be fully or partially recycled to the metathesis reactor 212. Indeed, the but-l-ene-rich stream 272 and but-2-ene-rich stream 276 of the illustrated example are recycled to the metathesis zone 210 along with the Cs-rich stream 262 and the remainder of the C4-Cs-rich stream 236 (e.g., that was not diverted to the C4 separation zone 250). One or more of these reactive C4-Cs-rich streams may be combined in any suitable manner upstream of the metathesis zone 210, in certain examples, to consolidate the number of inlets into the metathesis reactor 212. For example, the Cs-rich stream 262, the remainder of the CT-CVrich stream 236, the but-l-ene-rich stream 272, and/or the but-2-ene-rich stream 276 can be recycled to the metathesis zone 210 where the streams are combined with the pretreated C4 stream 208 before being metathesized to form the metathesis product stream 214. [0056] FIG. 3 is a schematic representation of a system 300 for production of desired olefins through metathesis of a C4 feed stream and recovery and recycle of a but-l-ene-rich stream and a combined reactive C5 and but-2-ene-rich stream, according to an example. The system 300 includes the treatment zone 304, the metathesis zone 310, the olefin separation zone 320, and the C4 separation zone 350, which each correspond to and include similar components as the zones discussed above with respect to FIG. 2. These components are similarly labeled, and their descriptions are not repeated in detail for improved clarity. As shown, the system 300 includes a single separator in the C4 separation zone 350 for recovery of reactive components to improve the operating efficiency of the system 300.

[0057] In particular, the system 300 includes a C4 separation zone 350 that is modified relative to the C4 separation zone 250 of FIG. 2. In the illustrated example, the C4 separation zone 350 includes a C4 fractionator 380 or super fractionator in place of the above-discussed C4 flash column and C4 separator. As such, the C4 fractionator 380 can combine the features of the C4 flash column and C4 separator in a single unit. The decision to select either the C4 flash column and C4 separator of FIG. 2 or the C4 fractionator 380 of the illustrated example can be determined based on properties of feedstocks, desired product yields, target operating and/or capital expenses, and so forth.

[0058] As discussed above, the C5 column 326 of the olefin separation zone 320 produces the C4-Cs-rich stream 336, and a portion of the CT-Cs-rich stream 336 is diverted from a recycle loop to the C4 separation zone 350 as a C4-C5 bleed stream 352. The C4 fractionator 380 receives the C4-C5 bleed stream 352 and produces a but-l-ene-rich stream 372 (e.g., a reactive C4-C5-rich stream) from a top of the C4 fractionator 380, a butane-rich stream 374 (e.g., an inert C4-rich stream) from a side or middle draw of the C4 fractionator 380, and a combined C5 olefin and but-2-ene-rich stream 376 (e.g., a reactive CT-CVrich stream, reactive C5 and but-2-ene-rich stream) from a bottom of the C4 fractionator 380. That is, the C5 olefin and but-2-ene-rich stream 376 of certain examples includes the both the C5 olefins and the but-2-enes respectively contained in the Cs-rich stream 262 and the but-2-ene-rich stream 276 produced by the C4 separation zone 250 of FIG. 2. Accordingly, the but-l-ene-rich stream 372 and the C5 olefin and but-2-ene-rich stream 376, along with the remainder of the C4-Cs-rich stream 336, can be recycled to the metathesis zone 310 where the streams are combined with the pretreated C4 stream 308 before being metathesized to form the metathesis product stream 314. [0059] FIG. 4 is a schematic representation of a control system 400 for controlling the examples of the system discussed above. The control system 400 includes at least one controller 401. Each controller 401 includes at least one processor 402, which may be or include a central processing unit (CPU), a graphics processing unit (GPU), a co-processing unit, a sub-processing unit, or any other suitable electronic data processor. Each controller 401 includes at least one memory 403, which may be or include random access memory (RAM), read-only memory (ROM), or any other suitable electronic memory or storage. For the illustrated example, the controller 401 is communicatively connected to or in signal communication with each of the zones present in a particular implementation of the systems discussed above. For example, the controller 401 can be communicatively coupled to a treatment zone 404, a metathesis zone 410, an olefin separation zone 420, and a C4 separation zone 450. The controller 401 can further be communicatively connected to any other elements that are included in or facilitate operation of the systems discussed above. The communicative connection between the controller 401 and the various zones and devices enables the controller 401 to receive monitoring and operational data from sensors and/or sub-controllers of each of these zones or devices present in the examples discussed above, and further enables the controller 401 to provide control signals (e.g., electrical signals, instructions, data packets) to modify the operation of each of these zones or devices.

[0060] The controller 401 can implement any suitable monitoring, analysis, and/or actuation steps to control the treatment zone 404, the metathesis zone 410, the olefin separation zone 420, and the C4 separation zone 450 operating in a suitable system. For example, the controller 401 may receive monitoring data from sensors (e.g., temperature sensors, pressure sensors, flow sensors, content analyzers) of the treatment zone 404, and based on predefined threshold values for certain operational parameters, provide suitable control signals to modify the operation of one or more components of the treatment zone 404 to ensure that the one or more guard beds therein operate in accordance with any predefined threshold values. Additionally, the controller 401 may receive monitoring data from sensors of the metathesis zone 410, and based on predefined threshold values for certain operational parameters, provide suitable control signals to modify the operation of one or more components of the metathesis zone 410 to ensure that the metathesis reactors therein operate within the temperatures, pressures, and WHSV disclosed above, and to manage the regeneration mode operation and standby operation of the metathesis reactor. The controller 401 may receive monitoring data from sensors of the olefin separation zone 420 and/or the C4 separation zone 450, and based on predefined threshold values for certain operational parameters, provide suitable control signals to modify the operation of one or more components of these zones, such that the components of these zones operate in accordance with any predefined threshold values.

Examples

[0061] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated and, therefore, are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some deviations should be accounted for.

[0062] There are numerous variations and combinations of reaction conditions, for example, component concentrations, desired solvents, solvent mixtures, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0063] Example 1 :

[0064] The systems and methods disclosed herein can efficiently utilize various C4 feedstocks to produce desired chemicals, at improved yields. In some examples, the C4 feedstock has a composition in accordance with a C4 raffinate II stream or a C4 raffinate III stream. As non-limiting examples, Table- 1 shown below illustrates sample compositions of two different C4 raffinate streams.

[0065] Table- 1: Composition of examples of C4 feedstocks

[0066] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0067] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific examples of the disclosure, are given by way of illustration only and are not meant to be limiting. In further examples, features from specific examples may be combined with features from other examples. For example, features from one example may be combined with features from any of the other examples. In further examples, additional features may be added to the specific examples described herein. It should be understood that although the disclosure contains certain aspects, examples, and optional features, modification, improvement, or variation of such aspects, examples, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.

Claims

1. A method for producing chemicals, the method comprising: supplying a C4 feed stream containing about 0.1-30 mole percent (mol. %) inert C4 compounds to a metathesis reactor containing a metathesis catalyst to produce a metathesis product stream containing ethene, propene, unreacted butenes, the inert C4 compounds, C5 olefins, and Ce olefins; supplying the metathesis product stream to a C3 distillation column to produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes, the inert C4 compounds, the C5 olefins, and the Ce olefins; supplying the C2-C3 product stream to a C2/C3 splitter to produce an ethene product stream and a propene product stream; supplying the C4+-rich stream to a C5 column to produce a C4-C5 recycle stream containing the unreacted butenes, the inert C4 compounds, and the C5 olefins and a Ce product stream containing the Ce olefins; diverting a portion of the C4-C5 recycle stream as a C4-C5 bleed stream to a C4 separation zone having at least one separator to produce one or more inert C4-rich streams and one or more reactive C4-Cs-rich streams; and recycling the one or more reactive C4-Cs-rich streams and a remainder of the C4-C5 recycle stream to the metathesis reactor along with the C4 feed stream.

2. The method of claim 1, wherein the at least one separator comprises a flash column, and wherein the method further comprises: cooling the C4-C5 bleed stream to a flash temperature threshold; and supplying the C4-C5 bleed stream to the flash column to produce a C4-rich stream as the one or more inert C4-rich streams and a Cs-rich stream as the one or more reactive C4-C5-rich streams.

3. The method of claim 1, wherein the at least one separator comprises a flash column and a C4 separator that includes a dividing-wall column or a fractionator, and wherein the method further comprises: cooling the C4-C5 bleed stream to a flash temperature threshold; and supplying the C4-C5 bleed stream to the flash column to produce a Cs-rich stream as the one or more reactive C4-Cs-rich streams and C4-rich stream; and supplying the C4-rich stream to the C4 separator to produce a but-l-ene-rich stream and a but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

4. The method of claim 1, wherein the at least one separator comprises a C4 fractionator, and wherein the method further comprises: supplying the C4-C5 bleed stream to the C4 fractionator to produce a but-l-ene-rich stream and a C5 olefin and but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

5. The method of any of claims 1-4, wherein the C4 feed stream contains about 20-30 mol. % of the inert C4 compounds and contains at least 15 mol. % of but-l-ene.

6. The method of any of claims 1-5, further comprising: removing one or more contaminants from the C4 feed stream upstream of the metathesis reactor with one or more guard beds containing adsorbent, wherein the one or more contaminants comprise a sulfur compound, a salt compound, a metal, or a combination thereof.

7. The method of any of claims 1-6, wherein the C4 feed stream is sourced from a steam cracker, a fluid catalytic cracker, or a methanol-to-olefins unit.

8. The method of any of claims 1-7, wherein the metathesis catalyst comprises a rhenium oxide-coated y-alumina-based catalyst that is non-reactive to the inert C4 compounds.

9. A system for producing chemicals, the system comprising: a metathesis reactor containing a metathesis catalyst and configured to receive a C4 feed stream containing about 0.1-30 mole percent (mol. %) inert C4 compounds and produce a metathesis product stream containing ethene, propene, unreacted butenes, the inert C4 compounds, C5 olefins, and Ce olefins; a C3 distillation column configured to receive the metathesis product stream and produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes, the inert C4 compounds, the C5 olefins, and the Ce olefins; a C2/C3 splitter configured to receive the C2-C3 product stream and produce an ethene product stream and a propene product stream; a C5 column configured to receive the C4+-rich stream and produce a C4-C5 recycle stream containing the unreacted butenes, the inert C4 compounds, and the C5 olefins and a Ce product stream containing the Ce olefins; and a C4 separation zone having at least one separator and configured to receive a diverted portion of the C4-C5 recycle stream as a C4-C5 bleed stream and produce one or more inert C4-rich streams and one or more reactive CACs-rich streams, the one or more reactive C4-Cs-rich streams and a remainder of the C4-C5 recycle stream being routed to the metathesis reactor along with the C4 feed stream to produce the metathesis product stream.

10. The system of claim 9, wherein the at least one separator comprises a flash column configured to separate the C4-C5 bleed stream into a C4-rich stream as the one or more inert C4-rich streams and a Cs-rich stream as the one or more reactive CT-Cs-rich streams.

11. The system of claim 9, wherein the at least one separator comprises a flash column and a C4 separator that includes a dividing-wall column or a fractionator, and wherein: the flash column is configured to separate the C4-C5 bleed stream into a Cs-rich stream as the one or more reactive C4-Cs-rich streams and a C4-rich stream; and the C4 separator is configured to separate the C4-rich stream into a but- 1-ene- rich stream and a but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

12. The system of claim 9, wherein the at least one separator comprises a C4 fractionator configured to separate the C4-C5 bleed stream into a but-l-ene-rich stream and a C5 olefin and but-2-ene-rich stream as the one or more reactive C4-Cs-rich streams and a butane-rich stream as the one or more inert C4-rich streams.

13. The system of any of claims 9-12, wherein the C4 feed stream contains about 20-30 mol. % of the inert C4 compounds, and wherein the inert C4 compounds include butane and 2-methylpropane.

14. The system of any of claims 9-12, further comprising: one or more guard beds containing adsorbent and configured to remove one or more contaminants from the C4 feed stream upstream of the metathesis reactor.

15. The system of claim 14, wherein the adsorbent comprises oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and wherein the one or more contaminants comprise a sulfur compound, a salt compound, a metal, or a combination thereof.