Systems and methods for metathesis to produce propene and HEX‑1-ENE from pretreated butene feedstock

Abstract

Provided here are methods for chemical production that include receiving a C4 feed stream containing one or more contaminants, supplying the C4 feed stream to one or more guard beds to produce a pretreated C4 feed stream with reduced contaminants, and supplying the pretreated C4 feed stream to a metathesis reactor to produce a metathesis product stream containing ethene, propene, unreacted butenes, and C6 olefins. The method further includes supplying the metathesis product stream to a light distillation column to produce a C2-C3 product stream and a C4+-rich stream containing the unreacted butenes and the C6 olefins, and 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 heavy distillation column to produce a recycle stream containing the unreacted butenes and a heavy product stream containing the C6 olefins.

Description

SYSTEMS AND METHODS FOR METATHESIS TO PRODUCE PROPENE AND HEX-l-ENE FROM PRETREATED BUTENE FEEDSTOCKCross-Reference to Related Applications

[0001] This application claims priority to and the benefit of European Application No. EP23216354.3, filed on December 13, 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 propene, hex-3-ene, and / or and hex-1 -ene from pretreated butene feedstock using metathesis reactions.Background

[0003] There is continued interest in production of light olefins, such as ethene and propene. These olefins have notable commercial viability, and may be produced in various manners. For example, ethene and propene may be produced by steam cracking of hydrocarbon feeds. In some cases, propene may be produced as a byproduct from steam cracking of hydrocarbons such as propane, natural gas liquid (NGL), and naphtha, as well as from fluid catalytic cracking (FCC) process in refineries. Due to the increasing availability of shale gas, the industry is shifting toward the use of lighter feedstocks in steam crackers. As such, this trend reduces an amount of propene that is produced as a byproduct from steam crackers. Additionally, the use of FCC to produce propene is also expected to decrease in the near future, such as based on a decrease in gasoline demand. Difference between demand and supply of propene is expected to increase based on these trends, among others.Summary

[0004] The present disclosure provides versatile, efficient systems and methods for the production of propene, hex-3-ene, and / or and hex-l-ene from pretreated butene feedstock using metathesis reactions. 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 various feedstock pretreatment steps or components, with an optional inclusion of upstream separation steps or components, to prepare the feedstock for processing in a metathesis reactor. The present disclosure includes a process for metathesis of a C4 product stream that is rich in but-l-ene and but-2-enes and that may be optionally integrated with a recycle stream containing ethene. This recycle stream may be supplied along with a recycle stream containing C5 olefins. The advancements disclosed herein may be broadly applied to various metathesis reactions, including those for C2 to C12 olefins.

[0005] In more detail, the C4 product stream or feedstock from the steam cracker may be directed through one or multiple operations, as discussed herein, to enrich the value of the C4 product stream. During this process, certain components may accumulate or build-up in the C4 product stream. For example, alcohols and oxygenates may come from methyl tert- butyl ether (MTBE) processes. Additionally, hydrogenation processes may include slippage of buta-l,3-dien, such as selective hydrogenation unit (SHU) processes. In some cases, high concentration of butanes can accumulate in the C4 product stream based on any upstream failure operations. For example, butane accumulation can result from excessive hydrogenation at a SHU and / or based on qualities of the feedstock that is processed in the steam cracker. The systems and methods disclosed herein thus address these issues via feed pretreatment steps, which may be optionally integrated with certain upstream operations and / or separations to prepare the feedstock for improved metathesis processing into high-value components.

[0006] 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. Additionally, a secondary metathesis reactor can be included to utilize C5 olefins along with ethene to produce additional propene and but-l-ene as products, thus decreasing an operating load of the first or primary metathesis reactor. One or both of the metathesis reactors may be fixed- bed reactors operating at low reaction temperatures and with a rhenium oxide-coated y-alumina- based catalyst (Re2O7 / yAhO3), in some examples. In some examples, isomers of Ce olefins can be valorized to produce hex-l-ene product streams via targeted isomerization in an isomerization reactor. The isomerization reactor can be a fixed-bed reactor operating with a KzO / y-AbChcatalyst, in some examples. Based on a current market demand, the present examples may optionally produce Cs and Ce intermediate olefins and / or enhance ethene and propene production, such as via metathesis processing alone or processing with an integrated steam cracker. These examples therefore provide flexibility to operate and produce the most desirable products of interest based on the current market demand.

[0007] The disclosure herein provides several embodiments of systems for the production of chemicals, such as propene, hex-3-ene, and / or and hex-1 -ene, and methods for producing chemicals. Examples include a method for producing chemicals that includes receiving a C4 feed stream containing one or more contaminants from a steam cracker. The method further includes supplying the C4 feed stream to one or more guard beds to produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants, and removing one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds. The method further includes supplying the pretreated C4 feed stream to a metathesis reactor containing a metathesis catalyst to produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins. The method further includes supplying the metathesis product stream to a light distillation column to produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes and the Ce olefins, and 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 heavy distillation column to produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins, and recycling the recycle stream to the metathesis reactor.

[0008] In some examples, the one or more contaminants include a sulfur compound, a salt compound, a metal, or a combination thereof. In some examples, the one or more guard beds include a plurality of layers of adsorbent, and the adsorbent includes oxides, molecular sieves, zeolites, activated carbon, or a combination thereof. In some examples, the method further includes removing one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor. In some examples, the method further includes fractionating the pretreated C4 feed stream upstream of the metathesis reactor to produce a but-l-ene-rich stream and a but-2-ene- rich stream, and supplying the but-l-ene-rich stream and the but-2-ene-rich stream to the metathesis reactor. In some examples, the heavy distillation column includes a C5 column and the recycle stream contains C5 olefins. In some examples, the heavy distillation column includes a C4column and the heavy product stream contains Cs olefins. In some examples, the method further includes supplying the ethene product stream and the Cs olefins to an additional metathesis reactor to produce a but-l-ene product stream and an additional propene stream. In some examples, the method further includes recycling the but-l-ene product stream to the metathesis reactor. In some examples, the heavy product stream contains hex-3 -ene, and the method further includes supplying the heavy product stream to an isomerization reactor containing an isomerization catalyst to produce an isomerized product stream in which at least a portion of the hex-3 -ene is converted into hex- 1 -ene. In some examples, the method further includes supplying the isomerized product stream to a Ce fractionator to produce a purified product stream containing the hex- 1 -ene. In some examples, the metathesis catalyst includes a rhenium oxide-coated y-alumina-based catalyst. In some examples, supplying the pretreated C4 feed stream to the metathesis reactor to produce the metathesis product stream includes operating the metathesis reactor at a temperature in a range between 35 and 100 degrees Celsius (°C).

[0009] Examples include a system for producing chemicals that includes one or more guard beds configured to receive a C4 feed stream containing one or more contaminants from a steam cracker and produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants. The system includes a C4 column in fluid communication with the one or more guard beds and configured to remove one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds. The system includes a metathesis reactor containing a metathesis catalyst and configured to receive the pretreated C4 feed stream and produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins. The system includes a light 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 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 heavy distillation column configured to receive the C4+-rich stream and produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins. The recycle stream is routed to the metathesis reactor along with the pretreated C4 feed stream to produce the metathesis product stream.

[0010] In some examples, the one or more contaminants include a sulfur compound, a salt compound, a metal, or a combination thereof. In some examples, the system further includes a C5column in fluid communication with the C4 column and configured to remove one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C4. In some examples, the system further includes a C4 fractionator in fluid communication with the C5 column and configured to fractionate the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C5 column to produce a but- l-ene- rich stream and a but- 2-ene-rich stream. The but-l-ene-rich stream and the but-2-ene-rich stream are each supplied to the metathesis reactor as the pretreated C4 feed stream. In some examples, the recycle stream contains C5 olefins. In some examples, the heavy product stream contains C5 olefins, and the system further includes an additional metathesis reactor configured to receive the ethene product stream and the C5 olefins and produce a but-l-ene product stream and an additional propene stream. The but-l-ene-rich stream is routed to the metathesis reactor along with the pretreated C4 feed stream to produce the metathesis product stream. In some examples, the system further includes an isomerization reactor containing an isomerization catalyst and configured to receive the heavy product stream and produce an isomerized product stream in which at least a portion of hex-3-ene is converted into hex-l-ene.

[0011] Still other aspects and advantages of these exemplary embodiments 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 embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.Brief Description of the Drawings

[0012] 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.

[0013] FIG. 1 is a schematic representation of a system for pretreating a feedstock from which desired olefins are produced, according to an example.

[0014] FIG. 2 is a schematic representation of a system for pretreating and separating a feedstock from which desired olefins are produced, according to an example.

[0015] FIG. 3 is a schematic representation of a system for pretreating and additionally separating a feedstock from which desired olefins are produced, according to an example.

[0016] FIG. 4 is a schematic representation of a system for pretreating and further separating a feedstock from which desired olefins are produced, according to an example.

[0017] FIG. 5 is a schematic representation of a system for pretreating and further separating a feedstock from which desired olefins are produced, including recycle of Cs olefins and ethene, according to an example.

[0018] FIG. 6 is a schematic representation of a system for pretreating and further separating a feedstock from which desired olefins are produced, including two metathesis reactors, according to an example.

[0019] FIG. 7 is a schematic representation of a system for pretreating and further separating a feedstock from which desired olefins are produced, including two metathesis reactors and an isomerization reactor, according to an example.

[0020] FIG. 8 is a schematic representation of a system for pretreating and further separating a feedstock from which desired olefins are produced, including recycle of Cs olefins and ethene and an isomerization reactor, according to an example.

[0021] FIG. 9 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

[0022] 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 thesystems 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.

[0023] 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 embodiments of the present disclosure, are synonymous.

[0024] 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 embodiments, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting embodiment, 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 embodiments, “about” refers to the specified value.

[0025] 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.

[0026] As used herein, the term “Cx-Cycompounds,” 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 refers to a mixture that substantially contains or entirely contains hydrocarbon-based compounds, each compound containing 3, 4, or 5carbon atoms. 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.

[0027] 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.

[0028] The present disclosure describes various examples related to systems and methods for the production of propene, hex-3-ene, and / or and hex-l-ene from a butene feedstock that is pretreated and metathesized. The present disclosure is directed to a feedstock treatment and olefin production system and methods for treating feedstocks for improved olefin production, while leveraging additional byproducts for enhanced overall system performance. The present disclosure further increases the yield of desired olefins, such as propene, hex-3-ene, and / or and hex-l-ene, through different process configurations and feedstock treatments, which are discussed below. Each system includes a treatment zone integrated with a metathesis zone and an olefin separation zone. The treatment zone is upstream of the metathesis zone, and the metathesis zone is upstream of the olefin separation zone. In some examples, the system further includes a feedstock separation zone integrated between the treatment zone and the metathesis zone for improved processing of a feedstock supplied to the system, such as from a feedstock provided directly from a steam cracker. The feedstock separation zone and the olefin separation zone interoperate with one another to provide for advantageous separation of unconverted feed components and product components. In some examples, the system further includes an additional metathesis zone, integrated with the metathesis zone and the olefin separation zone for increased yield of propene. In some examples,the system further includes an isomerization zone, integrated downstream of the olefin separation zone to increase the yield of hex-l-ene.

[0029] As will be understood, the treatment zone facilitates improved production of valuable olefins, such as propene, hex-3-ene, and / or and hex-l-ene. In some examples, concentrations of but-l-ene and but-2-enes in the feedstock provided to the treatment zone heavily influence the system and method to be utilized. In some examples, the feedstock contains greater than 20 wt. % of but-l-ene, along with but-2-enes and inert components such as / ?-butane, propane, and so forth. In some examples, the feedstock contains greater than 25 wt. %, or 30 wt. %, or 35 wt. %, or 40 wt. %, or 50 wt. % of but-l-ene. In some examples, the feedstock contains greater than 60 wt. %, or 70 wt. %, or 75 wt. % of but-l-ene. In some examples, the feedstock contains up to 90 wt. %, or 91 wt. %, or 92 wt. %, or 93 wt. %, or 94 wt. %, or 95 wt. %, or 96 wt. %, or 97 wt. %, or 98 wt. % of but-l-ene.

[0030] 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), 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 SHU, a MTBE reactor, a but-l-ene (Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, an MTO (methanol-to-olefins) process or refinery, and / or an FCC downstream process. As non-limiting examples, sample compositions of two different C4 feedstocks are provided in Table 1, shown below.

[0031] Table- 1: Composition of examples of C4 feedstocks

[0032] 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 (Re2O7 / yAhO3) 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.

[0033] 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.

[0034] 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.

[0035] 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-coatedy-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.

[0036] 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-l-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.

[0037] As noted herein, certain examples include an isomerization reactor to convert hex-2-ene and / or hex-3 -ene produced in the metathesis reactor to hex-l-ene. This Ce isomerization reactor can be operated at temperatures ranging from 350 to 500 °C, using a liquid feed, vapor feed or mixed phase feed. Operating pressures of the isomerization reactor can range from 0 barg to pressures up to 30 bar. However, it is noted that the isomerization reaction is pressure independent, and the process can generally be performed at a pressure that best suits the upstream and downstream operations. The isomerization catalyst can be a K2O / y-AhO3 catalyst. In some examples, the isomerization reactor produces a product or effluent stream that is provided to a Ce fractionator, in which hex-l-ene is separated as a desired product from other Ce olefins. Further, unconverted (t / c) hex-2-enes and (t / c) hex-3-enes can be separated from the bottom of the Ce fractionator and recycled back to the isomerization reactor for increased yield of hex-l-ene.

[0038] In an example, a method for producing chemicals includes receiving a C4 feed stream containing one or more contaminants from a steam cracker. The method further includes supplying the C4 feed stream to one or more guard beds to produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants, and removing one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds. The method furtherincludes supplying the pretreated C4 feed stream to a metathesis reactor containing a metathesis catalyst to produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins. The method further includes supplying the metathesis product stream to a light distillation column to produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes and the Ce olefins, and 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 heavy distillation column to produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins, and recycling the recycle stream to the metathesis reactor.

[0039] In some examples, the one or more contaminants include a sulfur compound, a salt compound, a metal, or a combination thereof. In some examples, the one or more guard beds include a plurality of layers of adsorbent, and the adsorbent includes oxides, molecular sieves, zeolites, activated carbon, or a combination thereof. In some examples, the method further includes removing one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor. In some examples, the method further includes fractionating the pretreated C4 feed stream upstream of the metathesis reactor to produce a but-l-ene-rich stream and a but-2-ene- rich stream, and supplying the but-l-ene-rich stream and the but-2-ene-rich stream to the metathesis reactor. In some examples, the heavy distillation column includes a C5 column and the recycle stream contains C5 olefins. In some examples, the heavy distillation column includes a C4 column and the heavy product stream contains C5 olefins. In some examples, the method further includes supplying the ethene product stream and the C5 olefins to an additional metathesis reactor to produce a but-l-ene product stream and an additional propene stream. In some examples, the method further includes recycling the but-l-ene product stream to the metathesis reactor. In some examples, the heavy product stream contains hex-3 -ene, and the method further includes supplying the heavy product stream to an isomerization reactor containing an isomerization catalyst to produce an isomerized product stream in which at least a portion of the hex-3 -ene is converted into hex- 1 -ene. In some examples, the method further includes supplying the isomerized product stream to a Ce fractionator to produce a purified product stream containing the hex- 1 -ene. In some examples, the metathesis catalyst includes a rhenium oxide-coated y-alumina-based catalyst. In some examples, supplying the pretreated C4 feed stream to the metathesis reactor to produce themetathesis product stream includes operating the metathesis reactor at a temperature in a range between 35 and 100 °C.

[0040] In an example, a system for producing chemicals includes one or more guard beds configured to receive a C4 feed stream containing one or more contaminants from a steam cracker and produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants. The system includes a C4 column in fluid communication with the one or more guard beds and configured to remove one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds. The system includes a metathesis reactor containing a metathesis catalyst and configured to receive the pretreated C4 feed stream and produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins. The system includes a light 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 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 heavy distillation column configured to receive the C4+-rich stream and produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins. The recycle stream is routed to the metathesis reactor along with the pretreated C4 feed stream to produce the metathesis product stream.

[0041] In some examples, the one or more contaminants include a sulfur compound, a salt compound, a metal, or a combination thereof. In some examples, the system further includes a C5 column in fluid communication with the C4 column and configured to remove one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C4. In some examples, the system further includes a C4 fractionator in fluid communication with the C5 column and configured to fractionate the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C5 column to produce a but- 1-ene- rich stream and a but- 2-ene-rich stream. The but-l-ene-rich stream and the but-2-ene-rich stream are each supplied to the metathesis reactor as the pretreated C4 feed stream. In some examples, the recycle stream contains C5 olefins. In some examples, the heavy product stream contains C5 olefins, and the system further includes an additional metathesis reactor configured to receive the ethene product stream and the C5 olefins and produce a but-l-ene product stream and an additional propene stream. The but-l-ene-rich stream is routed to the metathesis reactor along with the pretreated C4feed stream to produce the metathesis product stream. In some examples, the system further includes an isomerization reactor containing an isomerization catalyst and configured to receive the heavy product stream and produce an isomerized product stream in which at least a portion of hex-3-ene is converted into hex-l-ene.

[0042] FIG. 1 is a schematic representation of a system 100 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, 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), and a C4 column (or heavy distillation column or debutenizer) that provides a butene recycle stream to the metathesis reactor. In additional detail, the system 100 facilitates pretreatment and metathesis of a C4 stream 102 or butene feedstock to produce chemical feedstocks. As illustrated, the system 100 includes a treatment zone 104, a metathesis zone 140, and an olefin separation zone 150.

[0043] In some embodiments, the C4 stream 102 is a C4 raffinate stream. In some embodiments, the C4 stream 102 is produced from a steam cracker or steam cracker furnace. The steam cracker can be positioned at a common facility or shared physical location as the system 100, in some cases. In some embodiments, 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 embodiments, 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 C5 compounds, such as pentenes, in combination with the C4 compounds.

[0044] For the illustrated embodiment, the C4 stream 102 is directed to the treatment zone 104 and introduced into a guard bed 106 to produce a pretreated C4 stream 108 (or pretreated C4 feed stream) having a reduced amount of one or more impurities therein. For example, the guard bed 106 can pretreat the C4 stream 102 to remove impurities therefrom, including sulfur, salt content, and / or metals. In some examples, the guard bed 106 can remove oxygenates such as MTBE, methoxymethane or dimethyl ether (DME), methanol, and so forth from the C4 stream 102. Indeed,the guard bed 106 of certain examples can remove alcohols, oxygenates, green oil (heavy hydrocarbons), ethers, mercaptans, sulfides, and / or nitrogen compounds, such as 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. For example, certain examples include a minor selective hydrogenation unit to address any buta-l,3-diene in the C4 stream 102. In some examples, the treatment zone 104 includes multiple guard beds 106 therein, which can be implemented in series operation, in parallel operation, or a combination thereof. Each guard bed 106 may remove one or more types of contaminants, in some examples, such as a first guard bed 106 that removes a first type of contaminant and a second guard bed 106 that removes a second type of contaminant. For example, the guard beds 106 can contain adsorbents that are provided in different, respective layers. The adsorbents of certain examples are provided in one or more layers of high-surface-area or special / proprietary aluminum oxides, proprietary Ti, Zn, and / or Mg oxides, Type 13X molecular sieves, zeolites, activated carbon, and / or any combination thereof. In some examples, multiple guard beds 106 are combined within a suitable vessel through which the C4 stream 102 travels. Additionally, 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. The pretreated C4 stream 108 is thus prepared and conditioned before exiting the treatment zone 104

[0045] From the treatment zone 104, the pretreated C4 stream 108 is directed to the metathesis zone 140 and introduced into a metathesis reactor 142 in fluid communication with the guard bed 106. As such, the metathesis reactor 142 produces a metathesis product stream 144 that contains a mixture of C2-C6 olefin metathesis products. In an example, the metathesis product stream 144 contains ethene, propene, unreacted butenes, C5 olefins, and Ce olefins. In certain examples, the Ce olefins include hex-l-ene. The metathesis reactor 142 can operate with any suitable liquid feed, vapor feed, or mixed phase feed. The metathesis reactor 142 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 self-metathesis and cross-metathesis of pent-l-ene.

[0046] In some examples, the metathesis zone 140 includes multiple metathesis reactors 142 therein, which can be implemented in series or in parallel operation. In some embodiments, 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 142 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 142 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 142 reduce the operational cost and energy demands of the reactor compared to other systems. The operating pressures of the metathesis reactor 142 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 embodiments, the metathesis reactor 142 does not receive an ethene co-feed, which desirably avoids consumption of the higher value ethene olefin chemical feedstock to facilitate metathesis.

[0047] It is presently recognized that 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 embodiments, this is achieved by limiting the flow rate of C4 stream 102 into the metathesis reactor 142 to a weight hourly space velocity (WHSV) of between 0.1 h'1and 25 h’1, such as values between 0.5 h'1and 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 attemperatures 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 off-line, and / or with continuous catalyst replacement.

[0048] In the illustrated example, the metathesis product stream 144 exits the metathesis zone 140 and is directed to the olefin separation zone 150. For the illustrated embodiment, the olefin separation zone 150 includes a C3 column 152, a C2 / C3 splitter 154, and a C4 column 156. The metathesis product stream 144 is directed to the C3 column 152, which is in fluid communication with the metathesis reactor 142. The C3 column 152 separates the metathesis product stream 144 into a C2-C3 olefin stream 158 and a C4+-rich stream 160 or C4+ olefin stream. The C2-C3 olefin stream 158 contains ethene and propene, and the C4+-rich stream 160 contains the unreacted butenes, the C5 olefins, and the Ce olefins from the metathesis product stream 144. The C2-C3 olefin stream 158 is supplied to the C2 / C3 splitter 154, which is in fluid communication with the C3 column 152. The C2 / C3 splitter 154 separates ethene and propene of the C2-C3 olefin stream 158 into an ethene product stream 162 and a propene product stream 164.

[0049] For the illustrated embodiment, the C4+-rich stream 160 is directed to the C4 column 156, which is in fluid communication with the C3 column 152. The C3 column 152 separates the C4+-rich stream 160 into a C4 olefin stream 166 and a C5-C6 olefin stream 168. The C4 olefin stream 166 contains the unreacted butenes of the C4+-rich stream 160. In some embodiments, the C4 olefin stream 166 may include a limited amount of paraffins (e.g., butane, 2-methylpropane) that can be purged from the C4 olefin stream 166 and generate a purged stream 170. It may be appreciated that the purged stream 170 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. After any paraffin or other content removal, the C4 olefin stream 166 is sent to the metathesis zone 140 as a recycle stream, thus enabling conversion of any unreacted butenes therein. That is, the C4 olefin stream 166 is recycled to the metathesis zone 140 where it is combined with the pretreated C4 stream 108 before being metathesized to form the metathesis product stream 144. The C4 column 156 is thus in fluid communication with the metathesis reactor 142 to facilitate this recycle. The C5-C6 olefin stream 168 is output by the system 100 as a heavy product stream containing C5 and Ce internal olefins. In some examples, the Cs-Ce olefin stream 168 is provided or sold as gasoline octane boosters. In some examples, the Cs-Ce olefin stream 168 is provided as internal olefins to produce linearinternal olefins via further isomerization or utilized in a steam cracker to produce additional high value products.

[0050] FIG. 2 is a schematic representation of a system 200 for the pretreatment of a C4 stream 202 or feedstock and production of desired olefins through metathesis, according to an example. The system 200 includes the treatment zone 204, the metathesis zone 240, and the olefin 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 separation operation or C4 column for enhanced feedstock conditioning.

[0051] In particular, the system 200 includes a feedstock separation zone 210 integrated between the treatment zone 204 and the metathesis zone 240. For the illustrated example, the pretreated C4 stream 208 exits the treatment zone 204 and is directed to the feedstock separation zone 210. The feedstock separation zone 210 of the illustrated example includes a C4 column 212 (second C4 column or C3 / C4 column). The C4 column 212 receives the pretreated C4 stream 208 and produces a C3--rich stream 214 and C4+-rich stream 216. That is, the C4 column 212 can remove any undesirable C3- hydrocarbons, such as hydrogen and Ci, C2, and C3 compounds, from more valuable C4+ hydrocarbons of the pretreated C4 stream 208 that are to be metathesized. The C4 column 212 can be a separation column or a simple flash column. The C4 column 212 is in fluid communication with the guard bed 206 and the metathesis reactor 242. As such, the C3--rich stream 214 is free of contaminants that were removed in the guard bed 206 upstream of the C4 column 212, thereby enabling the C3--rich stream 214 to be efficiently directed for further use or export as a purified product.

[0052] As illustrated, the C4 column 212 separates the C4+-rich stream 216 from the lower- value C3--rich stream 214, which can be recycled to a steam cracker upstream of the system 200 or supplied to another suitable steam cracker to be upgraded into higher-value products. In some examples, the C3--rich stream 214 is recycled to the steam cracker that initially produced the C4 stream 202. After removal of these light components, the C4+-rich stream 216 is thus directed to the metathesis zone 240 and the metathesis reactor 242 therein. As such, the C4+-rich stream 216 is combined with the C4 olefin stream 266 that is produced by the C4 column 256 and recycled to the metathesis reactor 242. In combination, the feed pretreatment and removal of unwantedhydrocarbons discussed herein and below improves operation and yields of the metathesis reactor 242

[0053] FIG. 3 is a schematic representation of a system 300 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. The system 300 includes the treatment zone 304, the feedstock separation zone 310, the metathesis zone 340, and the olefin separation zone 350, which each correspond to and include similar components as the zones discussed above with respect to the system 200 of FIG. 2. These components are similarly labeled, and their descriptions are not repeated in detail for improved clarity. As shown, the system 300 includes an additional separation operation or C5 column for enhanced feedstock conditioning via the feedstock separation zone 310.

[0054] For example, the system 300 includes a feedstock separation zone 310 that is modified relative to the feedstock separation zone 210 of FIG. 2. In the illustrated embodiment, the feedstock separation zone 310 further includes a C5 column 318 (C4 / C5 column) that is downstream of the C4 column 312. In some examples, the pretreated C4 stream 308 contains C5+ hydrocarbons that may be desirably removed before remaining components of the pretreated C4 stream 308 are processed. For example, the C4 column 312 receives the pretreated C4 stream 308 and produces the C3--rich stream 314 and the C4+-rich stream 316, which is supplied to the C5 column 318. The C4 column 312 is in fluid communication with the guard bed 206 and the C5 column 318, and the C5 column 318 is in fluid communication with the C4 column 312 and the metathesis reactor 342.

[0055] The C5 column 318 receives the C4+-rich stream 316 and produces a C4 stream 320 and a Cs+-rich stream 322. The C5+- rich stream 322 can be directed from the C5 column 318 to be utilized in a steam cracker to produce additional high value products, in some examples. After desired component rejections, the C4 stream 320 is thus directed to the metathesis zone 340 and the metathesis reactor 342 therein. For example, the C4 stream 320 can be combined with the C4 olefin stream 366 that is directed to the metathesis reactor 342 from the C4 column 356. In combination, the feed pretreatment and additional sorting and removal of unwanted hydrocarbons improves operation and yields of the metathesis reactor 342.

[0056] FIG. 4 is a schematic representation of a system 400 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. The system 400 includes the treatment zone 404, the feedstock separation zone 410, the metathesis zone 440, and the olefin separation zone 450, which each correspond to and include similar components asthe zones discussed above with respect to the system 300 of FIG. 3. These components are similarly labeled, and their descriptions are not repeated in detail for improved clarity. As shown, the system 400 includes an additional separation operation or C4 fractionator for enhanced feedstock conditioning via the feedstock separation zone 410. That is, the feedstock separation zone 410 of the illustrated embodiment further includes a C4 fractionator 424 that is downstream of and in fluid communication with the C5 column 418, as well as upstream of and in fluid communication with the metathesis reactor 442.

[0057] In some examples, the pretreated C4 stream 408 contains inert C4 components, such as / ?-butane and 2-methylpropane ( / .s -butane). To further reduce a load of the metathesis reactor 442 and / or decrease the feed recycle quantity utilized for metathesis in the metathesis reactor 442, the present examples may include the C4 fractionator 424 to separate out C4 components having relatively close boiling points, such as butanes and butenes. The C4 fractionator 424 can be a distillation column, separation column, or super fractionator, in some examples. The C4 fractionator 424 receives the C4 stream 420 from the C5 column 418 and produces a but-l-ene-rich stream 426 from a top of the C4 fractionator 424, a butane-rich stream 428 from a side or middle draw of the C4 fractionator 424, and a but-2-ene-rich stream 430 from a bottom of the C4 fractionator 424. Indeed, the C4 fractionator 424 can separate the components therein based on their boiling points, of which but-2-ene is the highest and but-l-ene is the lowest. Based on desired on target operations of the metathesis reactor 442, one or both of the but-l-ene-rich stream 426 and but-2-ene-rich stream 430 can be fully or partially recycled to the metathesis reactor 442. The butane-rich stream 428 can be directly sent to the steam cracker as a recycle stream, in some examples. In some examples, the butane-rich stream 428 can be further processed before this recycling.

[0058] As recognized, this integrated arrangement of separation units facilitates additional control of the concentration of components in the one or more streams fed to the metathesis reactor 442. For example, preselected thresholds can be set and maintained for but-l-ene and but-2-ene as denoted via any suitable units, such as ratios, mol. %, and / or wt. %. In addition, this control allows the metathesis reactor 442 to produce a flexible array of chemical products, which can be readily modified to suit any change in chemical demand. In some examples, the C4 stream provided to the system 400 contains at least a threshold amount of buta-l,3-diene (e.g., greater than 30 ppm), and the system 400 and / or the treatment zone 404 can include a minor selective hydrogenation unit forfurther feed conditioning. Accordingly, the system 400 produces Cs and Ce intermediate olefins at improved yields based on inclusion of specifically targeted feed treatment and removal of inert or trace components from the feedstock to metathesis reactor 442. The system 400 can also reduce or fully eliminate any butane accumulation, in some examples.

[0059] Certain systems and accompanying methods disclosed herein can include additional downstream processing of products, in addition to the treatment zones, feedstock separation zones, metathesis zones, and olefin separation zones discussed above. For example, certain systems can include further component recycling, additional metathesis processing, and / or byproduct processing in a steam cracker integrated with the respective system. Certain examples of these systems are described below, with reference to FIGS. 5-8.

[0060] FIG. 5 is a schematic representation of a system 500 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. As shown, the system 500 includes the system 400 of FIG. 4, modified such that additional byproducts are recycled back to the metathesis reactor for enhanced productivity. The recycled byproducts can include produced C5+ intermediate olefins, in some examples. In some examples, the recycled byproducts include all or a portion of produced ethene. In detail, the system 500 includes the treatment zone 504, the feedstock separation zone 510, the metathesis zone 540, and the olefin separation zone 550, which each correspond to, are similarly labeled, and include similar components as the zones discussed above with respect to the system 400 of FIG. 4.

[0061] In some examples, the metathesis product stream 544 produced by the metathesis reactor 542 is supplied to the C3 column 552, which produces the C2-C3 olefin stream 558 and the C4+-rich stream 560. The illustrated embodiment also includes supplying the C2-C3 olefin stream 558 to the C2 / C3 splitter 554. The C2 / C3 splitter 554 separates the C2-C3 olefin stream 558 into an ethene product stream 562 and a propene product stream 564. The system 500 also includes an additional recycle stream of ethene to improve operation of the metathesis reactor 542. As such, the ethene product stream 562 can be recycled back to the metathesis zone 540 for improved yield of additional olefins, such as propene and hexene.

[0062] Additionally, the olefin separation zone 550 includes a C5 column 556 (or second heavy distillation column or depentenizer) in place of the previously referenced C4 column. The C5 column 556 is in fluid communication with the C3 column 552 to receive the C4+-rich stream 560 therefrom. As such, the C5 column 556 separates the C4+-rich stream 560 into a C4-C5 olefin stream566 and a Ce olefin stream 568. The Ce olefin stream 568 includes one or more Ce olefins, such as (t / c) hex-3 -ene. The Ce olefin stream 568 is output by the system 500 as a heavy product stream. In some examples, the Ce olefin stream 568 may also include a small amount of hex-2-ene, which can be supplied as a gasoline booster product. Similar to the above discussion of a purge of C4 compounds, certain examples also include outputting or purging an amount of the C4-C5 olefin stream 566 that can be further processed or utilized. The remaining amount of the C4-C5 olefin stream 566 is recycled or routed to the metathesis zone 540. Accordingly, the illustrated system 500 includes combining the ethene product stream 562, the C4-C5 olefin stream 566, and one or both of the but-l-ene-rich stream 526 and the but-2-ene-rich stream 530 for improved metathesis processing to form the metathesis product stream 544.

[0063] FIG. 6 is a schematic representation of a system 600 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. As shown, the illustrated system 600 includes an additional or second metathesis reactor. In detail, the system 600 includes the treatment zone 604, the feedstock separation zone 610, the metathesis zone 640, and the olefin separation zone 650, which each correspond to, are similarly labeled, and include similar components as the zones discussed above with respect to the system 400 of FIG. 4.

[0064] As illustrated, the olefin separation zone 650 additionally includes a C5 column 672 that is downstream of and in fluid communication with the C4 column 656 discussed above. The C4 column 656 separates the C4+-rich stream 660 into the C5-C6 olefin stream 668 and the C4 olefin stream 666, from which a removed or purged stream 670 can optionally be diverted. The C4 olefin stream 666 is recycled to the metathesis zone 640 where it can be combined with one or both of the but-l-ene-rich stream 626 and the but-2-ene-rich stream 630 before being metathesized to form the metathesis product stream 644. The C5-C6 olefin stream 668 contains C5 internal olefins and Ce internal olefins. As such, the C5 column 672 receives the Cs-Ce olefin stream 668 from the C4 column 656 and produces a C5 olefin stream 674 and a Ce olefin stream 676. The Ce olefin stream 676 is output by the system 600 as a heavy product stream containing Ce internal olefins, such as hex-3 -ene. In some examples, the Ce olefin stream 676 includes a small or trace amount of hex-2- ene.

[0065] Additionally, the illustrated example of the system 600 includes a second metathesis zone 680, integrated with the metathesis zone 640 (or first metathesis zone) and the olefin separation zone 650. The second metathesis zone 680 includes a second metathesis reactor 682,which is fluidly coupled to the Cs column 672, the C2 / C3 splitter 654, and the metathesis reactor 642 (or first metathesis reactor). Indeed, the second metathesis reactor 682 is in series with and in fluid communication with the metathesis reactor 642. The second metathesis reactor 682 receives the ethene product stream 662 from the C2 / C3 splitter 654 and receives the C5 olefin stream 674 from the C5 column 672. The second metathesis reactor 682 processes the ethene and C5 olefins with a metathesis catalyst to produce additional propene and but-l-ene as products. The second metathesis reactor 682 can therefore cooperate with the C2 / C3 splitter 654 to output the propene product stream 664 (or an additional propene product stream). Additionally, the second metathesis reactor 682 can produce a but-l-ene- rich stream 684 or but-l-ene product stream, which can be partly or fully recycled for utilization in the metathesis reactor 642 to uplift the productivity of the metathesis reactor 642. In some examples, all or a portion of the but-l-ene-rich stream 684 is removed from the system as a but-l-ene product stream 688. In certain examples, the but-l-ene product stream 688 is a high-purity product of but-l-ene that can be provided or sold for further use in chemical production.

[0066] FIG. 7 is a schematic representation of a system 700 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. In detail, the system 700 includes the treatment zone 704, the feedstock separation zone 710, the metathesis zone 740, the olefin separation zone 750, and the second metathesis zone 780, which each correspond to, are similarly labeled, and include similar components as the zones discussed above with respect to the system 600 of FIG. 6. As shown, the illustrated system 700 additionally includes an isomerization zone 790 downstream of the olefin separation zone 750. The isomerization zone 790 includes an isomerization reactor to provide a suitable yield of hex-l-ene. The dual metathesis processing and Ce isomerization, integrated with the feedstock pretreatment and the steam cracker increases the production of desired products.

[0067] More specifically, the olefin separation zone 750 supplies a Ce olefin stream 776 to an isomerization reactor 792 of the isomerization zone 790. The Ce olefin stream 776 includes one or more internal Ce olefins, such as hex-3 -ene, which can optionally include a small or trace amount of hex-2-ene. The isomerization zone 790 includes at least one isomerization reactor 792 to isomerize the Ce olefin stream 776 received from the olefin separation zone 750. The isomerization reactor 792 is designed to isomerize the Ce olefin stream 776 to yield an isomerized stream 794 that includes an increased content of hex-l-ene compared to the Ce olefin stream 776. Morespecifically, the isomerization reactor 792 isomerizes hex-2-ene and hex-3-ene supplied thereto into more the more valuable hex-l-ene.

[0068] In some examples, the isomerization zone 790 includes multiple isomerization reactors 792 therein, which can be implemented in series or in parallel operation. In some embodiments, at least one reactor remains online while at least one other reactor is in regeneration or standby mode, preparing for subsequent operation. The isomerization reactor 792 can be implemented as a suitable down-flow or up-flow, fixed-bed, plug flow reactor having a potassium-based isomerization catalyst (e.g., a K^O / yAhCh-based catalyst). In some examples, the isomerization catalyst is a Ce y-alumina-based catalyst. The operating temperature of the isomerization reactor 792 can be in a range from 350 °C to 500 °C, in some examples. The operating temperature of the isomerization reactor 792 can be in a range from 300 °C to 600 °C, in some examples, such as temperatures ranging from 300 °C to 550 °C, 300 °C to 500 °C, 300 °C to 550 °C, 300 °C to 500 °C, 350 °C to 550 °C, 350 °C to 600 °C, 400 °C to 500 °C, and so forth. In certain examples, the operating temperature is in a range between 250 °C and 500 °C. The operating pressures of the isomerization reactor 792 can range between 0 barg and 30 barg. In different implementations, the isomerization reactor 792 is capable of isomerizing a liquid feed, a vapor feed, or mixed phase feed. It is presently recognized that the isomerization catalyst is prone to gradual deactivation due to formation of intermediate species or carbon deposition, and as such, it is desirable to operate the isomerization reactor 792 to enable a suitable operating cycle time between 1 day and 100 days, such as between 1 day and 60 days. In some embodiments, this is achieved by limiting the flow rate of the C4 stream to the isomerization reactor 792 to a WHSV in a range from 0.1 h'1to 25 h'1. In some examples, the WHSV is in a range from 0.5 h'1to 10 h'1. Regeneration of the isomerization catalyst can be performed when the isomerization reactor 792 is in regeneration mode using nitrogen, air, enriched air, or oxygen at temperatures that are in a range from 350 °C to 600 °C.

[0069] From the isomerization reactor 792, the isomerized stream 794 is subsequently directed to a Ce fractionator 796 of the isomerization zone 790 to separate a substantially pure hex-l-ene product from other Ce+ olefins. The Ce fractionator 796 can thus produce and output a purified product stream 798 containing the hex-l-ene. The Ce fractionator 796 also produces an isomerization recycle stream containing the hex-2-ene and hex-3 -ene, which is recycled back tothe isomerization reactor 792 for increased production of hex-l-ene in the purified product stream 798.

[0070] FIG. 8 is a schematic representation of a system 800 for the pretreatment of a C4 feed stream and production of desired olefins through metathesis, according to an example. As shown, the illustrated system 800 includes a single metathesis reactor and an isomerization reactor, along with the above-discussed feed pretreatments and recycling of certain byproducts.

[0071] For example, the system 800 includes the treatment zone 804, the feedstock separation zone 810, the metathesis zone 840, and the olefin separation zone 850, which each correspond to, are similarly labeled, and include similar components as the zones discussed above with respect to the system 500 of FIG. 5. Additionally, the system 800 includes the isomerization zone 890 downstream of the olefin separation zone 850 to receive the Ce olefin stream 868 produced by the C5 column 856. The isomerization zone 890 can operate in a manner that is similar to the isomerization zone discussed above with reference to the system 700 of FIG. 7. As such, the Ce olefin stream 868 can be processed to produce and output the purified product stream 898 containing the hex-l-ene.

[0072] FIG. 9 is a schematic representation of a control system 900 for controlling the embodiments of the system discussed above. The control system 900 includes at least one controller 901. Each controller 901 includes at least one processor 902, which may be or include a central processing unit (CPU), a graphics processing unit (GPU), a co-processing unit, a subprocessing unit, or any other suitable electronic data processor. Each controller 901 includes at least one memory 903, which may be or include random access memory (RAM), read-only memory (ROM), or any other suitable electronic memory or storage. For the illustrated embodiment, the controller 901 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 901 can be communicatively coupled to a treatment zone 904, a metathesis zone 940, and an olefin separation zone 950. The controller 901 can be communicatively coupled to a treatment zone 904, a feedstock separation zone 910, a metathesis zone 940, and an olefin separation zone 950, in some examples. Certain examples may additionally include the controller 901 communicatively coupled to a second metathesis zone 980 and / or an isomerization zone 990, in some examples. The controller 901 can further be communicatively connected to any other elements that are included in or facilitate operation of the systems discussed above. Thecommunicative connection between the controller 901 and the various zones and devices enables the controller 901 to receive monitoring and operational data from sensors and / or sub-controllers of each of these zones or devices present in the embodiments discussed above, and further enables the controller 901 to provide control signals (e.g., electrical signals, instructions, data packets) to modify the operation of each of these zones or devices.

[0073] The controller 901 can implement any suitable monitoring, analysis, and / or actuation steps to control the treatment zone 904, the feedstock separation zone 910, the metathesis zone 940, the olefin separation zone 950, the second metathesis zone 980, and / or the isomerization zone 990 operating in a suitable system. For example, the controller 901 may receive monitoring data from sensors (e.g., temperature sensors, pressure sensors, flow sensors, content analyzers) of the treatment zone 904, 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 904 to ensure that the one or more guard beds therein operate in accordance with any predefined threshold values. Certain examples may include removing all or a portion of undesired contaminants from the C4 stream that is supplied to the treatment zone 904.

[0074] Additionally, the controller 901 may receive monitoring data from sensors of the metathesis zone 940 and / or second metathesis zone 980, 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 940 and / or second metathesis zone 980 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 901 may receive monitoring data from of the isomerization zone 990, 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 isomerization zone 990 to ensure that the isomerization reactor therein operates within the temperatures, pressures, and WHSV disclosed above, and to manage the regeneration mode operation and standby operation of the isomerization reactor. The controller 901 may receive monitoring data from sensors of the feedstock separation zone 910 and / or the olefin separation zone 950, 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

[0075] 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 deviations should be accounted for.

[0076] 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.

[0077] Example 1:

[0078] Experiments were performed implementing the process configuration of system 800, as discussed herein. The ultimate yields were calculated using preliminary lab experimental results. Reaction conditions for the experiment included a reaction temperature of 50 °C, a pressure of 6 barg, and a WHSV of 0.6 h’1. The sample feedstock composition is illustrated below in Table-2. The experimental results are confirmed with simulation results using ASPEN PLUS®, provided by Aspen Technology, Inc. of Bedford, Massachusetts, U.S.A. Table-3 illustrates the resulting product composition, which include Cs recycle calculated using Aspen simulations. It is noted that in some examples, purge removal may be implemented to remove any inert component accumulation at the metathesis reactor. These results demonstrate the benefit of recycling Cs olefins to the metathesis reactor, followed by Ce isomerization with a mixed feed of C4 olefins to metathesis reactor.

[0079] Table-2: Example feedstock composition of C4 feed stream

[0080] Table-3: Resulting product composition via metathesis

[0081] 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.

[0082] 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 embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. It should be understood that although the disclosure contains certain aspects, embodiments, and optional features, modification, improvement, or variation of such aspects, embodiments, 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

Claims1. A method for producing chemicals, the method comprising: receiving a C4 feed stream containing one or more contaminants from a steam cracker; supplying the C4 feed stream to one or more guard beds to produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants; removing one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds; supplying the pretreated C4 feed stream to a metathesis reactor containing a metathesis catalyst to produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins; supplying the metathesis product stream to a light distillation column to produce a C2-C3 product stream containing the ethene and the propene and a C4+-rich stream containing the unreacted butenes 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 heavy distillation column to produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins; and recycling the recycle stream to the metathesis reactor.

2. The method of claim 1 , wherein the one or more contaminants comprise a sulfur compound, a salt compound, a metal, or a combination thereof.

3. The method of claims 1 or 2, wherein the one or more guard beds comprise a plurality of layers of adsorbent, and wherein the adsorbent comprises oxides, molecular sieves, zeolites, activated carbon, or a combination thereof.

4. The method of any one of claims 1-3, further comprising: removing one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor.

5. The method of claim 4, further comprising: fractionating the pretreated C4 feed stream upstream of the metathesis reactor to produce a but- 1-ene- rich stream and a but-2-ene-rich stream; and supplying the but-l-ene-rich stream and the but-2-ene-rich stream to the metathesis reactor.

6. The method of any one of claims 1-5, wherein the heavy distillation column comprises a C5 column, and wherein the recycle stream contains C5 olefins.

7. The method of any one of claims 1-5, wherein the heavy distillation column comprises a C4 column, and wherein the heavy product stream contains C5 olefins.

8. The method of any one of claims 1-7, wherein the metathesis catalyst comprises a rhenium oxide-coated y-alumina-based catalyst.

9. The method of any one of claims 1-8, wherein supplying the pretreated C4 feed stream to the metathesis reactor to produce the metathesis product stream comprises operating the metathesis reactor at a temperature in a range between 35 and 100 degrees Celsius (°C).

10. A system for producing chemicals, the system comprising: one or more guard beds configured to receive a C4 feed stream containing one or more contaminants from a steam cracker and produce a pretreated C4 feed stream containing a reduced amount of the one or more contaminants; a C4 column in fluid communication with the one or more guard beds and configured to remove one or more C1-C3 compounds from the pretreated C4 feed stream downstream of the one or more guard beds; a metathesis reactor containing a metathesis catalyst and configured to receive the pretreated C4 feed stream and produce a metathesis product stream containing ethene, propene, unreacted butenes, and Ce olefins;a light 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 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; and a heavy distillation column configured to receive the C4+-rich stream and produce a recycle stream containing the unreacted butenes and a heavy product stream containing the Ce olefins, the recycle stream being routed to the metathesis reactor along with the pretreated C4 feed stream to produce the metathesis product stream.

11. The system of claim 10, wherein the one or more contaminants comprise a sulfur compound, a salt compound, a metal, or a combination thereof.

12. The system of claims 10 or 11, further comprising: a C5 column in fluid communication with the C4 column and configured to remove one or more C5+ compounds from the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C4.

13. The system of claim 12, further comprising: a C4 fractionator in fluid communication with the C5 column and configured to fractionate the pretreated C4 feed stream upstream of the metathesis reactor and downstream of the C5 column to produce a but-l-ene-rich stream and a but-2-ene- rich stream, the but-l-ene-rich stream and the but-2-ene-rich stream each supplied to the metathesis reactor as the pretreated C4 feed stream.

14. The system of any one of claims 10-13, wherein the heavy product stream contains C5 olefins, and wherein the system further comprises: an additional metathesis reactor configured to receive the ethene product stream and the C5 olefins and produce a but-l-ene product stream and an additional propenestream, the but-l-ene-rich stream being routed to the metathesis reactor along with the pretreated C4 feed stream to produce the metathesis product stream.

15. The system of any one of claims 10-14, further comprising: an isomerization reactor containing an isomerization catalyst and configured to receive the heavy product stream and produce an isomerized product stream in which at least a portion of hex-3 -ene is converted into hex-l-ene.

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