Methods and systems to produce ethylene, propylene, and / or 1-hexene from butenes using metathesis in combination with steam cracking or fluid catalytic cracking

Abstract

A method provided herein includes: cracking at least a hydrocarbon feedstock to produce a cracked stream; providing at least the cracked stream to a downstream separation section to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream; pretreating the C4 raffinate stream to produce a pretreated C4 stream; performing C4 isomerization of the pretreated C4 stream to produce a but-1-ene-rich stream; metathesizing at least the but-1-ene-rich stream to produce a metathesis product stream; separating the metathesis product stream into at least a C2-C3 olefin stream, a C4 olefin stream, and a C6 olefin stream; purging a portion of the C4 olefin stream to produce a purge stream that contains at least one paraffin; combining a remainder of the C4 olefin stream after purging with the but-1-ene-rich stream prior to metathesis; and providing the C2-C3 olefin stream to the downstream separation section along with the cracked stream to produce the ethene product stream and the propene product stream.

Description

METHODS AND SYSTEMS TO PRODUCE ETHYLENE, PROPYLENE, AND / OR 1-HEXENE FROM BUTENES USING METATHESIS IN COMBINATION WITH STEAM CRACKING OR FLUID CATALYTIC CRACKINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of European Application No. EP23211683.0, filed on November 23, 2023. The contents of the referenced application are incorporated into the present application by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to systems and methods for performing metathesis of a C4 raffinate stream, along with steam cracking or fluid catalytic cracking of a hydrocarbon feedstock, to produce chemical feedstocks, including olefins such as ethene (also referred to herein as ethylene), propene (also referred to herein as propylene) and / or hex-l-ene (also referred to herein as 1 -hexene). More specifically, the present disclosure relates to systems and methods for producing ethene, propene, and / or hex-l-ene involving metathesis of a C4 stream in combination with steam cracking or fluid catalytic cracking of at least a hydrocarbon feedstock.BACKGROUND

[0003] A hydrocarbon feedstock can be processed using steam cracking to produce ethene as a major product along with other side products, such as propene and various unsaturated C4 species (e.g., butenes, 2-methylprop- 1-ene, butynes, and buta- 1,3 -diene). While ethene and propene are considered high value olefins, many of the remaining side products are generally considered lower value olefins. While olefin metathesis can be used to convert lower value C4 and C5 olefins into higher value propene, this typically involves the use of an ethene co-feed, which undesirably consumes a higher value olefin as part of the process. As such, there remains a need to develop improved systems and methods for converting hydrocarbon feedstock into high value olefin chemical feedstocks.SUMMARY

[0004] To address these demands in the industry and other shortcomings in the art, Applicant has developed systems and methods for performing metathesis of a C4 raffinate stream to produce chemical feedstocks, including olefins such as ethene, propene, and / or hex-l-ene. Provided here are methods for production of ethene, propene, and / or hex-l-ene involving metathesis of a C4 raffinate stream. In certain examples, the method includes the step of cracking at least a hydrocarbon feedstock to produce a cracked stream. The method includes the step of providing at least the cracked stream to a downstream separation section to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream. The method includes the step of pretreating the C4 raffinate stream to produce a pretreated C4 stream. The method includes the step of performing C4 isomerization of the pretreated C4 stream to produce a but-l-ene-rich stream, wherein but-2-ene in the C4 raffinate stream is converted into but-l-ene during C4 isomerization and the but-l-ene-rich streamcontains greater than about 90 mol. % of but-l-ene. The method includes the step of metathesizing at least the but-l-ene-rich stream to produce a metathesis product stream. The method includes the step of separating the metathesis product stream into at least a C2-C3 olefin stream, a C4 olefin stream, and a G, olefin stream. The method includes the step of purging a portion of the C4 olefin stream to produce a purge stream that contains at least one paraffin. The method includes the step of combining a remainder of the C4 olefin stream after purging with the but-l-ene-rich stream prior to metathesis. The method includes the step of providing the C2- C3 olefin stream to the downstream separation section along with the cracked stream to produce the ethene product stream and the propene product stream.

[0005] In some examples, the C4 raffinate stream is a C4 raffinate II stream or a C4 raffinate III stream. In some example, pretreating includes the step of contacting the C4 raffinate stream with one or more guard beds containing one or more adsorbents configured to remove one or more species from the C4 raffinate stream, wherein the one or more adsorbents contain oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and wherein the one or more species include sulfur-containing species, alcohol-containing species, oxygen-containing species, salts, metals, or a combination thereof. In some example, performing C4 isomerization includes the step of heating the pretreated C4 stream to a temperature ranging from about 250 degrees Celsius (°C) to about 550 °C and pressurizing the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0. 1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase during C4 isomerization, and wherein the isomerization catalyst is a potassium- based isomerization catalyst. In some example, metathesizing at least the but-l-ene-rich stream includes the step of heating a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurizing the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and the metathesis catalyst is a rhenium- coated y-alumina-based metathesis catalyst.

[0006] In some examples, cracking includes the step of steam cracking at least the hydrocarbon feedstock to produce the cracked stream, wherein the hydrocarbon feedstock contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof. In some examples, the method includes hydrogenating the purge stream to produce a saturated stream and combining the saturated stream with the hydrocarbon feedstock prior to steam cracking to produce the cracked stream. In some examples, cracking includes the step of fluid catalytic cracking the hydrocarbon feedstock to produce the cracked stream, wherein providing at least the cracked stream includes providing at least the cracked stream and the C2-C3 olefin stream to the downstream separation section to produce at leastthe ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, a gasoline product stream, C9+ hydrocarbon stream, and fuel gas, and wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. In some embodiments, the method includes the step of combining the purge stream with the LPG product stream to increase a yield of the LPG product stream. In some examples, the method includes the step of combining the Ce olefin stream with the gasoline product stream to boost an octane number of the gasoline product stream.

[0007] In some examples, the method includes the steps of performing Ce isomerization of the Ce olefin stream to produce a Ce isomerized stream, wherein hex-2-enes and hex-3 -enes in the Ce olefin stream are converted into hex-l-ene during G, isomerization, and separating a first portion of the G, isomerized stream as a hex-1- ene product stream, wherein a remainder of the Ce isomerized stream is combined with the Ce olefin stream prior to Ce isomerization. In some examples, performing Ce isomerization of the Ce olefin stream includes the step of heating the Ce olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurizing the Ce olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0.1 h'1to about 25 h’1, wherein the Ce olefin stream is in a gas phase, a liquid phase, or a mixed phase during Ce isomerization, and the isomerization catalyst is a potassium-based isomerization catalyst.

[0008] Provided here are systems for production of ethene, propene, and / or hex-l-ene involving metathesis of a C4 raffinate stream. In certain examples, the system includes a cracking reactor configured to receive and crack at least a hydrocarbon feedstock to produce a cracked stream. The system includes a downstream separation section configured to receive and separate at least the cracked stream to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream. The system includes a pretreatment unit configured to receive and pretreat the C4 raffinate stream to produce a pretreated C4 stream. The system includes a C4 isomerization reactor configured to receive and perform C4 isomerization of the pretreated C4 stream to produce a but-1 -ene-rich stream, wherein but-2-ene in the C4 raffinate stream is converted into but-1 -ene within the C4 isomerization reactor and the but-1 -ene-rich stream contains greater than about 90 mol. % of but-l-ene. The system includes a metathesis reactor configured to receive and metathesize at least the but-1 -ene-rich stream to produce a metathesis product stream. The system includes a C3 column configured to receive and separate the metathesis product stream into a C2-C3 olefin stream and a C4+ olefin stream, the C2-C3 olefin stream being provided to the downstream separation section for separation into the ethene product stream and the propene product stream. The system includes a C4 column configured to receive and separate the C4+ olefin stream into a C4 olefin stream and a Ce olefin stream, a portion of the C4 olefin stream being purged to produce a purge stream containing at least one paraffin and a remainder of C4 olefin stream being provided to the metathesis reactor along with the but-1 -ene-rich stream for metathesis to produce the metathesis product stream.

[0009] In some examples, the C4 raffinate stream is a C4 raffinate II stream or a C4 raffinate III stream. In some examples, the pretreatment unit includes one or more guard beds containing one or more adsorbents configured to contact the C4 raffinate stream to remove one or more species from the C4 raffinate stream, wherein the one or more adsorbents contain oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and wherein the one or more species include sulfur-containing species, alcohol-containing species, oxygencontaining species, salts, metals, or a combination thereof. In some examples, the C4 isomerization reactor is a fixed -bed up-flow reactor or a fixed-bed down-flow reactor, wherein the C4 isomerization reactor is configured to heat the pretreated C4 stream to a temperature ranging from about 250 °C to about 550 °C and pressurize the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0.1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase, the isomerization catalyst is a potassium-based isomerization catalyst, and the C4 isomerization reactor has an operating cycle time from about 1 day to about 100 days. In some examples, the system has a plurality of C4 isomerization reactors that includes the C4 isomerization reactor, wherein a second C4 isomerization reactor of the plurality of C4 isomerization reactors is configured to operate in regeneration mode to regenerate the isomerization catalyst of the second C4 isomerization reactor, and regeneration mode operation includes the second C4 isomerization reactor being configured to receive a stream of nitrogen, air, a mixture of nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 600 °C. In some examples, the plurality of C4 isomerization reactors includes a third C4 isomerization reactor configured to remain in standby mode while the C4 isomerization reactor is configured to isomerize the pretreated C4 stream and the second C4 isomerization reactor is configured to operate in regeneration mode.

[0010] In some examples, the metathesis reactor is a fixed-bed up-flow reactor or a fixed-bed down-flow reactor, wherein the metathesis reactor is configured to heat a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurize the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and the metathesis catalyst is a rhenium -coated y-alumina-based metathesis catalyst. In some examples, the system has a plurality of metathesis reactors that includes the metathesis reactor, wherein a second metathesis reactor of the plurality of metathesis reactors is configured to operate in regeneration mode to regenerate the metathesis catalyst of the second metathesis reactor, and wherein regeneration mode operation includes the second metathesis reactor being configured to receive a stream of air, enriched air, or oxygen at a temperature ranging from about 350 °C to about 600 °C. In some examples, the plurality of metathesis reactors includes a third metathesis reactor configured to remain in standby mode while the metathesis reactor is configured tometathesize the combination of the remainder of the CL olefin stream and the but-l-ene-rich stream and the second metathesis reactor is configured to operate in regeneration mode.

[0011] In some examples, the cracking reactor comprises a steam cracking reactor, wherein the hydrocarbon feedstock contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof. In some examples, the system includes a total hydrogenation unit configured to receive and hydrogenate the purge stream to produce a saturated stream, wherein the saturated stream is combined with the hydrocarbon feedstock prior to being provided to the steam cracking reactor to produce the cracked stream. In some examples, the cracking reactor comprises fluid catalytic cracking (FCC) reactor, wherein the downstream separation section is configured to receive and separate the cracked stream and the C2-C3 olefin stream to produce at least the ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, a gasoline product stream, C9+ hydrocarbon stream, and fuel gas, and wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. In some examples, the purge stream is combined with the LPG product stream to increase a yield of the LPG product stream, and the Ce olefin stream is combined with the gasoline product stream to boost an octane number of the gasoline product stream.

[0012] In some examples, the system includes a Ce isomerization reactor configured to receive and perform Ce isomerization of the Ce olefin stream to produce a Ce isomerized stream, wherein hex-2-enes and hex-3 - enes in the Ce olefin stream are converted into hex-l-ene within the Ce isomerization reactor, and a Ce fractionator configured to receive and separate the Ce isomerized stream into a hex-l-ene product stream and a hex-2-ene / hex-3-ene stream, wherein the hex-2 -ene / hex-3-ene stream is combined with the G, olefin stream prior to Ce isomerization. In some examples, the Ce isomerization reactor is a fixed-bed up-flow reactor or a fixed -bed down-flow reactor, wherein the Ce isomerization reactor is configured heat the Ce olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurize the Ce olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0. 1 h'1to about 25 h’1, wherein the Ce olefin stream is in a gas phase, a liquid phase, or a mixed phase during Ce isomerization, and the isomerization catalyst is a potassium -based isomerization catalyst. In some examples, the system comprises a plurality of Ce isomerization reactors that includes the Ce isomerization reactor, wherein a second Ce isomerization reactor of the plurality of Ce isomerization reactors is configured to operate in regeneration mode to regenerate the isomerization catalyst of the second Ce isomerization reactor, and regeneration mode operation includes the second Ce isomerization reactor being configured to receive a stream of nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 500 °C. In some examples, the plurality of Ce isomerization reactors includes a third Ce isomerization reactor configured to remain in standby mode while the Ce isomerization reactor is configured to perform Ce isomerization of the Ce olefin stream and the second Ce isomerization reactor is configured to operate in regeneration mode.

[0013] 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 DRA INGS

[0014] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they may be practiced.

[0015] FIG. 1 is a diagrammatic representation of an embodiment of system that enables steam cracking, C4 olefin isomerization, and olefin metathesis, to facilitate the production of chemical feedstocks.

[0016] FIG. 2 is a diagrammatic representation of an embodiment of system that enables steam cracking, C4 olefin isomerization, olefin metathesis, and G, olefin isomerization and separation, to facilitate the production of chemical feedstocks.

[0017] FIG. 3 is a diagrammatic representation of an embodiment of system that enables fluid catalytic cracking, C4 olefin isomerization, and olefin metathesis, to facilitate the production of chemical feedstocks.

[0018] FIG. 4 is a diagrammatic representation of an embodiment of system that enables fluid catalytic cracking, C4 olefin isomerization, olefin metathesis, and G, olefin isomerization, to facilitate the production of chemical feedstocks.DETAILED DESCRIPTION

[0019] The present disclosure describes various embodiments related to processes, methods, and systems for using metathesis of a C4 raffinate stream to produce chemical feedstocks, such as ethene, propene, and / or hex- 1-ene. Further embodiments may be described and disclosed.

[0020] In the following description, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not have been described in particular detail in order not to unnecessarily obscure the various embodiments. Additionally, illustrations of the various embodiments may omit certain features or details in order to not obscure the various embodiments.

[0021] 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 differentembodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0022] 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.”

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The term “enriched” or “rich” or their variations mean an amount of at least generally about 15 mol. %, and preferably about 20 mol. %, of a compound or class of compounds in a stream. The term “ppmw” refers to part per million by weight.

[0027] 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 C2-C5 stream refers to a mixture that substantially contains or entirely contains hydrocarbonbased compounds, each compound containing 3, 4, or 5 carbon atoms.

[0028] As used herein, the term “Cx+ compounds,” in which x is a positive integer value, refers to hydrocarbonbased compounds, each compound containing at least x carbon atoms. For example, a C3+ stream 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.

[0029] As used herein, the term “Cx. compounds,” in which x is a positive integer value, refers to hydrocarbonbased compounds, each compound containing no more than x carbon atoms. For example, a C4- stream 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. stream” may also include hydrogen (H2), in addition to hydrocarbons having x or fewer carbon atoms.

[0030] As used herein, when a first component is described as receiving (or being configured to receive) a stream from a second component, or when a first component is described as providing (or being configured toprovide) a stream to a second component, the first and second components may be alternatively described as being in fluid communication with one another. It may be appreciated that, for the various streams discussed herein, a given stream substantially contains the compound or class of compounds in the name of the stream (e.g., an ethene product stream substantially contains ethene, a C4 olefin stream substantially contains C4 olefins, a G, olefin stream substantially contains G, olefins), and the stream may also include other components.

[0031] The term “substantially contains” means that the mixture includes at least 50 mol. % of the named compound or class of compounds, such as at least 60 mol. %, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, at least 98 mol. %, at least 99 mol. %, or 100 mol. %, or any sub-ranges therebetween.

[0032] The term “but-2-enes” includes (Z)-but-2-ene (cA-but-2-ene), or (E)-but-2-ene (traws-but-2-ene), or combinations thereof. The term “pent-2-enes” includes (Z)-pent-2-ene, or (E)-pent-2-ene, or combinations thereof. The term “hex-2-enes” includes (Z)-hex-2-ene, or (E)-hex-2-ene, or combinations thereof. The term “hex-3 -enes” includes (Z)-hex-3-ene, or (E)-hex-3-ene, or combinations thereof.

[0033] 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. As used herein, the term “LPG” refers to liquified petroleum gas.

[0034] Steam cracking processes are used to produce ethene as a major product along with the other side products, such as propene and a C4 species, such as but-l-ene, but-2-ene, 2-methylprop-l-ene, butynes, buta- 1,3 -diene, and so forth. In recent years, there has been a dramatic increase in the demand for propene to feed the growing markets for polypropylene, propylene oxide, and acrylic acid. Currently, about 85% of propene on the market is produced as the by-product of steam cracking of hydrocarbons (e.g., propane, NGL, naphtha) and fluid catalytic cracking (FCC) processes in refineries. Due to the recent abundance of shale gas in the U.S., there has been a shift towards lighter feedstocks in steam crackers. This is expected to cause a drop in propene as a byproduct from steam crackers. Also, due to the anticipated dip in gasoline demand, the FCC route to producing propene is also expected to be impacted. As a result, there will arise a gap between demand and supply of propene. In this context, intentional propene production routes are expected to see a revival. These intentional propene production routes include methanol to olefins / propene, propane dehydrogenation, and olefin metathesis. Metathesis offers a desirable route for valorization of low value olefins, like C4 and C5 olefins, into high value propene product. In certain existing metathesis methods and systems referred to as olefin conversion technology (OCT), ethene is often supplied as a co-feed to metathesis reactors. However, it is presently recognized that OCT has drawbacks, including the use of higher value ethene to produce propene, the selective use of but-2-enes for metathesis, relatively high carbon dioxide (CO2) production, and relatively high metathesis reaction temperatures (e.g., from 250 °C to 450 °C).

[0035] On-demand synthesis of propene has attracted attention in the recent years, and this disclosure describes a versatile route for the same. More specifically, the present disclosure relates to methods and systems for metathesis of a C4 stream (e.g., a C4 raffinate stream) that is rich in but-l-ene and contains 2-butenes. The disclosed technique uses a mixed feed that can include both but-l-ene and but-2-enes, and can operate without an ethene co-feed, eliminating consumption of this high value feedstock during metathesis. Further, in certain embodiments, integration with a steam cracker or fluid catalytic cracker enables a reduction in the number of downstream separation units, which reduces installation, maintenance, and operational costs. In addition, in certain embodiments, steam cracker integration further enhances the total production of ethene and propene from a C4 raffinate feedstock by utilizing intermediate products from metathesis process via a total hydrogenation unit followed by recycling the saturated stream to the steam cracker furnace. While these techniques are disclosed herein using examples related to the production of ethene, propene, and / or hex-l-ene, it may be appreciated that these techniques are broadly applicable to methods and systems involving metathesis reactions of C2 to C12 olefins.

[0036] With the foregoing in mind, present embodiments are directed to methods and systems involving metathesis of C4 olefins at low reaction temperature (e.g., from about 35 °C to about 100 °C), with steam cracker or fluid catalytic cracker integration, with recycle of C4 olefins to the metathesis reaction, with isomerization and separation of C4 olefins prior to metathesis, and with or without isomerization of G, olefin metathesis byproducts, to produce propene, ethene, and / or hex-l-ene. In some embodiments, the methods and systems include hydrogenation of a C4 purge stream before it is provided to a steam cracker to produce ethene and propene. Existing OCT technologies typically operates at high reaction temperatures above 250 °C, and selectively uses but-2-enes for the metathesis reaction. In contrast, the embodiments discussed herein use a but- 1-ene-rich feed without a co-feed such as ethene, which avoids consumption of this higher value olefin during metathesis. In some embodiments, the system integrates metathesis technology with steam cracking or fluid catalytic cracking, which can desirably reduce the number of downstream separation units.

[0037] Provided here are methods for production of ethene, propene, and / or hex-l-ene involving metathesis of a C4 raffinate stream. In certain examples, the method includes the step of cracking at least a hydrocarbon feedstock to produce a cracked stream. The method includes the step of providing at least the cracked stream to a downstream separation section to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream. The method includes the step of pretreating the C4 raffinate stream to produce a pretreated C4 stream. The method includes the step of performing C4 isomerization of the pretreated C4 stream to produce a but-l-ene-rich stream, wherein but-2-ene in the C4 raffinate stream is converted into but-l-ene during C4 isomerization and the but-l-ene-rich stream contains greater than about 90 mol. % of but-l-ene. The method includes the step of metathesizing at least the but-l-ene-rich stream to produce a metathesis product stream. The method includes the step of separating the metathesis product stream into at least a C2-C3 olefin stream, a C4 olefin stream, and a Ce olefin stream. The method includes the step of purging a portion of the C4 olefinstream to produce a purge stream that contains at least one paraffin. The method includes the step of combining a remainder of the C4 olefin stream after purging with the but- 1-ene -rich stream prior to metathesis. The method includes the step of providing the C2-C3 olefin stream to the downstream separation section along with the cracked stream to produce the ethene product stream and the propene product stream.

[0038] In some examples, the C4 raffinate stream is a C4 raffinate II stream or a C4 raffinate III stream. In some example, pretreating includes the step of contacting the C4 raffinate stream with one or more guard beds containing one or more adsorbents configured to remove one or more species from the C4 raffinate stream, wherein the one or more adsorbents contain oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and wherein the one or more species include sulfur-containing species, alcohol-containing species, oxygen-containing species, salts, metals, or a combination thereof. In some example, performing C4 isomerization includes the step of heating the pretreated C4 stream to a temperature ranging from about 250 °C to about 550 °C and pressurizing the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0.1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase during C4 isomerization, and wherein the isomerization catalyst is a potassium -based isomerization catalyst. In some example, metathesizing at least the but-l-ene-rich stream includes the step of heating a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurizing the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and the metathesis catalyst is a rhenium-coated y- alumina-based metathesis catalyst.

[0039] In some examples, cracking includes the step of steam cracking at least the hydrocarbon feedstock to produce the cracked stream, wherein the hydrocarbon feedstock contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof. In some examples, the method includes hydrogenating the purge stream to produce a saturated stream and combining the saturated stream with the hydrocarbon feedstock prior to steam cracking to produce the cracked stream. In some examples, cracking includes the step of fluid catalytic cracking the hydrocarbon feedstock to produce the cracked stream, wherein providing at least the cracked stream includes providing at least the cracked stream and the C2-C3 olefin stream to the downstream separation section to produce at least the ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, a gasoline product stream, C9+ hydrocarbon stream, and fuel gas, and wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. In some embodiments, the method includes the step of combining the purge stream with the LPG productstream to increase a yield of the LPG product stream. In some examples, the method includes the step of combining the G, olefin stream with the gasoline product stream to boost an octane number of the gasoline product stream.

[0040] In some examples, the method includes the steps of performing Ce isomerization of the Ce olefin stream to produce a Ce isomerized stream, wherein hex-2-enes and hex-3 -enes in the Ce olefin stream are converted into hex-l-ene during Ce isomerization, and separating a first portion of the Ce isomerized stream as a hex-1- ene product stream, wherein a remainder of the Ce isomerized stream is combined with the Ce olefin stream prior to Ce isomerization. In some examples, performing Ce isomerization of the Ce olefin stream includes the step of heating the Ce olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurizing the Ce olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0.1 h'1to about 25 h’1, wherein the Ce olefin stream is in a gas phase, a liquid phase, or a mixed phase during Ce isomerization, and the isomerization catalyst is a potassium-based isomerization catalyst.

[0041] Provided here are systems for production of ethene, propene, and / or hex-l-ene involving metathesis of a C4 raffinate stream. In certain examples, the system includes a cracking reactor configured to receive and crack at least a hydrocarbon feedstock to produce a cracked stream. The system includes a downstream separation section configured to receive and separate at least the cracked stream to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream. The system includes a pretreatment unit configured to receive and pretreat the C4 raffinate stream to produce a pretreated C4 stream. The system includes a C4 isomerization reactor configured to receive and perform C4 isomerization of the pretreated C4 stream to produce a but-1 -ene-rich stream, wherein but-2-ene in the C4 raffinate stream is converted into but-1 -ene within the C4 isomerization reactor and the but-1 -ene-rich stream contains greater than about 90 mol. % of but-l-ene. The system includes a metathesis reactor configured to receive and metathesize at least the but-1 -ene-rich stream to produce a metathesis product stream. The system includes a C3 column configured to receive and separate the metathesis product stream into a C2-C3 olefin stream and a C4+ olefin stream, the C2-C3 olefin stream being provided to the downstream separation section for separation into the ethene product stream and the propene product stream. The system includes a C4 column configured to receive and separate the C4+ olefin stream into a C4 olefin stream and a Ce olefin stream, a portion of the C4 olefin stream being purged to produce a purge stream containing at least one paraffin and a remainder of C4 olefin stream being provided to the metathesis reactor along with the but-1 -ene-rich stream for metathesis to produce the metathesis product stream.

[0042] In some examples, the C4 raffinate stream is a C4 raffinate II stream or a C4 raffinate III stream. In some examples, the pretreatment unit includes one or more guard beds containing one or more adsorbents configured to contact the C4 raffinate stream to remove one or more species from the C4 raffinate stream, wherein the one or more adsorbents contain oxides, molecular sieves, zeolites, activated carbon, or a combination thereof, and wherein the one or more species include sulfur-containing species, alcohol-containing species, oxygen-containing species, salts, metals, or a combination thereof. In some examples, the C4 isomerization reactor is a fixed -bed up-flow reactor or a fixed-bed down-flow reactor, wherein the C4 isomerization reactor is configured to heat the pretreated C4 stream to a temperature ranging from about 250 °C to about 550 °C and pressurize the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0.1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase, the isomerization catalyst is a potassium-based isomerization catalyst, and the C4 isomerization reactor has an operating cycle time from about 1 day to about 100 days. In some examples, the system has a plurality of C4 isomerization reactors that includes the C4 isomerization reactor, wherein a second C4 isomerization reactor of the plurality of C4 isomerization reactors is configured to operate in regeneration mode to regenerate the isomerization catalyst of the second C4 isomerization reactor, and regeneration mode operation includes the second C4 isomerization reactor being configured to receive a stream of nitrogen, air, a mixture of nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 600 °C. In some examples, the plurality of C4 isomerization reactors includes a third C4 isomerization reactor configured to remain in standby mode while the C4 isomerization reactor is configured to isomerize the pretreated C4 stream and the second C4 isomerization reactor is configured to operate in regeneration mode.

[0043] In some examples, the metathesis reactor is a fixed-bed up-flow reactor or a fixed-bed down-flow reactor, wherein the metathesis reactor is configured to heat a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurize the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and the metathesis catalyst is a rhenium -coated y-alumina-based metathesis catalyst. In some examples, the system has a plurality of metathesis reactors that includes the metathesis reactor, wherein a second metathesis reactor of the plurality of metathesis reactors is configured to operate in regeneration mode to regenerate the metathesis catalyst of the second metathesis reactor, and wherein regeneration mode operation includes the second metathesis reactor being configured to receive a stream of air, enriched air, or oxygen at a temperature ranging from about 350 °C to about 600 °C. In some examples, the plurality of metathesis reactors includes a third metathesis reactor configured to remain in standby mode while the metathesis reactor is configured to metathesize the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream and the second metathesis reactor is configured to operate in regeneration mode.

[0044] In some examples, the cracking reactor comprises a steam cracking reactor, wherein the hydrocarbon feedstock contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof. In some examples, the system includes atotal hydrogenation unit configured to receive and hydrogenate the purge stream to produce a saturated stream, wherein the saturated stream is combined with the hydrocarbon feedstock prior to being provided to the steam cracking reactor to produce the cracked stream. In some examples, the cracking reactor comprises fluid catalytic cracking (FCC) reactor, wherein the downstream separation section is configured to receive and separate the cracked stream and the C2-C3 olefin stream to produce at least the ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, a gasoline product stream, C9+ hydrocarbon stream, and fuel gas, and wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. In some examples, the purge stream is combined with the LPG product stream to increase a yield of the LPG product stream, and the Ce olefin stream is combined with the gasoline product stream to boost an octane number of the gasoline product stream.

[0045] In some examples, the system includes a Ce isomerization reactor configured to receive and perform Ce isomerization of the Ce olefin stream to produce a Ce isomerized stream, wherein hex-2-enes and hex-3 - enes in the Ce olefin stream are converted into hex-l-ene within the Ce isomerization reactor, and a Ce fractionator configured to receive and separate the Ce isomerized stream into a hex-l-ene product stream and a hex-2-ene / hex-3-ene stream, wherein the hex-2 -ene / hex-3-ene stream is combined with the Ce olefin stream prior to Ce isomerization. In some examples, the Ce isomerization reactor is a fixed-bed up-flow reactor or a fixed -bed down-flow reactor, wherein the Ce isomerization reactor is configured heat the Ce olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurize the Ce olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0. 1 h'1to about 25 h’1, wherein the Ce olefin stream is in a gas phase, a liquid phase, or a mixed phase during Ce isomerization, and the isomerization catalyst is a potassium -based isomerization catalyst. In some examples, the system comprises a plurality of Ce isomerization reactors that includes the Ce isomerization reactor, wherein a second Ce isomerization reactor of the plurality of Ce isomerization reactors is configured to operate in regeneration mode to regenerate the isomerization catalyst of the second Ce isomerization reactor, and regeneration mode operation includes the second Ce isomerization reactor being configured to receive a stream of nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 500 °C. In some examples, the plurality of Ce isomerization reactors includes a third Ce isomerization reactor configured to remain in standby mode while the Ce isomerization reactor is configured to perform Ce isomerization of the Ce olefin stream and the second Ce isomerization reactor is configured to operate in regeneration mode.

[0046] Embodiments of methods and systems for producing ethene, propene, and / or hex-l-ene from a C4 stream are described with respect to FIGS. 1-4. In some embodiments, the C4 stream is a C4 raffinate stream. For example, in certain embodiments, the C4 stream has a composition in accordance with the C4 raffinate II or the C4 raffinate III indicated in Table 1. The composition of the C4 stream may vary based on the source of the C4 stream. In some embodiments, the C4 stream may be at least partially 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 methyl tert-butyl ether (MTBE) reactor, downstream of a but-1- ene (Bl) column, downstream of a but-2-enes (B2) column, downstream of a butadiene hydrogenation reactor, as a C4 raffinate stream from a methanol-to-olefins (MTO) process or reactor, or as a C4 raffinate stream from a refinery fluid catalytic cracking (FCC) process or reactor, or any combination thereof. For such embodiments, the composition of the C4 stream may vary based on the source of the C4 stream.

[0047] Table 1. Example compositions of the C4 stream.

[0048] FIG. 1 is a diagrammatic representation of an embodiment of system that enables steam cracking, C4 olefin isomerization, and olefin metathesis, to facilitate the production of chemical feedstocks. For the embodiment illustrated in FIG. 1, the system 100 includes a pretreatment zone 102, a C4 isomerization zone 104, a metathesis zone 106, an olefin separation zone 108, a total hydrogenation zone 110, and a steam cracking zone 112. A C4 raffinate stream 114 is generated in the steam cracking zone 112, as discussed below, and is directed to the pretreatment zone 102 to remove one or more components of the C4 raffinate stream 114 prior to isomerization. The pretreatment zone 102 includes a pretreater 116 (also referred to herein as a pretreatment unit). In certain embodiments, the pretreater 116 includes one or more guard beds, each having one or more layers of an adsorbent (e.g., oxides, molecular sieves, zeolites, activated carbon, or a combination thereof). The pretreater 116 removes one or more species from the C4 raffinate stream 114 to generate the pretreated C4 stream 118, which is subsequently directed to the C4 isomerization zone 104. In some embodiments, the one or more species removed from the C4 raffinate stream 114 include species that can interfere with the C4 isomerization process and / or the metathesis process, such as sulfur-containing species, alcohol-containing species, oxygen-containing species (oxygenates), salts, metals, or a combination thereof. For example, in some embodiments, the one or more species removed from the C4 raffinate stream 114 during pretreatment can include one or more of Ce+ hydrocarbons, 4-tert-butylcatechol (TBC), arsenic, lead, mercury, phosphorus-containing compounds, hydrogen sulfide, mercaptans, methanol, carbonyl-containing compounds, peroxidecontaining compounds, oxygenates, water, basic nitrogen compounds, and / or organic nitrogen compounds.

[0049] For the embodiment illustrated in FIG. 1, the C4 isomerization zone 104 includes C4 isomerization reactors 120 (e.g., 120A, 120B) and a C4 separator 122. The pretreated C4 stream 118 is introduced into one of the C4 isomerization reactors 120. The C4 isomerization reactors 120 are designed to isomerize the received stream to yield a C4 isomerized stream 124 that is subsequently directed the C4 separator 122. The C4 isomerization reactors 120 are designed to isomerize but-2-enes present in the pretreated C4 stream 118 into but-l-ene within the C4 isomerized stream 124. The C4 separator 122 may be a distillation column, a fractionator, or a super fractionator that separates the C4 isomerized stream 124 into a but-l-ene-rich stream 126 (e.g., > 90 mol. % but-l-ene) that is directed to the metathesis zone 106, a but-2-ene-rich stream 125 that is returned to the C4 isomerization reactors 120 for further isomerization, and a butanes-rich stream 127 that may be collected as a product or provided as an input to another hydrocarbon processing operation.

[0050] For the embodiment illustrated in FIG. 1, the C4 isomerization reactors 120 are implemented such that one reactor remains online while the other reactor is in regeneration or standby mode. For embodiments having three C4 isomerization reactors 120, one C4 isomerization reactor remains online, a second C4 isomerization reactor is in regeneration mode, while a third C4 isomerization reactor is in standby mode. The C4 isomerization reactors 120 can be implemented as down-flow or up-flow, fixed-bed reactors having a potassium-based isomerization catalyst (e.g., K2O / 7AI2O3). The operating temperature of the C4 isomerization reactors 120 can range from about 250 °C to about 550 °C. The operating pressures of the C4 isomerization reactors 120 can range from about 0 bar gauge (barg) to about 30 barg. In different implementations, each of the C4 isomerization reactors 120 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 C4 isomerization reactors 120 to enable a suitable operating cycle time of about 1 day to about 100 days. In some embodiments, this is achieved by limiting the flow rate of the C4 stream to the C4 isomerization reactors 120 to a weight hourly space velocity (WHSV) from about 0.1 per hour (h-1) to about 25 h’1, and preferably from about 0.5 h'1to about 10 h’1. Regeneration of the isomerization catalyst can be performed when the C4 isomerization reactor 120A or 120B is in regeneration mode using nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 600 °C.

[0051] For the embodiment illustrated in FIG. 1, the but-l-ene-rich stream 126 is directed to the metathesis zone 106. In the metathesis zone 106, the but-l-ene-rich stream 126 is introduced into one of the metathesis reactors 128 (e.g., 128A or 128B) to yield a metathesis product stream 130 that contains a mixture of C2-C6 olefin metathesis products. The metathesis reactors 128 can be implemented as down-flow or up-flow, fixed- bed reactors with a metathesis catalyst. The metathesis catalyst enables self-metathesis and / or cross-metathesis of but-l-ene and but-2-enes.

[0052] In some embodiments, the metathesis catalyst is a rhenium-coated y-alumina-based metathesis catalyst (e.g., a Rc^O-ZyAbCh-bascd catalyst) or an alumina-supported rhenium-based metathesis catalyst. In some embodiments, the rhenium-coated y-alumina-based metathesis catalyst is an egg-shell catalyst or a shaped metal-supported catalyst. The metathesis catalyst can be spherical or an extrudate. The metathesis catalyst may be described as having an egg-shell structure. One such metathesis catalyst has y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium coating ranging from about 150 pm to about 250 pm in thickness. One such metathesis catalyst has rhenium completely dispersed on the alumina particle inner and outer surfaces. 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 coating ranging from about 150 pm to about 250 pm in thickness. In certain examples, the metathesis catalyst contains rhenium in an amount ranging from about 4.8 wt.% to about 5.6 wt.%. The metathesis 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-lene and 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 metathesis 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'1to 10 hr’1.

[0053] Methods of preparing a rhenium -coated y-alumina-based metathesis catalyst or an alumina-supported rhenium-based metathesis 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 or an alumina supported rhenium-based support. In certain examples, the aqueous rhenium -containing mixture is a NTUReC solution, an Al(ReC>4)3 solution, or a HReC>4 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 or an alumina supported rhenium -based support. The method also includes the steps of aging the rhenium-coated y-alumina- based support or an alumina supported rhenium-based support to form a rhenium-coated y-alumina-based metathesis catalyst or an alumina-supported rhenium-based metathesis catalyst after calcination, containing a rhenium coating ranging from about 150 micrometers (pm) to about 250 pm in thickness or rhenium completely dispersed on alumina inner or outer surfaces, drying the rhenium-coated y-alumina-based catalyst immediately after aging, and calcining the rhenium-coated ' -alumina or alumina-supported rhenium-based catalyst at atemperature ranging from about 450°C to about 550 °C to form rhenium coated y-alumina or alumina supported rhenium coated catalyst. In certain examples, the step of aging the rhenium -coated y-alumina-based support is conducted for a time less than 5 minutes, thereby to form a rhenium-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 temperature ranges from about 140 °C to about 160 °C.

[0054] The particle size of the ' -alumina or alumina-supported rhenium -based support can range from about 1.2 millimeters (mm) to about 3 mm. For example, the diameter of a spherical or a cylindrical ' -alumina or alumina-supported rhenium -based support can range from about 1.2 mm to about 3 mm. In certain examples, the ' -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 ' -alumina-based support has a pore diameter ranging from about 75 Angstroms (A) to about 110 A. In certain examples, the ' -alumina-based support has a total acidity ranging from about 0.58 millimole per gram (mmolNHs / g) to about 0.62 mmolNm / g. In certain examples, the rhenium-coated y- alumina-based catalyst or alumina-supported rhenium-based catalyst can contain rhenium in an amount ranging from about 4.8 weight percent (wt. %) to about 5.6 wt. %. The rhenium -coated 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 metathesis 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.

[0055] Examples include methods of preparing an activated rhenium-coated y-alumina-based catalyst or an alumina-supported rhenium -based catalyst. One such method includes the steps of treating the rhenium -coated y-alumina- based catalyst or alumina-supported rhenium-based catalyst under air at a temperature from about 500 °C to about 550 °C to produce an activated rhenium-coated y-alumina-based catalyst or alumina-supported rhenium-based catalyst, purging nitrogen into the activated rhenium-coated y-alumina-based catalyst or alumina-supported rhenium-based catalyst to displace the air, and cooling the activated rhenium-coated y- alumina-based catalyst or alumina-supported rhenium-based catalyst to a temperature of about 50 °C. In certain examples, the step of treating the rhenium-coated y-alumina-based catalyst or alumina-supported rhenium- based catalyst under air is conducted for about 4 hours to about 24 hours to produce an activated rhenium- coated y-alumina-based catalyst or alumina-supported rhenium-based catalyst. In certain examples, the step of treating the rhenium-coated y-alumina-based catalyst or alumina-supported rhenium-based catalyst under air is conducted for about 6 hours.

[0056] In some embodiments, the metathesis catalyst is a layered catalyst composition that contains an active layer and a base support. Examples of the base support are aluminum oxide, gallium oxide, silica oxide, zirconium oxide, niobium oxide, titanium oxide, lanthanum oxide, cerium oxide, or combinations thereof. The active layer of the catalyst contains an active metal component and an active support. The active metalcomponent can be a Group 6, 7, 8, or 9 metal oxide. The active metal component can be one or more of a chromium, molybdenum, or tungsten compound. The active metal component can be one or more of a manganese, technetium, or rhenium compound. The active metal component can be one or more of iron, cobalt, nickel, ruthenium, rhodium, palladium, and platinum compound. Examples of the active metal component can be rhenium oxide or ruthenium oxide. Examples of the active support can be aluminum oxide, gallium oxide, silica oxide, zirconium oxide, niobium oxide, titanium oxide, lanthanum oxide, cerium oxide, or combinations thereof.

[0057] Certain examples of an olefin metathesis catalyst have a base support containing aluminum oxide, an active layer containing rhenium oxide as the active metal component, and aluminum oxide as the active support. In certain examples, the acidic -OH groups of the active support are increased by incorporating about 0.5 % to 15 % of aluminum (or) zirconium precursor along with the rhenium precursor. The added aluminum (or) zirconium precursor (support precursor) along with the rhenium precursor produce an amorphous aluminum hydroxide or zirconium hydroxide with rhenium oxide. The amount of the metal component loaded in the active layer is reduced by at least about 10% to about 25% as compared to a rhenium oxide-alumina catalyst synthesized without aluminum / zirconium active support layer.

[0058] For the embodiment illustrated in FIG. 1, metathesis reactors 128 are implemented such that one reactor remains online while the other reactor is in regeneration or standby mode. For embodiments having three metathesis reactors 128, one metathesis reactor remains online, a second metathesis reactor is in regeneration mode, while the third metathesis reactor is in standby mode. The operating temperature of the metathesis reactors 128 is below 250 °C, such as from about 35 °C to about 100 °C. It is presently recognized that the metathesis reactors and catalysts used by other systems can demand substantially higher operating temperatures, such as greater than 250 °C, and as such, the lower operating temperatures of the disclosed metathesis reactors 128 reduces the operational cost and energy demands of these reactors compared to other systems. The operating pressures of the metathesis reactors 128 can range from about 0 barg to about 30 barg. In some embodiments, the metathesis reactors 128 do not receive an ethene co-feed, which desirably avoids consumption of the higher value ethene olefin chemical feedstock to facilitate metathesis. The metathesis reactors 128 can be operated in gas phase, liquid phase, or mixed phase. It is presently recognized that the rhenium-coated y-alumina-based 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 reactors such that a reasonable operating cycle time is about 1 day to about 100 days. In some embodiments, this is achieved by limiting the flow rate of the but-l-ene-rich stream 126 into the metathesis reactors 128 to a WHSV from about 0.1 per hour (h-1) to about 25 h’1, more preferably to values from about 0.5 h'1to about 10 h’1. Regeneration of the metathesis catalyst can be performed when a metathesis reactor 128A or 128B is in regeneration mode using air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 600 °C, and more preferably from about 350 °C to about 550 °C using air. The metathesis catalyst can beregenerated in-situ (online) and ex-situ (off-line) or using a bunker flow reactor with continuous catalyst replacement.

[0059] For the embodiment illustrated in FIG. 1, the metathesis product stream 130 exits the metathesis zone 106 and is directed to the olefin separation zone 108. For the illustrated embodiment, the olefin separation zone 108 includes a C3 column 132 (e.g., a depropenizer) and a C4 column 134 (e.g., a debutenizer). The metathesis product stream 130 is directed to the C3 column 132, which separates the metathesis product stream 130 into a C2-C3 olefin stream 136 and a C4+ olefin stream 138. The C2-C3 olefin stream 136 is directed to the downstream separation section 140 of the steam cracking zone 112 for separation, as discussed below. For the illustrated embodiment, the C4+ olefin stream 138 is directed to the C4 column 134, which separates C4+ olefin stream 138 into a C4 olefin stream 141 and a G, olefin stream 142. In some embodiments, the G, olefin stream 142 is collected as a product. In some embodiments, the C4 olefin stream 141 may include a limited amount of paraffins (e.g., butane, 2-methylpropane) that can be purged from the C4 olefin stream 141, which produces the purge stream 144. After purging, a remainder of the C4 olefin stream 146 is recycled to the metathesis zone 106 where it is combined with but-l-ene-rich stream 126 before being metathesized to form the metathesis product stream 130. The purge stream 144, which may include paraffins (e.g., butane, 2-methylpropane) and a limited quantity of C2-C6 olefins, and which may be optionally combined with at least a portion of the Ce olefin stream 142, is directed to a total hydrogenation unit (THU) 148 of the total hydrogenation zone 110 for hydrogenation, yielding a saturated stream 150.

[0060] For the embodiment of the system 100 illustrated in FIG. 1, the steam cracking zone 112 receives and steam cracks a hydrocarbon feedstock 152. In some embodiments, the hydrocarbon feedstock 152 contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof. The steam cracking zone 112 includes a steam cracker 154 and the downstream separation section 140 (also referred to herein as the downstream separation subzone). The steam cracker 154 receives and cracks the hydrocarbon feedstock 152, along with the saturated stream 150 received from the total hydrogenation zone 110 and the paraffinic-rich stream 156 discussed below, to generate a steam cracked stream 158 that is directed to the downstream separation section 140 for separation. The steam cracked stream 158 may include: hydrogen (H2), BTX hydrocarbons, ethene, propene, pyrolysis gasoline, fuel gas, and / or other C1-C12 hydrocarbons. BTX hydrocarbons include benzene, toluene, and dimethylbenzenes (also referred to herein as xylenes). The downstream separation section 140 receives the steam cracked stream 158 and the C2-C3 olefin stream 136. The downstream separation section 140 includes any suitable number of reactors and / or separation columns that process and / or separate the received streams into a number of streams, including: an ethene product stream 160, a propene product stream 162, the C4 raffinate stream 114, other product streams 164 (e.g., each containing H2, or C1-C12 hydrocarbons, or combinations thereof), and the paraffinic-rich stream 156 (e.g., containing ethane, propane, butane, or combinations thereof). In some embodiments, the downstream separation section 140 includes a C2 / C3 splitter, a MTBE reactor, a but-l-ene(Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, an acetylene hydrogenation reactor, any other suitable separation column (e.g., distillation column, fractional distillation column, deethanizer, depropanizer, debutanizer, depentanizer, C2 / C3 splitter, and so forth), or any combination thereof. In some embodiments, the C4 raffinate stream 114 has a composition consistent with the C4 raffinate II or C4 raffinate III streams indicated in Table 1. In some embodiments, the other product streams 164 may include a pyrolysis gasoline stream that contains pyrolysis gasoline and a fuel gas stream that is rich in methane along with other hydrocarbons. The paraffinic-rich stream 156 is recycled and combined with fresh hydrocarbon feedstock 152 and the saturated stream 150 before returning to the steam cracker 154 to generate the steam cracked stream 158. The C4 raffinate stream 114 is directed to the pretreatment zone 102, as discussed above. It may also be appreciated that, by utilizing the downstream separation section 140 to isolate the ethene product stream 160 and the propene product stream 162, the system 100 lacks a C2 / C3 splitter in the olefin separation zone 108, which reduces the installation, maintenance, and operational costs of the system 100 compared to other systems having olefin separation zones that include a C2 / C3 splitter.

[0061] FIG. 2 is a diagrammatic representation of an embodiment of a system 200 that enables steam cracking, C4 olefin isomerization, olefin metathesis, and G, olefin isomerization, to facilitate the production of chemical feedstocks. The system 200 includes the pretreatment zone 102, the C4 isomerization zone 104, the metathesis zone 106, the olefin separation zone 108, the total hydrogenation zone 110, and the steam cracking zone 112, as discussed above with respect to FIG. 1, as well as a Ce isomerization zone 202. As such, in addition to the advantages set forth above for the embodiment of the system 100 illustrated in FIG. 1, the embodiment of the system 200 illustrated in FIG. 2 enables isolation and isomerization of Ce olefins to produce a hex-l-ene product stream 205. In particular, rather than being collected as a product or routed to the THU 148, as illustrated for the system 100 of FIG. 1, for the embodiment of the system 200 illustrated in FIG. 2, the Ce olefin stream 142 is instead directed to the Ce isomerization zone 202 for Ce isomerization.

[0062] For the embodiment of the system 200 illustrated in FIG. 2, the Ce olefin stream 142 isolated by the C4 column 134 substantially contains hex-3-enes and a limited quantity of hex-2-enes. The illustrated Ce isomerization zone 202 includes Ce isomerization reactors 204 (e.g., 204A, 204B) and a Ce fractionator 206 (e.g., a Ce fractional distillation column, a Ce super fractionator). The Ce olefin stream 142 is introduced into one of the Ce isomerization reactors 204 (e.g., 204A, 204B). The Ce isomerization reactors 204 are designed to isomerize the received stream to yield a Ce isomerized stream 208. More specifically, the Ce isomerization reactors 204 isomerize hex-2-enes and hex-3 -enes present in the incoming stream into hex-l-ene within the Ce isomerized stream 208. The Ce isomerized stream 208 is directed to the Ce fractionator 206 to separate the hex- l-ene product stream 205 from a hex-2 -enes / hex-3-ene stream 210. The hex-2 -enes / hex-3-ene stream 210 is recycled back to the Ce isomerization reactors 204, where it is combined with the Ce olefin stream 142 for further Ce isomerization to yield the Ce isomerized stream 208.

[0063] For the embodiment of the system 200 illustrated in FIG. 2, the G, isomerization reactors 204 are implemented such that one reactor remains online while the other reactor is in regeneration or standby mode. For embodiments having three Ce isomerization reactors 204, one Ce isomerization reactor remains online, while a second Ce isomerization reactor is in regeneration mode, and a third Ce isomerization reactor is in standby mode. The Ce isomerization reactors 204 can be implemented as down-flow or up-flow, fixed-bed reactors having a potassium -based isomerization catalyst (e.g., K2O / 7AI2O2) to enable the isomerization ofhex- 3-enes and hex-2-enes into hex-l-ene. The operating temperature of the Ce isomerization reactors 204 can range from about 250 °C to about 500 °C. The operating pressures of the Ce isomerization reactors 204 can range from about 0 barg to about 30 barg. In different implementations, each of the Ce isomerization reactors 204 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 Ce isomerization reactors 204 to enable a suitable operating cycle time from about 1 day to about 100 days for a fixed-bed plug flow reactor design. In some embodiments, this is achieved by limiting the flow rate of the Ce olefin stream 142 to the Ce isomerization reactors 204 to a WHSV of from about 0.1 per hour (h-1) to about 25 h’1, and more preferably to values from about 0.5 h'1to about 10 h’1. Regeneration of the isomerization catalyst can be performed when the Ce isomerization reactor 204A or 204B is in regeneration mode using nitrogen, air, enriched air, or oxygen at a temperature ranging from about 300 °C to about 500 °C.

[0064] FIG. 3 is a diagrammatic representation of an embodiment of a system 300 that enables fluid catalytic cracking, C4 olefin isomerization and separation, and olefin metathesis to facilitate the production of chemical feedstocks. The system 300 includes the pretreatment zone 102, the C4 isomerization zone 104, the metathesis zone 106, and the olefin separation zone 108, as discussed above with respect to FIG. 1, as well as a fluid catalytic cracking (FCC) zone 302. As such, in addition to the advantages set forth above for the embodiment of the system 100 illustrated in FIG. 1, the embodiment of the system 300 illustrated in FIG. 3 enables the formation of gasoline from a FCC cracked stream, in which Ce olefins generated from olefin metathesis may be combined with the gasoline product stream as a gasoline booster (e.g., an octane number booster).

[0065] For the embodiment of the system 300 illustrated in FIG. 3, the FCC zone 302 receives and steam cracks a hydrocarbon feedstock 304. In some embodiments, the hydrocarbon feedstock 304 contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof. The FCC zone 302 includes a fluid catalytic cracker (FCC) 306 and a downstream separation section 308 (also referred to herein as the downstream separation subzone). The FCC 306 receives and cracks the hydrocarbon feedstock 304, along with the paraffinic-rich stream 310 discussed below, to generate a FCC cracked stream 312 that is directed to the downstream separation section 308 for separation. In some embodiments, the FCC 306 includes a reactor that receives the hydrocarbon streams (e.g., at a WHSV from about 2.5 h'1to about 20 h'1), and contacts the received hydrocarbon streams with a FCC catalyst (e.g., a ZSM-5-based cracking catalyst)at elevated temperatures (e.g., from about 450 °C to about 650 °C) to yield the FCC cracked stream 312. In some embodiments, the FCC 306 includes a regenerator that is fluidly connected to the reactor to receive the spent FCC catalyst, to regenerate the spent FCC catalyst, and to return the regenerated FCC catalyst to the reactor to continue producing the FCC cracked stream 312. As such, in some embodiments, the regenerator of the FCC 306 receives a regeneration gas 314 that regenerates the catalyst by removing carbon deposited on the surface of the FCC catalyst particles at elevated temperatures, resulting in one or more off gases 316 being produced.

[0066] For the embodiment of the system 300 illustrated in FIG. 3, the FCC cracked stream 312 may include: hydrogen (Hz), BTX hydrocarbons, ethene, propene, pyrolysis gasoline, fuel gas, and / or other C1-12 hydrocarbons. BTX hydrocarbons include benzene, toluene, and dimethylbenzenes (also referred to herein as xylenes). The downstream separation section 308 receives the FCC cracked stream 312 and the C2-C3 olefin stream 136 from the olefin separation zone 108. The downstream separation section 308 includes any suitable number of reactors and / or separation columns that process and / or separate the received streams into a number of streams, including: an ethene product stream 318, a propene product stream 320, a C4 raffinate stream 322, a gasoline product stream 324, a liquid petroleum gas (LPG) product stream 326, the paraffinic-rich stream 310, and potentially other product streams. In some embodiments, the downstream separation section 308 includes a C2 / C3 splitter, a MTBE reactor, a but-l-ene (Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, an acetylene hydrogenation reactor, any other suitable separation column (e.g., distillation column, fractional distillation column, deethanizer, depropanizer, debutanizer, depentanizer, C2 / C3 splitter, and so forth), or any combination thereof. In some embodiments, the C4 raffinate stream 322 has a composition consistent with the C4 raffinate II or C4 raffinate III streams indicated in Table 1. The paraffinic- rich stream 156 (e.g., containing ethane, propane, butane, or combinations thereof) is recycled and combined with fresh hydrocarbon feedstock 304 and the paraffinic -rich stream 310 before returning to the FCC 306 to generate the FCC cracked stream 312. The C4 raffinate stream 322 is directed to the pretreatment zone 102, the C4 isomerization zone 104, and the metathesis zone 106 as discussed above. It may also be appreciated that, by utilizing the downstream separation section 308 to isolate the ethene product stream 318 and the propene product stream 320, the system 300 lacks a C2 / C3 splitter in the olefin separation zone 108, which reduces the installation, maintenance, and operational costs of the system 300 compared to other systems having olefin separation zones that include a C2 / C3 splitter.

[0067] For the embodiment of the system 300 illustrated in FIG. 3, the purge stream 144 that is extracted from the C4 olefin stream 141 downstream of the C4 column 134 of the olefin separation zone 108 includes paraffins (e.g., C4-C5 alkanes) and a limited quantity of olefins (e.g., C4-C5 olefins). For the illustrated embodiment, the purge stream 144 is cooled, condensed, and combined with the LPG product stream 326, to improve the productivity of the system 300. The G, olefin stream 142 that is separated by the C4 column 134 of the olefin separation zone 108 substantially contains hex-3-ene. For the illustrated embodiment, the G, olefin stream 142is combined with the gasoline product stream 324 as a gasoline booster (e.g., an octane number booster), enhancing the quality and value of the gasoline product stream 324.

[0068] FIG. 4 is a diagrammatic representation of an embodiment of a system 400 that enables fluid catalytic cracking, C4 olefin isomerization, olefin metathesis, and Ce olefin isomerization, to facilitate the production of chemical feedstocks. The system 400 includes the pretreatment zone 102, the C4 isomerization zone 104, the metathesis zone 106, and the olefin separation zone 108, as discussed above with respect to FIG. 1, the Ce isomerization zone 202, as discussed above with respect to FIG. 2, and the fluid catalytic cracking (FCC) zone 302, as discussed above with respect to FIG. 3. As such, in addition to the advantages set forth above for the embodiment of the system 300 illustrated in FIG. 3, the embodiment of the system 400 illustrated in FIG. 4 enables the formation of gasoline from a FCC cracked stream, while also enabling the isolation and isomerization of Ce olefins to produce the hex-1 -ene product stream 205.

[0069] For the embodiment of the system 400 illustrated in FIG. 4, the hydrocarbon feedstock 304 is FCC cracked and separated, as discussed with respect to FIG. 3, to yield the ethene product stream 318, the propene product stream 320, the C4 raffinate stream 322, the gasoline product stream 324, the LPG product stream 326, the paraffinic-rich stream 310, and potentially other product streams. The C4 raffinate stream 322 is directed to the pretreatment zone 102, then the C4 isomerization zone 104, and then the metathesis zone to yield the metathesis product stream 130, as discussed above with respect to FIG. 1. The metathesis product stream 130 is then directed to the olefin separation zone 108 for separation. The C2-C3 stream 136 separated by the C3 column 132 is directed to the downstream separation section 308 for separation into the ethene product stream 318 and the propene product stream 320.

[0070] For the embodiment of the system 400 illustrated in FIG. 4, the purge stream 144 that is extracted from the C4 olefin stream 141 downstream of the C4 column 134 of the olefin separation zone 108 includes paraffins (e.g., C4-C5 alkanes) and a limited quantity of olefins (e.g., C4-C5 olefins). For the illustrated embodiment, the purge stream 144 is cooled, condensed, and combined with the LPG product stream 326, to improve the productivity of the system 400. The G, olefin stream 142 isolated by the C4 column 134 substantially contains hex-3 -enes and a limited quantity of hex-2-enes. Rather than being combined with the gasoline product stream 324, as illustrated for the embodiment of the system 300 illustrated in FIG. 3, for the embodiment of the system 400 illustrated in FIG. 4, the Ce olefin stream 142 is directed to the Ce isomerization zone 202. The Ce isomerization zone 202 isomerizes hex-3 -enes and / or hex-2-enes in the Ce olefin stream 142 into hex- 1 -ene, as discussed above with respect to FIG. 2, and the hex- 1 -ene product is separated to yield the hex- 1 -ene product stream 205.Examples

[0071] Example 1:

[0072] Table 2 indicates the composition of an example C4 raffinate stream in weight percentages. For this example, C4 raffinate stream indicated in Table 2 was used as the input stream to the C4 isomerization zone104 (e.g., pretreated C4 stream 118) to predict ultimate product yields for the embodiment of the system 200 illustrated in FIG. 2. The ultimate product yields were calculated based on preliminary lab experimental results. For this example, the metathesis reaction conditions include an operating temperature of 50 °C, an operating pressure of 6 barg, and a WHSV of 0.6 h’1. The experimental results were confirmed with simulation results using commercial simulation software. For this example, continuous purging of the C4 olefin stream 141 was performed to remove the build-up of inert materials (e.g., paraffins) at the metathesis reactor inlet, and the purge stream 144 was further processed within the total hydrogenation zone 110 and the steam cracking zone 112 to increase ethene and propene product yields. The ultimate product yields were calculated using simulation software, taking into account the recycling of the C4 olefin stream 146 to the metathesis reactor, the total hydrogenation and steam cracking of the purge stream 144, and the G, isomerization and isolation to yield the hex-l-ene product stream 205. The simulation software used for the examples discussed herein is available from Aspen Technology Inc. of Bedford, Massachusetts, U.S.A. The ultimate product yields are presented in Table 3. As indicated in Table 3, in addition to forming hex-l-ene and ethene as the major products, a minor amount of butanes product also formed.

[0073] Table 2. Composition of the C4 raffinate stream provided to the metathesis zone for Example 1.

[0074] Table 3. Total product yields for Example 1.

[0075] Example 2:

[0076] Table 4 indicates the composition of an example C4 raffinate stream in molar percentages.

[0077] For this example, this C4 raffinate stream was used as the input stream to the C4 isomerization zone104 (e.g., pretreated C4 stream 118) to predict the composition of the but-l-ene-rich stream 126 for the embodiment of the system 100 illustrated in FIG. 1, the embodiment of the system 200 illustrated in FIG. 2, the embodiment of the system 300 illustrated in FIG. 3, or the embodiment of the system 400 illustrated in FIG. 4, with the C4 isomerization reactor (e.g., 120A or 120B) isomerizing the input C4 stream at different simulated operating temperatures. The other simulated operating parameters were generally in accordance with the parameters set forth for Example 1, while the C4 isomerization reactor was simulated as having an operating temperature ranging from about 100 °C to about 600 °C, an operating pressure ranging from about 0 barg toabout 30 barg, and a WHSV from about 0.1 h'1to about 20 h’1. The compositions of the but-l-ene-rich stream 126 when the C4 isomerization reactor was operated at different operating temperatures are also presented in Table 4. For each of these operating temperatures, the composition of the but-l-ene-rich stream 126 was calculated using lab experimental and verified using the simulation software. For this example, there was no observed effect on the composition of the but-l-ene-rich stream 126 due to changes in reaction pressure or WHSV at the C4 isomerization reactor. However, since it is presently recognized that the catalysts generally deactivate faster with increased WHSV, a WHSV of 0.6 hr'1results in the C4 isomerization catalyst being stable for 30 days. For this example, it was also observed that only (Z)-but-2-ene (cis-2 -butene) and (E)-but-2-ene (trans -2 -butene) were isomerized to but-l-ene within the C4 isomerization reactor, despite the presence of other unsaturated C4 species in the input C4 stream provided to the isomerization zone 104.

[0078] Table 4. Composition of the C4 input stream to, and composition of the but-l-ene-rich stream 126 (in mol %) from, the C4 isomerization zone 104 for Example 2.

[0079] 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.

[0080] 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 embodimentsdescribed 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

CLAIMSWhat is claimed:

1. A method comprising : cracking at least a hydrocarbon feedstock to produce a cracked stream; providing at least the cracked stream to a downstream separation section to produce at least an ethene product stream, a propene product stream, and a C4 raffinate stream; pretreating the C4 raffinate stream to produce a pretreated C4 stream; performing C4 isomerization of the pretreated C4 stream to produce a but-l-ene-rich stream, wherein but- 2-ene in the C4 raffinate stream is converted into but-l-ene during C4 isomerization and the but-l- ene-rich stream contains greater than about 90 mol. % of but-l-ene; metathesizing at least the but-l-ene-rich stream to produce a metathesis product stream; separating the metathesis product stream into at least a C2-C3 olefin stream, a C4 olefin stream, and a C<, olefin stream; purging a portion of the C4 olefin stream to produce a purge stream that contains at least one paraffin; combining a remainder of the C4 olefin stream after purging with the but-l-ene-rich stream prior to metathesis; and providing the C2-C3 olefin stream to the downstream separation section along with the cracked stream to produce the ethene product stream and the propene product stream.

2. The method of claim 1, wherein performing C4 isomerization comprises: heating the pretreated C4 stream to a temperature ranging from about 250 degrees Celsius (°C) to about 550 °C and pressurizing the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0.1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase during C4 isomerization, and wherein the isomerization catalyst is a potassium-based isomerization catalyst.

3. The method of any of claims 1-2, wherein metathesizing at least the but-l-ene-rich stream comprises: heating a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurizing the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and wherein the metathesis catalyst is a rhenium-coated y-alumina-based metathesis catalyst.

4. The method of any of claims 1-3, wherein cracking comprises steam cracking at least the hydrocarbon feedstock to produce the cracked stream, wherein the hydrocarbon feedstock contains C2 hydrocarbons, C3 hydrocarbons, liquid petroleum gas (LPG), naphtha, condensate, liquid hydrocarbons, Arab light crude, or crude oil, or any mixture thereof.

5. The method of claim 4, comprising: hydrogenating the purge stream to produce a saturated stream; and combining the saturated stream with the hydrocarbon feedstock prior to steam cracking to produce the cracked stream.

6. The method of any of claims 1-3, wherein cracking comprises fluid catalytic cracking the hydrocarbon feedstock to produce the cracked stream, wherein providing at least the cracked stream comprises providing at least the cracked stream and the C2-C3 olefin stream to the downstream separation section to produce at least the ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, a gasoline product stream, a C9+ hydrocarbon stream, and fuel gas, and wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (VGO), or any mixture thereof.

7. The method of claim 6, comprising: combining the purge stream with the LPG product stream to increase a yield of the LPG product stream.

8. The method of any of claims 6 or 7, comprising: combining the G, olefin stream with the gasoline product stream to boost an octane number of the gasoline product stream.

9. The method of any of claims 1-8, comprising: performing C>, isomerization of the C>, olefin stream to produce a C>, isomerized stream by heating the G, olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurizing the G, olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0.1 h'1to about 25 h’1, wherein the G, olefin stream is in a gas phase, a liquid phase, or a mixed phase during G, isomerization, wherein the isomerization catalyst is a potassium -based isomerization catalyst, and wherein hex-2-enes and hex-3 -enes in the G, olefin stream are converted into hex-l-ene during G, isomerization; and separating a first portion of the G, isomerized stream as a hex-l-ene product stream, wherein a remainder of the G, isomerized stream is combined with the G, olefin stream prior to G, isomerization.

10. A system comprising: a cracking reactor configured to receive and crack at least a hydrocarbon feedstock to produce a cracked stream; a downstream separation section configured to receive and separate at least the cracked stream to produce at least an ethene product stream, a propene product stream, and a CT raffinate stream; a pretreatment unit configured to receive and pretreat the CT raffinate stream to produce a pretreated C4 stream; a C4 isomerization reactor configured to receive and perform C4 isomerization of the pretreated C4 stream to produce a but-l-ene-rich stream, wherein but-2-ene in the C4 raffinate stream is converted into but- 1-ene within the C4 isomerization reactor and the but-l-ene-rich stream contains greater than about 90 mol. % of but-l-ene; a metathesis reactor configured to receive and metathesize at least the but-l-ene-rich stream to produce a metathesis product stream; a C3 column configured to receive and separate the metathesis product stream into a C2-C3 olefin stream and a C4+ olefin stream, the C2-C3 olefin stream being provided to the downstream separation section for separation into the ethene product stream and the propene product stream; and a C4 column configured to receive and separate the C4+ olefin stream into a C4 olefin stream and a C>, olefin stream, a portion of the C4 olefin stream being purged to produce a purge stream containing at least one paraffin and a remainder of C4 olefin stream being provided to the metathesis reactor along with the but-l-ene-rich stream for metathesis to produce the metathesis product stream.

11. The system of claim 10, wherein the C4 isomerization reactor is a fixed-bed up-flow reactor or a fixed- bed down-flow reactor, wherein the C4 isomerization reactor is configured to heat the pretreated C4 stream to a temperature ranging from about 250 degrees Celsius (°C) to about 550 °C and pressurize the pretreated C4 stream to a pressure ranging from about 0 bar gauge (barg) to about 30 barg before contacting an isomerization catalyst at a weight hourly space velocity (WHSV) from about 0. 1 per hour (h-1) to about 25 h’1, wherein the pretreated C4 stream is in a gas phase, a liquid phase, or a mixed phase, wherein the isomerization catalyst is a potassium -based isomerization catalyst, and wherein the C4 isomerization reactor has an operating cycle time from about 1 day to about 100 days.

12. The system of any of claims 10-11, wherein the metathesis reactor is a fixed-bed up-flow reactor or a fixed-bed down-flow reactor, wherein the metathesis reactor is configured to heat a combination of the remainder of the C4 olefin stream and the but-l-ene-rich stream to a temperature ranging from about 35 °C to about 100 °C and pressurize the combination of the remainder of the C4 olefin stream and the but-1-ene-rich stream to a pressure ranging from about 0 barg to about 30 barg before contacting a metathesis catalyst at a WHSV from about 0.1 h'1to about 25 h'1and in the absence of an ethene co-feed, wherein the combination of the remainder of the C4 olefin stream and the but- 1 -ene-rich stream is in a gas phase, a liquid phase, or a mixed phase during metathesis, and wherein the metathesis catalyst is a rhenium-coated y-alumina-based metathesis catalyst.

13. The system of any of claim 10-12, comprising: a total hydrogenation unit configured to receive and hydrogenate the purge stream to produce a saturated stream, wherein the saturated stream is combined with the hydrocarbon feedstock prior to being provided to the cracking reactor to produce the cracked stream.

14. The system of any of claims 10-13, wherein the cracking reactor comprises fluid catalytic cracking (FCC) reactor, wherein the downstream separation section is configured to receive and separate the cracked stream and the C2-C3 olefin stream to produce at least the ethene product stream, the propene product stream, the C4 raffinate stream, a LPG product stream, and a gasoline product stream, a C9+ hydrocarbon stream, and fuel gas, wherein the hydrocarbon feedstock contains naphtha, condensate, liquid hydrocarbons, Arab light crude, crude oil, vacuum gas oil (V GO), or any mixture thereof, wherein the purge stream is combined with the LPG product stream to increase a yield of the LPG product stream, and wherein the Ce olefin stream is combined with the gasoline product stream to boost an octane number of the gasoline product stream.

15. The system of any of claims 10-14, comprising: a Ce isomerization reactor configured to receive and perform Ce isomerization of the Ce olefin stream to produce a Ce isomerized stream, wherein hex-2-enes and hex-3-enes in the Ce olefin stream are converted into hex-l-ene within the Ce isomerization reactor, wherein the Ce isomerization reactor is a fixed-bed up-flow reactor or a fixed-bed down-flow reactor, wherein the Ce isomerization reactor is configured heat the Ce olefin stream to a temperature ranging from about 250 °C to about 500 °C and pressurize the Ce olefin stream to a pressure ranging from about 0 barg to about 30 barg before contacting an isomerization catalyst at a WHSV from about 0.1 h'1to about 25 h’1, wherein the Ce olefin stream is in a gas phase, a liquid phase, or a mixed phase during Ce isomerization, and wherein the isomerization catalyst is a potassium-based isomerization catalyst; and a G, fractionator configured to receive and separate the G, isomerized stream into a hex-l-ene product stream and a hex-2 -ene / hex-3-ene stream, wherein the hex-2 -ene / hex-3-ene stream is combined with the Ce olefin stream prior to Ce isomerization.

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