Systems and methods of producing olefins products using alternate upstream and downstream separation processes at low-temperature metathesis conditions

Abstract

Provided here systems and methods for the production of C2-C6 olefins using C4 pre-treatment, C4 fractionation, and C4 isomerization at low-temperature metathesis operation conditions. Methods for the production of C2-C6 olefins include absorbing one or more contaminants from a C4 feed stream to output a pretreated C4 stream. The method includes separating the pretreated C4 stream to produce a C4-rich stream and a C4 paraffin stream. The method includes isomerizing the C4-rich stream to produce a but-1-ene-rich stream. The method includes metathesizing the but-1-ene-rich stream to produce a metathesis product stream. The method includes separating the metathesis product stream to produce a C2-C3 product stream and a C4+-rich stream. The method includes separating the C4+- rich stream to produce a C4 recycle stream and a C5-C6 olefins stream. The method includes splitting the C2-C3 product stream to produce an ethene product stream and a propene product stream.

Description

SYSTEMS AND METHODS OF PRODUCING OLEFINS PRODUCTS USING ALTERNATE UPSTREAM AND DOWNSTREAM SEPARATION PROCESSES AT LOW- TEMPERATURE METATHESIS CONDITIONSCross-Reference to Related Applications

[0001] This application claims priority to and the benefit of European Application No. EP24150049.5, filed on January 2, 2024. The contents of the referenced application are incorporated into the present application by reference.Technical Field

[0002] The disclosure relates to the production of C2-C6 olefins using C4 pre-treatment, C4 fractionation, and C4 isomerization at low-temperature metathesis conditions.Background

[0003] Steam cracking processes are used to produce ethene, propene, and C4 olefins, such as but- 1-ene, but-2ene, isobutene, butyne, and butadiene. With the abundance of United States (U.S.) shale gas, steam crackers have shifted toward using lighter feedstocks; this change causes reduction in the production of propene. As the demand for propene increases, there exists a need to increase the production of propene using alternative processes while producing other olefins, such as C2-C6 olefins.Summary

[0004] Applicant has identified a need for the production of C2-C6 olefins using low-temperature metathesis without the use of ethene as a co-feed. Provided here are systems and methods to address these shortcomings of the art and provide other additional or alternative advantages. Examples include systems and methods for the production C2-C6 olefins at low metathesis reaction temperatures ranging from about 35 degrees Celsius (°C) to about 100 °C using a C4 feedstock to produce high value products, such as C2-C6 olefins by altering upstream and downstream separation processes for improved production efficiencies. The butene feedstock can contain highly pure but-l-ene and / or highly pure but-2-enes, or a mixture of both with a molar percent (mol. %) ranging from 0 to 100 mol. % along with butanes and other trace feed components. The system components include units for metathesis, C4 feed treatment, C4 separation, C4 isomerization, and steam cracking to produce C2- Ce olefins. The metathesis recycle feed composition and fresh C4 feedstock ratios to the metathesis reactor along with C4 individual components can be varied. The metathesis reactions can be either of self- or cross-type metathesis or combination of both. In self-type metathesis, two molecules of onereactant are converted to two products, and in cross-type metathesis two different products are converted into two products.

[0005] An example of a C2-C6 olefins production system includes a feed pre-treater configured to receive and decontaminate a C4 feed stream and output a pretreated C4 stream. A C4 isomerization reactor is configured to receive the pretreated C4 stream and to facilitate the isomerization of the C4 components into a but-l-ene-rich stream. Additionally, a metathesis reactor is configured to receive and to facilitate metathesis of the but-l-ene-rich stream into a metathesis product stream containing C2-C6 olefins. The metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C. A C3 column is configured to receive and separate the metathesis product stream into a C2-C3 product stream containing ethene and propene and a C4+ olefins stream containing C4-C6 olefins. A C4 column is configured to receive and separate the C4+ olefins stream into a C4 recycle stream and Cs-Ce olefins stream containing C5 olefins and Ce olefins. Additionally, a C2 / C3 splitter column is configured to receive and split the C2-C3 product stream into an ethene product stream and a propene product stream.

[0006] In certain examples, the system includes a C4 fractionator that is configured to receive and separate the pretreated C4 stream into a C4-rich stream containing but-l-enes and but-2-enes, and a C4 paraffin stream containing C4 paraffins and traces of propane. The C4 isomerization reactor is configured to receive and to facilitate isomerization of the C4-rich stream into a but-l-ene-rich stream. Additionally, a C5 column is configured to receive and separate the C5-C 6 olefins into a C5 olefin stream and Ce olefins product stream. The C5 olefin stream is supplied to the metathesis reactor.

[0007] In certain examples, the system includes a second metathesis reactor that is configured to receive and to facilitate metathesis of the C5 olefin stream and the ethene product stream into a second metathesis product stream containing propene and but-l-ene that is supplied to the C3 column. The second metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C. In certain examples, the system includes a total hydrogenation unit that is configured to receive and convert the Ce olefin product stream into a Ce paraffins stream containing Ce paraffins. Additionally, a steam cracker is configured to receive and crack the Ce paraffins stream and the C4 paraffin stream into a cracked product stream.

[0008] In certain examples, the C4 recycle stream with a but-l-ene content less than 15 mol. % is supplied to the C4 isomerization reactor. In certain examples, the C4 recycle stream is supplied to the metathesis reactor directly when the C4 recycle stream has a but-l-ene content of at least 15 mol. %. In certain examples, the C4-rich stream is supplied to the metathesis reactor as a pretreated C4-richstream. The pretreated C^rich stream has a but-l-ene content of at least 15 mol. %. In certain examples, the pretreated C4 stream is supplied to the metathesis reactor as a pretreated but-l-ene-rich stream. The pretreated but-l-ene-rich stream has a but-l-ene content of at least 15 mol. %.

[0009] Another example of a C2-C6 olefins production system includes a feed pre-treater that is configured to receive and decontaminate a C4 feed stream and output a pretreated C4 stream. A C4 fractionator is configured to receive and separate the pretreated C4 stream into a C4-rich stream containing but-l-enes, but-2-enes, and a C4 paraffin stream containing C4 paraffins. Additionally, a C4 isomerization reactor is configured to receive and to facilitate isomerization of the C4-rich stream into a but-l-ene-rich stream. A metathesis reactor is configured to receive and to facilitate metathesis of the but-l-ene-rich stream into a metathesis product stream containing C2-C6 olefins. The metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C. A C5 column is configured to receive and separate the metathesis product stream into a C2-C5 olefin stream and a Ce olefins product stream. Additionally, a C4 column is configured to receive and separate the C2-C5 olefin stream into a C5 olefin stream and a C2-C4 olefins stream. The C5 olefin stream is supplied to the metathesis reactor. A C3 column is configured to receive and separate the C2-C4 olefins stream into a C2-C3 product stream containing ethene and propene and a C4 recycle stream. Additionally, a C2 / C3 splitter column is configured to receive and split the C2-C3 product stream into an ethene product stream and a propene product stream.

[0010] In certain examples, the C4-rich stream is supplied to the metathesis reactor as a pretreated C4-rich stream. The pretreated C4-rich stream has a but-l-ene content of at least 15 mol. %. In certain examples, the C4 recycle stream is supplied to the metathesis reactor as a second C4 recycle stream. The second C4 recycle stream has a but-l-ene content of at least 15 mol. %.

[0011] An example method for producing C2-C6 olefins includes the step of absorbing one or more contaminants from a C4 feed stream to output a pretreated C4 stream. The method includes the step of separating the pretreated C4 stream to produce a C4-rich stream containing but-l-enes, but-2-enes, and a C4 paraffin stream containing C4 paraffins. The method includes the step of isomerizing the C4- rich stream to produce a but-l-ene-rich stream. The method includes the step of metathesizing the but-l-ene-rich stream at temperatures ranging from about 35 °C to about 100 °C to produce a metathesis product stream. The method includes the step of separating the metathesis product stream to produce a C2-C3 product stream containing ethene and propene and a C4+-rich stream containing C4-C6 olefins. The method includes the step of separating the C4+-rich stream to produce a C4 recycle stream and Cs-Ce olefins stream containing C5 olefins and Ce olefins. The method includes the stepof splitting the C2-C3 product stream to produce an ethene product stream and a propene product stream.

[0012] In certain examples, the method further includes the step of separating the Cs-Ce olefins to produce a C5 olefin stream and Ce olefins product stream. In certain examples, the metathesizing the C5 olefin stream and the ethene product stream at temperatures ranging from about 35 °C to about 100 °C to produce a second metathesis product stream containing propene and but-l-ene. In certain examples, the converting the Ce olefin product stream into a Ce paraffins stream containing Ce paraffins and cracking the Ce paraffins stream and the C4 paraffin stream into a cracked product stream.Brief Description of the Drawings

[0013] Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements or procedures in a method. Embodiments are illustrated by way of example and not by way of limitation in the accompanying drawings. The present disclosure can be better understood by referring to the following figures. These drawings illustrate the principles of the disclosure and no limitation of the scope of the disclosure is thereby intended.

[0014] FIG. 1 is a schematic representation of a system for the production of C2-C6 olefins using a butene feed stream containing a but-l-ene content of less than 15 mol. %, according to an example.

[0015] FIG. 2 is a schematic representation of a system for the production of C2-C6 olefins using a C5 column downstream of a C4 column to recycle C5 olefins to the metathesis reactor, according to an example.

[0016] FIG. 3 is a schematic representation of a system for the production of C2-C6 olefins using a C5 column downstream of a metathesis reactor, according to an example.

[0017] FIG. 4 is a schematic representation of a system for the production of C2-C6 olefins using a second metathesis reactor downstream of a C5 column, according to an example.

[0018] FIG. 5 is a schematic representation of a system for the production of C2-C6 olefins using a steam cracker, according to an example.Detailed Description

[0019] So that the manner in which the features and advantages of the examples of the systems and methods disclosed herein, as well as others that will become apparent, may be understood in more detail, a more particular description of examples of systems and methods briefly summarized abovemay be had by reference to the following detailed description of examples thereof, in which one or more are further illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various examples of the systems and methods disclosed herein and are therefore not to be considered limiting of the scope of the systems and methods disclosed herein as it may include other effective examples as well.

[0020] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in certain embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “containing,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0021] 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.

[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.” The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non -limiting example, 10 grams of a component in 100 grams of the material is 10 wt. % of such component. The terms “enriched” or “rich” or their variations mean an amount of at least generally greater than about 10 mol. %, and preferably about 15 mol. %, of a compound or class of compounds in a stream. The term “ppmw” refers to part per million by weight.

[0023] Hydrocarbon molecules may be abbreviated Ci, C2, C3 . Cn where “n” represents the number of carbon atoms in the one or more hydrocarbon molecules. Furthermore, a superscript “+” or or the terms “plus” and “minus” may be used with an abbreviated one or more hydrocarbons notation, e.g., C3+ or C3-, which is inclusive of the abbreviated one or more hydrocarbons. As an example, the term C3+ means one or more hydrocarbon molecules of three carbon atoms and / or more.

[0024] As used herein, the term “Cx-Cycompounds,” in which x and y are positive integer values, refers to hydrocarbon-based compounds, each compound containing between x and y carbon atoms,x and y inclusive. For example, a C3-C5 fraction refers to a mixture that substantially contains or entirely contains hydrocarbon-based compounds, each compound containing 3, 4, or 5 carbon atoms.

[0025] The term “but-2-enes” includes (Z)-but-2-ene (c / .s-but-2-ene), or (E)-but-2-ene ( / ra / z.s-but- 2-ene), or combinations thereof. The term “pent-2-enes” includes (Z)-pent-2-ene, or (E)-pent-2-ene, or combinations thereof.

[0026] 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.

[0027] As used herein, when a first component is described as receiving (or being designed to receive) a stream from a second component, or when a first component is described as providing (or being designed to provide) 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 predominantly contains the compound or class of compounds in the name of the stream (e.g., an ethene stream predominantly contains ethene, a C4 olefin stream predominantly contains C4 olefins, a Ce olefin stream predominantly contains Ce olefins), and the stream may also include other components. As used herein, the term “predominantly contains” refers to a stream containing 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.

[0028] Steam cracking processes are used to produce ethene as a major product along with the other side products, such as propene and C4 species, such as but-l-ene, but-2-enes, 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 toward 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. Theseintentional 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 olefins 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 uses of but-l-ene for metathesis, relatively high carbon dioxide (CO2) production, and relatively high metathesis reaction temperatures (e.g., from 250 °C to 450 °C).

[0029] Disclosed herein are various examples of systems for the production of C2-C6 olefins and methods for producing C2-C6 olefins. Recognizing that metathesis reactions typically occur at high temperatures that expend high energy, the present disclosure relates to methods and systems for the metathesis of C4 olefins at low reaction temperatures, such as temperatures of 35-100 °C, to produce high value products including C2-C6 olefins. The production of the products is based on the market demand or based on the end value product demand. The methods and systems in the present disclosure can utilize a C4 feed stream that is pretreated and subject to metathesis at low temperatures to improve olefin production. The C4 olefins and C5 olefins can be but-l-ene, pent-l-ene, (Z -but-2-ene / Ej-but- 2-ene, or pent-2-enes. Examples of the methods and systems in the present disclosure include utilization of self-metathesis, cross-type metathesis, or combination of both metathesis reactions depending on the required product.

[0030] In one or more examples, the system includes a feed pre-treater. The feed pre-treater receives a C4 feed stream or C4 raffinate stream containing but-l-ene, but-2-enes, / / -butenes, / / -butane, / -butane, 2-methylpropene ( / -butylene), propane, trace components of butynes (<5 ppm), and butadiene (< 30 ppm). The C4 feed stream can also contain an allowable range of oxygenates, such as MTBE, methanol, etc. The composition of the C4 feedstock can depend on its source, including a gas / liquid / light crude / crude oil cut mixed steam cracker downstream of a MTBE reactor, a but-l-ene (Bl) column, a but-2-enes (B2) column, a butadiene hydrogenation reactor, an MTO (methanol -to- olefins) process or refinery, and / or an FCC downstream process. In some examples, the feedstock supplied to the system is a C4 raffinate stream. The composition of the C4 raffinate stream can include greater than 15 molar percent (mol. %) of but-l-enes, a non -zero amount of but-2-enes, as well as an amount of inert C4 compounds (e.g., n-butane and / or isobutene) in a range from 20 to 30 mol. %. As non-limiting examples, sample compositions of two different C4 feed stream are provided in Table 1, shown below.

[0031] Table 1.

[0032] The feed pre-treater is designed to absorb one or more components from the C4 feed stream. These components may include one or more of a sulfur compound, an alcohol compound, oxygenates, or a combination thereof. In certain examples, the feed pre-treater is a single guard bed or dual guard beds or multiple guard beds. The feed pre-treater can be a fixed-bed reactor. The feed pre-treater can be in a zone with two or three such units. The first feed pre-treater can be in a reaction mode, the second feed pre-treater can be in a regeneration mode, and the third feed pre-treater can be in a standby mode. After the one or more components are absorbed in the feed pre-treater, the feed pre-treater outputs a pretreated C4 stream.

[0033] In certain examples, the system includes a C4 fractionator. The C4 fractionator can be a super fractionator or conventional fractionator. The C4 fractionator is in fluid communication with the feed pre-treater and is designed to receive and fractionate the pretreated C4 stream to produce a C4 purge stream (also referred to as a C4 paraffin stream) that contains C4 paraffins (for example, butane, 2-methylpropane) and some C4 olefins and a C4-rich stream containing but-l-enes and but-2- enes.

[0034] The system further includes a C4 isomerization reactor. In certain examples, the C4 isomerization reactor is in fluid communication with the C4 fractionator and is designed to receive and to facilitate isomerization of the C4-rich stream to produce a but-l-ene-rich feed stream. In other examples, the C4 isomerization reactor is in fluid communication with the feed pre-treater and is designed to receive and to facilitate isomerization of the pretreated C4 stream to produce the but-l- ene-rich feed stream. The C4 isomerization reactor facilitates isomerization of the cA-but-2-ene and / ra / / .s-but-2-ene to but-l-ene. The but-l-ene-rich feed stream contains but-l-ene, butane, and unreacted but-2-enes. The C4 isomerization reactor can be operated at temperatures ranging fromabout 250 degrees Celsius (°C) to 650 °C and contains proprietary catalysts, such as K2O / Y-AI2O3, using a liquid feed, vapor feed or mixed phase feed. The C4 isomerization reactor can operate at pressures ranging from about 0 bar gauge (barg) to 30 barg. However, it is noted that the isomerization reaction is pressure independent, and the process can generally be performed at a pressure that best suits the upstream and downstream operations. The C4 isomerization reactor can also be a traditional packed bed reactor. The C4 isomerization reactor can have an operating cycle time ranging from about 1 days to about 100 days. The C4 isomerization reactor can have a weight hourly space velocity (WHSV) ranging from about 0.1 h'1to 25 h’1. For example, the WHSV can be from about 0.5 h'1to 10 h’1. Regeneration of isomerization reactor can be performed using nitrogen, air, enriched air, or oxygen at temperatures ranging from about 300 °C to about 650 °C. In certain examples, the system can include two or more C4 isomerization reactors with at least one C4 isomerization reactor is in service while the remaining C4 isomerization reactors are in regeneration mode or on standby. The C4 isomerization reactor can be in a C4 isomerization zone.

[0035] The system includes a metathesis reactor. The metathesis reactor (also referred to as a metathesis reactor I) is in fluid communication with C4 isomerization reactor and is designed to receive and to facilitate metathesis of the but-l-ene-rich feed stream to produce a metathesis product stream. In some examples, the metathesis reactor is in fluid communication with the C4 fractionator or the feed pre-treater depending on the but-l-ene content of the C4 feed stream to produce the metathesis product stream. In certain examples, the system includes a second metathesis reactor ((also referred to as a metathesis reactor II) to reduce the load on the first metathesis reactor and allow for additional production of high value products, such as propene and but-l-enes.

[0036] To facilitate the metathesis reactions in the metathesis reactor, a metathesis catalyst, such as a rhenium oxide-coated y-alumina-based catalyst, is provided in the metathesis reactor. The rhenium oxide-coated y-alumina-based catalyst (Re2O? / yA12O3) can be spherical or an extrudate. One such rhenium oxide-coated y-alumina-based catalyst has y-alumina-based spherical particles of a size ranging from about 1.2 mm to about 3 mm and a rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. Other examples include y-alumina-based extrudate particles of a size ranging from 1.2 mm to about 3 mm in diameter and from about 4 mm to about 8 mm in length, with the rhenium oxide coating ranging from about 150 pm to about 250 pm in thickness. In certain examples, the rhenium oxide-coated y-alumina-based catalyst contains rhenium oxide in an amount ranging from about 4.8 wt. % to about 5.6 wt. %. In certain examples, the rhenium oxide-coated y-alumina-based catalyst can be functional for at least 300 days in the operational metathesis reactor. In certain examples, the catalyst is regenerated for greater than 50 times in the operational metathesis reactor. Based on regeneration times, the catalyst can be functional for about 1000 days or longer. These days can vary based on the weight hourly space velocity that may range from 0.6 / hr to 10 / hr. In certain examples, in addition or alternative to the rhenium oxide-coated y-alumina-based catalyst, the metathesis catalyst is or includes rhenium oxide that is dispersed throughout a core or interior of the y-alumina. The y-alumina particles of these rhenium oxide-dispersed y-alumina-based catalyst can be spherical or an extrudate.

[0037] Methods of preparing a rhenium oxide-coated y-alumina-based catalyst include the steps of calcining a y-alumina-based support to form a calcined y-alumina-based support at a temperature ranging from about 450 Celsius (°C) to about 550 °C and treating the calcined y-alumina-based support with an aqueous rhenium-containing mixture in a rotating drum impregnation unit to form a rhenium-coated y-alumina-based support. In certain examples, the aqueous rhenium-containing mixture is a NFUReCU solution, an Al(ReO4)3 solution, or a HReC solution. In certain examples, the impregnation unit is rotated at a speed ranging from about 15 revolutions per minute (rpm) to about 25 rpm to form a rhenium-coated y-alumina-based support. The method also includes the steps of aging the rhenium-coated y-alumina-based support to form a rhenium oxide-coated y-alumina-based catalyst after calcination, containing a rhenium oxide coating ranging from about 150 micrometers (pm) to about 250 pm in thickness, drying the rhenium-coated y-alumina-based catalyst immediately after aging, and calcining the rhenium-coated y-alumina-based catalyst at a temperature ranging from about 450°C to about 550 °C to form rhenium oxide coated y-alumina. In certain examples, the step of aging the rhenium-coated y-alumina-based support is conducted for a time less than 5 minutes thereby to form a rhenium oxide-coated y-alumina-based catalyst after calcination. In certain examples, the step of drying the rhenium-coated y-alumina-based catalyst immediately after aging at a temperature ranges from about 140 °C to about 160 °C.

[0038] The particle size of the y-alumina-based support can range from about 1.2 millimeters (mm) to about 3 mm. For example, the diameter of a spherical or a cylindrical y-alumina-based support can range from about 1.2 mm to about 3 mm. In certain examples, the y-alumina-based support has a pore volume ranging from about 0.5 milliliter per gram (ml / g) to about 0.65 ml / g. In certain examples, the y-alumina-based support has a pore diameter ranging from about 75 Angstroms (A) to about 110 A. In certain examples, the y-alumina-based support has a total acidity ranging from about 0.58 millimoleper gram (mmolNm / g) to about 0.62 mmolNm / g. In certain examples, the rhenium oxide-coated y- alumina-based catalyst can contain rhenium oxide in an amount ranging from about 4.8 weight percent (wt. %) to about 5.6 wt. %. The rhenium oxide-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 rhenium oxide-coated y-alumina-based catalyst can be spherical in shape or an extrudate. An extrudate can be cylindrical or lobed or of other shapes. In certain examples, the rhenium particles of the coating have a particle size ranging from about 0.3 nanometer (nm) to about 1.2 nm.

[0039] Examples include methods of preparing an activated rhenium oxide-coated y-alumina- based catalyst. One such method includes the steps of treating the rhenium oxide-coated y-alumina- based catalyst under air at a temperature from about 500 °C to about 550 °C to produce an activated rhenium oxide-coated y-alumina-based catalyst, purging nitrogen into the activated rhenium oxidecoated y-alumina-based catalyst to displace the air, and cooling the activated rhenium oxide-coated y-alumina-based catalyst to a temperature of about 50 °C. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is conducted for about 4 hours to about 24 hours to produce an activated rhenium oxide-coated y-alumina-based catalyst. In certain examples, the step of treating the rhenium oxide-coated y-alumina-based catalyst under air is conducted for about 6 hours.

[0040] The metathesis reactor can operate at temperatures from about 35 °C to about 100 °C. In some examples, the metathesis reactor is a down-flow or up-flow, fixed bed reactors. The metathesis reactor can be operated in gas phase, liquid phase, or mixed phase. The metathesis reactor can operate at pressures ranging from about 0 barg to about 30 barg. The metathesis reactor can have an operating cycle time ranging from about 1 day to about 100 days. The metathesis reactor WHSV can range from about 0.1 h'1to about 25 h'1. For example, the metathesis WHSV can range from about 0.5 h'1to about 10 h’1.

[0041] Regeneration of metathesis reactor can be performed either using air, enriched air or oxygen at temperatures ranging from about 300 °C to about 600 °C. For example, using air, the regeneration temperatures range from about 350 °C to 550 °C. In certain examples, two or more metathesis reactors are contained within the system with one of the metathesis reactors being active while the other metathesis reactors are in standby mode or in a regeneration mode. The metathesis catalyst can be regenerated in-situ (online) and ex-situ off-line or a bunker flow reactor with continuous catalyst replacement.

[0042] The systems includes one or more separation columns of a C4 separation zone for separating unconverted feed and products. As described herein, various systems can be implemented to increase metathesis reactor productivity and / or increase the feedstock utilization based on recovery of reactive components from downstream of a metathesis reactor and recycling of the reactive components. To efficiently separate out the inert C4 compounds, as described below, the downstream separation zone can include a C3 column, a C4 column, a C5 column, a C2 / C3 splitter, a total hydrogenation unit (THU), and a steam cracker.

[0043] The system can be designed based on the feed stream or feedstock presented at the plant. The system also can be designed based on the product requirements. For example, the system can be designed based on steam cracker configurations in an existing plant or an upcoming plant, to thereby integrate with a metathesis plant.

[0044] An example method for producing C2-C6 olefins includes the step of absorbing one or more contaminants from a C4 feed stream to output a pretreated C4 stream. The method includes the step of separating the pretreated C4 stream to produce a C4-rich stream containing but-l-enes, but-2-enes, and a C4 paraffin stream containing C4 paraffins. The method includes the step of isomerizing the C4- rich stream to produce a but-l-ene-rich stream and metathesizing the but-l-ene-rich stream at temperatures ranging from about 35 °C to about 100 °C to produce a metathesis product stream. The method further includes the step of separating the metathesis product stream to produce a C2-C3 product stream containing ethene and propene and a C4+-rich stream containing C4-C6 olefins; and then separating the C4+-rich stream to produce a C4 recycle stream and Cs-Ce olefins stream containing C5 olefins and Ce olefins. The method includes the step of splitting the C2-C3 product stream to produce an ethene product stream and a propene product stream.

[0045] In certain examples, the method further includes the step of separating the Cs-Ce olefins to produce a C5 olefin stream and Ce olefins product stream. In certain examples, the method further includes the step of metathesizing the C5 olefin stream and the ethene product stream at temperatures ranging from about 35 °C to about 100 °C to produce a second metathesis product stream containing propene and but-l-ene. In certain examples, the method further includes the step of converting the Ce olefin product stream into a Ce paraffins stream containing Ce paraffins and cracking the Ce paraffins stream and the C4 paraffin stream into a cracked product stream.

[0046] FIG. 1 is a schematic representation of an embodiment of a system 100 for the production of C2-C6 olefins. A C4 feed stream 102 containing but-l-ene and but-2-enes is supplied as the input stream to the system 100 to the feed pre-treater 104. The feed pre-treater 104 absorbs contaminants,such as salts and sulfur to output a pretreated C4 stream 106. Depending on the source of the C4 feed stream 102, the C4 feed stream 102 can have a but-l-ene content of less than 15 mol. %, such as from about 0 mol. % to about 13 mol. %. As the metathesis reactor 114 is designed to consume a but-1- ene-rich stream 110 with a but-l-ene content of at least 15 mol. %, when the C4 stream 102 has a but- l-ene content less than 15 mol. %, the pretreated C4 stream 106 may be conditionally directed to the C4 isomerization reactor 108. In other examples, when the C4 feed stream 102 has a but-l-ene content greater than or equal to 15 mol. %, the C4 isomerization reactor 108 can be omitted or bypassed and the pretreated C4 stream 106 can be provided directly to the metathesis reactor 114 as the pretreated but-l-ene-rich stream 110.

[0047] For the example illustrated in FIG. 1, the C4 isomerization reactor 108 is in fluid communication with the feed pre-treater 104 and is designed to receive and to facilitate isomerization of the but-2-enes of the pretreated C4 stream 106 into but-l-ene to produce a but-l-ene-rich stream 112 with a but-l-ene content of at least 15 mol. %. For this C4 isomerization, the C4 isomerization reactor 108 can operate at a temperature ranging from about 250 °C to about 600 °C and at a pressure ranging from about 1 barg to about 30 barg. The C4 isomerization reactor 108 contains an isomerization catalyst, such as a K2O / Y-AI2O3 catalyst.

[0048] For the example illustrated in FIG. 1, the metathesis reactor 114 is in fluid communication with the C4 isomerization reactor 108 or the feed pre-treater 104 and is designed to receive and to facilitate metathesis of the but-l-ene-rich stream 112 or the pretreated but-l-ene-rich stream 110 from the C4 isomerization reactor 108 or the feed pre-treater 104, respectively, to produce a metathesis product stream 116. The metathesis reactor 114 contains a metathesis catalyst, such as a R^CF / YAhCh catalyst that facilitates cross-metathesis and / or self-metathesis reactions of the but-l-ene-rich stream 112 or the pretreated but-l-ene-rich stream 110. The metathesis reactor 114 operates at a temperature from about 35 °C to about 100 °C. The metathesis product stream 116 contains ethene, propene, and C4-C6 olefins, as well as a limited amount of C4-C6 paraffins.

[0049] For the example illustrated in FIG. 1, the C3 column 118 is in fluid communication with the metathesis reactor 114 and is designed to receive and separate the metathesis product stream 116 to produce a C2-C3 stream 120 (or C2-C3 product stream) and a C4+ olefins stream 122. The C3 column 118 can be a depropenizer. The C2-C3 stream 120 contains ethene and propene and the C4+ olefins stream 122 contains the C4-C6 olefins.

[0050] For the embodiment illustrated in FIG. 1, a C2 / C3 splitter 124 is in fluid communication with the C3 column 118 and is designed to receive and split the C2-C3 stream 120 into an etheneproduct stream 128 and a propene product stream 130. The C2 / C3 splitter 124 can be a C2 / C3 distillation column. The ethene product stream 128 and a propene product stream 130 are collected as a higher value olefin product stream, and the metathesis reaction proceeds in the absence of an ethene co-feed.

[0051] For the example illustrated in FIG. 1, a C4 column 126 is in fluid communication with the C3 column 118 and is designed to receive and separate the C4+ olefins stream 122 into a C4 recycle stream 132 and a Cs-Ce olefins stream 136. The C4 column 126 can be a debutenizer. To reduce or prevent the buildup of unreactive C4 paraffins at the metathesis reactor 114, a C4 purge stream 134 is extracted from the C4 recycle stream 132, in which the C4 purge stream 134 contains C4 paraffins (for example, butane, 2-methylpropane, etc.) and some C4 olefins. The C4 purge stream 134 can be collected as a product or provided as a feed stream to another system or unit of a hydrocarbon processing facility outside of this configuration. As the metathesis reactor 114 is designed to consume abut-l-ene-rich stream 110 with abut- 1-ene content of at least 15 mol. %, when the C4 recycle stream 132 has a but-l-ene content less than 15 mol. %, the C4 recycle stream 132 can be conditionally directed to the C4 isomerization reactor 108. In other examples, when the C4 recycle stream 132 has a but-l-ene content greater than or equal to 15 mol . %, the C4 isomerization reactor 108 can be omitted or skipped and the C4 recycle stream 132 can be provided as a second C4 recycle stream 138 to mix with the but-l-ene-rich stream 112 as an input into the metathesis reactor 114.

[0052] FIG. 2 is a schematic representation of an embodiment of a system 200 for the production of C2-C6 olefins using a C5 column downstream of a C4 column to recycle C5 olefins to the metathesis reactor. A C4 feed stream 202 containing but-l-ene and but-2-enes is supplied as the input stream to the system 200 to the feed pre-treater 204. The feed pre-treater 204 absorbs contaminants, such as salts and sulfur, to output a pretreated C4 stream 206.

[0053] For the example illustrated in FIG. 2, the C4 fractionator 208 is in fluid communication with the feed pre-treater 204 and is designed to receive and fractionate the pretreated C4 stream 206 to produce a C4-rich stream 210 and a C4 purge stream 207. To reduce or prevent the buildup of unreactive C4 paraffins at the metathesis reactor 218, a C4 purge stream 207 is extracted at the C4 fractionator 208 to improve downstream metathesis reactions. The C4 purge stream 207 contains C4 paraffins (for example, butane, 2-methylpropane, etc.) and some C4 olefins. The C4 purge stream 207 can be collected as a product or provided as a feed stream to another system or unit of a hydrocarbon processing facility outside of this configuration. Depending on the source of the C4 feed stream 202, the C4 feed stream 202 can have a but-l-ene content of less than 15 mol. %. When the C4 stream 202has a but-l-ene content less than 15 mol. %, the C^rich stream 210 can be conditionally directed to the C4 isomerization reactor 212. In other examples, when the C4 feed stream 202 has a but-l-ene content greater than or equal to 15 mol. %, the C4-rich stream 210 can be provided directly to the metathesis reactor 218 as the pretreated C4-rich stream 214 with a but-l-ene content of at least 15 mol. %.

[0054] For the example illustrated in FIG. 2, the C4 isomerization reactor 212 is in fluid communication with the C4 fractionator 208 and is designed to receive and to facilitate isomerization of the but-2-enes of the C4-rich stream 210 into but-l-ene to produce a but-l-ene-rich stream 216 with a but-l-ene content of at least 15 mol. %. For this C4 isomerization, the C4 isomerization reactor 212 can operate at a temperature ranging from about 250 °C to about 650 °C and at a pressure ranging from about 1 barg to about 30 barg. The C4 isomerization reactor 212 contains an isomerization catalyst, such as a K2O / Y-AI2O3 catalyst.

[0055] For the example illustrated in FIG. 2, the metathesis reactor 218 is in fluid communication with the C4 isomerization reactor 212 or the C4 fractionator 208 and is designed to receive and to facilitate metathesis of the but-l-ene-rich stream 216 or the pretreated C4-rich stream 214 from the C4 isomerization reactor 212 or the C4 fractionator 208, respectively, to produce a metathesis product stream 220. The metathesis reactor 218 contains a metathesis catalyst, such as a R^CF / YAhCh catalyst that facilitates cross-metathesis and / or self-metathesis reactions of the but-l-ene-rich stream 216 or the pretreated C4-rich stream 214. The metathesis reactor 218 operates at a temperature from about 35 °C to about 100 °C. The metathesis product stream 220 contains ethene, propene, and C4-C6 olefins, as well as a limited amount of C4-C6 paraffins.

[0056] For the example illustrated in FIG. 2, the C3 column 222 is in fluid communication with the metathesis reactor 218 and is designed to receive and separate the metathesis product stream 220 to produce C2-C3 stream 224 and a C4+ olefins stream 226. The C3 column 222 can be a depropenizer. The C2-C3 stream 224 contains ethene and propene, and the C4+ olefins stream 226 contains the C4- Ce olefins.

[0057] For the example illustrated in FIG. 2, a C2 / C3 splitter 228 is in fluid communication with the C3 column 222 and is designed to receive and split the C2-C3 stream 224 into an ethene product stream 230 and a propene product stream 232. The ethene product stream 230 and a propene product stream 232 are collected as a higher value olefin product stream, and the metathesis reaction proceeds in the absence of an ethene co-feed.

[0058] For the example illustrated in FIG. 2, a C4 column 234 is in fluid communication with the C3 column 222 and is designed to receive and separate the C4+ olefins stream 226 into a C4 recycle stream 244 and a Cs-Ce olefins stream 236. The C4 column 234 can be a debutenizer. As the metathesis reactor 218 is designed to consume an input stream with a but-l-ene content of at least 15 mol. %, when the C4 recycle stream 244 has a but-l-ene content less than 15 mol. %, the C4 recycle stream 244 can be conditionally directed to the C4 isomerization reactor 212. In other examples, when the C4 recycle stream 244 has a but-l-ene content of at least 15 mol. %, the C4 recycle stream 244 can be provided as a second C4 recycle stream 246 to mix with the but-l-ene-rich stream 216 as an input into the metathesis reactor 218.

[0059] For the example illustrated in FIG. 2, the C5 column 238 is in fluid communication with the C4 column 234 and is designed to receive and separate the Cs-Ce olefins stream 236 to produce C5 olefin stream 240 and a Ce olefin product stream 242. The C5 column 238 can be a depentenizer. The C5 olefin stream 240 is recycled back to the metathesis reactor 218 to increase the propene product stream 232 yield and the Ce olefin product stream 242 yield. The Ce olefin product stream 242 can be used or sold as a gasoline booster.

[0060] FIG. 3 is a schematic representation of an embodiment of a system 300 for the production of C2-C6 olefins using a C5 column downstream of a metathesis reactor. A C4 feed stream 302 containing but-l-ene and but-2-enes is supplied as the input stream to the feed pre-treater 304. The feed pre-treater 304 absorbs contaminants, such as salts and sulfur to output a pretreated C4 stream 306

[0061] For the example illustrated in FIG. 3, the C4 fractionator 308 is in fluid communication with the feed pre-treater 304 and is designed to receive and fractionate the pretreated C4 stream 306 to produce a C4-rich stream 310 and a C4 purge stream 307. The C4 purge stream 307 removes C4 paraffins as previously mentioned in system 200. When the C4 stream 302 has a but-l-ene content of less than 15 mol. %, the C4-rich stream 310 can be conditionally directed to the C4 isomerization reactor 312. In other examples, when the C4 feed stream 302 has a but-l-ene content greater than or equal to 15 mol. %, the C4-rich stream 310 can be provided directly to the metathesis reactor 318 as the pretreated C4-rich stream 316 with a but-l-ene content of at least 15 mol. %.

[0062] For the example illustrated in FIG. 3, the C4 isomerization reactor 312 is in fluid communication with the C4 fractionator 308 and is designed to receive and to facilitate isomerization of the but-2-enes of the C4-rich stream 310 into but-l-ene to produce a but-l-ene-rich stream 314 with a but-l-ene content of at least 15 mol. %. For this C4 isomerization, the C4 isomerization reactor 312can operate at a temperatures and pressures as previously mentioned in system 200. The C4 isomerization reactor 312 contains an isomerization catalyst, such as a K2O / Y-AI2O3 catalyst.

[0063] For the example illustrated in FIG. 3, the metathesis reactor 318 is in fluid communication with the C4 isomerization reactor 312 or the C4 fractionator 308 and is designed to receive and to facilitate metathesis of the but-l-ene-rich stream 314 or the pretreated C4-rich stream 316 to produce a metathesis product stream 320. The metathesis reactor 218 contains a metathesis catalyst, such as a Re2O7 / yA12O3 catalyst that facilitates cross-metathesis and / or self-metathesis reactions of the but-l- ene-rich stream 314 or the pretreated C4-rich stream 316. The metathesis reactor 318 operates at a temperature from about 35 °C to about 100 °C. The metathesis product stream 320 contains ethene, propene, and C4-C6 olefins.

[0064] For the example illustrated in FIG. 3, the C5 column 322 is in fluid communication with the metathesis reactor 318 and is designed to receive and separate the metathesis product stream 320 to produce C4-C5 olefins stream 324 and a Ce olefin product stream 326. The Ce olefin product stream 326 can be collected as a product or provided as a feed stream to another system or unit of a hydrocarbon processing facility outside of this configuration or used / sold as gasoline booster. The C5 column 322 can be a depentenizer.

[0065] For the example illustrated in FIG. 3, a C4 column 330 is in fluid communication with the C5 column 322 and is designed to receive and separate the C2-C5 olefins stream 324 into a C5 olefin stream 344 and a C2-C4 olefins stream 332. The C4 column 330 can be a debutenizer. The C5 olefin stream 344 is recycled back to the metathesis reactor 218.

[0066] For the example illustrated in FIG. 3, the C3 column 334 is in fluid communication with the C4 column 330 and is designed to receive and separate the C2-C4 olefins stream 332 to produce C2-C3 stream 336 and a C4 recycle stream 338. The C2-C3 stream 336 contains ethene and propene. The C3 column 334 can be a depropenizer. As the metathesis reactor 318 is designed to consume an input stream with a but-l-ene content of at least 15 mol. %, when the C4 recycle stream 338 has a but- 1-ene content less than 15 mol. %, the C4 recycle stream 338 can be conditionally directed to mix with C4-rich stream 310 prior to being isomerized in the C4 isomerization reactor 312. In some examples, the C4 recycle stream 338 can be conditionally directed to the C4 isomerization reactor 312. In other examples, when the C4 recycle stream 338 has a but-l-ene content of at least 15 mol. %, the C4 recycle stream 338 can be provided as a second C4 recycle stream 346 to mix with the but-l-ene- rich stream 314 as an input into the metathesis reactor 318.

[0067] For the embodiment illustrated in FIG. 3, a C2 / C3 splitter 337 is in fluid communication with the C3 column 334 and is designed to receive and split the C2-C3 stream 336 into an ethene product stream 340 and a propene product stream 342. The ethene product stream 340 and a propene product stream 342 are collected as a higher value olefin product stream, and the metathesis reaction proceeds in the absence of an ethene co-feed.

[0068] FIG. 4 is a schematic representation of an embodiment of a system 400 for the production of C2-C6 olefins using a second metathesis reactor downstream of a C5 column. A C4 feed stream 402 containing but-l-ene and but-2-enes is supplied as the input stream to the system 400 to the feed pretreater 404 to produce a pretreated C4 stream 406 as previously mentioned. A C4 fractionator 408 receives and fractionates the pretreated C4 stream 406 to produce a C4-rich stream 410 and a C4 purge stream 407 as previously mentioned. In certain examples, the C4-rich stream 410 with a but-l-ene content of at least 15 mol. % depending on the type of C4 feed stream 402, can be provided directly to the first metathesis reactor 418 as the pretreated C4-rich stream 414 with a but-l-ene content of at least 15 mol. %.

[0069] For the example illustrated in FIG. 4, when the C4 feed stream 402 has a but-l-ene content less than 15 mol. %, the C4-rich stream 410 is conditionally directed to a C4 isomerization reactor 412. The C4 isomerization reactor 412 is in fluid communication with the C4 fractionator 408 and is designed to receive and to facilitate isomerization of the but-2-enes of the C4-rich stream 410 into but-l-ene to produce a but-l-ene-rich stream 416 with a but-l-ene content of at least 15 mol. %. For this C4 isomerization, the C4 isomerization reactor 412 can operate at a temperature ranging from about 250 °C to about 650 °C and at a pressure ranging from about 1 barg to about 30 barg. The C4 isomerization reactor 412 contains an isomerization catalyst, such as a K2O / Y-AI2O3 catalyst.

[0070] For the example illustrated in FIG. 4, the first metathesis reactor 418 is in fluid communication with the C4 isomerization reactor 412 or the C4 fractionator 408 and is designed to receive and to facilitate metathesis of the but-l-ene-rich stream 416 or the pretreated C4-rich stream 414 to produce a first metathesis product stream 420. The first metathesis reactor 418 operates with a metathesis catalyst and at temperatures and pressures previously mentioned. The first metathesis product stream 420 contains ethene, propene, and C4-C6 olefins.

[0071] For the example illustrated in FIG. 4, the C3 column 422 is in fluid communication with the metathesis reactor 418 and is designed to receive and separate the first metathesis product stream 420 to produce C2-C3 stream 424 and a C4+ olefins stream 426. The C3 column 422 can be adepropenizer. The C2-C3 stream 424 contains ethene and propene and the C4+ olefins stream 426 contains the C4-C6 olefins.

[0072] For the example illustrated in FIG. 4, a C2 / C3 splitter 428 is in fluid communication with the C3 column 422 and is designed to receive and split the C2-C3 stream 424 into an ethene product stream 430 and a propene product stream 432. The propene product stream 432 are collected as a higher value olefin product stream, and the ethene product stream 430 is directed to a second metathesis reactor 444 to increase propene product stream 432 yield and also increase the production of C4 olefins with a but-l-ene content of at 15 mol. %.

[0073] For the example illustrated in FIG. 4, a C4 column 434 is in fluid communication with the C3 column 422 and is designed to receive and separate the C4+ olefins stream 426 into a C4 recycle stream 446 and a Cs-Ce olefins stream 436. The C4 column 434 can be a debutenizer. As the metathesis reactor 418 is designed to consume an input stream with a but-l-ene content of at least 15 mol. %, when the C4 recycle stream 446 has a but-l-ene content less than 15 mol. %, the C4 recycle stream 446 can be conditionally directed to the C4 isomerization reactor 412. In other examples, when the C4 recycle stream 446 has a but-l-ene content of at least 15 mol. %, the C4 recycle stream 446 can be provided as a second C4 recycle stream 448 to mix with the but-l-ene-rich stream 416 as an input into the metathesis reactor 418.

[0074] For the example illustrated in FIG. 4, the C5 column 438 is in fluid communication with the C4 column 434 and is designed to receive and separate the Cs-Ce olefins stream 436 to produce C5 olefin stream 440 and a Ce olefin product stream 442. The C5 column 438 can be a depentenizer. The Ce olefin product stream 442 are collected as a higher value olefin product stream, and the C5 olefin stream 440 is directed to the second metathesis reactor 444.

[0075] For the example illustrated in FIG. 4, the second metathesis reactor 444 is in fluid communication with the C5 column 438 and is designed to receive and to facilitate metathesis of the C5 olefin stream 440 and the ethene product stream 430 to produce a second metathesis product stream 450 containing propene and but-l-ene. The second metathesis reactor 444 operates similar to the first metathesis reactor 418.

[0076] FIG. 5 is a schematic representation of an embodiment of a system 500 for the production of C2-C6 olefins using a steam cracker. A C4 feed stream 502 containing but-l-ene and but-2-enes is supplied as the input stream to the system 500 to the feed pre-treater 504 to produce a pretreated C4 stream 506 as previously mentioned. A C4 fractionator 508 receives and fractionates the pretreated C4 stream 506 to produce a C4-rich stream 510 and a C4 purge stream 507 as previously mentioned.The C4 purge stream 507 contains C4 paraffins (for example, butane, 2-methylpropane) and some C4 olefins. The C4 purge stream 507 can be collected and directed to a steam cracker 554. In certain examples, the C4-rich stream 510 with a but-l-ene content of at least 15 mol. % depending on the type of C4 feed stream 502, can be provided directly to the first metathesis reactor 518 as the pretreated C4-rich stream 514 with a but-l-ene content of at least 15 mol. %.

[0077] For the example illustrated in FIG. 5, when the C4 feed stream 502 has a but-l-ene content less than 15 mol. %, the C4-rich stream 510 is conditionally directed to a C4 isomerization reactor 512. The C4 isomerization reactor 512 is in fluid communication with the C4 fractionator 508 and is designed to receive and to facilitate isomerization of the but-2-enes of the C4-rich stream 510 into but-l-ene to produce a but-l-ene-rich stream 516 with a but-l-ene content of at least 15 mol. %. For this C4 isomerization, the C4 isomerization reactor 512 can operate at a temperature ranging from about 250 °C to about 650 °C and at a pressure ranging from about 1 barg to about 30 barg. The C4 isomerization reactor 512 contains an isomerization catalyst, such as a K2O / Y-AI2O3 catalyst.

[0078] For the example illustrated in FIG. 5, the first metathesis reactor 518 is in fluid communication with the C4 isomerization reactor 512 or the C4 fractionator 508 and is designed to receive and to facilitate metathesis of the but-l-ene-rich stream 516 or the pretreated C4-rich stream 514 to produce a first metathesis product stream 520. The first metathesis reactor 518 operates with a metathesis catalyst and at temperatures and pressures previously mentioned. The first metathesis product stream 520 contains ethene, propene, and C4-C6 olefins.

[0079] For the example illustrated in FIG. 5, the C3 column 522 is in fluid communication with the metathesis reactor 518 and is designed to receive and separate the first metathesis product stream 520 to produce C2-C3 stream 524 and a C4+ olefins stream 526. The C3 column 522 can be a depropenizer. The C2-C3 stream 524 contains ethene and propene and the C4+ olefins stream 526 contains the C4-C6 olefins.

[0080] For the example illustrated in FIG. 5, a C2 / C3 splitter 528 is in fluid communication with the C3 column 522 and is designed to receive and split the C2-C3 stream 524 into an ethene product stream 530 and a propene product stream 532. The propene product stream 532 are collected as a higher value olefin product stream, and the ethene product stream 530 is directed to a second metathesis reactor 544 to increase propene product stream 532 yield and also increase the production of C4 olefins with a but-l-ene content of at 15 mol. %.

[0081] For the example illustrated in FIG. 5, a C4 column 534 is in fluid communication with the C3 column 522 and is designed to receive and separate the C4+ olefins stream 526 into a C4 recyclestream 546 and a Cs-Ce olefins stream 536. The C4 column 534 can be a debutenizer. The C4 recycle stream 546 can be conditionally directed as a second C4 recycle stream 548 to the metathesis reactor 518 or conditionally directed to the C4 isomerization reactor 512 depending on the butene content as described in system 400.

[0082] For the example illustrated in FIG. 5, a C5 column 538 is in fluid communication with the C4 column 534 and is designed to receive and separate the C5-C6 olefins stream 536 to produce C5 olefin stream 540 and a Ce olefin product stream 542. The C5 column 538 can be a depentenizer.

[0083] For the example illustrated in FIG. 5, the second metathesis reactor 544 is in fluid communication with the C5 column 538 and is designed to receive and to facilitate metathesis of the C5 olefin stream 540 and the ethene product stream 530 to produce a second metathesis product stream 560. The second metathesis reactor 544 operates similar to the first metathesis reactor 518.

[0084] For the example illustrated in FIG. 5, a total hydrogenation unit (THU) 550 is in fluid communication with the C5 column 538 and is designed to receive and convert the Ce olefin product stream 542 to produce a Ce paraffins stream 552.

[0085] For the example illustrated in FIG. 5, a steam cracker 554 is in fluid communication with the THU 550 and the C4 fractionator 508 and is designed to receive and crack the Ce paraffins stream 552 and the C4 paraffin stream 507 to produce a cracked product stream 556 containing lighter olefins. The lighter olefins can be collected as a higher value olefin product stream.Examples

[0086] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and / or methods claimed herein are made and evaluated and, therefore, are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but deviations should be accounted for.

[0087] There are numerous variations and combinations of reaction conditions, for example, component concentrations, desired solvents, solvent mixtures, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0088] Example 1:

[0089] Experiments were performed implementing the process configuration of system 200, as discussed herein. The ultimate yields were calculated using preliminary lab experimental results. The experimental results are confirmed with simulation results using ASPEN PLUS. The sample feedstock composition is illustrated above in Table 1. Table 2 illustrates the but-l-ene-rich feed stream after C4 isomerization. Table 3 illustrates the resulting product composition with Raffinate III feedstock of Table 2, which include a C5 olefins recycle calculated using Aspen simulations. It is noted that in some examples, purge removal may be implemented to remove any inert component accumulation at the metathesis reactor. These results demonstrate the benefit of C5 recycle to the metathesis reactor and Ce isomerization along with a mixed feed C4 olefins to the metathesis reactor.

[0090] Table 2.

[0091] Table 3.

[0092] 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 ownlower 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.

[0093] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. It should be understood that although the disclosure contains certain aspects, embodiments, and optional features, modification, improvement, or variation of such aspects, embodiments, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.

Claims

Claims1. A C2-C6 olefins production system, the system comprising: a feed pre-treater configured to receive and decontaminate a C4 feed stream and output a pretreated C4 stream; a C4 isomerization reactor configured to receive and to facilitate isomerization of the pretreated C4 stream into a but-l-ene-rich stream; a metathesis reactor configured to receive and to facilitate metathesis of the but-l-ene-rich stream into a metathesis product stream containing C2-C6 olefins, the metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C; a C3 column configured to receive and separate the metathesis product stream and produce (i) a C2-C3 product stream containing ethene and propene and (ii) a C4+ olefins stream containing C4-C6 olefins; a C4 column configured to receive and separate the C4+ olefins stream and produce a C4 recycle stream and a Cs-Ce olefins stream containing C5 olefins and Ce olefins; and a C2 / C3 splitter column configured to receive and split the C2-C3 product stream into an ethene product stream and a propene product stream.

2. The system of claim 1, further comprising: a C4 fractionator configured to receive and separate the pretreated C4 stream into a C4-rich stream containing but-l-enes, but-2-enes, and a C4 paraffin stream containing C4 paraffins and traces of propane, and wherein the C4 isomerization reactor is configured to receive and to facilitate isomerization of the C4-rich stream into the but-l-ene-rich stream; and a C5 column configured to receive and separate the Cs-Ce olefins and produce a C5 olefin stream and a Ce olefins product stream, the C5 olefin stream supplied to the metathesis reactor.

3. The system of claim 2, further comprising: a second metathesis reactor configured to receive and to facilitate metathesis of the C5 olefin stream and the ethene product stream into a second metathesis product stream containing propene and but-l-ene supplied to the C3 column, the second metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C.

4. The system of claim 3, further comprising: a total hydrogenation unit configured to receive and convert the Ce olefin product stream into a Ce paraffins stream containing Ce paraffins; and a steam cracker configured to receive and crack the Ce paraffins stream and the C4 paraffin stream into a cracked product stream.

5. The system of any of claims 1-4, wherein the C4 recycle stream with a but-l-ene content less than 15 mol. % supplied to the C4 isomerization reactor.

6. The system of any of claims 1-4, wherein the C4 recycle stream is supplied to the metathesis reactor, the C4 recycle stream with a but-l-ene content of at least 15 mol. %.

7. The system of any of claims 2-4, wherein the C4-rich stream is supplied to the metathesis reactor as a pretreated C4-rich stream, the pretreated C4-rich stream with a but-l-ene content of at least 15 mol. %.

8. The system of claim 1, wherein the pretreated C4 stream is supplied to the metathesis reactor as a pretreated but-l-ene-rich stream, the pretreated but-l-ene-rich stream with a but-l-ene content of at least 15 mol. %.

9. A C2-C6 olefins production system, the system comprising: a feed pre-treater configured to receive and decontaminate a C4 feed stream and output a pretreated C4 stream; a C4 fractionator configured to receive and separate the pretreated C4 stream into a C4-rich stream containing but-l-enes and but-2-enes, and a C4 paraffin stream containing C4 paraffins and traces of propane; a C4 isomerization reactor configured to receive and to facilitate isomerization of the C4-rich stream into a but-l-ene-rich stream; a metathesis reactor configured to receive and to facilitate metathesis of the but-l-ene-rich stream into a metathesis product stream containing C2-C6 olefins, the metathesis reactor configured to operate at temperatures ranging from about 35 °C to about 100 °C;a Cs column configured to receive and separate the metathesis product stream into a C2-C5 olefin stream and a Ce olefins product stream; a C4 column configured to receive and separate the C2-C5 olefin stream into a C5 olefin stream and a C2-C4 olefins stream, the C5 olefin stream is supplied to the metathesis reactor; a C3 column configured to receive and separate the C2-C4 olefins stream into (i) a C2-C3 product stream containing ethene and propene and (ii) a C4 recycle stream; and a C2 / C3 splitter column configured to receive and split the C2-C3 product stream into an ethene product stream and a propene product stream.

10. The system of claim 9, wherein the C4-rich stream is supplied to the metathesis reactor as a pretreated C4-rich stream with a but-l-ene content of at least 15 mol. %.

11. The system of claim 9, wherein the C4 recycle stream is supplied to the metathesis reactor as a second C4 recycle stream with a but-l-ene content of at least 15 mol. %.

12. A method for producing C2-C6 olefins, the method comprising: absorbing one or more contaminants from a C4 feed stream to output a pretreated C4 stream; separating the pretreated C4 stream to produce a C4-rich stream containing but-l-enes and but-2-enes, and a C4 paraffin stream containing C4 paraffins and traces of propane; isomerizing the C4-rich stream to produce a but-l-ene-rich stream; metathesizing the but-l-ene-rich stream at temperatures ranging from about 35 °C to about 100 °C to produce a metathesis product stream; separating the metathesis product stream to produce a C2-C3 product stream containing ethene and propene and a C4+-rich stream containing C4-C6 olefins; separating the C4+-rich stream to produce a C4 recycle stream and a Cs-Ce olefins stream containing C5 olefins and Ce olefins; and splitting the C2-C3 product stream to produce an ethene product stream and a propene product stream.

13. The method of claim 12, further comprising: separating the Cs-Ce olefins to produce a C5 olefin stream and a Ce olefins product stream.

14. The method of claim 13, further comprising: metathesizing the C5 olefin stream and the ethene product stream at temperatures ranging from about 35 °C to about 100 °C to produce a second metathesis product stream containing propene and but- 1-ene.

15. The method of claim 14, further comprising: converting the Ce olefin product stream into a Ce paraffins stream containing Ce paraffins; and cracking the Ce paraffins stream and the C4 paraffin stream to produce a cracked product stream.

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