Process for producing 1-hexene

Abstract

The invention discloses a system and a method for producing 1-hexene. The process comprises subjecting ethylene to oligomerization in a reactor unit to produce 1-hexene, which comprises flowing a first solvent system into the reactor unit, the first solvent system being adapted to increase the selectivity of 1-hexene in the oligomerization of ethylene. The method may include flowing a portion of a second solvent system into the reactor unit in a wash mode, the second solvent system adapted to dissolve by-products in the washed reactor unit. The method may include flowing a portion of a second solvent system into a catalyst preparation unit, the second solvent system adapted to dissolve the catalyst in a catalyst preparation step. The system may include a reactor, a waxiness / polymer removal unit, and at least two C6 distillation columns in series for the production of 1-hexene.

Description

Background of the Invention A. Field of the Invention

[0001] The present invention generally relates to the production of 1-hexene. More particularly, the present invention relates to the use of a solvent system and a non-conventional polymer removal unit to improve the efficiency of 1-hexene production by ethylene oligomerization.

[0002] B. Related technical description

[0003] Methods for producing linear alpha-olefins (LAOs) by ethylene oligomerization are known and have been described by industry and research entities. The oligomerization of ethylene typically involves contacting ethylene with a catalyst, a cocatalyst, and a solvent. Ethylene oligomerization typically produces a variety of products. Consequently, technologies developed for oligomerization processes include methods for separating and processing these different products. One of the olefins produced during the oligomerization of ethylene is 1-hexene, which typically represents a product fraction of 10% to 27% by weight of the total LAO product produced in commercial processes (see, for example, A. Meiswinke et al., 2011 (describing a commercial process - α-SABLIN)) and can be deliberately promoted by catalysts comprising chromium compounds, ligand compounds and solvents selected from aromatic hydrocarbons (see, for example, US Pat. No. 8,778,827 B2 and US Pat. No. 8,637,721 B2). The formation of waxy substances, i.e., the formation of heavy, long-chain, high-carbon-number products, and the formation of polymers (polyethylene, branched and / or crosslinked PE have been detected in selective ethylene trimerization reactions) can lead to equipment fouling (see, for example, US Pat. No. 8,637,721 B2).

[0004] With respect to separation and purification processes for 1-hexene and other by-products, there is a need in the art for improved 1-hexene yield and purity, as well as efficient wax / polymer removal. Summary of the Invention

[0005] The present inventors have made a discovery that provides a solution to the needed improvements in the art for 1-hexene production. In an embodiment of the present invention, a technique targeting 1-hexene utilizes two solvent systems for different purposes, resulting in a higher proportion of 1-hexene forming oligomerized products compared to conventional processes. Embodiments of the present invention also include improvements to existing methods for separating 1-hexene from various products produced by ethylene oligomerization.

[0006] Embodiments of the present invention include a method for producing 1-hexene, the method comprising: flowing ethylene into a reactor unit in a reaction mode and having a catalyst disposed therein, and contacting the ethylene with the catalyst. The method comprises: oligomerizing ethylene in the reactor unit to produce 1-hexene, and flowing a first solvent system into the reactor unit, wherein the first solvent system is suitable for improving the selectivity of 1-hexene in the oligomerization of ethylene. The method further comprises: flowing a reactor unit effluent from the reactor unit to a downstream separation unit, the reactor unit effluent comprising 1-hexene and the first solvent system. The method further comprises: switching the reactor unit from a reaction mode to a wash mode. The method further comprises: flowing a second solvent system into the reactor unit in the wash mode. The second solvent system is suitable for dissolving by-products in the reactor unit, wherein the by-products include: oligomers, polymers, and waxy substances having 20 to 500 carbon atoms.

[0007] The present disclosure includes, but is not limited to, the following embodiments.

[0008] Embodiment 1: A method for producing 1-hexene by ethylene oligomerization, the method comprising: flowing a first solvent system into a reactor unit in a reaction mode, the first solvent system being suitable for improving the selectivity of 1-hexene in ethylene oligomerization; flowing ethylene into a reactor unit, the reactor unit comprising a catalyst and a first portion of a second solvent system, the second solvent system being different from the first solvent system; contacting ethylene with the catalyst; oligomerizing ethylene in the reactor unit to produce 1-hexene; flowing a reactor unit effluent from the reactor unit, the reactor unit effluent comprising 1-hexene and the first solvent system and the second solvent system; optionally, switching the reactor unit from a reaction mode to a wash mode; and optionally, flowing a second portion of the second solvent system into the reactor unit in the wash mode, the second solvent system being suitable for dissolving by-products in the reactor unit, the by-products comprising oligomers, polymers and waxy substances having 20 to 500 carbon atoms.

[0009] Embodiment 2: The method as described in embodiment 1 also includes: using a first distillation column to separate unreacted ethylene from the reactor unit effluent to form a recycled ethylene stream mainly comprising ethylene and a first product stream comprising linear α-olefins (LAO), by-products, a first solvent system and a second solvent system.

[0010] Embodiment 3: The method of embodiment 2, wherein the first distillation column comprises a rectification section suitable for absorbing 1-hexene.

[0011] Embodiment 4: The method as described in embodiment 2 or 3 further includes: separating by-products from the first product stream to produce a wax / polymer stream mainly comprising waxes and polymers and a second product stream comprising C4 to C8 hydrocarbons, a first solvent system and a second solvent system.

[0012] Embodiment 5: The method of any one of Embodiments 2-4, further comprising: flowing a recycle ethylene stream into the reactor unit in reaction mode.

[0013] Embodiment 6: A method as described in embodiment 4 or 5, wherein separating the by-products from the first product stream includes: flashing the first product stream in a first flash vessel to produce a second product stream and a bottom flash stream comprising a second solvent system and the by-products; and separating some of the second solvent system from the bottom flash stream in a manner that allows sufficient second solvent system to remain in the waxes / polymer stream to form a solvent system recovery stream comprising the first solvent system and the second solvent system and a waxes / polymer stream comprising waxes, polymers, and the second solvent system.

[0014] Embodiment 7: The method of any one of Embodiments 4-6, further comprising: separating 1-butene from the second product stream to produce a 1-butene stream primarily comprising 1-butene and a third product stream comprising C6 to C8 hydrocarbons, the first solvent system, and the second solvent system.

[0015] Embodiment 8: The method as described in Embodiment 7 further includes: separating the third product stream by a separation unit including at least two C6 distillation towers connected in series, wherein separating the third product stream includes: separating C6 hydrocarbons from the third product stream by a first C6 distillation tower to form a fourth product stream mainly comprising C6 hydrocarbons and a first bottom stream comprising C7 to C8 hydrocarbons, a first solvent system and a second solvent system; and separating 1-hexene from the fourth product stream by a second C6 distillation tower to form a fifth product stream comprising 1-hexene and a C6 product stream comprising other C6 components (such as n-hexane, 2-ethyl-1-butene and one or more trans-hexene and cis-hexene isomers).

[0016] Embodiment 9: The method of Embodiment 8, wherein the fifth product stream comprises 99.5 wt% to 99.9 wt% 1-hexene.

[0017] Embodiment 10: The method as described in embodiment 8 or 9 further includes: separating the first solvent system and the second solvent system from the first bottom stream to form a first solvent system recycling stream mainly comprising the first solvent system and a second solvent system recycling stream mainly comprising the second solvent system.

[0018] Embodiment 11: The method of Embodiment 10, further comprising flowing a first portion of the first solvent system recycle stream to the reactor unit in reaction mode.

[0019] Embodiment 12: The method according to embodiment 10 or 11, further comprising: flowing a second portion of the first solvent system recycle stream into the rectifying section of the first distillation column for absorbing 1-hexene.

[0020] Embodiment 13: The method of any one of Embodiments 1 to 12, wherein the first solvent system comprises an alkane solvent system and the second solvent system comprises an aromatic solvent system.

[0021] Embodiment 14: The method of embodiment 13, wherein the paraffin solvent system includes n-heptane and the aromatic solvent system includes xylene.

[0022] Embodiment 15: The method of any one of Embodiments 1 to 14, further comprising: flowing a portion of the second solvent system into the catalyst preparation unit, wherein the second solvent system is suitable for dissolving the one or more catalysts prepared in the catalyst preparation unit.

[0023] Embodiment 16: A system for producing 1-hexene by ethylene oligomerization, the system comprising: a reactor unit; a source of a first solvent system suitable for improving the selectivity of 1-hexene in the ethylene oligomerization reaction, fluidically connected to the reactor unit; an ethylene source fluidically connected to the reactor unit; a catalyst and a second solvent system within the reactor unit, the second solvent system being different from the first solvent system; and a reactor unit effluent fluidically connected to the reactor unit, the reactor unit effluent comprising 1-hexene and the first solvent system and the second solvent system.

[0024] Embodiment 17: The system of Embodiment 16, wherein the first solvent system and ethylene are premixed to form a feed source that is in fluid communication with the reactor unit.

[0025] Embodiment 18: The system of Embodiment 16 or 17, further comprising: a catalyst preparation unit in fluid communication with the reactor unit, the catalyst preparation unit comprising a mixture of the catalyst and the second solvent system.

[0026] These and other features, aspects, and advantages of the present disclosure will become apparent by reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The present disclosure includes any combination of two, three, four, or more of the features or elements set forth herein, regardless of whether such features or elements are expressly combined or otherwise referenced in the specific exemplary embodiments described herein. The present disclosure is intended to be understood as a whole such that any separable features or elements of the present disclosure, in any aspect and exemplary embodiment thereof, should be considered combinable unless the context of the present disclosure clearly dictates otherwise.

[0027] These and other embodiments of the present invention are discussed in this application.Any embodiment discussed with regard to one aspect of the present invention is also suitable for other aspects of the present invention, and vice versa.Each embodiment described herein can be understood as an embodiment of the present invention that is suitable for other aspects of the present invention.It is envisioned that any embodiment or aspect discussed herein can be combined with other embodiments or aspects discussed herein and / or implemented with any method or composition of the present invention, and vice versa.In addition, composition of the present invention can be used to realize method of the present invention.

[0028] The following include definitions of various terms and phrases used throughout the specification and claims.

[0029] As understood by those skilled in the art, the term "about" or "approximately" is defined as close to. In one non-limiting embodiment, the term is defined as within ±10%, preferably within ±5%, more preferably within ±1%, and most preferably within ±0.5%.

[0030] The terms "wt %," "volume %," or "mole %" refer to the weight percent, volume percent, or mole percent, respectively, of a component based on the total weight, total volume, or total moles, respectively, of the material containing the component. In one non-limiting example, 10 grams of a component in 100 grams of a material is 10% by weight of the component.

[0031] The term "substantially" and variations thereof are defined to include ranges within ±10%, within ±5%, within ±1%, or within ±0.5%.

[0032] The terms "inhibit" or "reduce" or "prevent" or "avoid" or any variation of these terms, when used in the claims and / or specification, include any measurable reduction or complete inhibition to achieve the desired result.

[0033] As used in the specification and / or claims, the term "effective" means sufficient to accomplish a desired, intended, or predetermined result.

[0034] When used in conjunction with "comprising," "including," "containing," and "having" in the claims and the specification, the word "a" or "an" may mean "one," but is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0035] The words "comprise" (and any form of comprising, such as "comprising" and "containing"), "have" (and any form of having, such as "have" and "have"), "include" (and any form of including, such as "including" and "encompass"), or "contain" (and any form of containing, such as "including" and "including") are inclusive or open-ended and do not exclude additional unrecited elements or method steps.

[0036] The language of the present invention may "comprise," "consist essentially of," or "consist of" specific ingredients, components, compositions, etc. disclosed throughout the specification.

[0037] The term "solvent system" refers to a single solvent or a combination of solvents. Non-limiting examples of solvent systems include: n-heptane alone or with one or more other paraffin solvents; and xylene alone or with one or more other aromatic solvents.

[0038] The term "paraffin solvent" refers to an alkane solvent, such as a C5 to C8 cyclic or straight-chain alkane, including n-heptane, cycloheptane, isoheptane, n-hexane, methylcyclohexane, and the like.

[0039] The term "aromatic solvent" refers to a solvent including at least one aromatic ring, such as toluene, benzene, xylene, monochlorobenzene, dichlorobenzene, chlorotoluene, and the like.

[0040] It will be easier to see other objects, features and advantages of the present invention through the following drawings, detailed description and examples. However, it should be understood that although the following drawings, detailed description and examples represent specific embodiments of the present invention, they are also given by way of illustration only and are not meant to be limiting. In addition, it is expected that, based on this detailed description, changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art. In other embodiments, features from specific embodiments can be combined with features from other embodiments. For example, features of one embodiment can be combined with features of any other embodiment. In other embodiments, other features can be added to the specific embodiments described herein.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Advantages of the present invention will become apparent to those skilled in the art upon benefit of the following detailed description and with reference to the accompanying drawings.

[0043] Figure 1 shows a system for producing 1-hexene according to an embodiment of the present invention; and

[0044] Figure 2A and Figure 2B A method for producing 1-hexene according to an embodiment of the present invention is shown.

[0045] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings, which may not be to scale. DETAILED DESCRIPTION

[0046] The present inventors have developed at least one solution to address the aforementioned needs for 1-hexene production. In an embodiment of the present invention, the solution comprises utilizing two solvent systems for different purposes within a reactor unit where ethylene oligomerization occurs. The first solvent system according to an embodiment of the present invention is suitable for improving 1-hexene selectivity during ethylene oligomerization. Furthermore, the second solvent system according to an embodiment of the present invention is suitable for dissolving byproducts in the reactor unit, wherein the byproducts include oligomers, polymers, and waxy substances having 20 to 500 carbon atoms. Figure 1 Shown is a system 10 for producing 1-hexene according to an embodiment of the present invention. Figure 2A and Figure 2B A method for producing 1-hexene according to an embodiment of the present invention is shown. The method can be implemented using system 10.

[0047] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

[0048] A. System for producing 1-hexene

[0049] Figure 1A system 10 for producing 1-hexene according to an embodiment of the present invention is shown. In an embodiment of the present invention, system 10 includes a reactor unit 101 adapted to oligomerize ethylene present in a feed 111. In an embodiment of the present invention, feed 111 includes ethylene and a first solvent system. In an embodiment of the present invention, reactor unit 101 has disposed therein an oligomerization catalyst and / or cocatalyst in a second solvent system. In an embodiment of the present invention, the oligomerization catalyst and / or cocatalyst in the second solvent system is contained in a catalyst preparation unit effluent 137 flowing from a catalyst preparation unit 141. In an embodiment of the present invention, catalyst preparation unit 141 is adapted to receive a fresh second solvent system stream 140 and a first recovered portion of the second solvent system 136 (a portion of the second solvent system recycle stream 129), and is further adapted to receive the oligomerization catalyst and / or cocatalyst used in reactor unit 101. In an embodiment of the present invention, reactor unit 101 is adapted to oligomerize ethylene in feed 111, thereby forming a reactor unit effluent 113. In an embodiment of the present invention, system 10 includes a plurality of reactors; for example, system 10 may include four separate reactors. Thus, system 10 can be operated with at least one reactor being washed to remove waxes and / or polymers (wash mode) while the other reactors are operated to oligomerize ethylene (reaction mode). Thus, as used herein, "reaction mode" refers to a configuration configured to oligomerize ethylene, and "wash mode" refers to a configuration configured to perform washing to remove waxes and / or polymers.

[0050] Figure 1 The reactor unit 101 is shown as a reactor operating in a reaction mode and a reactor unit 139 operating in a wash mode to remove waxes / polymers. Figure 1 As shown, reactor unit 139 is in wax / polymer wash mode and is therefore configured to receive a second solvent system second recovery portion 135 (a portion of the second solvent system recycle stream 129) for washing. In embodiments of the present invention, system 10 is configured so that any reactor unit can be switched from reaction mode to wash mode. For example, in embodiments of the present invention, when reactor unit 101 is switched to wash mode to remove wax / polymer therefrom, it will have Figure 1 The input and output of the reactor unit 139 are shown. And according to an embodiment of the present invention, when the reactor unit 139 is switched to a reactor operating in a reaction mode, the reactor unit 139 will have Figure 1 The input and output of the reactor unit 101 are shown. According to an embodiment of the present invention, the wash effluent 138 (from the reactor where the wash is performed, Figure 1 The reactor unit 139 in the figure flows into the second flash vessel 104 for treatment.

[0051] According to an embodiment of the present invention, system 10 further comprises a first distillation column 102 in fluid communication with reactor unit 101, wherein first distillation column 102 is adapted to receive reactor unit effluent 113 from reactor unit 101 and to separate reactor unit effluent 113 into a recycle ethylene stream 112 and a first product stream 114. In an embodiment of the present invention, first distillation column 102 comprises a rectifying section located above the feed inlet point and adapted to absorb 1-hexene. According to an embodiment of the present invention, first distillation column 102 comprises a stripping section below the feed inlet point, wherein ethylene is stripped from reactor unit effluent 113, and an absorption section above the feed inlet point, wherein heavier components, including 1-hexene, are removed from the stripped ethylene by contact with the first solvent system in first solvent system recovery column 126.

[0052] In an embodiment of the present invention, system 10 includes a polymer and wax removal unit comprising a first flash vessel 103 in fluid communication with a first distillation column 102 such that a first product stream 114 flows from the first distillation column 102 to the first flash vessel 103. In an embodiment of the present invention, the first flash vessel 103 is adapted to remove heavier components, such as waxes and polymers, from the first product stream 114 to produce a second product stream 116 and a bottoms flash stream 115. In an embodiment of the present invention, the first flash vessel 103 is in fluid communication with a second flash vessel 104 such that the bottoms flash stream 115 can flow from the first flash vessel 103 to the second flash vessel 104. The second flash vessel 104 is adapted to recover solvent from the bottoms flash stream 115 to produce a wax / polymer stream 117 and a solvent system recovery stream 134. As shown, at least a portion of the solvent system recovery stream 134 can be recycled to the first flash vessel 103. According to an embodiment of the present invention, the first flash vessel 103 and the second flash vessel 104 may include one or more flash / distillation drums. However, the first flash vessel 103 and the second flash vessel 104 of the polymer and wax removal unit may be replaced with other equipment or combined with other equipment that can perform the same function.

[0053] According to an embodiment of the present invention, system 10 includes a second distillation column 105 in fluid communication with first flash vessel 103 such that a second product stream 116 can flow from first flash vessel 103 to second distillation column 105. In an embodiment of the present invention, second distillation column 105 is adapted to separate second product stream 116 to form a butene stream 119 (predominantly comprising 1-butene) and a third product stream 118 (comprising C6 to C8 hydrocarbons).

[0054] In an embodiment of the present invention, the system 10 includes a first C6 distillation column 106 in fluid communication with a second distillation column 105, such that a third product stream 118 can flow from the second distillation column 105 to the first C6 distillation column 106. According to an embodiment of the present invention, the first C6 distillation column 106 is adapted to separate the third product stream 118 to produce a fourth product stream 121 comprising C6 hydrocarbons and a first bottoms stream 120 comprising C7 to C8 hydrocarbons. According to an embodiment of the present invention, the system 10 includes a second C6 distillation column 107 in fluid communication with the first C6 distillation column 106, such that a fourth product stream 121 can flow from the first C6 distillation column 106 to the second C6 distillation column 107. According to an embodiment of the present invention, the second C6 distillation column 107 is adapted to separate the fourth product stream 121 to produce a fifth product stream 122 comprising 1-hexene and a C6 product stream 123 comprising other C6 components, such as n-hexane, 2-ethyl-1-butene, and one or more trans-hexene and cis-hexene isomers.

[0055] According to an embodiment of the present invention, the system 10 includes a third distillation column 108 in fluid communication with the first C6 distillation column 106, such that a first bottoms stream 120 can flow from the first C6 distillation column 106 to the third distillation column 108. In an embodiment of the present invention, the third distillation column 108 is adapted to separate the first bottoms stream 120 to produce a first solvent system recycle stream 124 comprising primarily C8 hydrocarbons and a second bottoms stream 125. As shown, the first solvent system recycle stream 124 can be recycled for reuse as the first solvent system in the ethylene oligomerization reactor, as well as recycled for removal of heavier components, including 1-hexene, from the ethylene stripped from the first distillation column 102, as described above.

[0056] In an embodiment of the present invention, the system 10 includes a fourth distillation column 109 in fluid communication with the third distillation column 108, such that the second bottom stream 125 can flow from the third distillation column 108 to the fourth distillation column 109. In an embodiment of the present invention, the fourth distillation column 109 is adapted to separate the second bottom stream 125, separating the C8 hydrocarbons from other hydrocarbons, particularly from the second solvent system, thereby forming a C8 hydrocarbon stream 127 primarily comprising 1-octene and a third bottom stream 128.

[0057] According to an embodiment of the present invention, the system 10 further comprises a fifth distillation column 110 in fluid communication with the fourth distillation column 109, such that the third bottoms stream 128 can flow from the fourth distillation column 109 to the fifth distillation column 110. In an embodiment of the present invention, the fifth distillation column 110 is adapted to separate the third bottoms stream 128 into a second solvent system recycle stream 129 and a fourth bottoms stream 130 comprising 1-decanol. As shown, the second solvent recycle stream 129 can be recycled for use as the second solvent system in the catalyst preparation unit 141 and reused as a wash solvent in the oligomerization reactor.

[0058] B. Process for the Production of 1-Hexene

[0059] Figure 2A and Figure 2B A method for producing 1-hexene according to an embodiment of the present invention is shown. In an embodiment of the present invention, the method includes: at block 200, providing a first solvent system and a second solvent system, and flowing the second solvent system into the catalyst preparation unit 141. According to an embodiment of the present invention, the second solvent system is suitable for dissolving the oligomerization catalyst and dissolving oligomers, polymers and waxes having 20 to 500 carbon atoms formed during the oligomerization of ethylene. According to an embodiment of the present invention, the second solvent system includes a C8 aromatic solvent, such as xylene. Figure 1 As shown, in an embodiment of the present invention, the second solvent system can be fed to the catalyst preparation unit 141 as a fresh second solvent system stream 140 and / or a separate stream such as the second solvent system first recycle portion 136 (part of the second solvent system recycle stream 129). The catalyst is prepared in the catalyst preparation unit 141 by dissolving the catalyst in the second solvent system.

[0060] At block 201 , according to an embodiment of the present invention, the method includes flowing the catalyst preparation unit effluent 137 (which includes the second solvent system and dissolved catalyst) into the reactor unit 101 (which is in reaction mode).

[0061] At block 202, according to an embodiment of the present invention, the method includes flowing ethylene into a reactor unit 101, which contains a catalyst for ethylene oligomerization. In an embodiment of the present invention, a feed 111 contains ethylene and a first solvent system, and the feed 111 flows into the reactor unit 101 as at least one ethylene source. Optionally or alternatively, the first solvent system can flow to the reactor unit 101 in a different stream, such as a recycled ethylene stream 112.

[0062] In an embodiment of the present invention, the first solvent system is suitable for improving the selectivity of 1-hexene in ethylene oligomerization.According to an embodiment of the present invention, the first solvent system comprises an alkane solvent, for example a C7 alkane solvent, such as n-heptane.

[0063] According to an embodiment of the present invention, at block 203, the method includes contacting ethylene with a catalyst in reactor unit 101 and oligomerizing the ethylene to produce 1-hexene. In an embodiment of the present invention, the catalyst includes, but is not limited to, chromium salts, ligands, aluminum alkyls, and ammonium salts.

[0064] Exemplary catalysts useful in the present disclosure are described, for example, in WO 2020 / 100010 to Al-Nezari et al., which is incorporated herein by reference, and describes ligands having an NPN(CH3)PN framework. Examples of chromium compounds include: organometallic Cr(III) species, such as Cr(III) acetylacetonate, Cr(III) octanoate, CrCl3(tetrahydrofuran)3, Cr(III)-2-ethylhexanoate, Cr(III) chloride, or any combination thereof. The catalyst may include an activator (also known in the art as a co-catalyst), such as an aluminum compound. Non-limiting examples of aluminum compounds include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, methylaluminoxane, or mixtures thereof. In some embodiments, the activator may be a modified methylaluminoxane such as MMAO-3A (CAS No. 146905-79-5).

[0065] According to an embodiment of the present invention, the method includes, at block 204, flowing a reactor unit effluent 113 from a reactor unit 101, wherein the reactor unit effluent 113 includes 1-hexene, a first solvent system, and a second solvent system. At block 205, in an embodiment of the present invention, the method includes, flowing the reactor unit effluent 113 into a first distillation column 102, the distillation column being adapted to receive and separate the reactor unit effluent 113. In an embodiment of the present invention, the first distillation column separates the reactor unit effluent 113 to form a recycled ethylene stream 112 comprising primarily ethylene (unreacted ethylene) and a first product stream 114 comprising linear alpha olefins (LAO), byproducts, the first solvent system, and the second solvent system. In an embodiment of the present invention, the first distillation column 102 includes, at block 205, a rectifying section that absorbs the 1-hexene. According to an embodiment of the present invention, at block 205, the first distillation column 102 includes a stripping section below the feed inlet point for stripping ethylene from the reactor unit effluent 113, and an absorption or rectification section above the feed inlet point for removing heavier components from the stripped ethylene by contacting the stripped ethylene with the first solvent system in the first solvent system column recycle section 126. In this way, in an embodiment of the present invention, the recycled ethylene stream 112 contains 97 to 99 weight percent ethylene (purified ethylene), which can be compressed and returned to the reactor unit 101. A small purge stream (not shown) of the recycled ethylene stream 112 is sent to a flare system to prevent the accumulation of lighter components, such as nitrogen, in the process. According to an embodiment of the present invention, the first product stream 114 flowing from the bottom of the first distillation column 102 contains very little ethylene, for example, 1 to 3 weight percent ethylene.

[0066] In an embodiment of the present invention, the method includes passing the first product stream 114 to a polymer and waxes removal unit at block 206, and separating byproducts from the first product stream in the polymer and waxes removal unit at block 207 to produce (1) a waxes / polymer stream 117 comprising primarily waxes and polymers and (2) a second product stream 116 comprising C4 to C8 hydrocarbons, a first solvent system, and a second solvent system. In this way, the polymer and waxes removal unit protects the primary separation train of the process from potential contamination due to the presence of polymers and waxes.

[0067] According to an embodiment of the present invention, the polymer and wax removal unit includes a first flash vessel 103 and a second flash vessel 104, wherein the first flash vessel 103 receives a first product stream 114 from the first distillation column 102. In an embodiment of the present invention, at block 207a, the first flash vessel 103 removes heavier components, such as waxes and polymers, from the first product stream 114 by flash distillation to produce (1) a second product stream 116 and (2) a bottom flash stream 115 comprising a second solvent system and by-products. In an embodiment of the present invention, the second product stream 116 comprises 0 to 0.1 wt% polymer (i.e., only trace amounts), and the bottom flash stream 115 comprises 5 to 10 wt% polymer. In this way, embodiments of the present invention can avoid excessive polymer concentrations (greater than 10 wt% or temperatures below 140°C) in the bottom flash stream 115. Excessive polymer concentrations can cause the polymer to precipitate from the solution, which can lead to excessive fouling of the equipment. On the other hand, excessive polymer entrainment in the second product stream 116 can lead to fouling problems in the main separation train. At block 207b, in an embodiment of the present invention, the second flash vessel 104 receives the bottom flash stream 115 from the first flash vessel 103, and the second flash vessel 104 separates some of the second solvent system from the bottom flash stream 115 to form (1) a solvent system recovery stream 134 comprising the first solvent system and / or the second solvent system and (2) a wax / polymer stream 117 that allows enough of the second solvent system to remain in the wax / polymer stream so that the wax / polymer stream 117 is a fluid stream comprising wax, polymer, and the second solvent system. The fluidity of the wax / polymer stream 117 can reduce the risk of accidental blockage of equipment and / or accidental accumulation of solids in pipes and valves. In other words, removing the polymer / wax as a flowable liquid can provide advantages in terms of ease of operation and / or reduced maintenance issues. According to an embodiment of the present invention, block 207 including block 207a and block 207b may be implemented by equipment other than the first flash vessel 103 and the second flash vessel 104 or equipment combined with the first flash vessel 103 and the second flash vessel 104 .

[0068] In an embodiment of the invention, the method includes, at block 208, flowing the recycle ethylene stream 112 to the reactor unit 101. At block 209, in an embodiment of the invention, the method includes, at block 209, receiving the second product stream 116 from the first flash vessel 103 to the second distillation column 105, the second distillation column 105 separating 1-butene from the second product stream 116 to form (1) a C4 hydrocarbon stream, a butene stream 119 comprising primarily 1-butene, and (2) a third product stream 118 comprising C6 to C8 hydrocarbons, the first solvent system, and the second solvent system. In an embodiment of the invention, the second product stream 116 may be cooled and condensed before entering the separation train of the second distillation column 105.

[0069] In an embodiment of the present invention, the method includes separating the third product stream 118 by a separation unit comprising at least two C6 distillation towers connected in series. By using two towers in series, a higher product purity of 1-hexene can be achieved (for example, when it is needed for use as a PE copolymer, high purity is required, and n-hexane can be troublesome in the polymerization process). According to an embodiment of the present invention, separating the third product stream 118 includes: at block 210, the first C6 distillation tower 106 receives the third product stream 118 from the second distillation tower 105, and the first C6 distillation tower 106 separates C6 hydrocarbons from the third product stream 118 to form (1) a fourth product stream 121 primarily comprising C6 hydrocarbons and (2) a first bottom stream 120 comprising C7 to C8 hydrocarbons, a first solvent system, and a second solvent system.

[0070] According to an embodiment of the present invention, the method includes: at block 211, the second C6 distillation column 107 receives the fourth product stream 121 from the first C6 distillation column 106, and the second C6 distillation column 107 separates 1-hexene from the fourth product stream 121 to form (1) a fifth product stream 122 comprising 1-hexene and (2) a C6 product stream 123 comprising n-hexane, 2-ethyl-1-butene, and one or more trans-hexene and cis-hexene isomers. In an embodiment of the present invention, the fifth product stream 122 comprises 99.5 wt% to 99.9 wt% 1-hexene.

[0071] According to an embodiment of the present invention, the method includes separating the first solvent system and the second solvent system from the first bottom stream 120 to form a first solvent system recycle stream 124 comprising primarily the first solvent system. According to an embodiment of the present invention, block 212 includes the third distillation column 108 receiving the first bottom stream 120 from the first C6 distillation column 106, and the third distillation column 108 separating the first solvent system to produce (1) the first solvent system recycle stream 124 and (2) the second bottom stream 125 comprising primarily C8 hydrocarbons. At block 213, in an embodiment of the present invention, the method includes flowing a first portion of the first solvent system recycle stream 124 (first solvent system reactor recycle 133) to the reactor unit 101 and / or flowing a second portion of the first solvent system recycle stream 124 (first solvent system column recycle 126) to the rectifying section of the first distillation column 102 to absorb 1-hexene. Recycling a portion of the first solvent system recycle stream 124 (first solvent system reactor recycle 133) to the reactor unit 101 can help prevent undesirable chemical reactions. And recycling the second portion of the first solvent system recycle stream 124 (first solvent system column recycle 126) to the top of the first distillation column 102 as an extraction medium can help purify the ethylene distillate stream (recycled ethylene stream 112), thereby 4+ The olefins are pushed more to the bottom.

[0072] According to an embodiment of the present invention, at block 214, the method includes: the fourth distillation column 109 receives the second bottom stream 125 from the third distillation column 108, and the third distillation column 108 separates the second bottom stream 125 so that the C8 hydrocarbons are separated from other hydrocarbons, in particular, from the second solvent system, thereby forming (1) a C8 hydrocarbon stream 127 mainly comprising 1-octene and (2) a third bottom stream 128.

[0073] At block 215, in an embodiment of the present invention, the method includes: receiving the third bottom stream 128 from the fourth distillation column 109 by the fifth distillation column 110, and separating the third bottom stream 128 by the fifth distillation column 110 to form (1) a second solvent system recycle stream 129 and (2) a fourth bottom stream 130 comprising 1-decanol. In this way, according to an embodiment of the present invention, the content of the catalyst deactivator (1-decanol) is reduced by the fifth distillation column 110. According to an embodiment of the present invention, at block 216, the second solvent system recycle stream 129 is split, and the first portion of the second solvent system recycle stream 129 (i.e., the second solvent system first recycle portion 136) flows into the catalyst preparation unit 141 for dissolving the catalyst in the catalyst preparation step.

[0074] In an embodiment of the present invention, at block 217, one or more of the plurality of reactors in the reactor unit 101 that require cleaning are switched from a reaction mode to a wash mode (i.e., they are configured as follows). Figure 1 At block 218, in an embodiment of the present invention, a second portion of the second solvent system recycle stream 129 (second solvent system second recycle portion 135) flows into the reactor unit 139 in the wash mode, as shown. Figure 1 shown. Figure 1 The reactor unit is depicted in two modes; first, it depicts the reactor unit 109 in the reaction mode, and second, it depicts the reactor unit 139 in the wash mode. In other words, when the reactor unit is in the reaction mode, it is the reactor unit 101, and when the reactor unit is in the wash mode, it is the reactor unit 139. Washing the reactor unit 139 with the second solvent system recycle stream 129 results in a wash effluent 138 flowing from the reactor unit 139. In an embodiment of the present invention, the method includes, at block 219, flowing the wash effluent 138 (including the second solvent system having the waxy material / polymer dissolved therein) into the second flash vessel 104 for processing. According to an embodiment of the present invention, the fourth bottoms stream 130 has an elevated amount of 1-decanol, and block 220 includes passing a portion of the fourth bottoms stream 130 (recycling a portion of the fourth bottoms stream 131 ) to the second flash vessel 104 to recover more of the second solvent system, and the remaining portion of the fourth bottoms stream 130 may be purged from the process in a purge stream 132 .

[0075] In summary, embodiments of the process disclosed herein can achieve one or more of the following: (1) separation and purification of the main product 1-hexene from the reactor unit effluent, (2) separation and purification of unreacted ethylene for recycling back to the reactor, (3) separation and purification of the process first solvent system (paraffin solvent) for recycling back to the reactor and ethylene separation column (first distillation column 102), (4) separation and purification of the second solvent system (aromatic solvent) and recycling it back to the reactor wash system and catalyst preparation section, and (5) separation of reaction by-products - polymer, butene and octene.

[0076] Example

[0077] The present invention will be described in more detail by specific examples. The following examples are provided for illustrative purposes only and are not intended to limit the present invention in any way. Those skilled in the art will readily recognize the various non-critical parameters that can be changed or modified to produce substantially the same results.

[0078] Example (Simulation)

[0079] The methods described herein were applied to simulated situations in which ethylene Figure 1 The system shown achieves catalytic conversion to 1-hexene with a selectivity of 92% by weight. During the ethylene oligomerization reaction in reactor unit 101, the temperature is approximately 70°C and the pressure is approximately 30 bar. n-heptane is selected as the first solvent system (paraffinic) solvent for enhancing 1-hexene selectivity, and xylene is selected as the second solvent system (aromatic) solvent for catalyst dissolution and reactor purging. Approximately 2.6% recycled n-heptane is added to the top of first distillation column 102 to absorb the product 1-hexene, preventing it from accumulating in the headspace and being destroyed in the reactor.

[0080] A dual C6 column design is arranged to obtain a high purity 1-hexene product in the fifth product stream 122, wherein the first C6 distillation column 106 has about 36 theoretical stages and the second C6 distillation column 107 has about 86 theoretical stages. As a result, the fifth product stream 122 achieves a 1-hexene purity of 99.5 wt. % with a trace amount of n-hexane.

[0081] The heavy ends removal section (polymer and wax removal unit) removes almost all of the polymer and waxes, with a loss of about 40% of the xylene solvent. However, in this design, no vacuum flash is required and the polymer mixture is always mobile in the liquid phase - 9.8% by weight of polymer in the total polymer product (waxes / polymer stream 117). Only two units are used, namely a conventional first flash vessel 103 operating at 3 bar and a second flash vessel 104 with 12 theoretical stages operating at 1.2 bar. Compared to designs with lower xylene losses that require the purchase and operation of a vacuum system, this design can provide significant savings in capital expenditure (CAPEX) and operating expenditure (OPEX), and has significant advantages in terms of easier operation and reduced maintenance issues.

[0082] Table 1 lists the flow rates and concentrations of key streams in this example.

[0083] Table 1

[0084]

[0085] In the context of the present invention, at least fifteen embodiments will now be described below. Embodiment 1 is a method for producing 1-hexene. The method comprises: flowing ethylene into a reactor unit that is in a reaction mode and in which a catalyst is disposed. The method further comprises: in the reactor unit, contacting ethylene with a catalyst and oligomerizing the ethylene to produce 1-hexene. The method further comprises: flowing a first solvent system into the reactor unit, the first solvent system being suitable for increasing the selectivity of 1-hexene in the oligomerization of ethylene. The method further comprises: flowing a reactor unit effluent from the reactor unit, the reactor unit effluent comprising 1-hexene and the first solvent system. The method further comprises: switching the reactor unit from a reaction mode to a wash mode and flowing a first portion of a second solvent system into the reactor unit in the wash mode, the second solvent system being suitable for dissolving by-products in the reactor unit, the by-products comprising oligomers, polymers, and waxy substances having 20 to 500 carbon atoms. Embodiment 2 is a method as in embodiment 1, further comprising: separating unreacted ethylene from the reactor unit effluent using a first distillation column to form a recovered ethylene stream comprising primarily ethylene and a first product stream comprising linear alpha olefins (LAOs), byproducts, a first solvent system, and a second solvent system. Embodiment 3 is a method as in embodiment 2, wherein the first distillation column comprises a rectification section suitable for absorbing 1-hexene. Embodiment 4 is a method as in embodiment 3, further comprising: separating byproducts from the first product stream to produce a wax / polymer stream comprising primarily waxes and polymers and a second product stream comprising C4 to C8 hydrocarbons, the first solvent system, and the second solvent system. Embodiment 5 is a method as in embodiment 4, further comprising: passing a recycle ethylene stream to the reactor unit. Embodiment 6 is a method as in embodiment 5, wherein separating byproducts from the first product stream comprises: flashing the first product stream in a first flash vessel to produce a second product stream and a bottoms flash stream comprising the second solvent system and the byproducts. The method further comprises separating some of the second solvent system from the bottom flash stream in a manner that allows sufficient second solvent system to remain in the waxy / polymer stream to form a solvent system recovery stream comprising the first solvent system and the second solvent system and a waxy / polymer stream comprising waxy, polymer, and the second solvent system. Embodiment 7 is the method of embodiment 5, further comprising separating 1-butene from the second product stream to produce a 1-butene stream comprising primarily 1-butene and a third product stream comprising C6 to C8 hydrocarbons, the first solvent system, and the second solvent system.Embodiment 8 is the method of embodiment 7, further comprising separating the third product stream via a separation unit comprising at least two C6 distillation columns connected in series, wherein separating the third product stream comprises separating C6 hydrocarbons from the third product stream via a first C6 distillation column to form a fourth product stream comprising primarily C6 hydrocarbons, a first bottoms stream comprising C7 to C8 hydrocarbons, a first solvent system, and a second solvent system. The method further comprises separating 1-hexene from the fourth product stream via a second C6 distillation column to form a fifth product stream comprising 1-hexene and a C6 product stream comprising n-hexane, 2-ethyl-1-butene, and one or more trans-hexene and cis-hexene isomers. Embodiment 9 is the method of embodiment 8, wherein the fifth product stream comprises 99.5% to 99.9% by weight 1-hexene. Embodiment 10 is the method of embodiment 8, further comprising separating the first solvent system and the second solvent system from the first bottoms stream to form a first solvent system recycle stream comprising primarily the first solvent system and a second solvent system recycle stream comprising primarily the second solvent system. Embodiment 11 is the method of embodiment 10, further comprising: flowing a first portion of the first solvent system recycle stream to the reactor unit. Embodiment 12 is the method of embodiment 11, further comprising: flowing a second portion of the first solvent system recycle stream to the rectifying section of the first distillation column for absorbing 1-hexene. Embodiment 13 is the method of any one of embodiments 1 to 12, wherein the first solvent system comprises a paraffinic solvent system and the second solvent system comprises an aromatic solvent system. Embodiment 14 is the method of embodiment 13, wherein the paraffinic solvent system comprises n-heptane and the aromatic solvent system comprises xylene. Embodiment 15 is the method of any one of embodiments 1 to 14, further comprising: flowing a second portion of the second solvent system to the catalyst preparation unit, the second solvent system being suitable for dissolving one or more catalysts prepared in the catalyst preparation unit.

[0086] Unless explicitly excluded, all embodiments described above and herein can be combined in any way.

[0087] Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications may be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. In addition, the scope of this application is not intended to be limited to the specific embodiments of the process, machine, manufacture, and composition of the form, means, method, and steps described in this specification. It will be readily understood by those of ordinary skill in the art from the contents of this disclosure that any process, machine, manufacture, and composition of materials, means, methods, or steps that are currently or subsequently developed and that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be used. Therefore, the appended claims are intended to include within their scope the process, machine, manufacture, and composition of the form, means, method, or steps.

Claims

1. A method for producing 1-hexene by ethylene oligomerization, the method comprising: flowing a first solvent system into the reactor unit in a reaction mode, wherein the first solvent system is suitable for increasing the selectivity for 1-hexene in the oligomerization of ethylene; flowing ethylene into a reactor unit comprising a catalyst and a first portion of a second solvent system, the second solvent system being different from the first solvent system; contacting ethylene with a catalyst; oligomerizing ethylene in a reactor unit to produce 1-hexene; flowing a reactor unit effluent from the reactor unit, the reactor unit effluent comprising 1-hexene and the first solvent system and the second solvent system; Optionally, switching the reactor unit from a reaction mode to a wash mode; and Optionally, a second portion of a second solvent system is flowed into the reactor unit in the wash mode, the second solvent system being suitable for dissolving by-products in the reactor unit, the by-products including oligomers, polymers, and waxes having 20 to 500 carbon atoms.

2. The method according to claim 1, further comprising: Unreacted ethylene is separated from the reactor unit effluent using a first distillation column to form a recycle ethylene stream comprising primarily ethylene and a first product stream comprising linear alpha olefins (LAOs), byproducts, a first solvent system, and a second solvent system.

3. The method according to claim 2, wherein: The first distillation column includes a rectification section adapted to absorb 1-hexene.

4. The method of claim 3, further comprising: The byproducts are separated from the first product stream to produce a wax / polymer stream comprising primarily waxes and polymers and a second product stream comprising C4 to C8 hydrocarbons, the first solvent system, and the second solvent system.

5. The method of claim 4, further comprising: A recycle ethylene stream is passed to the reactor unit which is in reaction mode.

6. The method according to claim 5, wherein: Separating the by-products from the first product stream comprises: flashing the first product stream in a first flash vessel to produce a second product stream and a bottoms flash stream comprising a second solvent system and byproducts; and Some of the second solvent system is separated from the bottoms flash stream in a manner that allows sufficient second solvent system to remain in the waxes / polymer stream to form a solvent system recovery stream comprising the first solvent system and the second solvent system and a waxes / polymer stream comprising waxes, polymer, and the second solvent system.

7. The method of claim 5, further comprising: 1-Butene is separated from the second product stream to produce a 1-butene stream comprising primarily 1-butene and a third product stream comprising C6 to C8 hydrocarbons, the first solvent system, and the second solvent system.

8. The method of claim 7, further comprising: separating a third product stream by a separation unit comprising at least two C6 distillation columns connected in series, wherein separating the third product stream comprises: separating C6 hydrocarbons from the third product stream by a first C6 distillation column to form a fourth product stream primarily comprising C6 hydrocarbons and a first bottom stream comprising C7 to C8 hydrocarbons, a first solvent system, and a second solvent system; and 1-Hexene is separated from the fourth product stream by a second C6 distillation column to form a fifth product stream comprising 1-hexene and a C6 product stream comprising other C6 components such as n-hexane, 2-ethyl-1-butene and one or more trans-hexene and cis-hexene isomers.

9. The method of claim 8, wherein: The fifth product stream comprises from 99.5 wt% to 99.9 wt% 1-hexene.

10. The method of claim 8, further comprising: The first solvent system and the second solvent system are separated from the first bottoms stream to form a first solvent system recycle stream comprising primarily the first solvent system and a second solvent system recycle stream comprising primarily the second solvent system.

11. The method of claim 10, further comprising: A first portion of the first solvent system recycle stream is flowed to the reactor unit in reaction mode.

12. The method of claim 11, further comprising: A second portion of the first solvent system recycle stream is passed to the rectifying section of the first distillation column for absorption of 1-hexene.

13. The method according to any one of claims 1 to 12, wherein The first solvent system includes a paraffinic solvent system, and the second solvent system includes an aromatic solvent system.

14. The method of claim 13, wherein: The paraffinic solvent system includes n-heptane, and the aromatic solvent system includes xylene.

15. The method of any one of claims 1 to 14, further comprising: A portion of the second solvent system is flowed into the catalyst preparation unit, the second solvent system being suitable for dissolving one or more catalysts prepared in the catalyst preparation unit.

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