Triethyl-aluminum as an additive to control catalyst activity and reduce formation of polymer byproducts during ethylene oligomerization

Abstract

The disclosure provides a catalyst composition for the oligomerization of ethylene to produce one or more linear alpha olefins, the catalyst composition including a chromium compound, a heteroatomic multidentate ligand having an NPNPN backbone, wherein each P is an optionally substituted phosphino group and each N is an optionally substituted amino group, a methylaluminoxane, and triethyl-aluminum.

Description

S105923-10650WO-24CHEM0001-WO-PC TRIETHYL-ALUMINUM AS AN ADDITIVE TO CONTROL CATALYST ACTIVITY AND REDUCE FORMATION OF POLYMER BYPRODUCTS DURING ETHYLENE OLIGOMERIZATION TECHNOLOGICAL FIELD

[0001] The present disclosure relates to methods for producing linear alpha olefin products through oligomerization of ethylene and catalyst compositions for use in such methods. BACKGROUND

[0002] Linear olefins are a class of hydrocarbons useful as raw materials in the petrochemical industry and among these the linear alpha olefins, unbranched olefins whose double bond is located at a terminus of the chain, form an important subclass. Linear alpha olefins can be converted to linear primary alcohols by hydroformylation. Hydroformylation can also be used to prepare aldehydes, which in turn can be oxidized to afford synthetic fatty acids, especially those with an odd carbon number, useful in the production of lubricants. Linear alpha olefins are also used in the production of detergents, such as linear alkylbenzenesulfonates, which are prepared by Friedel-Crafts reaction of benzene with linear olefins followed by sulfonation. Another important use of linear alpha olefins relates to production of linear low- density polyethylene (LLDPE) through catalytic co-polymerization with ethylene.

[0003] Preparation of linear alpha olefins is based largely on oligomerization of ethylene in the presence of a suitable catalyst system, which produces oligomer compounds with an even number of carbon atoms. Certain suitable catalyst systems utilize chromium-based metal-organic complexes with ligands as catalysts in the presence of a co-catalyst such as methyl aluminoxane (MAO). Traditionally, by increasing the amount of co-catalyst within the catalyst system, target oligomers can be selectively produced in larger quantities. Increasing the amount of co-catalyst, however, also increases the activity of the catalyst, which increases the amount of polymer formed during the reaction and leads to fouling both in the reactor and in downstream processing units. Increasing the amount of co-catalyst also makes the process significantly more expensive due to the typically high price of co-catalyst.

[0004] Accordingly, there remains a need in the art for increasing catalytic activity in oligomerization reactions without significantly increasing polymer formation and / or reducing polymer formation while maintaining acceptable catalyst activity. BRIEF SUMMARY

[0005] Example implementations of the present disclosure are directed to catalyst compositions, methods of using said catalyst compositions, and systems and processes for reducing polymer fouling in an oligomerization reactor. It has been discovered that addition of triethyl-aluminum to a catalyst composition adapted for ethylene oligomerization has a marked effect on catalytic activity and polymer formation. According to some embodiments of the present disclosure, reduction in polymer formation can beS105923-10650WO-24CHEM0001-WO-PC accomplished by employing relatively small amounts of triethyl-aluminum in combination with a chromium compound, a heteroatomic multidentate ligand, and a methylaluminoxane without sacrificing catalyst activity or selectivity.

[0006] The present disclosure includes, without limitation, the following embodiments.

[0007] Embodiment 1: A catalyst composition for the oligomerization of ethylene to produce 1-hexene and / or 1-octene, the catalyst composition comprising: a chromium compound; a heteroatomic multidentate ligand having an NPNPN backbone, wherein each P is an optionally substituted phosphino group and each N is an optionally substituted amino group; a methylaluminoxane; and triethyl-aluminum.

[0008] Embodiment 2: The catalyst composition of Embodiment 1, wherein the triethyl-aluminum is present in an amount of 1 to 100 moles, 5 to 90 moles, 10 to 80 moles, 15 to 70 moles, 20 to 60 moles, or 30 to 40 moles per mole of chromium.

[0009] Embodiment 3: The catalyst composition of Embodiment 1 or 2, wherein the methylaluminoxane is present in an amount of 50 to 1000 moles, 100 to 800 moles, 200 to 600 moles, or 250 to 450 moles per mole of chromium.

[0010] Embodiment 4: The catalyst composition of any one of Embodiments 1 to 3, wherein the heteroatomic multidentate ligand is present in an amount of 0.5 to 50 moles per mole of chromium, such as 0.8 to 20 moles per mole of chromium.

[0011] Embodiment 5: The catalyst composition of any one of Embodiments 1 to 4, wherein the methylaluminoxane is a modified methylaluminoxane (MMAO), such as MMAO-3A, MMAO-7, or MMAO-12.

[0012] Embodiment 6: The catalyst composition of any one of Embodiments 1 to 5, wherein the chromium compound is selected from organic or inorganic salts, coordination complexes and organometallic complexes of Cr(III), such as Cr(III)Cl3(tetrahydrofuran)3, Cr(III) acetylacetonate, Cr(III) octanoate, Cr(III)- 2-ethylhexanoate, Cr(III)tris(2,2,6,6,-tetramethyl-3,5-heptanedionate), Cr(III)chloride, Cr(III)-naphthenate, and combinations thereof.

[0013] Embodiment 7: The catalyst composition of any one of Embodiments 1 to 6, wherein the NPNPN backbone comprises the formula (R1)(R2)N—P(R3)—N(R4)—P(R5)—N(R6)(R7), wherein R1, R2, R3, R4, R5, R6, and R7are each independently selected from the group consisting of optionally substituted amino, optionally substituted thiol, optionally substituted alkoxy, trimethylsilyl, or optionally substituted C1-20hydrocarbyl, such as optionally substituted C1-10alkyl or optionally substituted C6-20aryl.

[0014] Embodiment 8: The catalyst composition of Embodiment 7, wherein each of R1, R2, R4, R6, and R7are independently-selected optionally substituted C1-5alkyl, and R3and R5are optionally substituted phenyl or optionally substituted C5-7cycloalkyl.

[0015] Embodiment 9: The catalyst composition of any one of Embodiments 1 to 8, further comprising one or more solvents, optionally wherein the one or more solvents are selected from the group consisting of aliphatic hydrocarbon solvents, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, and combinations thereof, wherein the aliphatic hydrocarbon solvents optionally include oneS105923-10650WO-24CHEM0001-WO-PC or more C5 to C8 cyclic or straight chain alkanes such as n-heptane, cycloheptane, isoheptane, n-hexane, isohexane, cyclohexane, and methylcyclohexane.

[0016] Embodiment 10: A method of producing one or more linear alpha olefins by ethylene oligomerization, the method comprising: contacting ethylene with a catalyst composition according to any one of Embodiments 1 to 9 in a reaction chamber; oligomerizing the ethylene to produce one or more linear alpha olefins; and withdrawing a product stream comprising the one or more linear alpha olefins, optionally wherein the product stream comprises a C6 fraction and a C8 fraction.

[0017] Embodiment 11: The method of Embodiment 10, wherein the product stream comprises a C8 fraction, the C8 fraction comprising 1-octene in an amount of 99% by weight or higher, based on the total weight of the C8 fraction.

[0018] Embodiment 12: The method of Embodiments 10 or 11, wherein the product stream comprises at least 64% by weight of the C8 fraction, such as at least 65% by weight, or at least 66% by weight, or at least 67% by weight, at least 68% by weight, at least 69% by weight, or at least 70% by weight, based on the total weight of reaction products.

[0019] Embodiment 13: The method of any one of Embodiments 10 to 12, wherein the product stream further comprises polymeric byproduct material in an amount of about 1% by weight or less, such as about 0.2% by weight to about 0.6% by weight, based on the total weight of reaction products.

[0020] Embodiment 14: The method of any one of Embodiments 10 to 13, wherein a catalyst activity in units of kg·gCr-1·h-1is about 40 or higher, such as about 40 to about 160 or about 45 to about 105 or about 50 to about 80.

[0021] Embodiment 15: The method of any one of Embodiments 10 to 14, wherein, during the contacting step, in a continuous process, the concentration of triethyl-aluminum in the reaction chamber is decreased from a first concentration to a second concentration, optionally wherein the first concentration is about 50 moles of triethyl-aluminum per mole of chromium or higher, such as about 50 moles to about 100 moles of triethyl-aluminum per mole of chromium, and the second concentration is about 40 moles of triethyl-aluminum per mole of chromium or lower, such as about 10 to about 40 moles of triethyl-aluminum per mole of chromium.

[0022] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

[0023] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of theS105923-10650WO-24CHEM0001-WO-PC disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations. BRIEF DESCRIPTION OF THE FIGURES

[0024] Having thus described aspects of the disclosure in the foregoing general terms, reference will now be made to the accompanying figure, which is not necessarily drawn to scale, and wherein:

[0025] FIG.1 is a simplified schematic diagram of an example ethylene oligomerization reaction system in accordance with the present disclosure. DETAILED DESCRIPTION

[0026] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0027] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0028] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt. % to 25 wt. %,” etc.). “Combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0029] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form.S105923-10650WO-24CHEM0001-WO-PC

[0030] The term “aliphatic” means an organic functional group or compound containing carbon and hydrogen joined together in straight chains, branched chains, or non-aromatic rings.

[0031] The term “hydrocarbyl” refers to any univalent radical derived from a hydrocarbon, such as any aliphatic group (e.g., alkyl groups such as methyl or cycloalkyl groups such as cyclohexyl) or any aryl group (e.g., phenyl).

[0032] The term “alkyl” refers to a linear or a branched saturated hydrocarbon. Non limiting examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl, etc.

[0033] An “aryl” group or an “aromatic” group is a substituted or unsubstituted, mono- or polycyclic hydrocarbon with alternating single and double bonds within each ring structure, such as a phenyl group. Non-limiting examples of aryl group substituents include alkyl, substituted alkyl groups, linear or branched alkyl groups, linear or branched unsaturated hydrocarbons, halogen, hydroxyl, alkoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, nitro, amide, nitrile, acyl, alkyl silane, thiol and thioether substituents. Non- limiting examples of alkyl groups include linear and branched C1to C5hydrocarbons. Non-limiting examples of unsaturated hydrocarbons include C2to C5hydrocarbons containing at least one double bond (e.g., vinyl). The aryl or alkyl group can be substituted with the halogen, hydroxyl, alkoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, ether, amine, nitro (-NO2), amide, nitrile (-CN), acyl, alkylsilane, thiol and thioether substituents. Non-limiting examples of polycyclic groups include ring systems that include 2 or more conjugated rings (e.g., fused aromatic rings) and substituted conjugated rings.

[0034] A “cyclohexyl” group is a substituted or unsubstituted, cyclic hydrocarbon group containing 6 carbon atoms. When fully saturated with hydrogen and having the formula C6H11, the cyclohexyl group is an unsubstituted cyclohexyl group. When at least one of they hydrogen atoms is replaced by another atom or functional group, the cyclohexyl group is a substituted cyclohexyl group.

[0035] Reference herein is made to “optionally substituted” groups. Non-limiting examples of substituents that can be used for optional substitution include linear or branched alkyl, linear or branched unsaturated hydrocarbons, halogen, hydroxyl, alkoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, nitro, amide, nitrile, acyl, alkyl silane, thiol, and thioether substituents. CATALYST COMPOSITION

[0036] According to the present disclosure, a catalyst system is provided for catalyzing an oligomerization reaction. The catalyst system comprises a chromium compound, a heteroatomic multidentate ligand, a methylaluminoxane (MAO) co-catalyst, triethyl-aluminum, and optionally one or more solvents.

[0037] It has been surprisingly discovered that, in some embodiments, modifying a catalyst formulation with triethyl-aluminum results in an increase in the catalytic activity, but significantly reduces the amount of polymer produced during the reaction. Additionally, in some embodiments, the addition of triethyl- aluminum does not affect the selectivity of the catalyst, does not require other adjustment of the ingredients of the catalyst formulation, and does not alter downstream separation processes. By varying the concentration of triethyl-aluminum in the reactor system, the activity of the catalyst can be controlled over aS105923-10650WO-24CHEM0001-WO-PC wide range, which can improve temperature control of the reaction system, particularly during reactor start- up.

[0038] The chromium compound can be, for example, an organic salt, an inorganic salt, a coordination complex, or an organometallic complex of Cr(III). Example chromium compounds include Cr(III)Cl3(tetrahydrofuran)3, Cr(III) acetylacetonate, Cr(III) octanoate, Cr(III)-2-ethylhexanoate, Cr(III)tris(2,2,6,6,-tetramethyl-3,5-heptanedionate), Cr(III)chloride, Cr(III)-naphthenate, and combinations thereof.

[0039] The concentration of the chromium compound can vary depending on the particular compound used and the desired reaction rate. For example, the concentration of the chromium compound can be from about 0.01 to about 100 millimole per liter of catalyst (mmol / 1), such as about 0.01 to about 10 mmol / 1, about 0.01 to about 1 mmol / 1, about 0.1 to about 100 mmol / 1, about 0.1 to about 10 mmol / 1, about 1 to about 10 mmol / 1, and about 1 to about 100 mmol / 1. In some embodiments, the concentration of the chromium compound is from about 0.1 to about 1.0 mmol / 1 per liter of catalyst.

[0040] The molar quantity of the chromium compound can likewise vary depending on the molar quantity of the heteroatomic multidentate ligand. For example, the molar ratio of the total moles of chromium supplied by the chromium compound to the total moles of the heteroatomic multidentate ligand can range from 1:0.5 to 1:50 total moles of Cr per total moles of ligand, such as 1:0.8 to 1:20, 1:0.5 to 1:5, 1:0.8 to 1:2, 1:1 to 1:5, or 1:1 to 1:1.5.

[0041] Typical ligand structures are organophosphorus compounds with at least two phosphino groups covalently linked through a linkage. Example ligands include compounds with NPNPN backbone structures, wherein each P is an optionally substituted phosphino group (typically a secondary or tertiary phosphino group) and each N is an optionally substituted amino group (typically a secondary or tertiary amino group). Example substituents for both the phosphino and amino groups include optionally substituted amino, trialkylsilyl, or optionally substituted Cl- C20hydrocarbyl (e.g., optionally substituted phenyl or optionally substituted cyclohexyl) groups. See, for example, US 2017 / 0203288 A1 to Al-Hazmi et al., WO 2020 / 100010 A1 to Al-Nezari et al., US 2023 / 0053092 A1 to Al-Nezari et al., and WO2023118226A1 to Korobkov, et al., and Dalton Transactions, 201645; 8869-8874 by Paulecke, all of which are incorporated by reference herein.

[0042] In some embodiments, the NPNPN heteroatomic multidentate ligand is of the formula: (R1)(R2)N— P(R3)— N(R4)— P(R5)— N(R6)(R7), wherein R1, R2, R3, R4, R5, R6, and R7can each independently be an optionally substituted amino, optionally substituted alkoxy, optionally substituted thiol, a trialkylsilyl group (e.g., trimethylsilyl or triethylsilyl), or an optionally substituted C1-C20hydrocarbyl group. Examples of the C1-C20hydrocarbyl groups that can be optionally substituted include straight-chain or branched C1-C10alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, etc.), C3-C7cycloalkyl groups (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc.), C6-C20aryl groups (e.g., phenyl, methylbenzyl, dimethylbenzyl (ortho, meta, and para substituted), ethylbenzyl, chlorobenzyl, bromobenzyl,S105923-10650WO-24CHEM0001-WO-PC propylbenzyl, nitrobenzyl, benzonitrile, tri-fluorotolyl, dichlorotolyl, phenylamine, trimethylbenzylsilane, benzylmethylether, etc.), and C6-C20alkyl-substituted C6-C20aryl groups.

[0043] In some embodiments, R1, R2, R4, R6, and R7are each independently selected from C1-C10alkyl groups, and R3and R5are each independently selected from optionally substituted C6-C20aryl groups or optionally substituted C3-C7cycloalkyl groups. In some embodiments, R1, R2, R4, R6, and R7are each independently selected from optionally substituted C1-C5alkyl groups, and R3and R5are each independently an optionally substituted C5-C7cycloalkyl group, or an optionally substituted phenyl group.

[0044] Specific suitable ligands include, but are not limited to: Et(Me)N—P(Ph)—N(Me)—P(Ph)— N(Me)Et,nHe(Me)N—P(Ph)—N(Me)—P(Ph)—N(Me)nHe,iPr(Me)N—P(Ph)—N(Me)—P(Ph)—N(Me)iPr, (nHe)2N—P(Ph)—N(Me)—P(Ph)—N(nHe)2,iPr(Ph)N—P(Ph)—N(Me)—P(Ph)—N(Ph)iPr, Et(Me)N— P(Ph)—N(nHe)—P(Ph)—N(Me)Et, Et(Me)N—P(Me)—N(Me)—P(Me)—N(Me)Et,nBu(Me)N—P(Ph)— N(Me)—P(Ph)—N(Me)nBu,nPe(Et)N— P(Ph)—N(Me)—P(Ph)—N(Et)nPe,nBu(Me)N—P(cHe)— N(Me)— P(cHe)—N(Me)nBu,nPe(Et)N— P(cHe)—N(Me)—P(cHe)—N(Et)nPe, or combinations thereof, where Me is an optionally substituted methyl group, Et is an optionally substituted ethyl group,iPr is an optionally substituted isopropyl group,nBu is an optionally substituted n-butyl group,tBu is an optionally substituted tert-butyl group,nPe is an optionally substituted n-pentyl group,nHe is an optionally substituted n-hexyl group,cHe is an optionally substituted cyclohexyl group, and Ph is an optionally substituted phenyl group.

[0045] In some embodiments, the structure of the ligand can be illustrated by the following Structural Formula (A): (A) In some embodiments, R1and R7are n-4methyl groups, R is a C1-C5alkyl group, and R3and R5are each independently a cyclohexyl or phenyl group that are each optionally substituted with one or more C1-C10alkyl groups.S105923-10650WO-24CHEM0001-WO-PC

[0046] Specific examples of suitable ligands are shown in TABLE 1 below: TABLE 1

[0047] Optionally, the ligand can be a cyclic derivative wherein at least one of the P or N atoms of the NPNPN backbone is a member of a ring system, or any cyclic derivative thereof. The ring system can beS105923-10650WO-24CHEM0001-WO-PC formed from one or more constituent compounds of the ligand by substitution, i.e., by formally eliminating per constituent compound either two whole groups selected from R1to R7(as defined herein), one atom from each of two groups selected from R1to R7(as defined herein), or a whole group selected from R1to R7(as defined herein) and an atom from another group selected from R1to R7(as defined herein), and joining the formally so-created valence-unsaturated sites by one covalent bond per constituent compound to provide the same valence as initially present at a given site.

[0048] In some embodiments, the MAO co-catalyst is a modified methyl aluminoxane. Suitable modified MAO co-catalyst include modified methyl aluminoxane type 3A (MMAO-3A), modified methyl aluminoxane type 7 (MMAO-7), modified methyl aluminoxane type 12 (MMAO-12), or combinations thereof. In some embodiments, the MAO co-catalyst is MMAO-3A. The molar ratio of the MAO co- catalyst to the total moles of chromium can range from 1:1 to 1000:1, such as 50:1 to 1000:1, 100:1 to 800:1, 200:1 to 600:1, 250:1 to 450:1, or 275:1 to 325:1. In some embodiments, the MAO co-catalyst is provided in a solution. For example, Akzo Nobel supplies MMAO-3A in an n-heptane solvent that contains 7% aluminum (CAS No.146905-79-5), which corresponds to an MMAO-3A concentration in the solution of about 18%.

[0049] The triethyl-aluminum can be used, for example, in neat form. “Neat” as used herein indicates that the triethyl-aluminum is provided as a liquid without any additional solvent. The molar ratio of the triethyl-aluminum to the total moles of chromium can range from 1:1 to 100:1, such as 5:1 to 90:1, 10:1 to 80:1, 20:1 to 60:1, or 30:1 to 40:1.

[0050] Optionally, one or more solvents can be present in the catalyst composition. Specific suitable solvents include aromatic hydrocarbons, aliphatic hydrocarbons, and combinations thereof. Example aromatic solvents include toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, and combinations thereof. In some embodiments, the one or more solvents include an aromatic solvent present in an amount of about 10% by weight or less or an amount of about 7.5% by weight or less, such as about 3 to about 7% by weight or about 4 to about 6% by weight, based on the total weight of the catalyst composition. Example aliphatic hydrocarbon solvents include C5to C8cyclic or straight chain alkanes, such as n-heptane, cycloheptane, isoheptane, n-hexane, isohexane, cyclohexane, methylcyclohexane, and combinations thereof. In some embodiments, the one or more solvents include an aliphatic hydrocarbon solvent present in an amount of about 90% by weight or more or about 92.5% or more, such as about 93 to about 97% by weight or about 94 to about 96% by weight, based on the total weight of the catalyst composition.

[0051] In some embodiments, one or more solvents are added to a mixture of the chromium compound and the heteroatomic multidentate ligand to form a first portion of the catalyst composition. Example solvents include aromatic hydrocarbons selected from the group consisting of: xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, and combinations thereof. In some embodiments, the aromatic solvent is selected in part based on solubility of the chromium compound and the heteroatomicS105923-10650WO-24CHEM0001-WO-PC multidentate ligand within the solvent. The chromium compound and the heteroatomic multidentate ligand dissolve in the aromatic solvent when mixed, thus forming a homogenous mixture.

[0052] In some embodiments, the MAO co-catalyst is mixed with the triethyl-aluminum co-catalyst to form a second portion of the catalyst composition prior to mixing with the first portion of the catalyst composition. In one embodiment, the MAO co-catalyst and the triethyl-aluminum co-catalyst together form a homogenous mixture by adding neat triethyl-aluminum to a stock solution of MAO in solvent (such as n- heptane). ETHYLENE OLIGOMERIZATION PROCESS AND SYSTEM

[0053] Also provided in the present disclosure is a method for producing one or more linear alpha olefins by ethylene oligomerization. The method comprises contacting ethylene with a catalyst composition as disclosed herein, oligomerizing the ethylene to produce one or more linear alpha olefins, and withdrawing a product stream comprising the one or more linear alpha olefins.

[0054] Linear alpha olefins (LAOs) are olefins with a chemical formula CxH2x, distinguished from other mono-olefins with a similar molecular formula by linearity of the hydrocarbon chain and the position of the double bond at the primary or alpha position. Linear alpha olefins comprise a class of industrially important alpha-olefins, including 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and higher blends of C20-C24, C24-C30, and C20-C30olefins. Linear alpha olefins are useful intermediates for the manufacture of detergents, synthetic lubricants, copolymers, plasticizers, and many other important products.

[0055] The oligomerization process can occur at temperatures of about 10 to about 200 °C, such as about 20 to about 100 °C, or about 50 to about 80 °C, or about 55 °C to about 80 °C, or about 60 °C to about 75 °C, or about 70 °C. Operating pressures can be 1 to 200 bar, such as 10 to 50 bar or about 25 to about 30 bar. The process can be continuous and mean residence times can be 10 minutes to 20 hours, for example 30 minutes to 4 hours or 1 to 2 hours. Residence times can be chosen so as to achieve the desired conversion at high selectivity.

[0056] The process can be carried out in any reactor, such as a loop reactor, a plug-flow reactor, a bubble column reactor, or a continuous stirred tank reactor (CSTR), and can be carried out in batch, semi- batch, or continuous mode. However, in some embodiments, a loop reactor can be used with the catalyst composition of the present disclosure as the use of triethyl-aluminum as additional co-catalyst can limit polymer formation significantly. Loop reactors provide a high degree of reaction efficiency, but are particularly sensitive to polymer fouling, which can lead to extended reactor downtime for cleaning.

[0057] Oligomerization of ethylene is an exothermic reaction and, thus, the reaction system can include a heat exchanger for cooling. A product stream leaving the oligomerization reaction system can contain the active catalyst and unreacted ethylene. The reaction can be quenched with a quenching medium (e.g., 1- decanol) to avoid undesirable side reactions and catalyst components can be removed from the product stream through extraction with a caustic aqueous phase. Contact with the caustic aqueous phase can result in formation of nonreactive minerals corresponding to the catalyst components. Advantageously, addition ofS105923-10650WO-24CHEM0001-WO-PC triethyl-aluminum does not alter downstream separation processes, since alkyl-aluminum compounds react with the quenching agent in a similar way to MMAO-3A and can be separated at the same stage of the process.

[0058] The product stream, after passage through the catalyst removal system, can pass through a molecular sieve absorption bed and can then be fed to a distillation column to recover dissolved ethylene. The separation train can be configured to separate the linear alpha olefins from the solvent, catalyst, and any unreacted ethylene. Recovered ethylene and solvent can be recycled back to the reaction system. The separation train can separate each linear alpha olefin, for example, yielding a C4stream, C6stream, C8stream, and so on. The separation train can also separate the linear alpha olefins into certain fractions, such as C4-C10fraction, C12-C16fraction, C18-C20fraction, C20+fractions, or any other desired fraction.

[0059] An example loop reaction system 10 is set forth in FIG.1. As shown, the reaction system can include a reaction chamber 12, a pump 14, and a heat exchanger 16, all in fluid communication with each other within a recirculation loop 18. The reaction chamber 12 can be, for example, an autoclave adapted for mixing of the reagents introduced into the reaction system 10. The illustrated embodiment is in the form of a jet loop reactor that includes a nozzle arrangement 24 that accelerates the flow of liquid reaction mixture into the reaction chamber 12 and entrains the gaseous feed 26 therein. The gaseous feed 26 can be ethylene gas, optionally in combination with hydrogen gas. In some embodiments, hydrogen gas is added to the reaction system to reduce polymer formation. An example amount of hydrogen introduced is between about 0.1 and about 10 mol% with respect to the ethylene molar concentration. The reaction chamber 12 is charged with the catalyst composition 28 dissolved in, for example, an aromatic solvent. If desired, an aliphatic hydrocarbon solvent 30 can be injected into the recirculation loop 18. A discharge stream 20 can be removed from the recirculation loop 18 and directed into a separation train 22 as disclosed above. Although not shown, the reaction system 10 can also include a filter for filtering polymeric material circulating within the recirculation loop 18.

[0060] The type of pump 14 is not limiting, and any pump capable of pumping the reaction mixture through the recirculation loop 18 can be used. The type of heat exchanger 16 is not limiting, and any heat exchanger configured to cool the reaction mixture during circulation within the recirculation loop 18 can be used.

[0061] Polymer fouling within the reaction system can occur during the oligomerization reaction process. Such fouling is typically detected by, for example, reduced product flow rate or reduced heat exchanger or pump performance. Such fouling can be treated by flushing the reaction system with a solvent. The flushing solvent comprising the polymeric material can then be directed into the separation train 22.

[0062] In some embodiments, a triethyl-aluminum solution (e.g., a solution comprising about 1 to about 5% by weight of triethyl-aluminum) can be used as a rinsing solution for preparation of the reactor system before the catalyst is charged to the system after reactor downtime. Since triethyl-aluminum does not adversely affect catalyst selectivity, it is not necessary to remove small amounts of triethyl-aluminum left in the reactor after this preparation stage with any additional reactor wash. Instead, any remaining amounts ofS105923-10650WO-24CHEM0001-WO-PC triethyl-aluminum in the system can have a positive effect on start-up procedures due to suppression of catalyst activity during start-up.

[0063] The reaction process of the present disclosure can be characterized by the amount of polymer material produced by the reaction. In some embodiments, the product stream contains about 1% polymer material by weight or less, such as about 0.2% by weight to about 0.6% by weight, based on the total weight of the of the reaction products (i.e., excluding solvent, catalyst, or unreacted ethylene).

[0064] The reaction process of the present disclosure also can be characterized by catalyst activity, which can be determined by ethylene (e.g., C2) consumption per weight of chromium compound during one hour of reaction time using units kg C2·gCr-1·h-1. In some embodiments, the catalyst activity in units of kg·gCr-1·h-1ranges from about 5 to about 160, such as from about 30 to about 105, about 35 to about 80, about 40 to about 65, from about 40 to about 55, or from about 40 to about 55. Since the catalyst activity of the catalyst composition of the present disclosure is inversely proportional to the concentration of triethyl- aluminum in the reaction system, catalyst activity in a continuous process can be readily controlled through control of the triethyl-aluminum concentration. In this manner, improvement in temperature control within the reactor system can be achieved, particularly during reactor start-up. For example, in a continuous process, the concentration of triethyl-aluminum in the reaction chamber can be decreased from a first concentration at reactor start-up to a second concentration intended for normal production mode, such as wherein the first concentration is about 50 moles of triethyl-aluminum per mole of chromium or higher, such as about 50 moles to about 100 moles of triethyl-aluminum per mole of chromium, and the second concentration is about 40 moles of triethyl-aluminum per mole of chromium or lower, such as about 10 to about 40 moles of triethyl-aluminum per mole of chromium.

[0065] The reaction process of the present disclosure also can be characterized by selectivity of C6 fractions and C8 fractions within the product stream, which can each be calculated as Selectivity (Cn) = [(1Cn+ Cnisomers + Cn(saturated)isomers) / total C4to C20+]. In some embodiments, the selectivity for the C6 fraction ranges from about 20% to about 40%, such as about 25% to about 35%, or about 28% to about 35%, based on the total weight of the reaction products. In some embodiments, the selectivity for the C8 fraction ranges from about 50% to about 80%, such as about 55% to about 75%, or about 60% to about 70%, based on the total weight of the reaction products. In some embodiments, the product stream comprises at least 64% by weight of the C8 fraction, such as at least 65% by weight, or at least 66% by weight, or at least 67% by weight, at least 68% by weight, at least 69% by weight, or at least 70% by weight, based on the total weight of reaction products.

[0066] The reaction process of the present disclosure also can be characterized by purity of the 1-octene within the C8fraction, which can be calculated as Purity (1Cn) = [1Cn / (1Cn+ Cnisomers + Cn(saturated)isomers) x 100]. In some embodiments, the purity of 1-octene is greater than 90%, such as greater than 99%, greater than 99.3%, or greater than 99.4% (e.g., about 99% to about 99.8%.

[0067] In general, the present disclosure may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The disclosure may additionally, or alternatively, beS105923-10650WO-24CHEM0001-WO-PC formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objectives of the present disclosure. EXPERIMENTAL Example 1: Evaluation of Addition of Alkyl-Aluminum Co-catalyst to Benchmark Catalyst Composition

[0068] An ethylene oligomerization reaction was conducted in a semi-batch PARR reactor system in accordance with the experiment conditions provided below to examine the impact of addition of various alkyl-aluminum co-catalysts to a benchmark catalyst composition. The benchmark catalyst composition included the imidodiphosphonous diamide ligand structure shown below, a Cr(III) source, and MMAO-3A as co-catalyst (in the form of a solution in n-heptane with 21 wt.% Al). N-heptane was used as a reaction media. The molar ratio of Cr:ligand:MMAO-3A was 1:1.2:300. Reaction conditions were 45 °C, 30 bar, and a run duration of 1 hour. Ligand

[0069] Using the same reaction benchmark catalyst was compared to the performance of the benchmark catalyst modified by addition of a small amount of one of various trialkyl- aluminum co-catalysts (trimethyl-aluminum or TMA; triethyl-aluminum or TEAl; or tributyl-aluminum or TiBAl). Each trialkyl-aluminum catalyst was added neat to the catalyst composition.

[0070] The resulting data is set forth in TABLE 2, below. As shown in the table, each alkyl-aluminum was added at a molar ratio of Cr:alkyl-aluminum of 1:10. TABLE 2 Exp. Activity % %wt 1- % wt. %wt 1- % wt. %wt 1- Polyme Conditions (kg / gCr wt. C4 C6 C6 C8 Oct in r (g) * h) C4 in in "C6" "C8" "C4" Benchmark 53.58 0.64 42.08 32.64 69.51 64.84 99.47 0.2566 Cr : TMA = 1 : 101.03 0.66 45.35 31.95 70.75 65.93 99.47 0.3000 10 Cr : TEAl = 1 : 100.09 0.70 43.02 31.26 71.59 67.11 99.53 0.1125 10 Cr : TiBAl = 1 : 87.71 0.61 44.50 34.13 73.29 63.85 99.42 0.2538 10

[0071] Surprisingly, it was observed that polymer formation was greatly reduced when triethyl- aluminum (TEAl) was used as the additional co-catalyst, despite greatly increasing catalyst activity. InS105923-10650WO-24CHEM0001-WO-PC contrast, the other alkyl-aluminum species either maintained the same level of polymer formation as the benchmark or increased polymer formation, while also increasing catalyst activity. Advantageously, addition of TEAl maintained desirable yield and selectivity of 1-C6 (1-hexene) and 1-C8 (1-octene) products as compared to the benchmark catalyst. It is clear from this data that addition of triethyl-aluminum leads to far superior catalyst performance as compared to other tri-alkyl-aluminum compounds. Example 2 – Optimization of Triethyl-Aluminum Concentration

[0072] To establish the relationship between triethyl-aluminum concentration and catalyst activity, the same experimental conditions used in Example 1 were repeated for catalyst compositions including triethyl- aluminum co-catalyst at six different concentrations. The resulting data is set forth in TABLE 3, below. The same benchmark data from Example 1 is included in the table for comparison. As shown in the table, triethyl-aluminum addition was varied from a molar ratio of Cr:triethyl-aluminum of 1:10 to 1:60. TABLE 3 Activity %wt 1- %wt 1- %wt 1- Exp. (kg / % C4 % wt. C6 % wt. Polyme Conditions gCr * Oct in h) wt. in "C C6 C8 r (g) C4 4" in "C6" "C8" Benchmark 53.58 0.64 42.08 32.64 69.51 64.84 99.47 0.2566 Cr : TEAl = 1 : 100.09 0.70 43.02 31.26 71.59 67.11 99.53 0.1125 10 Cr : TEAl = 1 : 75.91 0.82 33.45 28.75 70.04 65.92 99.55 0.0380 20 Cr : TEAl = 1 : 51.75 0.90 32.99 29.63 67.29 68.72 99.38 0.0479 30 Cr : TEAl = 1 : 45.95 1.17 26.96 29.24 67.48 69.03 99.55 0.0249 40 Cr : TEAl = 1 : 23.57 1.47 21.51 31.71 65.25 66.29 100.00 0.0165 50 Cr : TEAl = 1 : 27.84 1.43 22.94 30.09 63.51 67.78 100.00 0.0676 60

[0073] The data confirm that TEAl addition in small amounts reduces polymer formation and increases catalyst activity as compared to the benchmark, but increasing the amount of TEAl reduces catalyst activity (while also reducing polymer formation further). This data provides guidance as to the optimal level of TEAl addition, depending on the desired outcome.

[0074] Significant increase in catalytic activity could present difficulties in temperature control of the process, especially at the start-up of the reactor, due to the exothermic character of the reaction. From the above-provided data, it is clear that catalytic activity could be maintained on the same level as the benchmark by using, for example, a Cr:TEAl molar ratio of about 1:30 to 1:40. At that level of catalyst activity, formation of polymer byproducts is considerably lower in comparison to the benchmark. Catalytic activity can be decreased even further with increase of triethyl-aluminum concentration. In such case, polymerization side reaction becomes practically negligible.S105923-10650WO-24CHEM0001-WO-PC

[0075] This provides valuable information for reactor start-up procedure, especially temperature control at start-up of a continuous process. For example, this data suggests use of higher concentrations of triethyl- aluminum at start-up to suppress catalyst activity (and therefore reactor temperature), followed by slowly reducing triethyl aluminum concentration until the desired window of operation is achieved.

[0076] Many modifications and other implementations of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed herein and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

S105923-10650WO-24CHEM0001-WO-PC WHAT IS CLAIMED IS:

1. A catalyst composition for the oligomerization of ethylene to produce 1-hexene and / or 1-octene, the catalyst composition comprising: a chromium compound; a heteroatomic multidentate ligand having an NPNPN backbone, wherein each P is an optionally substituted phosphino group and each N is an optionally substituted amino group; a methylaluminoxane; and triethyl-aluminum.

2. The catalyst composition of claim 1, wherein the triethyl-aluminum is present in an amount of 1 to 100 moles, 5 to 90 moles, 10 to 80 moles, 15 to 70 moles, 20 to 60 moles, or 30 to 40 moles per mole of chromium.

3. The catalyst composition of any one of claims 1 or 2, wherein the methylaluminoxane is present in an amount of 50 to 1000 moles, 100 to 800 moles, 200 to 600 moles, or 250 to 450 moles per mole of chromium.

4. The catalyst composition of any one of claims 1 to 3, wherein the heteroatomic multidentate ligand is present in an amount of 0.5 to 50 moles per mole of chromium, such as 0.8 to 20 moles per mole of chromium.

5. The catalyst composition of any one of claims 1 to 4, wherein the methylaluminoxane is a modified methylaluminoxane (MMAO), such as MMAO-3A, MMAO-7, or MMAO-12.

6. The catalyst composition of any one of claims 1 to 5, wherein the chromium compound is selected from organic or inorganic salts, coordination complexes and organometallic complexes of Cr(III), such as Cr(III)Cl3(tetrahydrofuran)3, Cr(III) acetylacetonate, Cr(III) octanoate, Cr(III)-2- ethylhexanoate, Cr(III)tris(2,2,6,6,-tetramethyl-3,5-heptanedionate), Cr(III)chloride, Cr(III)- naphthenate, and combinations thereof.

7. The catalyst composition of any one of claims 1 to 6, wherein the NPNPN backbone comprises the formula (R1)(R2)N—P(R3)—N(R4)—P(R5)—N(R6)(R7), wherein R1, R2, R3, R4, R5, R6, and R7are each independently selected from the group consisting of optionally substituted amino, optionally substituted thiol, optionally substituted alkoxy, trimethylsilyl, or optionally substituted C1-20hydrocarbyl, such as optionally substituted C1-10alkyl or optionally substituted C6-20aryl.S105923-10650WO-24CHEM0001-WO-PC 8. The catalyst composition of claim 7, wherein each of R1, R2, R4, R6, and R7are independently- selected optionally substituted C1-5alkyl, and R3and R5are optionally substituted phenyl or optionally substituted C5-7cycloalkyl.

9. The catalyst composition of any one of claims 1 to 8, further comprising one or more solvents, optionally wherein the one or more solvents are selected from the group consisting of aliphatic hydrocarbon solvents, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, and combinations thereof, wherein the aliphatic hydrocarbon solvents optionally include one or more C5 to C8 cyclic or straight chain alkanes such as n-heptane, cycloheptane, isoheptane, n-hexane, isohexane, cyclohexane, and methylcyclohexane.

10. A method of producing one or more linear alpha olefins by ethylene oligomerization, the method comprising: contacting ethylene with a catalyst composition according to any one of claims 1 to 9 in a reaction chamber; oligomerizing the ethylene to produce one or more linear alpha olefins; and withdrawing a product stream comprising the one or more linear alpha olefins.

11. The method of claim 10, wherein the product stream comprises a C8 fraction, the C8 fraction comprising 1-octene in an amount of 99% by weight or higher, based on the total weight of the C8 fraction.

12. The method of claim 11, wherein the product stream comprises at least 64% by weight of the C8 fraction, such as at least 65% by weight, or at least 66% by weight, or at least 67% by weight, at least 68% by weight, at least 69% by weight, or at least 70% by weight, based on the total weight of reaction products.

13. The method of claim 10, wherein the product stream further comprises polymeric byproduct material in an amount of about 1% by weight or less, such as about 0.2% by weight to about 0.6% by weight, based on the total weight of reaction products.

14. The method of claim 10, wherein a catalyst activity in units of kg·gCr-1·h-1is about 40 or higher, such as about 40 to about 160 or about 45 to about 105 or about 50 to about 80.

15. The method of claim 10, wherein, during the contacting step, in a continuous process, the concentration of triethyl-aluminum in the reaction chamber is decreased from a first concentration to a second concentration, optionally wherein the first concentration is about 50 moles of triethyl- aluminum per mole of chromium or higher, such as about 50 moles to about 100 moles of triethyl-S105923-10650WO-24CHEM0001-WO-PC aluminum per mole of chromium, and the second concentration is about 40 moles of triethyl- aluminum per mole of chromium or lower, such as about 10 to about 40 moles of triethyl-aluminum per mole of chromium.

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