A catalyst composition for ethylene selective dimerization reaction and use thereof

Abstract

This invention discloses a catalyst composition for the selective dimerization of ethylene, comprising an organotitanium compound, at least one organoaluminum compound, a non-polymeric ether modifier, a water-carrying agent, and water. The water-carrying agent includes one or more of sulfonates or sulfonates, phosphonium salts, alkyl quaternary ammonium salts, polyoxyethylene ethers, and alkylphenols. Using this catalyst composition for ethylene dimerization effectively inhibits polymer formation while maintaining high catalytic activity and butene-1 selectivity, exhibiting rapid initiation, a stable reaction process, and good reproducibility.

Description

Technical Field

[0001] This invention relates to the field of ethylene oligomerization, and more specifically, to catalyst compositions, preparation methods, and applications for ethylene dimerization processes. Background Technology

[0002] Butene-1 is an important petrochemical feedstock, mainly used as a comonomer in the production of polyolefins and in the production of poly1-butene. Currently, the primary source of butene-1 is mixed C4 separation, with refinery catalytic cracking units, ethylene cracking units, and coal / methanol-to-olefins units providing abundant mixed C4 feedstocks for this technology route. Because the feedstock contains substances with relatively high volatility similar to butene-1, such as 1,3-butadiene, isobutene, and butane, ordinary distillation processes are insufficient for effective separation. Complex separation processes and energy-intensive superdistillation are required to obtain high-purity butene-1 products.

[0003] Another technical approach involves the oligomerization of ethylene, particularly selective dimerization, to produce butene-1. The French Institute of Petroleum (IFP) has successfully developed Alphabutol. TM The process involves the selective dimerization of two ethylene molecules to form one molecule of butene-1 under the action of a catalyst. A side reaction occurs when one molecule of butene reacts with one molecule of ethylene to form hexene and its isomers. The selective dimerization process for ethylene is relatively simple, with mild reaction conditions, low utility consumption, low equipment investment, and readily yields high-purity butene-1 products.

[0004] However, the selective dimerization process of ethylene presents the problem of byproduct polymers. Due to the multi-active-site characteristics of the catalytic system and the influence of long residence times, the dimerization reaction almost inevitably generates high-molecular-weight polyethylene as a byproduct. This polyethylene readily adheres to equipment and pipelines, causing blockages. Furthermore, the polymer adhering to the reactor inner wall is a poor conductor of heat, hindering heat dissipation from the reaction system and forming localized high-temperature zones. The high reactivity within these zones exacerbates the formation of byproduct polymers, further impeding heat transfer until cooling capacity is lost, easily leading to runaway polymerization. Affected by byproduct polymers, the unit must be frequently shut down to open pipelines and equipment for polymer removal, significantly increasing operating and maintenance costs and posing considerable safety hazards.

[0005] Because the main catalyst and co-catalyst used are highly sensitive to impurities such as water and oxygen, water is generally considered to be very detrimental to the ethylene oligomerization and dimerization process. CN108602058A discloses a method for selective dimerization of ethylene, which is strictly controlled to be carried out in an anhydrous and oxygen-free environment. Therefore, the current ethylene oligomerization and dimerization reactions have very demanding process requirements, produce a lot of by-product polymers, and have very poor reaction initiation and repeatability. Summary of the Invention

[0006] To address the prominent problems in the aforementioned ethylene dimerization process, the inventors conducted in-depth research in the field of ethylene selective dimerization catalysts and unexpectedly discovered that introducing a certain amount of water into a catalyst composition composed of organotitanium complexes, organoaluminum compounds, and ether modifiers via a water-carrying agent can effectively inhibit polymer formation while maintaining high catalytic activity and butene-1 selectivity. The initiation is rapid, the reaction process is stable, and the results are reproducible, thus overcoming the technical biases of those skilled in the art and achieving unexpected technical effects.

[0007] According to one aspect of the present invention, a catalyst composition for selective dimerization of ethylene is provided, the composition comprising an organotitanium compound, an organoaluminum compound, an ether modifier, a water carrier, and water.

[0008] In the catalyst composition of the present invention, the molar ratio of the water-carrying agent to the organoaluminum compound is 0.001:1 to 10:1, preferably 0.05:1 to 0.5:1. Based on the weight of the water-carrying agent, the water content is 5 to 500 ppm (i.e., based on the addition of 1 g of water-carrying agent, the catalyst composition contains 5 × 10⁻⁶ ppm water). -6 ~500×10 -6 (g of water). Within the range of the water-carrying agent and water content, the catalyst composition can effectively suppress polymer formation while maintaining high catalytic activity and butene-1 selectivity.

[0009] In this invention, the molar ratio of aluminum in the organoaluminum compound to titanium in the organotitanium compound is 0.01:1 to 100:1, preferably 1:1 to 10:1.

[0010] In this invention, the molar ratio of the ether modifier to the titanium in the organotitanium compound is 0.01:1 to 100:1, preferably 1:1 to 10:1.

[0011] As previously described in this invention, the embodiments of the described catalyst compositions may include one or more water-carrying agents. While the catalyst composition may include several water-carrying agents, in some embodiments, the catalyst composition may include a single water-carrying agent compound. In one or more embodiments, the water-carrying agent is selected from one or more of sulfonates or sulfonates, phosphonium salts, alkyl quaternary ammonium salts, polyoxyethylene ethers, and alkylphenols. The water-carrying agent can adequately disperse water into the catalyst composition to interact with the active sites, thereby effectively inhibiting polymer formation while maintaining high catalytic activity and butene-1 selectivity.

[0012] In this invention, the sulfonate has the general formula (R1-SO3). - ) n (A n+), wherein R1 is a straight-chain or branched alkyl group, a phenyl group with a straight-chain or branched alkyl group, a naphthyl group with a straight-chain or branched alkyl group, or an alkyl group with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, pyridyl groups, etc., and A n+ It can be a monovalent, divalent, or trivalent metal cation, a quaternary ammonium ion, or a quaternary phosphorus cation. For example, sulfonates suitable as water-carrying agents include, but are not limited to, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium diisopropylnaphthalene sulfonate, sodium dioctyl succinate sulfonate, tetrabutylphosphine methanesulfonate, and hexadecyltrimethyl-p-toluene sulfonate ammonium.

[0013] In this invention, the sulfonate has the general formula (R1-SO2–OR2), where R1 and R2 are straight-chain or branched alkyl groups or phenyl groups with straight-chain or branched alkyl groups. For example, sulfonates suitable as water-carrying agents include, but are not limited to, dodecyl p-toluenesulfonate and methyl dodecylbenzenesulfonate.

[0014] In this invention, the phosphonium salt has the general formula [PR1R2R3R4]. + X - R1, R2, R3, and R4 are straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, or alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. X - Selected from halogen anions and tetrahaloborate anions, for example, phosphonium salts suitable as water-carrying agents may include tetrabutylphosphonium tetrafluoroborate, tetrabutylphosphonium bromide, trihexyltetradecyltetrafluoroborate, and trihexyltetradecylphosphonium bromide.

[0015] In this invention, the alkyl quaternary ammonium salt has the general formula [NR1R2R3R4]. + X - R1, R2, R3, and R4 are straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, or alkyl groups with functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. X - Selected from halogen anions, tetrahaloborate anions, fluorophenylborate anions, hexahalophosphonate anions, and fluorophenylphosphonate anions. For example, alkyl quaternary ammonium salts suitable as water-carrying agents may include hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium tetrafluoroborate, tetraoctyltetrafluoroborate, and hexadecyltrimethylammonium hexafluorophosphate.

[0016] In this invention, the polyoxyethylene ether has the general formula shown in Formula 1:

[0017]

[0018] Where R is a hydrogen atom, a straight-chain or branched alkyl group, a cycloalkyl group, a phenyl group with a straight-chain or branched alkyl group, a naphthyl group with a straight-chain or branched alkyl group, or an alkyl group with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. x and y are positive integers, with x ranging from 3 to 1227 and y ranging from 2 to 4. For example, suitable polyoxyethylene ethers for use as water-carrying agents include, but are not limited to, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyethylene glycol octylphenyl ether, α-2-naphthyl-ω-hydroxy-polyethylene glycol, polyethylene glycol monomethyl ether, and α,ω-dihydroxy-terminated polyoxyethylene ether.

[0019] In this invention, the alkylphenol has the general formula shown in Formula 2:

[0020]

[0021] R1, R2, R3, R4, and R5 are each independently selected from hydrogen atoms, hydroxyl groups, straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, and alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. At least one of R1, R2, R3, R4, and R5 is selected from straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, and alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, and pyridyl groups. Examples include decylphenol, 2-cyclohexylphenol, 2-methoxy-5-methylphenol, 4-methoxycarbonylphenol, 2-acetamidophenol, and 4-(pyridin-4-yl)phenol.

[0022] In this invention, the term "halogen" refers to fluorine, chlorine, bromine, and iodine, with fluorine, chlorine, and bromine being particularly preferred.

[0023] In this invention, the ether regulator is a non-polymeric ether compound. As used in this invention, a "non-polymeric" ether compound refers to a compound whose molecular structure contains one or more ether bonds but does not contain long-chain polyethers. These non-polymeric ether compounds typically contain fewer than 10 ether bonds, preferably 1 to 4. In this invention, the non-polymeric ether compound may include cyclic ether compounds. In one or more embodiments, the non-polymeric ether compound is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, tetrahydropyran, and dioxane, preferably ethylene glycol dimethyl ether or tetrahydrofuran.

[0024] In this invention, the organoaluminum compound is selected from alkylaluminum compounds and aluminum oxanes, preferably alkylaluminum compounds.

[0025] In this invention, the alkylaluminum compound has the general formula AlR. k X 3-kIn this invention, R is independently selected from hydrogen atoms, C1-C8 straight-chain or branched alkyl groups, X is a halogen, and k is a positive number ranging from 1 to 3. The organoaluminum compound is selected from trimethylaluminum, diethylaluminum hydride, triethylaluminum, tripropylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, and ethylaluminum dichloride, preferably triethylaluminum.

[0026] In this invention, the aluminum oxane is a C1-C4 alkyl aluminum oxane, wherein the C1-C4 alkyl group is a straight-chain or branched alkyl group, and the aluminum oxane is preferably selected from methyl aluminum oxane, modified methyl aluminum oxane, ethyl aluminum oxane, and isobutyl aluminum oxane, with methyl aluminum oxane being the most preferred.

[0027] In this invention, the organotitanium compound has the general formula Ti(OR)4, wherein each R is independently selected from C1-C10 straight-chain or branched alkyl, cycloalkyl, phenyl, or phenyl with C1-C10 straight-chain or branched alkyl groups. In this invention, the organotitanium compound is selected from tetraethyl titanate, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisooctyl titanate, and tetraphenyl titanate, preferably tetra-n-butyl titanate.

[0028] On the other hand, the present invention also provides a method for selective dimerization of ethylene, the method comprising the following steps:

[0029] (1) Vacuuming and nitrogen replacement at high temperature; (2) Repeated replacement with ethylene; (3) Injecting catalyst composition and organic solvent into the reaction system and stirring thoroughly; (4) Introducing ethylene to start the dimerization reaction, maintaining the reaction pressure at 0.1 MPaG to 30 MPaG, the reaction temperature at -20 to 250℃, and the reaction time at 30 min to 250 min; (5) Stopping the reaction and cooling down.

[0030] In this invention, the water carrier and water are premixed in the catalyst composition to prepare a mixture, which is prepared by the following method: (1) after the water carrier and organic solvent are mixed evenly in a container, deionized water is added dropwise and stirred to make it evenly mixed with the water carrier and organic solvent; (2) the mixture is taken and the water content is measured with a moisture meter until the target value is reached.

[0031] In this invention, the organic solvent is selected from n-hexane, cyclohexane, methylcyclohexane, n-heptane, benzene, toluene, and xylene, with methylcyclohexane being preferred. The concentration of the organotitanium compound in the catalytic system based on the organic solvent is 0.001–10 mmol / L.

[0032] In this invention, the mixture of organotitanium compound, organoaluminum compound, non-polymeric ether compound regulator, water-carrying agent, and water mentioned in step (3) can be dissolved separately in an organic solvent and then injected into the reaction system, or any two or more of them can be pre-mixed before being injected into the reaction system. For example, the organoaluminum compound can be dissolved in an organic solvent and injected into the reaction system, then the mixture of water-carrying agent and water can be injected, and finally the organotitanium compound and non-polymeric ether regulator can be mixed and injected. The above examples are only for illustrative purposes, and different mixing methods and different feeding sequences can be adopted in actual operation.

[0033] The beneficial effects of this invention are as follows:

[0034] Using the catalyst composition described in this invention for selective dimerization of ethylene, the selectivity of butene-1 can reach over 96%, the polymer selectivity is less than 20 ppm, and the catalytic activity is maintained at over 8000 g ethylene / (mol Ti·min).

[0035] According to the catalyst composition provided by the present invention, ethylene undergoes selective dimerization under the action of a composition comprising an organotitanium compound, an organoaluminum compound, a non-polymeric ether compound modifier, a water carrier and water, which can effectively inhibit polymer formation while maintaining high catalytic activity and butene-1 selectivity. Detailed Implementation

[0036] The present invention will be further described and illustrated below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0037] Raw materials and sources:

[0038]

[0039]

[0040]

[0041] Test method:

[0042] (1) Water content testing: In all examples and comparative examples, the water content was measured using a Metrohm 851titrando coulometric Karl Fischer titrator, with the weight of the water-carrying agent as the calculation reference. 4 mL of the test sample (a mixture of 0.02 mol / L methylcyclohexane solution of the water-carrying agent described below and water) was added to the test chamber via a syringe. The mass of the added sample was calculated by weighing the difference in mass before and after the syringe addition. The sample mass was then input into the instrument, which automatically titrated to calculate the water content. Each sample was measured in triplicate, and the average value was taken. The water content, with the weight of the water-carrying agent as the calculation reference, was calculated using the following formula:

[0043] The weight of water (ppm) is calculated using the weight of the water-carrying agent as the reference. This is calculated as follows: Water content (ppm) as measured by the instrument × [Methylcyclohexane density (g / L) + 0.02 mol / L × water-carrying agent molecular weight (g / mol)] / [0.02 mol / L × water-carrying agent molecular weight (g / mol)].

[0044] The density of methylcyclohexane at room temperature (25℃) is 770 g / L.

[0045] (2) Gas chromatography analysis method: The composition of the reaction solution in all examples and comparative examples was tested according to "SH / T 1492-2020 Determination of purity and hydrocarbon impurities of industrial 1-butene by gas chromatography". The analytical instrument was an Agilent 8890 gas chromatograph equipped with a G3539A high-pressure liquid injection device suitable for the 8890 gas chromatograph.

[0046] Preparation of water-containing water-carrying agents:

[0047] Add 4 mmol of water-carrying agent and 200 mL of methylcyclohexane to a 500 mL three-necked flask, and stir magnetically at 300 rpm to prepare a 0.02 mol / L solution. Using a microsyringe, draw deionized water and slowly add it dropwise through one of the necks of the three-necked flask, mixing the deionized water with the methylcyclohexane solution. During the addition of deionized water, take a sample and measure the water content using a moisture analyzer until the target value is reached. Stop adding deionized water, transfer the mixture from the three-necked flask to a sealed bottle for later use.

[0048] To evaluate the catalytic effect of the described catalyst compositions, several catalyst compositions were prepared. The water carrier, the weight content of water (calculated based on the weight of the water carrier), and the molar ratio of each component are listed in Table 1. For the experiments, a catalyst mixture containing a mixture of tetrabutyl titanate (represented as "Ti" in Table 1), tetrahydrofuran (represented as "THF" in Table 1), triethylaluminum (represented as "Al" in Table 1), the water carrier as described above (represented as "WLA" in Table 1), and deionized water was used.

[0049] The process of ethylene dimerization:

[0050] The catalyst composition was prepared and transferred to metal feed tanks in a high-pressure reactor. Tetrabutyl titanate was mixed with tetrahydrofuran and injected into metal feed tank A; a triethylaluminum solution in methylcyclohexane was injected into metal feed tank B; and a mixture of water-carrying agent and water was injected into metal feed tank C. Before the experiment, the 500 mL high-pressure reactor was heated to 120 °C, 0.5 MPaG of high-purity nitrogen was introduced, and then a vacuum was applied. This process was repeated three times, and vacuum was maintained for 4 hours to remove water, oxygen, and other impurities from the reactor. The high-pressure reactor was then cooled to 50 °C and maintained at 50 °C. The high-purity ethylene used for displacement and reaction was purified by columns containing molecular sieves and copper catalysts before being added to the high-pressure reactor. 0.5 MPaG of ethylene was introduced into the high-pressure reactor, and then a vacuum was applied. This process was repeated three times, and finally, the reactor was kept under vacuum. The materials from feed tanks B, A, and C, along with 200 mL of methylcyclohexane solvent, were sequentially injected into the reactor, and stirring was started at 500 rpm. Next, the reaction temperature was set and maintained at 50°C, and 2.4 MPaG of ethylene was continuously introduced into the high-pressure reactor for 40 minutes.

[0051] After a 40-minute reaction time, the ethylene flow was stopped, and 1 mL of ethanol was injected into the reactor to terminate the reaction. The reactor temperature was lowered to 15–20°C, and the material inside the reactor was discharged into a high-pressure sampling cylinder through the bottom outlet. The sample was then injected through the high-pressure injection valve for gas chromatography analysis. After the reaction solution was tested, solid polymer was obtained by filtration. The reactor was then depressurized through the vent valve, opened, and the polymer adhering to the reactor was collected. This polymer was combined with the filtered polymer, placed in a vacuum oven at 110°C for at least 12 hours, and then weighed.

[0052] Table 1 shows the polymer selectivity, catalytic activity, and butene-1 selectivity of catalyst compositions containing a water-carrying agent and water, as well as the polymer selectivity, catalytic activity, and butene-1 selectivity of comparative examples. The reaction data in Table 1 show that the catalyst system with a certain amount of water introduced by the water-carrying agent can effectively suppress polymer formation while maintaining high catalytic activity and butene-1 selectivity. Furthermore, the reaction initiation is rapid, the reaction process is stable, and the results are reproducible.

[0053] Table 1 shows that the organotitanium compound used was n-butyl titanate, the ether modifier was tetrahydrofuran, the organoaluminum compound was triethylaluminum, the concentration of n-butyl titanate was 1.25 mmol / L based on methylcyclohexane organic solvent, the reaction pressure was 2.4 MPaG, the reaction temperature was 50℃, and the reaction time was 40 min.

[0054]

[0055]

[0056]

[0057] Table 2 shows the fixed water carrier as AEO-7, with a molar ratio of tetrabutyl titanate: ether regulator: organoaluminum compound: AEO-7 = 1:6:4:0.08, a water content of 35 ppm (calculated based on the weight of water carrier AEO-7), a reaction pressure of 2.4 MPaG, a reaction temperature of 50℃, and a reaction time of 40 min.

[0058]

[0059] Table 3 shows that the organotitanium compound selected is n-butyl titanate, the ether regulator is tetrahydrofuran, the organoaluminum compound is triethylaluminum, and the water-carrying agent is AEO-7. The molar ratio of n-butyl titanate:tetrahydrofuran:triethylaluminum:AEO-7 is 1:6:4:0.08. The water content is 35 ppm by weight (based on the weight of the water-carrying agent AEO-7). The concentration of n-butyl titanate is 1.25 mmol / L based on methylcycloalkyl solvent.

[0060]

Claims

1. A catalyst composition for selective dimerization of ethylene, the composition comprising an organotitanium compound, an organoaluminum compound, an ether modifier, a water-carrying agent, and water; wherein the molar ratio of the water-carrying agent to the organoaluminum compound is 0.001:1 to 10:1, preferably 0.05:1 to 0.5:1; and the water content is 5 to 500 ppm by weight, calculated based on the weight of the water-carrying agent.

2. The catalyst composition according to claim 1, characterized in that, The molar ratio of aluminum in the organoaluminum compound to titanium in the organotitanium compound is 0.01:1 to 100:1, preferably 1:1 to 10:1; and / or, the molar ratio of the ether modifier to titanium in the organotitanium compound is 0.01:1 to 100:1, preferably 1:1 to 10:

1.

3. The catalyst composition according to claim 1 or 2, characterized in that, The water-carrying agent is selected from one or more of sulfonates or sulfonates, phosphorus salts, alkyl quaternary ammonium salts, polyoxyethylene ethers, and alkylphenols; preferably, the sulfonate has the general formula (R1-SO3). - ) n (A n+ ), wherein R1 is a straight-chain or branched alkyl group, a phenyl group with a straight-chain or branched alkyl group, a naphthyl group with a straight-chain or branched alkyl group, or an alkyl group with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, pyridyl groups, etc., and A n+ The sulfonate is a monovalent, divalent, or trivalent metal cation, a quaternary ammonium ion, or a quaternary phosphorus cation, such as sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium diisopropylnaphthalene sulfonate, sodium dioctyl succinate sulfonate, tetrabutylphosphine methanesulfonate, or hexadecyltrimethyl-p-toluenesulfonate ammonium; and / or, the sulfonate has the general formula (R1-SO2–OR2), where R1 and R2 are straight-chain or branched alkyl groups or phenyl groups with straight-chain or branched alkyl groups, for example, the sulfonate includes, but is not limited to, dodecyl p-toluenesulfonate and methyl dodecylbenzene sulfonate.

4. The catalyst composition according to claim 3, characterized in that, The general formula for the phosphonium salt is [PR1R2R3R4]. + X - R1, R2, R3, and R4 are straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, or alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. X - The salt is selected from halide anions and tetrahaloborate anions, for example, phosphonium salts are selected from tetrabutylphosphonium tetrafluoroborate, tetrabutylphosphonium bromide, trihexyltetradecyltetrafluoroborate, and trihexyltetradecylphosphonium bromide; and / or, the alkyl quaternary ammonium salt has the general formula [NR1R2R3R4]. + X - R1, R2, R3, and R4 are straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, or alkyl groups with functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. X - The alkyl quaternary ammonium salt is selected from halogen anions, tetrahaloborate anions, fluorophenylborate anions, hexahalophosphonate anions, and fluorophenylphosphonate anions. For example, the alkyl quaternary ammonium salt is selected from hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium tetrafluoroborate, tetraoctyltetrafluoroborate, and hexadecyltrimethylammonium hexafluorophosphate.

5. The catalyst composition according to claim 3 or 4, characterized in that, The polyoxyethylene ether has the general formula shown in Formula 1: Where R is a hydrogen atom, a straight-chain or branched alkyl group, a cycloalkyl group, a phenyl group with a straight-chain or branched alkyl group, a naphthyl group with a straight-chain or branched alkyl group, or an alkyl group with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, pyridyl groups, etc., and x and y are positive integers, with x ranging from 3 to 1227 and y ranging from 2 to 4; for example, polyoxyethylene ethers suitable as water-carrying agents include but are not limited to octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyethylene glycol octylphenyl ether, α-2-naphthyl-ω-hydroxy-polyethylene glycol, polyethylene glycol monomethyl ether, and α,ω-dihydroxy-terminated polyoxyethylene ether.

6. The catalyst composition according to any one of claims 3-5, characterized in that, The alkylphenol has the general formula shown in Formula 2: R1, R2, R3, R4, and R5 are each independently selected from hydrogen atoms, hydroxyl groups, straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, and alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, urea groups, and pyridyl groups. At least one of R1, R2, R3, R4, and R5 is selected from straight-chain or branched alkyl groups, cycloalkyl groups, phenyl groups with straight-chain or branched alkyl groups, naphthyl groups with straight-chain or branched alkyl groups, and alkyl groups with other functional groups including but not limited to ether bonds, ester groups, amide groups, and pyridyl groups. For example, the alkylphenol is selected from decylphenol, 2-cyclohexylphenol, 2-methoxy-5-methylphenol, 4-methoxycarbonylphenol, 2-acetamidophenol, and 4-(pyridin-4-yl)phenol.

7. The catalyst composition according to any one of claims 1-6, characterized in that, The ether regulator is a non-polymeric ether compound, which contains fewer than 10 ether bonds, preferably 1 to 4; for example, the non-polymeric ether compound is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, tetrahydropyran, and dioxane, preferably ethylene glycol dimethyl ether and tetrahydrofuran.

8. The catalyst composition according to any one of claims 1-7, characterized in that, The organoaluminum compound is selected from alkylaluminum compounds and aluminum oxanes, preferably alkylaluminum compounds; the alkylaluminum compound has the general formula AlR. k X 3-k In this compound, R is independently selected from hydrogen atoms, C1-C8 straight-chain or branched alkyl groups, X is a halogen, and k is a positive number ranging from 1 to 3; for example, the organoaluminum compound is selected from trimethylaluminum, diethylaluminum hydride, triethylaluminum, tripropylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, and ethylaluminum dichloride, preferably triethylaluminum; and / or, the aluminum oxane is a C1-C4 alkylaluminum oxane, wherein the C1-C4 alkyl group is a straight-chain or branched alkyl group, and the aluminum oxane is preferably... Methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, and more preferably methylaluminoxane.

9. The catalyst composition according to any one of claims 1-7, characterized in that, The organotitanium compound has the general formula Ti(OR)4, wherein each R is independently selected from C1-C10 straight-chain or branched alkyl, cycloalkyl, phenyl, or phenyl with C1-C10 straight-chain or branched alkyl groups. For example, the organotitanium compound is selected from tetraethyl titanate, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisooctyl titanate, and tetraphenyl titanate, preferably tetra-n-butyl titanate.

10. A method for selective dimerization of ethylene, the method comprising the following steps: (1) High-temperature vacuuming and nitrogen purging; (2) Repeated purging with ethylene; (3) Injecting the catalyst composition and organic solvent as described in any one of claims 1-9 into the reaction system and stirring thoroughly; (4) Introducing ethylene to initiate the dimerization reaction. Maintain the reaction pressure at 0.1 MPaG to 30 MPaG, the reaction temperature at -20 to 250℃, and the reaction time at 30 min to 250 min; (5) Stop the reaction and cool down.

11. The method as described in claim 10, characterized in that, The catalyst composition is prepared by pre-mixing the water carrier with water to prepare a mixture, which is prepared by the following method: (1) mixing the water carrier and organic solvent evenly in a container and then adding deionized water dropwise, stirring to make it evenly mixed with the water carrier and organic solvent; (2) taking the mixture and measuring the water content with a moisture meter until the target value is reached.

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