Catalyst composition and method for preparing 1-hexene through ethylene trimerization

Abstract

The invention provides a catalyst composition. The catalyst composition comprises the following components: a chromium compound a, a ligand b, an organic aluminum compound c and a modifier d, the ligand b has a structure as shown in a formula I: # imgabs0 #, wherein R1, R2, R3, R4, R5, R6 and R7 are respectively and independently selected from hydrogen, C1-C5 straight chain or branched chain alkyl or halogen; the general formula of the modifier d is XmRYn, X is Cl or F, m is 3-6, Y is Cl, F, H or CCl3, n is 0-3, and R is C5-C7 monoester cycloalkyl or phenyl; the molar ratio of the chromium compound a to the ligand b to the organic aluminum compound c to the modifier d is 1: (0.5-25): (50-500): (0.5-50). When the catalyst composition is used for ethylene oligomerization reaction, the catalyst composition has good 1-hexene selectivity, and the number of polymers is small.

Description

Technical Field

[0001] The invention relates to the technical field of 1-hexene preparation, and in particular to a catalyst composition and a method for preparing 1-hexene by ethylene trimerization. Background Art

[0002] Ethylene oligomerization is one of the most important reactions in the olefin polymerization industry. Through oligomerization, cheap small molecule olefins can be converted into products with high added value, such as ethylene trimerization to produce 1-hexene and ethylene tetramerization to produce 1-octene. Among them, 1-hexene is an important comonomer for the production of LLDPE and HDPE, and is also a raw material for some fine chemicals. Compared with the copolymer of 1-butene, the LLDPE resin copolymerized with 1-hexene has significantly better tensile strength, impact strength, tear resistance and durability, and is particularly suitable for packaging films and agricultural covering films for greenhouses, sheds, etc.

[0003] The reaction process of ethylene trimerization is that ethylene is trimerized in a hydrocarbon solvent at a certain temperature and pressure under the action of a highly selective multi-catalyst to obtain 1-hexene. The mainstream catalyst system for preparing 1-hexene by traditional ethylene trimerization is a four-way catalytic composition composed of metal chromium salts, pyrrole compounds, alkyl aluminum, and halogenated hydrocarbons (mainly chlorinated hydrocarbons). In order to control the performance of the 1-hexene catalyst, it is mainly adjusted by changing the steric hindrance effect of the catalyst ligand or the substituent on the ligand and the electronic effect of the coordinated atom. Traditional pyrrole ligands and maleimide ligands are similar, and the selectivity of 1-hexene is low. PNP ligands are synthesized from alkyl phosphines, which are expensive, sensitive to oxygen, and demanding to operate.

[0004] For example, Chinese patent document CN1872416A discloses an ethylene trimerization catalyst and its application, specifically, chromium compound a, ligand containing P and N, activator c and promoter are introduced into a reactor, and ethylene is introduced for trimerization reaction; a:b:c:d is preferably 1:1-5:100-500:1-20, the temperature is preferably 30-70°C, and the pressure is preferably 2-6MPa. However, the preparation process of the ligand containing P and N involved in this scheme is complicated and the operation is strict.

[0005] In view of the above problems, Chinese patent document CN115445666A discloses a catalyst composition for preparing 1-hexene by polymerization of ethylene, which is composed of chromium metal salt, indole compound, alkyl aluminum and inorganic phosphorus halide depolymerization agent, and the temperature is 30-250°C, the pressure is 0.5-20MPa, and the time is 0.1-2h. This method uses inorganic phosphorus halide as depolymerization agent for the first time, which can reduce environmental pollution and physical harm to operators, but the reaction activity and selectivity of the catalytic system need to be improved.

[0006] Chinese patent document CN1128776C discloses a catalyst for preparing 1-hexene by oligomerization of ethylene, comprising a chromium compound a, a pyrrole derivative b, an alkyl aluminum c and a modifier d to form a four-way catalyst composition, wherein the molar ratio of the composition is a: b: c: d = 1: 3-6: 50-150: 5-20, and the modifier d is 1,2,3,4,5,6-hexachlorocyclohexane gamma-body, 1,4-bis(trichloromethyl)-2,3,5,6-tetrachlorobenzene, 1,3,5-tris(trichloromethyl)-2,4,6-trichlorobenzene. The disadvantage of this method is that the polymerization process is carried out at a relatively low temperature, particularly at 50°C to 60°C, and the polymer byproducts are insoluble, which leads to the formation of deposits in reactors, heat exchangers and other equipment.

[0007] Therefore, developing a new ligand that reduces industrialization costs while having high 1-hexene selectivity has important economic and practical value and scientific research significance. Summary of the invention

[0008] In view of this, the present invention provides a catalyst composition, in which the catalyst system is composed of isoindolin series compounds as ligands, combined with chromium compounds, organic aluminum compounds and modifiers. When used for ethylene polymerization reaction, the catalyst system has good 1-hexene selectivity and less polymers, providing a new choice for industrial production.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A catalyst composition comprises the following components: a chromium compound a, a ligand b, an organic aluminum compound c and a modifier d;

[0011] The ligand b has a structure shown in the following formula I:

[0012]

[0013] Wherein, R1, R2, R3, R4, R5, R6 and R7 are independently selected from hydrogen, C1-C5 straight or branched alkyl or halogen;

[0014] The general formula of the modifier d is X m RY n , X is Cl or F, m=3-6, Y is Cl, F, H or CCl3, n=0-3, R is C5-C7 monocycloalkyl or phenyl;

[0015] The molar ratio of the chromium compound a, the ligand b, the organic aluminum compound c and the modifier d is 1:0.5-25:50-500:0.5-50.

[0016] Optionally, in the catalyst composition provided by the present invention, the molar ratio of the chromium compound a, the ligand b, the organic aluminum compound c and the modifier d is 1:1-5:100-250:1-20.

[0017] Optionally, in the catalyst composition provided by the present invention, the ligand b is isoindoline, and its structural formula is as follows:

[0018]

[0019] Optionally, in the catalyst composition provided by the present invention, the modifier d is selected from any one of 1,2,3,4,5,6-hexachlorocyclohexane gamma body, 1,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene, 1,3-bis(trichloromethyl)-2,4,5,6-tetrachlorobenzene and 1,4-bis(trichloromethyl)-2,3,5,6-tetrachlorobenzene.

[0020] Optionally, in the catalyst composition provided by the present invention, the general formula of the organoaluminum compound c is R'3Al, R' is a C1-20 straight chain or branched alkyl group; preferably any one of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri-n-dodecylaluminum, tri-n-tetradecylaluminum and tri-n-hexadecylaluminum.

[0021] Optionally, in the catalyst composition provided by the present invention, the chromium compound a is selected from any one of chromium n-octoate, chromium isooctanoate, chromium acetylacetonate and tetrahydrofuran chromium chloride.

[0022] The present invention also provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0023] In an inert atmosphere, ethylene is trimerized in a solvent at 100-130°C and 4.5-5.5 MPa under the action of the above catalyst composition to obtain 1-hexene.

[0024] Optionally, in the method for preparing 1-hexene by ethylene trimerization provided by the present invention, in the ethylene trimerization reaction system, the concentration of chromium compound a in the catalyst composition in the reaction system is 5 to 50 ppm.

[0025] Optionally, in the method for preparing 1-hexene by ethylene trimerization provided by the present invention, the solvent is selected from at least one of C5-C10 straight-chain or branched alkanes, C5-C10 unsubstituted or substituted cycloalkanes, C5-C10 unsubstituted or substituted aromatics, and C5-C10 olefins.

[0026] Preferably, the solvent is selected from at least one of n-heptane, cyclohexane, methylcyclohexane, toluene, xylene and octene.

[0027] The method for preparing 1-hexene by ethylene trimerization recommended by the present invention comprises the following steps:

[0028] First, add the solvent into a reactor (the reactor has stirring, heating and cooling functions), then adjust the temperature to 100-130°C, introduce ethylene to control the pressure to 4.5-5.5MPa, and then introduce the chromium compound a, ligand b, organic aluminum compound c and modifier d into the reactor in a molar ratio of 1:0.5-100:50-5000:0.5-100 for reaction, wherein the concentration of the chromium compound a is 5-50ppm. After the reaction is completed, 1-hexene is obtained.

[0029] Specifically, after the reaction is completed, you can choose to use a mobile liquid phase bottle to collect the liquid phase product, use a ziplock bag to collect the solid phase product, and use conventional methods in the industry to analyze and calculate the obtained liquid phase product and solid phase product respectively.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] Beneficial effect 1: The catalyst composition of the present invention uses isoindoline as a ligand, is combined with other components and limits the usage ratio of each component. When used for ethylene polymerization to prepare 1-hexene, it has good 1-hexene selectivity and less polymer, providing a new choice for industrial production.

[0032] Beneficial effect 2: The method for preparing 1-hexene by ethylene trimerization provided by the present invention has simple operation, short process, high product purity and low industrialization cost. DETAILED DESCRIPTION

[0033] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0034] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0035] In the following examples and comparative examples, the conditions for analyzing the composition of the liquid product by gas chromatography are shown in the following table.

[0036] Table 1 Gas chromatography operating conditions

[0037]

[0038] Example 1

[0039] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0040] 600 mL of cyclohexane was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110°C, the temperature was lowered after 20 minutes to drain the cyclohexane in the autoclave, and then heated and evacuated. After ensuring that the autoclave was completely dry, nitrogen was replaced 4 times, and ethylene gas was used for evacuation 4 times. 200 mL of cyclohexane solvent was injected into the autoclave, and the catalyst composition chromium octanoate a, isoindoline b, triethylaluminum c and 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of chromium octanoate a is 7.5ppm; the temperature is adjusted to 100°C, ethylene is introduced and the reaction pressure is controlled to be 5.5MPa, the reaction is completed after 30min, the liquid product is collected using a mobile liquid phase bottle, the solid product is collected using a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0041] Example 2

[0042] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0043] Inject 600mL of methylcyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the methylcyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of methylcyclohexane solvent into the autoclave, and inject chromium isooctanoate a, isoindoline b, triisobutylene glycol in a molar ratio of 1:3:120:10 Aluminum c, 1,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene d, wherein the concentration of chromium isooctanoate a is 45ppm; the temperature is adjusted to 105°C, ethylene is introduced and the reaction pressure is controlled to be 5.0MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0044] Example 3

[0045] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0046] 600 mL of toluene was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110°C, and the toluene in the autoclave was emptied after 20 minutes of cooling, and then heated and vacuumed. After ensuring that the autoclave was completely dry, it was replaced with nitrogen 4 times, and then ethylene gas was used to exhaust 4 times. 200 mL of toluene solvent was injected into the autoclave, and acetylacetonate chromium a, isoindoline b, triisohexyl aluminum c, 1,4-bis(trichloromethyl)-2,3,5,6-tetrachlorobenzene d were injected according to the molar ratio of a, b, c, and d of 1:5:120:5, where the concentration of acetylacetonate chromium a was 25 ppm; the temperature was adjusted to 110°C, ethylene was introduced and the reaction pressure was controlled to 4.5 MPa, the reaction was terminated after 50 minutes, the liquid product was collected using a mobile liquid phase bottle, the solid product was collected using a self-sealing bag, and the 1-hexene content in the liquid product was analyzed by gas chromatography for the obtained liquid product, and the solid product was dried and weighed.

[0047] Example 4

[0048] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0049] 600 mL of xylene was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110 ° C, and the xylene in the autoclave was emptied after 20 minutes of cooling, and then heated and vacuumed. After ensuring that the autoclave was completely dry, it was replaced with nitrogen 4 times, and then ethylene gas was used for 4 times. 200 mL of xylene solvent was injected into the autoclave, and tetrahydrofuran chromium chloride a, isoindoline b, tri-n-octyl chloride were injected according to the molar ratio of a, b, c, and d of 1:5:120:15 Aluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of tetrahydrofuran chromium chloride a is 7.5ppm; the temperature is adjusted to 115°C, ethylene is introduced and the reaction pressure is controlled to 5.5MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0050] Example 5

[0051] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0052] Inject 600mL of n-heptane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the n-heptane in the autoclave, then heat and evacuate, after ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times, inject 200mL of n-heptane solvent into the autoclave, and inject chromium octanoate a, isoindoline b, triethylaluminum c, according to the molar ratio of a, b, c, d of 1:3:240:15 1,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene d, wherein the concentration of chromium a n-octoate is 7.5ppm; the temperature is adjusted to 120°C, ethylene is introduced and the reaction pressure is controlled to 5.0MPa, the reaction is completed after 80min, the liquid product is collected using a mobile liquid phase bottle, the solid product is collected using a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0053] Example 6

[0054] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0055] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of cyclohexane solvent into the autoclave, and inject tetrahydrofuran chromium chloride a, isoindoline b, triethylamine according to the molar ratio of a, b, c, d of 1:3:240:15 Aluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of tetrahydrofuran chromium chloride a is 7.5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 4.5MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0056] Example 7

[0057] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0058] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of cyclohexane solvent into the autoclave, and inject chromium octanoate a, isoindoline b, tri-n-octyl octanoate according to the molar ratio of a, b, c, d of 1:0.5:50:0.5 Aluminum c, 1,4-bis(trichloromethyl)-2,3,5,6-tetrachlorobenzene d, wherein the concentration of chromium isooctanoate a is 5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 4.5MPa, the reaction is completed after 30min, the liquid product is collected using a mobile liquid phase bottle, the solid product is collected using a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0059] Example 8

[0060] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0061] 600 mL of methylcyclohexane was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110°C, and the methylcyclohexane in the autoclave was emptied after 20 minutes of cooling, and then heated and evacuated. After ensuring that the autoclave was completely dry, it was replaced with nitrogen 4 times, and then evacuated with ethylene gas 4 times, and 200 mL of methylcyclohexane solvent was injected into the autoclave, and acetylacetonate chromium a and isoindoline b were injected according to the molar ratio of a, b, c, and d of 1:25:500:50 , triethylaluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of acetylacetonate chromium a is 50ppm; the temperature is adjusted to 125°C, ethylene is introduced and the reaction pressure is controlled to 5.0MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0062] Example 9

[0063] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0064] 600 mL of toluene was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110 ° C, and the toluene in the autoclave was emptied after 20 minutes of cooling, and then heated and evacuated. After ensuring that the autoclave was completely dry, it was replaced with nitrogen 4 times, and then evacuated with ethylene gas 4 times, and 200 mL of toluene solvent was injected into the autoclave. Acetylacetonate chromium a, isoindoline b, triisohexyl aluminum c, 1 ,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene d, wherein the concentration of acetylacetonate chromium a is 7.5ppm; the temperature is adjusted to 130°C, ethylene is introduced and the reaction pressure is controlled to 4.5MPa, the reaction is completed after 30min, the liquid product is collected using a mobile liquid phase bottle, the solid product is collected using a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0065] Example 10

[0066] This embodiment provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0067] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of cyclohexane solvent into the autoclave, and inject chromium isooctanoate a, isoindoline b, triethylamine according to the molar ratio of a, b, c, d of 1:5:240:10 Aluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of chromium isooctanoate a is 7.5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 5.0MPa, the reaction is completed after 30min, the liquid product is collected using a mobile liquid phase bottle, the solid product is collected using a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0068] Comparative Example 1

[0069] The method for preparing 1-hexene by ethylene trimerization provided in this comparative example is similar to that in Example 10, except that the pressure during the polymerization reaction is different. The specific steps in this comparative example are as follows:

[0070] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of cyclohexane solvent into the autoclave, and inject chromium isooctanoate a, isoindoline b, triethylamine according to the molar ratio of a, b, c, d of 1:5:240:10 Aluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of chromium isooctanoate a is 7.5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 3.0MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0071] Comparative Example 2

[0072] The method for preparing 1-hexene by ethylene trimerization provided in this comparative example is similar to that in Example 10, except that the temperature during the polymerization reaction is different. The specific steps in this comparative example are as follows:

[0073] 600 mL of cyclohexane was injected into the autoclave, the autoclave was sealed, stirring was started, the temperature was adjusted to 110°C, and the cyclohexane in the autoclave was emptied after 20 minutes of cooling, and then heated and vacuumed. After ensuring that the autoclave was completely dry, it was replaced with nitrogen 4 times, and then ethylene gas was used to exhaust 4 times. 200 mL of cyclohexane solvent was injected into the autoclave, and chromium isooctanoate a, isoindoline b, triethylaluminum c, and 1,2,3,4,5,6-hexachlorocyclohexane gamma body d were injected according to the molar ratio of a, b, c, and d of 1:5:240:10, wherein the concentration of chromium isooctanoate a was 7.5 ppm; the temperature was adjusted to 80°C, ethylene was introduced and the reaction pressure was controlled to 5.0 MPa, the reaction was terminated after 30 minutes, the liquid product was collected using a mobile liquid phase bottle, the solid product was collected using a self-sealing bag, and the 1-hexene content in the obtained liquid product was analyzed by gas chromatography, and the solid product was dried and weighed.

[0074] Comparative Example 3

[0075] The method for preparing 1-hexene by ethylene trimerization provided in this comparative example is similar to that in Example 10, except that the ligand b used is different. The specific steps in this comparative example are as follows:

[0076] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate. After ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times. Inject 200mL of cyclohexane solvent into the autoclave, and inject chromium isooctanoate a, 2-methylindole b, triethylamine according to the molar ratio of a, b, c, d of 1:5:240:10 Base aluminum c, 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of chromium isooctanoate a is 7.5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 5.0MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed.

[0077] Comparative Example 4

[0078] The method for preparing 1-hexene by ethylene trimerization provided in this comparative example is similar to that in Example 10, except that the molar ratios of a, b, c, and d in the catalyst composition used are different. The specific steps in this comparative example are as follows:

[0079] Inject 600mL of cyclohexane into the autoclave, seal the autoclave, start stirring, adjust the temperature to 110°C, cool down after 20 minutes to drain the cyclohexane in the autoclave, then heat and evacuate, after ensuring that the autoclave is completely dry, replace it with nitrogen 4 times, and then use ethylene gas to evacuate 4 times, inject 200mL of cyclohexane solvent into the autoclave, and inject chromium isooctanoate a, isoindoline b, triethylaluminum c, according to the molar ratio of a, b, c, d of 1:50:20:60 1,2,3,4,5,6-hexachlorocyclohexane gamma body d, wherein the concentration of chromium isooctanoate a is 7.5ppm; the temperature is adjusted to 110°C, ethylene is introduced and the reaction pressure is controlled to 5.0MPa, the reaction is completed after 30min, the liquid product is collected by a mobile liquid phase bottle, the solid product is collected by a ziplock bag, and the 1-hexene content in the obtained liquid product is analyzed by gas chromatography, and the solid product is dried and weighed (polymer).

[0080] The polymer content and 1-hexene selectivity results obtained in each embodiment and comparative example are shown in the following table. Wherein, 1-hexene selectivity %=m(mass of 1-hexene in liquid phase product) / m(mass of liquid phase product)×100%Polymer content %=mmass of solid phase product / (mmass of solid phase product+mmass of liquid phase product)×100%.

[0081] Table 2

[0082] 1-Hexene selectivity wt% Polymer wt% Example 1 90.8 0.23 Example 2 91.2 0.25 Example 3 91.5 0.21 Example 4 91.0 0.22 Example 5 89.2 0.30 Example 6 91.8 0.21 Example 7 87.5 0.32 Example 8 87.9 0.30 Example 9 92.6 0.19 Example 10 93.1 0.17 Comparative Example 1 82.2 0.62 Comparative Example 2 80.5 0.55 Comparative Example 3 89.1 0.41 Comparative Example 4 43 2.54

[0083] It can be seen from the data in the above table that when the catalyst composition provided by the present invention is used to trimerize ethylene at a specific temperature and pressure to prepare 1-hexene, the selectivity for 1-hexene is better and the polymer is less.

[0084] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A catalyst composition, characterized in that The invention comprises the following components: a chromium compound a, a ligand b, an organic aluminum compound c and a modifier d; The ligand b has a structure shown in the following formula I: Wherein, R1, R2, R3, R4, R5, R6 and R7 are independently selected from hydrogen, C1-C5 straight or branched alkyl or halogen; The general formula of the modifier d is X m RY n , X is Cl or F, m=3-6, Y is Cl, F, H or CCl3, n=0-3, R is C5-C7 monocycloalkyl or phenyl; The molar ratio of the chromium compound a, the ligand b, the organic aluminum compound c and the modifier d is 1:0.5-25:50-500:0.5-50.

2. The catalyst composition according to claim 1, characterized in that The molar ratio of the chromium compound a, the ligand b, the organic aluminum compound c and the modifier d is 1:1-5:100-250:1-20.

3. The catalyst composition according to claim 1, characterized in that The ligand b is isoindoline.

4. The catalyst composition according to claim 1, characterized in that The modifier d is selected from any one of 1,2,3,4,5,6-hexachlorocyclohexane gamma isoform, 1,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene, 1,3-bis(trichloromethyl)-2,4,5,6-tetrachlorobenzene and 1,4-bis(trichloromethyl)-2,3,5,6-tetrachlorobenzene.

5. The catalyst composition according to claim 1, characterized in that The general formula of the organoaluminum compound c is R'3Al, where R' is a C1-20 straight or branched alkyl group; preferably any one of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri-n-dodecylaluminum, tri-n-tetradecylaluminum and tri-n-hexadecylaluminum.

6. The catalyst composition according to claim 1, characterized in that The chromium compound a is selected from any one of chromium n-octoate, chromium isooctanoate, chromium acetylacetonate and tetrahydrofuran chromium chloride.

7. A method for preparing 1-hexene by ethylene trimerization, characterized in that: The steps include: In an inert atmosphere, ethylene is trimerized in a solvent at 100-130° C. and 4.5-5.5 MPa under the action of the catalyst composition described in any one of claims 1-6 to obtain 1-hexene.

8. The method for preparing 1-hexene by ethylene trimerization according to claim 7, characterized in that: The concentration of the chromium compound a of the catalyst composition in the ethylene trimerization reaction system is 5 to 50 ppm.

9. The method for preparing 1-hexene by ethylene trimerization according to claim 7, characterized in that: The solvent is selected from any one of C5-C10 straight-chain or branched alkanes, C5-C10 unsubstituted or substituted cycloalkanes, C5-C10 unsubstituted or substituted aromatic hydrocarbons, and C5-C10 olefins.

10. The method for preparing 1-hexene by ethylene trimerization according to claim 9, characterized in that: The solvent is selected from any one of n-heptane, cyclohexane, methylcyclohexane, toluene, xylene and octene.

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