A catalyst composition and a process for the trimerization of ethylene to 1-hexene

Abstract

The application provides a catalyst composition, which comprises the following components: a chromium compound a, a ligand b, an organic aluminum compound c and a modifier d; the ligand b has the following formula I: wherein R1, R2, R3, R4, R5, R6 and R7 are independently selected from hydrogen, C1-C5 linear 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, and R is C5-C7 mono-naphthenic alkyl 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. When the catalyst composition is used for ethylene oligomerization, it has good 1-hexene selectivity and less polymer.

Description

TECHNICAL FIELD

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

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

[0003] The reaction process of ethylene trimerization is that under the action of a high-selectivity multi-component catalyst, ethylene is trimerized in a hydrocarbon solvent at a certain temperature and pressure to obtain 1-hexene. The mainstream catalyst system for preparing 1-hexene by ethylene trimerization in the traditional way is a four-component catalytic composition composed of a metal chromium salt, a pyrrole compound, an alkyl aluminum, and a halogenated hydrocarbon (mainly chlorinated hydrocarbon). In order to control the performance of the 1-hexene catalyst, the space steric hindrance effect of the substituent group on the ligand or the electronic effect of the ligand atoms is mainly adjusted. The traditional pyrrole ligand and the maleimide ligand are similar, and the selectivity of 1-hexene is low. The PNP ligand is synthesized from alkyl phosphine, which is expensive and sensitive to oxygen, and the operation is harsh.

[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 reaction kettle, 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℃, and the pressure is preferably 2-6MPa. However, the preparation process of the ligand containing P and N involved in this scheme is complex and the operation is harsh.

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

[0006] Chinese patent document CN1128776C discloses a catalyst for ethylene oligomerization to 1-hexene, which comprises a chromium compound a, a pyrrole derivative b, an alkyl aluminum c and a modifier d to form a quaternary catalyst composition, the molar ratio of the composition is a:b:c:d=1:3-6:50-150:5-20, 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 oligomerization process is carried out at a relatively low temperature, especially at 50-60 DEG C, and the polymer by-product is not dissolved, which leads to the formation of deposits in the reactor, heat exchanger and other equipment.

[0007] Therefore, it is of important economic practical value and scientific research significance to develop a new ligand with high 1-hexene selectivity and low industrialization cost. SUMMARY

[0008] Therefore, the application provides a catalyst composition, which comprises a heteroindoline series compound as a ligand, a chromium compound, an organic aluminum compound and a modifier to form a catalyst system, and has good 1-hexene selectivity and less polymer when used in ethylene oligomerization, thereby providing a new option for industrial production.

[0009] To achieve the above object, the application provides the following technical scheme.

[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 the following structure I:

[0012]

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

[0014] The modifier d has the following general formula X m RY n X is Cl or F, m=3-6, Y is Cl, F, H or CCl3, n=0-3, and 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 application, 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 application, the ligand b is isoindoline, and its structural formula is as follows:

[0018]

[0019] Optionally, in the catalyst composition provided by the present application, the modifier d is selected from any one of 1,2,3,4,5,6-hexachlorocyclohexane γ, 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 application, the general formula of the organic aluminum compound c is R'3Al, and R' is C1-20 linear or branched alkyl; 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 application, the chromium compound a is selected from any one of chromium n-octoate, chromium iso-octoate, chromium acetylacetonate and chromium tetrahydrofuran chloride.

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

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

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

[0025] Optionally, in the method for preparing 1-hexene by ethylene trimerization provided by the present application, the solvent is selected from at least one of C5-C10 linear or branched alkane, C5-C10 unsubstituted or substituted cycloalkane, C5-C10 unsubstituted or substituted aromatic hydrocarbon, and C5-C10 olefin.

[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 trimerization of ethylene according to the present application comprises the following steps:

[0028] First, the solvent is added into the reactor (the reactor is provided with stirring, heating and cooling functions), and then the temperature is adjusted to 100-130℃, ethylene is introduced to control the pressure of 4.5-5.5 MPa, and then the chromium compound a, the ligand b, the organic aluminum compound c and the modifier d are introduced into the reactor according to the molar ratio of 1:0.5-100:50-5000:0.5-100 for reaction, wherein the concentration of the chromium compound a is 5-50 ppm, and after the reaction is completed, 1-hexene is obtained.

[0029] Specifically, after the reaction is completed, the liquid phase product can be collected by selecting a flow liquid phase bottle, the solid phase product can be collected by using a self-sealing bag, and the obtained liquid phase product and solid phase product can be analyzed and calculated by using conventional methods in the industry, respectively.

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

[0031] Beneficial effect 1: The catalyst composition of the present application, using isoindoline as the ligand, combining with other components and limiting the use amount ratio of each component, has good 1-hexene selectivity and less polymer when used for preparing 1-hexene by ethylene oligomerization, which provides a new choice for industrial production.

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

[0033] The present application will be described in detail by the following examples. It is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application, and those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.

[0034] If the specific experimental steps or conditions are not specified in the examples, the operations or conditions can be carried out according to the conventional experimental steps described in the literature in the art. If the reagents or instruments used are not specified by the manufacturer, they are all conventional reagent products that can be obtained by market purchase.

[0035] In each of the following examples and comparative examples, the conditions for analyzing the composition of the liquid phase 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, including the following steps:

[0040] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor, and the catalyst composition chromium n-octanoate (a), isoindoline (b), and chromium n-octanoate (d) were injected in a molar ratio of 1:3:120:10. Triethylaluminum (c) and 1,2,3,4,5,6-hexachlorocyclohexane (γ) were reacted, with chromium octanoate (a) at a concentration of 7.5 ppm. The temperature was adjusted to 100°C, ethylene was introduced, and the reaction pressure was controlled at 5.5 MPa. The reaction was stopped after 30 min. The liquid phase product was collected using a flowing liquid chromatography bottle, and the solid phase product was collected using a self-sealing bag. The 1-hexene content in the liquid phase product was analyzed by gas chromatography, and the solid phase product was dried and weighed.

[0041] Example 2

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

[0043] 600 mL of methylcyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the methylcyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of methylcyclohexane solvent was injected into the reactor, and chromium isooctanoate (a), isoindoline (b), and triisobutylene (d) were injected in a molar ratio of 1:3:120:10. The reaction mixture consisted of aluminum (c), 1,2-bis(trichloromethyl)-3,4,5,6-tetrachlorobenzene (d), and chromium isooctanoate (a) at a concentration of 45 ppm. The temperature was adjusted to 105 °C, ethylene was introduced, and the reaction pressure was controlled at 5.0 MPa. The reaction was stopped after 30 min. The liquid phase product was collected using a flowing liquid chromatography bottle, and the solid phase product was collected using a self-sealing bag. The 1-hexene content in the liquid phase product was analyzed by gas chromatography, and the solid phase product was dried and weighed.

[0044] Example 3

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

[0046] 600 mL of toluene was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C. After 20 min, the temperature was lowered and the toluene in the reactor was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times and then evacuated with ethylene gas four times. 200 mL of toluene solvent was injected into the reactor. Chromium acetylacetone (a), isoindoline (b), triisohexylaluminum (c), and 1,4-di(trichloromethyl)-2,3,5,6-tetrachlorobenzene (d) were injected in a molar ratio of 1:5:120:5, where the concentration of chromium acetylacetone (a) was 25 ppm. The temperature was adjusted to 110 °C, ethylene was introduced, and the reaction pressure was controlled at 4.5 MPa. The reaction was stopped after 50 min. The liquid phase product was collected using a flowing liquid chromatography bottle, and the solid phase product was collected using a self-sealing bag. The 1-hexene content in the liquid phase product was analyzed by gas chromatography. The solid phase product was dried and weighed.

[0047] Example 4

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

[0049] 600 mL of xylene was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled to purge the xylene. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of xylene solvent was then injected into the reactor. Tetrahydrofuran chromium chloride (a), isoindoline (b), and tri-n-octyl chloride (d) were injected in a molar ratio of 1:5:120:15. Aluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ-solution) (d), wherein the concentration of tetrahydrofuran chromium chloride (a) is 7.5 ppm; the temperature is adjusted to 115℃, ethylene is introduced and the reaction pressure is controlled at 5.5 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0050] Example 5

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

[0052] 600 mL of n-heptane was injected into a high-pressure reactor. The reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C. After 20 minutes, the reactor was cooled and the n-heptane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of n-heptane solvent was injected into the reactor. Chromium octanoate (a), isoindoline (b), triethylaluminum (c), and chromium octanoate (d) were injected in a molar ratio of 1:3:240:15. 1,2-Di(trichloromethyl)-3,4,5,6-tetrachlorobenzene d, wherein the concentration of chromium octanoate a is 7.5 ppm; the temperature is adjusted to 120℃, ethylene is introduced and the reaction pressure is controlled at 5.0 MPa, and the reaction is stopped after 80 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0053] Example 6

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

[0055] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Tetrahydrofuran chromium chloride (a), isoindoline (b), and triethyl chloride (d) were injected in a molar ratio of 1:3:240:15. Aluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ-solution) (d), wherein the concentration of tetrahydrofuran chromium chloride (a) is 7.5 ppm; the temperature is adjusted to 110℃, ethylene is introduced and the reaction pressure is controlled at 4.5 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0056] Example 7

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

[0058] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Chromium isooctanoate (a), isoindoline (b), and tri-n-octyl ester were injected in a molar ratio 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 5 ppm; the temperature is adjusted to 110℃, ethylene is introduced and the reaction pressure is controlled at 4.5 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0059] Example 8

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

[0061] 600 mL of methylcyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the temperature was lowered to purge the methylcyclohexane from the reactor. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of methylcyclohexane solvent was then injected into the reactor. Chromium acetylacetone (a) and isoindoline (b) were injected according to the molar ratio of a, b, c, d of 1:25:500:50. Triethylaluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ-solvent) (d), wherein the concentration of chromium acetylacetone (a) is 50 ppm; the temperature is adjusted to 125℃, ethylene is introduced and the reaction pressure is controlled at 5.0 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0062] Example 9

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

[0064] 600 mL of toluene was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110°C, and after 20 minutes, the toluene in the reactor was purged by cooling. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of toluene solvent was injected into the reactor. Chromium acetylacetone (a), isoindoline (b), triisohexylaluminum (c), and 1% acetylacetone (d) were injected in a molar ratio of 1:3:120:10. 2-Di(trichloromethyl)-3,4,5,6-tetrachlorobenzene d, wherein the concentration of chromium acetylacetone a is 7.5 ppm; the temperature is adjusted to 130℃, ethylene is introduced and the reaction pressure is controlled at 4.5 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase product is dried and weighed.

[0065] Example 10

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

[0067] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Chromium isooctanoate (a), isoindoline (b), and triethyl oxocyanate (d) were injected in a molar ratio of 1:5:240:10. Aluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ-solvent) (d), wherein the concentration of chromium isooctanoate (a) is 7.5 ppm; the temperature is adjusted to 110℃, ethylene is introduced and the reaction pressure is controlled at 5.0 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase 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, the only difference being the pressure during the polymerization reaction. The specific steps in this comparative example are as follows:

[0070] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Chromium isooctanoate (a), isoindoline (b), and triethyl oxocyanate (d) were injected in a molar ratio of 1:5:240:10. Aluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ-solvent) (d), wherein the concentration of chromium isooctanoate (a) is 7.5 ppm; the temperature is adjusted to 110℃, ethylene is introduced and the reaction pressure is controlled at 3.0 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography, and the solid phase 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, the only difference being the temperature during the polymerization reaction. The specific steps in this comparative example are as follows:

[0073] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 min, the cyclohexane in the reactor was purged by cooling. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Chromium isooctanoate (a), isoindoline (b), triethylaluminum (c), and 1,2,3,4,5,6-hexachlorocyclohexane (d) were injected in a molar ratio of 1:5:240:10, where 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 at 5.0 MPa. The reaction was stopped after 30 min. The liquid phase product was collected using a flowing liquid chromatography bottle, and the solid phase product was collected using a self-sealing bag. The 1-hexene content in the liquid phase product was analyzed by gas chromatography. The solid phase product was dried and weighed.

[0074] Comparative Example 3

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

[0076] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled and the cyclohexane was purged. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, and then evacuated with ethylene gas four times. 200 mL of cyclohexane solvent was injected into the reactor. Chromium isooctanoate, 2-methylindole, triethylamine, and chromium isooctanoate were injected in a molar ratio of 1:5:240:10. The reaction mixture consisted of aluminum (c), 1,2,3,4,5,6-hexachlorocyclohexane (γ), and chromium isooctanoate (a) at a concentration of 7.5 ppm. The temperature was adjusted to 110 °C, ethylene was introduced, and the reaction pressure was controlled at 5.0 MPa. The reaction was stopped after 30 min. The liquid phase product was collected using a flowing liquid chromatography bottle, and the solid phase product was collected using a self-sealing bag. The 1-hexene content in the liquid phase product was analyzed by gas chromatography. The solid phase product was 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 ratio of a, b, c, and d in the catalyst composition used is different. The specific steps in this comparative example are as follows:

[0079] 600 mL of cyclohexane was injected into a high-pressure reactor, the reactor was sealed, and stirring was started. The temperature was adjusted to 110 °C, and after 20 minutes, the reactor was cooled to purge the cyclohexane. Then, the reactor was heated and evacuated. After ensuring that the reactor was completely dry, the reactor was purged with nitrogen four times, followed by evacuation with ethylene gas four times. 200 mL of cyclohexane solvent was then injected into the reactor. Chromium isooctanoate (a), isoindoline (b), triethylaluminum (c), and chromium isooctanoate (d) were injected in a molar ratio of 1:50:20:60. 1,2,3,4,5,6-Hexachlorocyclohexane γ-molecule d, wherein the concentration of chromium isooctanoate a is 7.5 ppm; the temperature is adjusted to 110℃, ethylene is introduced and the reaction pressure is controlled at 5.0 MPa, and the reaction is stopped after 30 min. The liquid phase product is collected using a flowing liquid chromatography bottle, and the solid phase product is collected using a self-sealing bag. The 1-hexene content in the liquid phase product is analyzed by gas chromatography. The solid phase product is dried and weighed (polymer).

[0080] The polymer content and 1-hexene selectivity results obtained in each example and comparative example are shown in the table below. Wherein, 1-hexene selectivity % = m(mass of 1-hexene in the liquid product) / m(mass of the liquid product) × 100%; polymer content % = m(mass of the solid product) / (m(mass of the solid product + m(mass of the liquid 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] As can be seen from the data in the table above, when ethylene trimerization to prepare 1-hexene is carried out using the catalyst composition provided by the present invention under specific temperature and pressure, the 1-hexene selectivity is better and the polymer content is lower.

[0084] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A catalyst composition, characterized in that, It includes the following components: chromium compound a, ligand b, organoaluminum compound c, and modifier d; The ligand b has the structure shown in Formula I: Formula I R1, R2, R3, R4, R5, R6 and R7 are each independently selected from hydrogen, C1-C5 straight-chain or branched alkyl groups or halogens; 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 organoaluminum compound c, and the modifier d is 1:0.5~25:50~500:0.5~50; The ligand b is isoindoline; The modifier d is selected from any one of 1,2,3,4,5,6-hexachlorocyclohexane γ-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; The general formula of the organoaluminum compound c is R'3Al, where R' is a C1-20 straight-chain or branched alkyl group. The chromium compound a is selected from any one of chromium octanoate, chromium isooctanoate, chromium acetylacetone, and chromium chloride tetrahydrofuran.

2. The catalyst composition according to claim 1, characterized in that, The molar ratio of the chromium compound a, the ligand b, the organoaluminum 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 organoaluminum compound c is selected from 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.

4. A method for preparing 1-hexene by ethylene trimerization, characterized in that, Includes the following steps: In an inert atmosphere, ethylene undergoes a trimerization reaction in a solvent at 100–130°C and 4.5–5.5 MPa under the action of the catalyst composition according to any one of claims 1–3, to obtain 1-hexene.

5. The method for preparing 1-hexene by ethylene trimerization as described in claim 4, characterized in that, The concentration of chromium compound a in the catalyst composition within the ethylene trimerization system is 5–50 ppm.

6. The method for preparing 1-hexene by ethylene trimerization as described in claim 4, 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 aromatics, and C5-C10 alkenes.

7. The method for preparing 1-hexene by ethylene trimerization as described in claim 6, characterized in that, The solvent is selected from any one of n-heptane, cyclohexane, methylcyclohexane, toluene, xylene, and octene.

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