Heterocyclic amine catalyst ligand and method for preparing high-carbon alpha-olefin by using heterocyclic amine catalyst ligand

Abstract

The invention provides a heterocyclic amine catalyst ligand and a method for preparing high-carbon alpha-olefin by using the heterocyclic amine catalyst ligand. The heterocyclic amine catalyst ligand is used for catalytically synthesizing high-carbon alpha-olefin of C8 or above. Wherein the structural formula of the catalyst ligand is as follows: # imgabs0 #, R is aryl or alkyl, and R1 is hydrogen or methyl. In the scheme, when the catalyst ligand with the structure, a chromium source, a cocatalyst and the like are mixed and introduced into an ethylene reaction system for in-situ polymerization, the ligand structure has four nitrogen atoms, so that the ligand structure can be more easily coordinated with transition metal, the reaction is rapid, and the yield is high. According to the present invention, with the ligand structure, the in-situ polymerization of the olefin can be directly achieved without the catalyst synthesis, and the R group (phenyl or alkyl) in the ligand structure can increase the steric hindrance of the ligand and limit the approaching angle and direction of the reactant molecule so as to easily and selectively generate the high-carbon alpha-olefin with the carbon number of more than C8.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a heterocyclic amine catalyst ligand and a method for preparing high-carbon alpha-olefins by using the same. Background Art

[0002] α-olefins can be used as comonomers to develop polyethylene products with higher monomer content and better performance, but their slow pace of localization has become a bottleneck in the development of polyethylene in my country. α-olefins refer to monoolefins with double bonds at the ends of the molecular chain. Generally, C8 and above are called high-carbon α-olefins. Both low-carbon α-olefins and high-carbon α-olefins have indispensable uses. C4-C8 are used as polyethylene comonomers, C6-C8 are used for POE and low molecular weight fatty acids, and C8-C 12 For PAO, lubricating oil and amine additives, C 12 -C 16 Used in the production of detergents, C 18 + Used in lubricants and drilling fluids.

[0003] At present, the main production processes of α-olefins are: wax cracking method, mixed C4 separation method, ethylene oligomerization / polymerization method, and vegetable oil method. Among them, ethylene oligomerization and polymerization method are the main methods for producing α-olefins. In order to produce α-olefins efficiently and in high yield, catalysts play a vital role in this process. It is now generally accepted that chromium catalysts catalyze ethylene trimerization with a metal cycle mechanism. Chromium catalysts have received widespread attention due to their high selectivity for linear olefins (especially 1-hexene and 1-octene). Slight changes in the structure of the catalyst ligand will cause significant changes in its metal coordination ability and the catalytic activity of the complex. Therefore, a high-activity transition metal polyolefin catalyst can be developed by reasonably adjusting and changing the structure of the ligand. Although a large number of transition metal polyolefin catalysts have been studied, at present, such catalysts have a high selectivity for C8 α-olefins and are mostly used to synthesize C8 α-olefins, and cannot be applied to the synthesis reaction of α-olefins above C8.

[0004] Based on this, there is an urgent need to provide a heterocyclic amine catalyst ligand and a method for preparing high-carbon α-olefins using the same. Summary of the invention

[0005] The embodiment of the present invention provides a heterocyclic amine catalyst ligand and a method for preparing high-carbon α-olefins using the same, which can solve the problem of low selectivity of traditional catalysts for α-olefins above C8.

[0006] In a first aspect, the present invention provides a heterocyclic amine catalyst ligand, wherein the heterocyclic amine catalyst ligand is used for catalytic synthesis of high carbon α-olefins above C8;

[0007] Wherein, the structural formula of the catalyst ligand is as follows:

[0008]

[0009] In the formula, R is an aromatic group or an alkyl group, and R1 is a hydrogen or a methyl group.

[0010] Preferably, the aromatic group is a phenyl group, and the number of carbon atoms in the alkyl group is an even number between 2 and 8.

[0011] Preferably, the structural formula of the catalyst ligand is as follows:

[0012]

[0013] In a second aspect, the present invention further provides a method for preparing the heterocyclic amine catalyst ligand described in any one of the first aspects above, the preparation method comprising: using a first organic solvent to dissolve an aldehyde reactant and an amine reactant respectively, and then mixing the two to react to obtain the heterocyclic amine catalyst ligand; wherein the aldehyde reactant is pyrrole-2-carboxaldehyde or 3,5-dimethyl-2-pyrrolecarboxaldehyde, and the amine reactant is ethylenediamine, butanediamine, hexamethylenediamine, octanediamine or p-phenylenediamine.

[0014] Preferably, the first organic solvent is methanol, and the molar ratio of the aldehyde reactant to the amine reactant is (10-11):(0.5-5).

[0015] Preferably, the temperature of the mixed reaction is 20-35°C and the time is 12-24h.

[0016] In a third aspect, the present invention further provides a method for preparing high carbon α-olefins using the heterocyclic amine catalyst ligand described in any one of the first aspects above, the method comprising:

[0017] The heterocyclic amine catalyst ligand, chromium source, co-catalyst and second organic solvent are introduced into the ethylene gas reaction system to carry out in-situ polymerization reaction to obtain the high-carbon α-olefin; wherein the high-carbon α-olefin is an α-olefin above C8.

[0018] Preferably, the chromium source is chromium 2-ethylhexanoate, the second organic solvent is cyclohexane, n-hexane or methylcyclohexane, and the co-catalyst is a composite system of diethylaluminum monochloride and triethylaluminum.

[0019] Preferably, the content of the heterocyclic amine catalyst ligand is 2-5 μmol, the content of the chromium source is 2-5 μmol, the content of the second organic solvent is 15-25 mL, and the molar ratio of the co-catalyst to the chromium source is (100-800):1.

[0020] Preferably, the reaction temperature is 50-70°C, the reaction time is 30-60 min, and the reaction pressure is 1.0-3.0 MPa.

[0021] In a fourth aspect, the present invention further provides a heterocyclic amine metal catalyst obtained by mixing the heterocyclic amine catalyst ligand described in any one of the first aspects and a trivalent chromium salt.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The invention provides a five-membered heterocyclic amine catalyst ligand structure. The catalyst ligand of the structure has high selectivity for high-carbon alpha-olefins above C8 and can effectively catalyze and synthesize high-carbon alpha-olefins above C8 with a chromium source. Specifically, when the catalyst ligand is mixed with a chromium source, a co-catalyst and the like and introduced into an ethylene reaction system for in-situ polymerization, the ligand structure has four nitrogen atoms, so it can be more easily coordinated with a transition metal and react rapidly, so that the ligand structure can directly realize in-situ polymerization of olefins without synthesizing a catalyst. At the same time, the R group (phenyl or alkyl) in the ligand structure can increase the spatial steric hindrance of the ligand, limit the approach angle and direction of reactant molecules, and thus is conducive to the selective generation of high-carbon alpha-olefins above C8. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 is the infrared spectrum of the catalyst ligand prepared in Examples 1 to 3 of the present invention;

[0026] Figure 2 is the nuclear magnetic hydrogen spectrum of the catalyst ligand prepared in Example 1 of the present invention;

[0027] Figure 3 is the nuclear magnetic hydrogen spectrum of the catalyst ligand prepared in Example 2 of the present invention;

[0028] Figure 4 This is the nuclear magnetic hydrogen spectrum of the catalyst ligand prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The embodiment of the present invention provides a heterocyclic amine catalyst ligand, wherein the heterocyclic amine catalyst ligand is used for catalytic synthesis of high carbon α-olefins above C8;

[0031] Wherein, the structural formula of the catalyst ligand is as follows:

[0032]

[0033] In the formula, R is an aromatic group or an alkyl group, and R1 is a hydrogen or a methyl group.

[0034] In an embodiment of the present invention, a five-membered heterocyclic amine catalyst ligand of the above structure is provided. The catalyst ligand of this structure has high selectivity for high-carbon α-olefins above C8, and can effectively catalyze the synthesis of high-carbon α-olefins above C8 with a chromium source; specifically, when the catalyst ligand is mixed with a chromium source, a co-catalyst, etc. and introduced into an ethylene reaction system, it can be seen from the above formula that the ligand structure has four nitrogen atoms, which can be more easily coordinated with a transition metal and react rapidly, so that the ligand structure can directly realize in-situ polymerization of olefins without the need for a synthetic catalyst. At the same time, the R group (phenyl or alkyl) in the ligand structure can increase the steric hindrance of the ligand, limit the approach angle and direction of the reactant molecules, and thus facilitate the selective generation of high-carbon α-olefins above C8.

[0035] According to some preferred embodiments, the aromatic group is a phenyl group, and the number of carbon atoms in the alkyl group is an even number between 2 and 8 (for example, 2, 4, 6 or 8).

[0036] In the embodiments of the present invention, the structural formula of the catalyst ligand may be as follows:

[0037]

[0038]

[0039] According to some more preferred embodiments, the structural formula of the catalyst ligand is as follows:

[0040]

[0041] In the embodiments of the present invention, the inventors have found through a large number of experimental verifications that since the five-membered heterocyclic structure and the p-phenylenediamine structure in the catalyst ligand of the above structure have a synergistic effect with each other, and the ligand has two methyl electron-donating groups, when the catalyst ligand of the above structure is coordinated with a chromium source, its catalytic activity for ethylene polymerization and selectivity for high carbons above C8 can be maximized, thereby being more conducive to the catalytic synthesis of high carbon α-olefins above C8.

[0042] The embodiment of the present invention further provides a method for preparing the heterocyclic amine catalyst ligand described in any one of the above items, the preparation method comprising: using a first organic solvent to dissolve an aldehyde reactant and an amine reactant respectively, and then mixing the two to react to obtain the heterocyclic amine catalyst ligand;

[0043] Wherein, the aldehyde reactant is pyrrole-2-carboxaldehyde or 3,5-dimethyl-2-pyrrolecarboxaldehyde, and the amine reactant is ethylenediamine, butanediamine, hexamethylenediamine, octanediamine or p-phenylenediamine.

[0044] In the embodiment of the present invention, a series of heterocyclic amine catalyst ligands with coordination ability are prepared by using the above-mentioned types of aldehyde reactants and the above-mentioned types of amine reactants to carry out Schiff base reaction under certain conditions.

[0045] According to some preferred embodiments, the first organic solvent is methanol, and the molar ratio of the aldehyde reactant to the amine reactant is (10-11):(0.5-5) (for example, it can be 10:0.5, 10:2, 10:3, 10:4, 10:5, 11:0.5, 11:1, 11:3 or 11:5).

[0046] According to some preferred embodiments, the temperature of the mixed reaction is 20-35°C (for example, 20°C, 25°C, 30°C or 35°C), and the time is 12-24h (for example, 12h, 16h, 20h or 24h).

[0047] In the embodiment of the present invention, under the protection of nitrogen, methanol is first used to dissolve the aldehyde reactant and the amine reactant, and then the dissolved amine reactant is added dropwise to the aldehyde reactant solution. After the addition is completed, the solution is heated to react, and by controlling the raw material ratio and reaction conditions of the reaction process, a heterocyclic amine catalyst ligand with higher yield and higher purity can be obtained.

[0048] It should be noted that after the reaction is completed, the temperature of the reaction solution must first be lowered to room temperature, and then the reaction product is washed and filtered three times with n-hexane, and finally the reaction product is dried in a vacuum drying oven at 55° C. for 24 hours to obtain a heterocyclic amine catalyst ligand solid powder.

[0049] The embodiment of the present invention further provides a method for preparing high carbon α-olefins using any of the heterocyclic amine catalyst ligands described above, the method comprising:

[0050] The heterocyclic amine catalyst ligand, chromium source, co-catalyst and second organic solvent are introduced into the ethylene gas reaction system to carry out in-situ polymerization reaction to obtain the high-carbon α-olefin; wherein the high-carbon α-olefin is an α-olefin above C8.

[0051] In the embodiment of the present invention, the reaction of synthesizing high carbon α-olefins by catalyzing the heterocyclic amine catalyst ligand needs to be carried out under the condition of anhydrous and oxygen-free. Specifically, the stainless steel reactor equipped with magnetic stirring, temperature control system and pressure control system can be dried first, and its air tightness can be checked. It is replaced with ethylene three times to ensure that there is no influence of oxygen and water, and a predetermined temperature is set for preheating. After that, in the ethylene gas environment, a certain amount of cyclohexane, a co-catalyst, the heterocyclic amine catalyst ligand prepared above and a chromium source are introduced into the reactor together to catalyze the oligomerization of ethylene. During the reaction, the catalyst ligand structure can effectively catalyze the synthesis of high carbon α-olefins above C8 with the chromium source, the co-catalyst, etc. through its unique characteristics such as double coordination, rigid structure, electronic effect and steric hindrance.

[0052] After the reaction is completed, the reactor is cooled to room temperature, unreacted ethylene is discharged, and the reaction is quenched with a diluted HCl (10%) ethanol solution. The liquid reaction product is separated from the catalyst, quantitatively analyzed by gas chromatography, and the catalyst activity is calculated based on the reaction product.

[0053] According to some preferred embodiments, the chromium source is chromium 2-ethylhexanoate, the second organic solvent is cyclohexane, n-hexane or methylcyclohexane, and the co-catalyst is a composite system of diethylaluminum monochloride and triethylaluminum.

[0054] In the embodiment of the present invention, chromium 2-ethylhexanoate is used as the chromium source, which has good solubility in organic solvents. The in-situ polymerization using the chromium source has higher activity and better selectivity for high carbon, thus being more conducive to the catalytic synthesis of high carbon α-olefins. Moreover, it is found in the embodiment of the present invention that, compared with a single type of co-catalyst, the co-catalyst formed by mixing diethylaluminum monochloride and triethylaluminum with the chromium source and the heterocyclic amine catalyst ligand is not only more conducive to enhancing the catalytic activity of the heterocyclic amine catalyst ligand, but also more conducive to improving the C8 + The yield of high-carbon olefin products, therefore, the co-catalyst in the embodiment of the present invention is preferably a mixture of diethylaluminum monochloride and triethylaluminum in a molar ratio of 1:1.

[0055] At the same time, compared with n-hexane and methylcyclohexane, ethylene has a higher solubility in cyclohexane, so that the co-catalyst, heterocyclic amine catalyst ligand, chromium source and ethylene can be fully dissolved in it, which is conducive to a higher effective collision between ethylene and the active center, thereby increasing the chain growth rate, so that the polymerization product C8 in cyclohexane is + The selectivity is higher, so the second organic solvent in the embodiment of the present invention is preferably cyclohexane.

[0056] According to some preferred embodiments, the content of the heterocyclic amine catalyst ligand is 2-5 μmol (for example, it can be 2 μmol, 3 μmol, 4 μmol or 5 μmol), the content of the chromium source is 2-5 μmol (for example, it can be 2 μmol, 3 μmol, 4 μmol or 5 μmol), the content of the second organic solvent is 15-25 mL (for example, it can be 15 mL, 18 mL, 20 mL, 23 mL or 25 mL), and the molar ratio of the co-catalyst to the chromium source is (100-800): 1 (for example, it can be 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1 or 800:1).

[0057] The experiments of the present invention confirm that suitable contents of heterocyclic amine catalyst ligands, co-catalysts and chromium sources are beneficial to better promote ethylene polymerization to form high-carbon α-olefins above C8; for example, if the content of heterocyclic amine catalyst ligands is too low, part of the chromium source will fail to effectively complex with the ligands, and the number of effective active centers formed is small, which not only makes the catalytic activity low, but also the ineffective active centers induce side reactions including isomerization and ethylene dimerization at higher temperatures, which can easily induce bimolecular deactivation reactions: chain transfer occurs after collision of two molecules of chain growth reaction active intermediates to form high-carbon olefin products, which also reduces the selectivity of decene; although increasing the content of heterocyclic amine catalyst ligands can improve the initial activity of the catalyst to a certain extent, too much ligand will lead to interaction or aggregation between active centers, which may reduce the overall catalytic efficiency. At the same time, it was found in the examples of the present invention that with the continuous increase in the molar ratio of the co-catalyst to the chromium source, the catalytic activity as a whole showed an upward trend, but the distribution of high-carbon α-olefin products above C8 showed a trend of first increasing and then decreasing. Therefore, the molar ratio of the co-catalyst to the chromium source in the examples of the present invention is (100-800):1.

[0058] According to some preferred embodiments, the reaction temperature is 50-70°C (for example, 50°C, 55°C, 60°C, 65°C or 70°C), the reaction time is 25-50min (for example, 25min, 30min, 35min, 40min or 50min), and the pressure is 1.0-2MPa (for example, 1MPa, 1.2MPa, 1.5MPa, 1.8MPa or 2MPa).

[0059] In the embodiments of the present invention, high reaction pressure, i.e., increased ethylene concentration in the system, is beneficial to increasing the probability of collision between ethylene and active centers, thereby increasing the catalytic activity. However, when the pressure continues to increase after reaching a certain pressure, its solubility reaches saturation, and the ethylene insertion process is hindered, thereby making chain growth difficult and accelerating the chain termination reaction, ultimately leading to a decrease in the selectivity of higher carbon olefins in the polymerization product. Therefore, based on the catalytic ethylene polymerization activity and the selectivity of higher carbon α-olefins above C8 and economic considerations, the pressure conditions in the above range are adopted in the embodiments of the present invention.

[0060] The embodiment of the present invention further provides a heterocyclic amine metal catalyst, which is obtained by mixing and reacting any of the heterocyclic amine catalyst ligands described above with a trivalent chromium salt.

[0061] The heterocyclic amine catalyst ligand prepared in the embodiment of the present invention can be mixed with a trivalent chromium salt to react and prepare a chromium metal catalyst. Specifically, 5 mol of the heterocyclic amine catalyst ligand can be first ultrasonically dissolved using 50 mL of tetrahydrofuran, and then, 10 mol of CrCl(THF)3 tetrahydrofuran solution is added dropwise to the dissolved heterocyclic amine catalyst ligand solution under nitrogen conditions. After the addition is completed, the temperature is raised and stirred to react, and the product is filtered, washed three times with tetrahydrofuran, and vacuum dried at 55°C for 48 hours to finally obtain a heterocyclic amine metal catalyst with the following structure:

[0062]

[0063] Wherein, R is an aromatic group or an alkyl group, and R1 and R2 are the same, both are hydrogen or methyl.

[0064] It should be noted that the heterocyclic amine metal catalyst prepared in the embodiment of the present invention also has excellent catalytic activity and selectivity for high-carbon α-olefins above C8. When using it to catalyze the synthesis of high-carbon α-olefins, the above-mentioned method for preparing high-carbon α-olefins using heterocyclic amine catalyst ligands can be adopted, and adaptive adjustments can be made to the above-mentioned conditions to efficiently catalyze the synthesis of high-carbon α-olefins above C8.

[0065] In order to more clearly illustrate the technical solution and advantages of the present invention, a heterocyclic amine catalyst ligand and a method for preparing high-carbon α-olefins using the same are described in detail below through several embodiments.

[0066] Embodiment 1:

[0067] Under nitrogen protection, in a 100 mL three-necked flask with a round bottom, 10.0 mmol of an aldehyde compound (pyrrole-2-carboxaldehyde) was dissolved in 7.5 mL of the first organic solvent (methanol), and 5.0 mmol of an amine compound (p-phenylenediamine) was dissolved in 7.5 mL of the first organic solvent (methanol);

[0068] At room temperature (25°C), the dissolved amine compound is added dropwise to the aldehyde compound solution. After the addition is completed, the solution is heated to 27°C and reacted for 24 hours. After the reaction is completed and the temperature of the reaction solution drops to room temperature, the product is filtered and washed with n-hexane three times. The product is dried in a vacuum drying oven at 55°C for 24 hours to obtain a light yellow solid powder compound, which is the heterocyclic amine catalyst ligand (referred to as compound (I)) with a yield of 66.66%.

[0069] The present invention has carried out structural characterization on the compound (I) obtained in Example 1, and the results are as follows Figure 1 and Figure 2 shown; from Figure 1 It can be seen that at the wave number of 1610cm -1 and 1645cm -1 , there are strong characteristic absorption peaks on the left and right, which belong to the characteristic peak of C=N, indicating the formation of Schiff base and obtaining compound (Ⅰ). Figure 2 It can be seen that the chemical shift at 8.39ppm is the hydrogen proton peak in -CH=N-, around 7.20 is the hydrogen proton peak on the benzene ring, around 7.10ppm corresponds to the hydrogen proton peak connected to the nitrogen atom on the pyrrole ring, and around 6.30ppm and 6.80ppm correspond to the hydrogen proton peaks connected to the carbon atom on the pyrrole ring. This further indicates the formation of Schiff base, indicating that compound (I) was successfully obtained.

[0070] Embodiment 2:

[0071] Under nitrogen protection, in a 100 mL three-necked flask with a round bottom, 5.0 mmol of an amine compound (hexanediamine) was dissolved in 7.5 mL of the first organic solvent (methanol), and 10.0 mmol of an aldehyde compound (pyrrole-2-carboxaldehyde) was dissolved in 7.5 mL of the first organic solvent (methanol);

[0072] At room temperature (25°C), the dissolved aldehyde compound is added dropwise to the amine compound solution. After the addition is completed, the solution is heated to 27°C and reacted for 24 hours. After the reaction is completed and the temperature of the reaction solution drops to room temperature, the product is filtered and washed with n-hexane three times. The obtained product is dried in a vacuum drying oven at 55°C for 24 hours to obtain a white solid powder compound, which is the heterocyclic amine catalyst ligand (referred to as compound (II)) with a yield of 65.32%.

[0073] The present invention has carried out structural characterization on the compound (II) obtained in Example 2, and the results are as follows Figure 1 and Figure 3 shown; from Figure 1 It can be seen that at the wave number of 1610cm -1 A strong C=N characteristic absorption peak appears around Figure 3 It can be seen that the chemical shift at around 8.40 ppm is the hydrogen proton peak in -CH=N-, at around 4.80, 6.65 and 7.00 ppm are the hydrogen proton peaks connected to the carbon atom on the pyrrole ring, and at around 6.20 ppm corresponds to the hydrogen proton peak connected to the nitrogen atom on the pyrrole ring. This further indicates the formation of Schiff base, indicating that compound (II) was successfully obtained.

[0074] Embodiment 3:

[0075] Under nitrogen protection, in a 100 mL three-necked round-bottom flask, 0.5 mmol of an amine compound (p-phenylenediamine) was dissolved in 3 mL of the first organic solvent (methanol), and 10.0 mmol of an aldehyde compound (3,5-dimethyl-2-pyrrolecarboxaldehyde) was dissolved in 3 mL of the first organic solvent (methanol);

[0076] At room temperature (25°C), the dissolved aldehyde compound is added dropwise to the amine compound solution. After the addition is completed, the solution is heated to 27°C and reacted for 24 hours. After the reaction is completed and the temperature of the reaction solution drops to room temperature, the product is filtered and washed with n-hexane three times. The obtained product is dried in a vacuum drying oven at 55°C for 24 hours to obtain a light yellow solid powder compound, which is the heterocyclic amine catalyst ligand (referred to as compound (III)) with a yield of 82.32%.

[0077] The present invention has carried out structural characterization on the compound (III) obtained in Example 3, and the results are as follows Figure 1 and Figure 4 shown; from Figure 1 It can be seen that at the wave number of 1615cm -1 、1618cm -1 、1645cm -1 、1605cm -1A strong characteristic absorption peak appeared, which was attributed to the characteristic peak of C=N, indicating the formation of Schiff base and obtaining compound (III). Figure 4 It can be seen that the chemical shift at 8.39ppm is the hydrogen proton peak in -CH=N-, around 7.08-7.28ppm is the hydrogen proton peak on the benzene ring, around 5.90ppm corresponds to the hydrogen proton peak connected to the nitrogen atom on the pyrrole ring, and around 4.80ppm corresponds to the hydrogen proton peak connected to the carbon atom on the pyrrole ring; around 2.20ppm is the hydrogen proton peak on -CH3, which further indicates the formation of Schiff base, indicating that compound (III) was successfully obtained.

[0078] Embodiment 4:

[0079] Under anhydrous and oxygen-free conditions, a 100 mL stainless steel reactor equipped with magnetic stirring, temperature control system and pressure control system was dried, its air tightness was checked, ethylene was replaced three times to ensure that there was no influence of oxygen and water, and a predetermined temperature (60°C) was set for preheating;

[0080] Under ethylene gas environment, 20mL of the second organic solvent (cyclohexane), 5μmol of chromium source (chromium 2-ethylhexanoate), 5μmol of heterocyclic amine catalyst ligand (compound (III)) and co-catalyst (diethylaluminum chloride and triethylaluminum in a molar ratio of 1:1) were introduced into the reactor to carry out ethylene oligomerization reaction. The autoclave was filled with ethylene and the required pressure (1.5Mpa) was reached. After the reaction was completed at 60°C for 30min, the reactor was cooled to room temperature (25°C), the unreacted ethylene was discharged, and the reaction was quenched with a diluted HCl (10%) ethanol solution. The liquid phase was separated from the catalyst, and the distribution of the catalyst activator product was calculated by gas chromatography using the area normalization method, and the catalyst activity was calculated based on the product; wherein, the molar ratio of the co-catalyst to the chromium source was 600.

[0081] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high-carbon α-olefins reached 42.06% and the catalytic activity reached 4.04×10 5 g / (mol Cr·h).

[0082] Embodiment 5:

[0083] Under anhydrous and oxygen-free conditions, a 100 mL stainless steel reactor equipped with magnetic stirring, temperature control system and pressure control system was dried, its air tightness was checked, ethylene was replaced three times to ensure that there was no influence of oxygen and water, and a predetermined temperature (60°C) was set for preheating;

[0084] Under ethylene gas environment, 20mL of the second organic solvent (cyclohexane), 5μmol of chromium source (chromium 2-ethylhexanoate), 5μmol of heterocyclic amine catalyst ligand (compound (II)) and co-catalyst (diethylaluminum chloride and triethylaluminum in a molar ratio of 1:1) were introduced into the reactor to carry out ethylene oligomerization reaction. The autoclave was filled with ethylene and the required pressure (1.5Mpa) was reached. After the reaction was completed at 60°C for 30min, the reactor was cooled to room temperature (25°C), the unreacted ethylene was discharged, and the reaction was quenched with a diluted HCl (10%) ethanol solution. The liquid phase was separated from the catalyst, and the distribution of the catalyst activator product was calculated by gas chromatography using the area normalization method, and the catalyst activity was calculated based on the product; wherein, the molar ratio of the co-catalyst to the chromium source was 600.

[0085] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high-carbon α-olefins reached 36.78% and the catalytic activity reached 2.24×10 5 g / (mol Cr·h).

[0086] Embodiment 6:

[0087] Under anhydrous and oxygen-free conditions, a 100 mL stainless steel reactor equipped with magnetic stirring, temperature control system and pressure control system was dried, its air tightness was checked, ethylene was replaced three times to ensure that there was no influence of oxygen and water, and a predetermined temperature (60°C) was set for preheating;

[0088] Under ethylene gas environment, 20mL of the second organic solvent (cyclohexane), 5μmol of chromium source (chromium 2-ethylhexanoate), 5μmol of heterocyclic amine catalyst ligand (compound (I)) and co-catalyst (diethylaluminum chloride and triethylaluminum in a molar ratio of 1:1) were introduced into the reactor to carry out ethylene oligomerization reaction. The autoclave was filled with ethylene and the required pressure (1.5Mpa) was reached. After the reaction was completed at 60°C for 30min, the reactor was cooled to room temperature (25°C), the unreacted ethylene was discharged, and the reaction was quenched with a diluted HCl (10%) ethanol solution. The liquid phase was separated from the catalyst, and the distribution of the catalyst activator product was calculated by gas chromatography using the area normalization method, and the catalyst activity was calculated based on the product; wherein, the molar ratio of the co-catalyst to the chromium source was 600.

[0089] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high-carbon α-olefins reached 41.02% and the catalytic activity reached 4.68×10 5 g / (mol Cr·h).

[0090] Embodiment 7:

[0091] Example 7 is substantially the same as Example 4, except that the heterocyclic amine catalyst ligand is 8 mol.

[0092] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high carbon α-olefins is 41.28%, and the catalytic ethylene polymerization activity of the catalyst is 4.11×10 5 g / (mol Cr·h).

[0093] Embodiment 8:

[0094] Example 10 is substantially the same as Example 4, except that the molar ratio of the promoter to the chromium source is 100:1.

[0095] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high carbon α-olefins is 21.86%, and the catalytic ethylene polymerization activity of the catalyst is 2.09×10 4 g / (mol Cr·h).

[0096] Embodiment 9:

[0097] Example 9 is substantially the same as Example 4, except that the molar ratio of the promoter to the chromium source is 800:1.

[0098] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high carbon α-olefins is 40.64%, and the catalytic ethylene polymerization activity of the catalyst is 4.12×10 5 g / (mol Cr·h).

[0099] Embodiment 10:

[0100] Example 10 is substantially the same as Example 4, except that the second organic solvent is n-hexane.

[0101] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high carbon α-olefins is 31.49%, and the catalytic ethylene polymerization activity of the catalyst is 3.14×10 5 g / (mol Cr·h).

[0102] Embodiment 11:

[0103] 5 mmol of the heterocyclic amine ligand compound (III) prepared in Example 3 was respectively put into a three-necked flask, 50 mL of tetrahydrofuran was added and dissolved by ultrasonication at 25 ° C for 5 min, 10.00 mmol of CrCl (THF) 3 tetrahydrofuran solution was added dropwise at room temperature under nitrogen conditions, and after the addition was completed, the temperature was raised to 40 ° C and stirred for 24 h; after the reaction was completed, the three products were filtered respectively, washed three times with tetrahydrofuran, and vacuum dried at 55 ° C for 48 h to finally obtain a heterocyclic amine metal catalyst, referred to as L6-Cat.

[0104] The above heterocyclic amine metal catalyst is used to catalyze the polymerization of ethylene:

[0105] Under anhydrous and oxygen-free conditions, a 100 mL stainless steel reactor equipped with magnetic stirring, temperature control system and pressure control system was dried, its air tightness was checked, ethylene was replaced three times to ensure that there was no influence of oxygen and water, and a predetermined temperature (60°C) was set for preheating;

[0106] Under ethylene gas environment, 5 μmol of heterocyclic amine metal catalyst L6-Cat and 20 mL of the second organic solvent (cyclohexane) and the co-catalyst (diethylaluminum chloride and triethylaluminum in a molar ratio of 1:1) were introduced into the reactor to carry out ethylene oligomerization. The autoclave was filled with ethylene, and after reaching the required pressure (0.5Mpa), the reaction was completed at 25°C for 30 minutes, and the reactor was cooled to room temperature (25°C), the unreacted ethylene was discharged, and the reaction was quenched with a diluted HCl (10%) ethanol solution. The liquid phase was separated from the catalyst, and the distribution of the catalyst activator product was calculated by gas chromatography using the area normalization method, and the catalyst activity was calculated based on the product; wherein, the molar ratio of the co-catalyst to the heterocyclic amine metal catalyst was 400.

[0107] In the embodiment of the present invention, C is obtained by calculation 8+ The selectivity of high-carbon α-olefins reached 37.04%, and the catalytic ethylene polymerization activity of the catalyst was 2.62×10 5 g / (mol·Cr·h).

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heterocyclic amine catalyst ligand, characterized in that: The heterocyclic amine catalyst ligand is used for catalytic synthesis of high carbon α-olefins above C8; Wherein, the structural formula of the catalyst ligand is as follows: In the formula, R is an aromatic group or an alkyl group, and R1 is a hydrogen or a methyl group.

2. The catalyst ligand according to claim 1, characterized in that The aromatic group is a phenyl group, and the number of carbon atoms in the alkyl group is an even number between 2 and 8.

3. The catalyst ligand according to claim 2, characterized in that The structural formula of the catalyst ligand is as follows:

4. A method for preparing a heterocyclic amine catalyst ligand according to any one of claims 1 to 3, characterized in that: The preparation method comprises: using a first organic solvent to dissolve an aldehyde reactant and an amine reactant respectively, and then mixing the two to react to obtain the heterocyclic amine catalyst ligand; Wherein, the aldehyde reactant is pyrrole-2-carboxaldehyde or 3,5-dimethyl-2-pyrrolecarboxaldehyde, and the amine reactant is ethylenediamine, butanediamine, hexamethylenediamine, octanediamine or p-phenylenediamine.

5. The preparation method according to claim 4, characterized in that: The first organic solvent is methanol, and the molar ratio of the aldehyde reactant to the amine reactant is (10-11): (0.5-5).

6. The preparation method according to claim 5, characterized in that: The temperature of the mixed reaction is 20-35°C and the time is 12-24h.

7. A method for preparing high carbon α-olefins using a heterocyclic amine catalyst ligand according to any one of claims 1 to 3, characterized in that: The method comprises: The heterocyclic amine catalyst ligand, chromium source, co-catalyst and second organic solvent are introduced into the ethylene gas reaction system to carry out in-situ polymerization reaction to obtain the high-carbon α-olefin; wherein the high-carbon α-olefin is an α-olefin above C8.

8. The method according to claim 7, characterized in that The chromium source is chromium 2-ethylhexanoate, the second organic solvent is cyclohexane, n-hexane or methylcyclohexane, and the co-catalyst is a composite system of diethylaluminum monochloride and triethylaluminum; and / or The content of the heterocyclic amine catalyst ligand is 2-5 μmol, the content of the chromium source is 2-5 μmol, the content of the second organic solvent is 15-25 mL, and the molar ratio of the co-catalyst to the chromium source is (100-800):

1.

9. The method according to claim 7, characterized in that: The reaction temperature is 50-70°C, the reaction time is 20-60 min, and the pressure is 1.0-3.0 MPa.

10. A heterocyclic amine metal catalyst, characterized in that: The catalyst is obtained by mixing the heterocyclic amine catalyst ligand described in any one of claims 1 to 3 with a trivalent chromium salt.

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