Method for preparing alpha-olefin oligomer for synthetic lubricant base oil

Abstract

The present invention provides a method for preparing α-olefin oligomers for synthetic lubricant base oils, belonging to the technical field of α-olefin oligomer synthesis for lubricant oils. A rare earth metallocene catalyst is used to catalyze the homopolymerization and copolymerization of α-olefins, efficiently obtaining α-olefin oligomers without the need for chain transfer agents and solvents. The rare earth metallocene catalyst consists of three parts: A, B, and C. A is a rare earth metallocene complex LLnCl2X n , wherein: L is a cyclopentadienyl ligand selected from cyclopentadienyl, indenyl, and fluorenyl ligands; Ln is a rare earth metal; X is a coordinating group on the rare earth metal, with n being the number of coordinating groups; B is an alkyl metal reagent; and C is an organoboron reagent. The α-olefin is a C6-C20 linear α-olefin. The rare earth cyclopentadienyl catalyst system employed in the present invention features simple synthesis and high catalytic efficiency. The catalytic process does not require the addition of chain transfer agents or solvents, providing an efficient, economical, simple, and green method for developing medium- and low-viscosity synthetic lubricant base oils.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis of alpha-olefin oligomers used in lubricating oils, and relates to a method for preparing oligomers by polymerizing alpha-olefins using a rare earth cyclopentadienyl catalyst. Background Art

[0002] α-Olefin oligomers are synthetic base oils with excellent performance, produced by the oligomerization of α-olefins under the action of a catalyst and subsequent hydrogenation and saturation. Compared to traditional mineral base oils and natural lubricants, they offer a wide operating temperature range, a high viscosity index, a low pour point, excellent thermal and oxidative stability, and stable shear performance under pressure. This allows for longer oil drain intervals, reduces component corrosion and damage, and thus increases equipment life. Currently, α-olefin oligomerization is achieved using Lewis acid catalysts, Zeigler–Natta catalysts, and metallocene catalysts. Metallocene catalysts have a single active center, and the resulting α-olefin oligomers possess a unique comb-like structure that imparts high structural regularity and lacks upright side chains. This results in a higher viscosity index, excellent lubricity at high temperatures, improved shear stability that helps extend oil drain intervals, and a lower pour point for adequate lubricity at low temperatures, attracting increasing attention. Bis-titaniumocene, zirconium, and hafnium catalysts can catalyze α-olefin oligomerization, but these catalysts exhibit low polymerization activity, with 24-hour polymerization yields below 80%. Compared to diocene catalysts, constrained geometry (CGC) and monoocene-type titanium, zirconium, and hafnium catalysts have a more open coordination space and enhance α-olefin polymerization activity. However, the resulting polyα-olefins have a high degree of polymerization, making them unsuitable for use in medium- and low-viscosity lubricants. To obtain α-olefin oligomers, a large amount of chain transfer reagents must be added to the polymerization system. Therefore, the development of highly efficient metallocene catalysts to achieve efficient conversion of α-olefins and produce low-degree-of-polymerization polyα-olefins is crucial for the development of medium- and low-viscosity synthetic lubricant base stocks.

[0003] Rare earth metals, due to their unique outer electron structures, give catalysts containing these elements as central metals numerous unique properties. In recent years, they have garnered significant attention in the field of catalytic polyolefin synthesis. Rare earth metal catalysts are highly active, require minimal dosage, and produce polymers with minimal residual metal ions, making them excellent catalysts for the preparation of lubricant base oils. Summary of the Invention

[0004] In view of the problems of complex structure, difficult preparation and low catalytic activity of metallocene catalysts in the prior art, the first object of the present invention is to provide a simple-to-prepare rare earth metallocene catalyst to achieve efficient oligomerization of α-olefins.

[0005] To achieve the first object, the present invention provides the following technical solution: a rare earth metal cyclopentadienyl catalyst is composed of three parts: A, B, and C. A is a rare earth metal cyclopentadienyl complex LLnCl2X n , wherein: L is a cyclopentadienyl ligand selected from cyclopentadienyl ligand C5(R1)(R2)(R3)(R4)(R5), indenyl ligand (C4H4)C5H2(R1)(R2), fluorenyl ligand (C6H5)C(R1)(C6H5), R1-R5 are selected from H, CH3, CH2CH3, i- Pr, t- Bu, Ph, CH2Ph, SiMe3, CH2SiMe3; Ln is a rare earth metal selected from Nd, Sc, Y, Lu, Gd, Sm; X is a group coordinated with the rare earth metal selected from Lewis bases containing O, N, P, S heteroatoms; n is the number of Lewis bases. B is an alkyl metal reagent selected from alkyl lithium, alkyl aluminum, alkyl magnesium halide, methyl aluminoxane, modified methyl aluminoxane. C is an organic boron reagent selected from [HNMe(C 18 H 37 )2][B(C6F5)4], [Ph3C][B(C6F5)4], [PhMe2NH][B(C6F5)4], B(C6F5)3 or Ph3CB[(CF3)2C6H3]4.

[0006] Furthermore, the alkyllithium is selected from at least one of methyllithium, ethyllithium, propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, pentyllithium, hexyllithium, cyclohexyllithium, n-eicosyllithium, phenyllithium, naphthyllithium, trimethylsilylmethylenelithium or N,N-dimethylbenzyllithium;

[0007] The alkylaluminum is selected from at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, diisobutylaluminum chloride, dichloromethylaluminum, dichloroethylaluminum, dichloroisobutylaluminum, diethylaluminum hydride, diisobutylaluminum hydride or methylaluminoxane.

[0008] The alkyl magnesium halide is selected from at least one of methyl magnesium bromide, ethyl magnesium bromide, allyl magnesium bromide, cycloheptyl magnesium bromide, n-butyl magnesium bromide, ethyl magnesium chloride, isopropyl magnesium chloride or 2-methylbutyl magnesium chloride.

[0009] The preparation scheme of the organic solution of the rare earth metal cyclopentadiene catalyst is as follows: dissolve component A in one or two of toluene, chlorobenzene or α-olefin, then add components B and C in sequence, stir and react at 20°C to 120°C for 5 minutes to 2 hours, the concentration of A is 0.05 to 3 μmol / mL, and the molar ratio of A, B, and C is 1:2 to 100:1.

[0010] In view of the problem that a large amount of chain transfer agent and organic solvent must be added to prepare α-olefin oligomers in the prior art, the second object of the present invention is to provide a simple method for preparing α-olefin oligomers, which has the advantages of being economical, efficient, green and simple.

[0011] To achieve the second objective, the α-olefin oligomer preparation process is as follows: under nitrogen protection, α-olefin is added to a dry, deoxygenated polymerization reactor, the temperature is raised to a polymerization temperature of 20°C to 120°C, an organic solution of a rare earth metallocene catalyst composed of A, B, and C is added with stirring, and the polymerization is carried out with stirring for 0.5 to 5 hours to obtain the α-olefin oligomer.

[0012] Furthermore, the α-olefin is one or more linear α-olefins of C6 to C20, and the molar ratio of α-olefin to A is 5×10 3 ~1×10 5 .

[0013] In summary, the present invention has the following beneficial effects:

[0014] (1) The rare earth cyclopentadienyl catalyst has a simple structure, is easy to synthesize, and has low cost. It has high activity in catalyzing the oligomerization of α-olefins, and the single-pass conversion rate can reach over 95%.

[0015] (2) The use of rare earth metallocene catalysts can achieve efficient bulk polymerization of α-olefins, and α-olefin oligomers can be prepared without any chain transfer agents, providing an efficient, economical, simple and green method for the development of medium and low viscosity synthetic lubricant base oils. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The 1-decene oligomer prepared in Example 4 of the present invention 1 H-NMR spectrum;

[0017] Figure 2 The 1-decene oligomer prepared in Example 4 of the present invention 13 C-NMR spectrum;

[0018] Figure 3 This is the GPC curve of the 1-decene oligomer prepared in Example 4 of the present invention;

[0019] Figure 4 The 1-decene oligomer prepared in Example 5 of the present invention 1 H-NMR spectrum. DETAILED DESCRIPTION

[0020] The present invention provides the following examples as further illustrations, but does not limit the scope of protection of the present invention. 1The average polymerization degree of the obtained α-olefin oligomer was determined by H-NMR, and the kinematic viscosity of the polyα-olefin was determined by a kinematic viscosity meter.

[0021] Example 1A Preparation of Component (C5H5)ScCl2(THF)

[0022] In a glove box, take 1.513 g (10 mmol) of anhydrous ScCl3, put it into a Schlenk flask containing a magnetic stirrer, add 20 mL of THF solvent, seal it, take out the glove box, stir at 80°C for 12 hours, and take the obtained ScCl3(THF)3 white suspension into the glove box; weigh 0.660 g (10 mmol) of C5H6 ligand, react with an equivalent amount of n-butyllithium, and add it to the white suspension of ScCl3(THF)3. After reacting at room temperature for 60 minutes, the solution becomes clear, and the solvent is drained to obtain (C5H5)ScCl2(THF), with a product yield of 91%.

[0023] Example 2A Preparation of Component (C5Me4SiMe3)YCl2(THF)

[0024] In a glove box, take 1.953 g (10 mmol) of anhydrous YCl3, put it into a Schlenk flask containing a magnetic stirrer, add 20 mL of THF solvent, seal it, take out the glove box, stir at 80°C for 12 hours, and take the obtained YCl3(THF)3 white suspension into the glove box; weigh 2.004 g (10 mmol) of C5Me4SiMe3H ligand, react with an equivalent amount of methyllithium, and add it to the white suspension of YCl3(THF)3. After reacting at room temperature for 30 minutes, the solution becomes clear, and the solvent is drained to obtain (C5Me4SiMe3)YCl2(THF), with a product yield of 93%.

[0025] Example 3A Preparation of Component (C9H7)NdCl2(Furan)

[0026] In a glove box, 2.506 g (10 mmol) of anhydrous NdCl₃ was weighed and placed in a Schlenk flask containing a magnetic stirrer. 10 mL of furan solvent was added, the flask was sealed, and the glove box was removed and stirred at 40°C for 12 hours. The resulting white suspension of NdCl₃(Furan)₃ was brought back into the glove box. 1.162 g (10 mmol) of C₆Hₐ ligand was reacted with an equal amount of isobutyllithium and added to the white suspension of NdCl₃(Furan)₃. After reacting at room temperature for 90 minutes, the solution clarified and the solvent was drained to obtain (C₆Hₐ)NdCl₂(Furan) in an 82% yield.

[0027] Example 4 Preparation of 1-decene oligomer

[0028] In a glove box, 5 μmol of the catalyst component A (C5Me4SiMe3)YCl2(THF) prepared in Example 2 was added to an eggplant-shaped flask, and 1 mL of toluene solvent was added to dissolve the mixture. 20 μmol of ethylmagnesium bromide in 2 mL of toluene solution was added under stirring at 20°C and reacted for 1 h. Then, 5 μmol of [Ph3C][B(C6F5)4] in 2 mL of toluene solution was added and stirred to obtain a toluene solution of a cyclopentadiene rare earth metal catalyst.

[0029] 50 mmol of 1-decene monomer was added to a polymerization flask, heated to 20°C, and then the obtained rare earth metallocene catalyst in toluene was injected. The reaction was stirred and polymerized for 0.5 h. Methanol was added to terminate the reaction, and the solvent and unreacted monomer were removed by vacuum distillation at 60°C. 6.8 g of poly-1-decene was obtained, with a yield of 97.1%, an average degree of polymerization of 15, and a kinematic viscosity of 35 mm at 100°C. 2 / s.

[0030] Figure 1 The 1-decene oligomer prepared in Example 4 of the present invention 1 H-NMR spectrum, from which the average degree of polymerization of 1-decene can be calculated to be 15.

[0031] Figure 2 The 1-decene oligomer prepared in Example 4 of the present invention 13 C-NMR spectrum. It can be seen from the figure that the synthesized 1-decene oligomer is atactic.

[0032] Figure 3 The GPC curve of 1-decene oligomer prepared in Example 4 of the present invention is shown in the figure. The number average molecular weight (M n ) is 2295, and 1 The degree of polymerization calculated by H-NMR is consistent with that of 1-decene oligomer, and the molecular weight distribution of 1-decene oligomer is very narrow, only 1.28.

[0033] Example 5 Preparation of 1-decene oligomer

[0034] In a glove box, 6 μmol of the catalyst component A (C5H5)ScCl2(THF) prepared in Example 1 was added to a polymerization bottle, and 585 mmol of 1-decene was added to dissolve it. 30 μmol of hexyllithium was added under stirring at 120°C and the reaction was stirred for 10 minutes. Then, 6 μmol of [HNMe(C 18 H 37)2][B(C6F5)4] in a 15 mmol 1-decene solution and stirred for polymerization at 120°C for 30 minutes. Methanol was added to terminate the reaction, and unreacted monomers were removed by distillation under reduced pressure at 60°C. 79.97 g of poly-1-decene was obtained, with a yield of 95.2%, an average degree of polymerization of 5, and a kinematic viscosity of 7 mm at 100°C. 2 / s.

[0035] Figure 3 The 1-decene oligomer prepared in Example 5 of the present invention 1 H-NMR spectrum, from which the average degree of polymerization of 1-decene can be calculated to be 5.

[0036] Example 6 Preparation of 1-eicosene oligomer

[0037] In a glove box, 100 μmol of catalyst A (C5H5)ScCl2(THF) prepared in Example 1 was added to an eggplant-shaped flask and dissolved in 1 mL of chlorobenzene. 1 μmol of methylaluminoxane was added with stirring at 100°C for 2 minutes. Then, a 100 μmol solution of [PhMe2NH][B(C6F5)4] in 1 mL of chlorobenzene was added and stirred for 100 minutes to obtain a chlorobenzene solution of the rare earth metallocene catalyst.

[0038] 100 mmol of 1-eicosene monomer was added to a polymerization flask, heated to 100°C, and then the chlorobenzene solution of the rare earth metallocene catalyst was injected. The polymerization was stirred for 5 hours, and methanol was added to terminate the reaction. Unreacted monomer and solvent were removed by vacuum distillation at 80°C. 26.93 g of poly-1-eicosene was obtained, with a yield of 96%, an average degree of polymerization of 6, and a kinematic viscosity of 14 mm at 100°C. 2 / s.

[0039] Example 7 Preparation of 1-hexene oligomer

[0040] In a glove box, 50 μmol of catalyst A (C9H7)NdCl2 (Furan), prepared in Example 3, was added to an eggplant-shaped flask and dissolved in 1 mL of chlorobenzene. A 1 mL chlorobenzene solution of 5 μmol of lithium trimethylsilylmethylene was added with stirring at 40°C, and the mixture was stirred for 10 minutes. Then, a 2 mL chlorobenzene solution of 50 μmol of B(C6F5)3 was added, and the mixture was stirred for 50 minutes to obtain a chlorobenzene solution of the rare earth metallocene catalyst.

[0041] 100 mmol of 1-hexene monomer was added to a polymerization flask, heated to 40°C, and then injected with the obtained rare earth metallocene catalyst in chlorobenzene solution. The mixture was stirred and polymerized for 30 minutes. Methanol was added to terminate the reaction, and unreacted monomer and solvent were removed by vacuum distillation at 60°C. 8.08 g of poly-1-hexene was obtained, with a yield of 96%, an average degree of polymerization of 9, and a kinematic viscosity of 13 mm at 100°C. 2 / s.

[0042] Example 8 Preparation of 1-octene-1-decene copolymer

[0043] In a glove box, 10 μmol of the catalyst component A (C9H7)NdCl2 (Furan) prepared in Example 3 was added to a polymerization bottle, and 20 mmol of 1-octene and 35 mmol of 1-decene were added to dissolve. 20 μmol of diethylaluminum chloride was added under stirring at 60°C and the mixture was stirred for 10 minutes. Then, 10 μmol of [HNMe(C 18 H 37 )2][B(C6F5)4] in a 15 mmol 1-decene solution and stirred at 60°C for 120 minutes. Methanol was added to terminate the reaction, and unreacted monomers and solvent were removed by distillation under reduced pressure at 60°C. 8.81 g of a copolymer of 1-octene and 1-decene was obtained with a yield of 95.3%, an average degree of polymerization of 8, and a kinematic viscosity of 15 mm at 100°C. 2 / s.

[0044] The above-described embodiments merely express the implementation methods of the present invention, but should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for preparing α-olefin oligomers for synthetic lubricant base oil, characterized in that: The preparation method uses a rare earth metallocene catalyst to catalyze the homopolymerization and copolymerization of α-olefins, and can efficiently obtain α-olefin oligomers without chain transfer reagents and solvents. The method comprises the following steps: adding α-olefins to a dry and deoxygenated polymerization reactor under nitrogen protection, heating the reactor to a polymerization temperature of 20° C. to 120° C., adding an organic solution of the rare earth metallocene catalyst under stirring, and stirring and polymerizing for 0.5 to 5 hours to obtain the α-olefin oligomers; The rare earth metallocene catalyst is composed of three parts: A, B, and C: A is a rare earth cyclopentadienyl complex LLnCl2X n , wherein: L is a cyclopentadienyl ligand, Ln is a rare earth metal, X is a group coordinated with the rare earth metal, and n is the number of Lewis bases; the LLnCl2X n In: the cyclopentadienyl ligand L is selected from the cyclopentadienyl ligand C5 (R1) (R2) (R3) (R4) (R5), the indenyl ligand (C4H4) C5H2 (R1) (R2), the fluorenyl ligand (C6H5) C (R1) (C6H5), R1-R5 are selected from H, CH3, CH2CH3, i- Pr, t- Bu, Ph, CH2Ph, SiMe3, CH2SiMe3; rare earth metal Ln is selected from Nd, Sc, Y, Lu, Gd, Sm; the coordination group X is selected from Lewis bases containing O, N, P, S heteroatoms; B is an alkyl metal reagent; C is an organoboron reagent; The preparation method of the rare earth metal ocene catalyst is as follows: dissolving component A in one or two of toluene, chlorobenzene or α-olefin, then sequentially adding components B and C, stirring and reacting at 20°C to 120°C for 5 minutes to 2 hours, the concentration of A is 0.05 to 3 μmol / mL, and the molar ratio of A, B, and C is 1:2 to 100:

1.

2. The method for preparing an α-olefin oligomer for synthetic lubricant base oil according to claim 1, characterized in that: The alkyl metal reagent B is selected from alkyl lithium, alkyl aluminum, alkyl magnesium halide, methyl aluminoxane, and modified methyl aluminoxane; The organoboron reagent C is selected from [HNMe(C 18 H 37 )2][B(C6F5)4], [Ph3C][B(C6F5)4], [PhMe2NH][B(C6F5)4], B(C6F5)3 or Ph3CB[(CF3)2C6H3]4.

3. The method for preparing an α-olefin oligomer for synthetic lubricant base oil according to claim 1, characterized in that: The molar ratio of the α-olefin to the A component of the rare earth metal catalyst is 5×10 3 ~1×10 5 .

4. The method for preparing an α-olefin oligomer for synthetic lubricant base oil according to claim 1, characterized in that: The α-olefin is one or more linear α-olefins of C6 to C20.

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