A poly-alpha-olefin pour point depressant and a method for preparing the same

Abstract

The application relates to a preparation method of a poly-alpha-olefin pour point depressant, which comprises the following steps: obtaining a mixed hydrocarbon component by distillation cutting and refining Fischer-Tropsch synthesis oil, the average carbon number of alpha-olefins in the mixed hydrocarbon component being 10.2-16.5, and then polymerizing to obtain the poly-alpha-olefin pour point depressant under the catalysis of a metallocene catalyst system. The application also relates to a poly-alpha-olefin pour point depressant. The preparation method has the advantages of high polymerization activity, small catalyst consumption, simple post-treatment, environmental protection and the like; and the prepared pour point depressant has the characteristics of moderate molecular weight, narrow molecular weight distribution and good pour point depressing effect.

Description

Technical Field

[0001] This invention belongs to the field of pour point depressant synthesis, and specifically relates to a method for preparing a polyalphaolefin pour point depressant using Fischer-Tropsch synthetic oil as raw material, and the polyalphaolefin pour point depressant obtained by the preparation method. Background Technology

[0002] Low-pour-point components in petroleum products, such as waxes, gums, and water, adsorb, crystallize, and aggregate at lower temperatures, forming a paste-like substance. This reduces or eliminates the fluidity of the petroleum, affecting its pipeline transportation and performance. Currently, the most efficient method to improve the low-temperature fluidity of petroleum products is to add pour point depressants. A small amount of pour point depressant can effectively inhibit the growth and aggregation of crystals, thereby improving the low-temperature fluidity of the petroleum. This method is characterized by low production cost, simple operation, and wide application, and has therefore become a hot topic in pour point depressant technology research both domestically and internationally.

[0003] Currently, commonly used oil pour point depressants mainly include alkylnaphthalenes, polyesters, and polyalphaolefins. Alkylnaphthalenes offer good economic benefits, and their combination with other types of pour point depressants yields even better results. However, alkylnaphthalenes are dark in color and are generally used in medium and heavy lubricating oils, not suitable for light-colored oils, thus limiting their application. Polyesters offer the widest variety of pour point depressants, with good performance and the ability to be modified to obtain various high-performance depressants. While polyesters provide excellent pour point depressing effects, modification is necessary to meet the needs of different oil types, leading to higher prices. Polyalphaolefins offer advantages such as light color and good pour point depressing effect, making them suitable for various lubricating oils. Furthermore, their pour point depressing effect is comparable to that of PMA (poly(alpha-aluminum) precipitate) and their price is lower than that of polyesters. Therefore, the development of polyalphaolefins has a promising future.

[0004] Currently, the raw materials commonly used to prepare polyalphaolefin pour point depressants mainly come from ethylene oligomerization and wax-cracked olefins. CN1279247A discloses a polyalphaolefin pour point depressant and its preparation method, which uses C8-C4 olefins obtained from wax cracking. 18 C of α-olefin oligomerization with ethylene 20 ~C 24 Olefin mixtures are used as raw materials for polymerization under the action of Ziegler-Natta catalysts. Industrially, polyalphaolefin (PAO) pour point depressants are prepared using PAOs obtained from the cracking of soft wax as raw materials. After purification, these PAOs are polymerized in the presence of a Ziegler-Natta catalyst, with hydrogen used to adjust the molecular weight. Using PAOs obtained from ethylene oligomerization has the disadvantages of limited raw material resources and high prices. POP depressants prepared from PAOs obtained from the cracking of soft wax not only have high molecular weights but also face difficulties in post-processing. Furthermore, with the phasing out of wax cracking technology and the insufficient supply of soap wax, this method cannot meet the market demand for inexpensive pour point depressants. Therefore, finding an abundant and inexpensive alternative raw material will undoubtedly promote the rapid development of PAO pour point depressant technology.

[0005] In their paper "Optimization of Poly(α-olefin) Pour Point Depressant Polymerization Process Using Orthogonal Experiments" (Petrochemical Technology and Application, 2001, 19(3): 148-150), Peng Junqing, Cheng Lihua, et al. used orthogonal experimental design to investigate the factors affecting the polymerization yield and product quality of poly(α-olefin) pour point depressants. The raw material was a mixture of kerosene olefins (160-260℃) and diesel olefins (240-320℃), and the catalyst was the Ziegler-Natta catalytic system, with an addition amount of 0.3%-0.5%. However, this technology uses a mixture of kerosene olefins (160-260℃) and diesel olefins (240-320℃) as the raw material, which is not abundant; the catalyst is the Ziegler-Natta catalytic system, which requires a large addition amount; and the catalyst removal is difficult.

[0006] In their paper "The Influence of Alkyl Side Chain Structure on Pour Depression Effect and Adaptability of Poly-α-olefins" (Petrochemical Technology and Application, 2001, 19(1):15-17), Peng Junqing, Yan Yiming, et al. used α-olefins obtained from soap wax cracking as raw materials, and the carbon atom distribution of the α-olefins was C7-C6. 20 The pour point depressant effects and adaptability of different alkyl side chain carbon numbers obtained were investigated on base oils with different properties. TiCl3 was used as the polymerization catalyst; however, the raw material used in this technology is α-olefins from soap wax cracking, which are not abundant; the catalyst is a Ziegler-Natta catalytic system, requiring a large addition amount; and catalyst removal is difficult.

[0007] In summary, the raw materials for preparing poly-α-olefin pour point depressants currently mainly come from ethylene oligo-α-olefins and wax-cracked α-olefins. Using ethylene oligo-α-olefins as raw materials has the disadvantages of limited raw material resources and high prices. Pour point depressants prepared from soft wax-cracked α-olefins not only have high molecular weights and are difficult to process, but also cannot meet the market demand for inexpensive pour point depressants due to the phasing out of wax cracking technology and the insufficient supply of soap wax.

[0008] In recent years, the processing route of preparing liquid fuels or chemical products using the Fischer-Tropsch synthesis method has gradually gained support and achieved rapid development. However, the processing scheme dominated by the production of fuel oil has low economic benefits. The issue of how to carry out secondary processing and produce more high value-added products has attracted much attention. Many companies have used Fischer-Tropsch synthetic oil α-olefins as raw materials to prepare lubricating oil base oils, but there are no reports on the research of Fischer-Tropsch synthetic oil α-olefin synthesis pour point depressants. Summary of the Invention

[0009] Based on the above, the purpose of this invention is to provide a method for preparing polyalphaolefin pour point depressants using Fischer-Tropsch synthetic oil as raw material. The Fischer-Tropsch synthetic oil used in this method has the advantages of being inexpensive and readily available.

[0010] Therefore, the present invention provides a method for preparing a polyalphaolefin pour point depressant, comprising the following steps: distilling, cutting and refining Fischer-Tropsch synthetic oil to obtain a mixed hydrocarbon component, wherein the average carbon number of the alpha-olefin in the mixed hydrocarbon component is 10.2 to 16.5, and then polymerizing it under the catalysis of a metallocene catalytic system to obtain the polyalphaolefin pour point depressant.

[0011] Specifically, the metallocene catalyst type is a bridged metallocene catalyst; Fischer-Tropsch synthesis oil is obtained by high-temperature or low-temperature Fischer-Tropsch synthesis reaction.

[0012] Specifically, the preparation method of this invention uses abundant Fischer-Tropsch synthetic oil as raw material, which can be used to produce high value-added products, improving the economics of processing schemes dominated by Fischer-Tropsch synthesis for fuel oil production. Furthermore, the pour point depressant prepared by the method of this invention has advantages such as moderate molecular weight and narrow molecular weight distribution, and exhibits significant pour point depressing effect.

[0013] The preferred method for preparing the poly-α-olefin pour point depressant of the present invention involves introducing hydrogen gas during the polymerization process to adjust the molecular weight, controlling the hydrogen partial pressure to be 0.1-1 MPa, thereby obtaining a poly-α-olefin pour point depressant with a weight-average molecular weight of 10,000-150,000 and a molecular weight distribution of 1.5-3.

[0014] The method for preparing the polyα-olefin pour point depressant of the present invention preferably comprises a mixture of hydrocarbons with a distillation range of 50-380°C and an average carbon number of 6-25 for the Fischer-Tropsch synthetic oil; and a distillation range of 80-340°C for the mixed hydrocarbon component. For the distillation range of the Fischer-Tropsch synthetic oil, the initial boiling point is 50°C and the final boiling point is 380°C. Any Fischer-Tropsch synthetic oil with an initial boiling point greater than 50°C and a final boiling point less than 380°C is included in the above range. Similarly, for the distillation range of the mixed hydrocarbon component, the initial boiling point is 80°C and the final boiling point is 340°C. Any Fischer-Tropsch synthetic oil with an initial boiling point greater than 80°C and a final boiling point less than 340°C is included in the above range.

[0015] The method for preparing the poly-α-olefin pour point depressant of the present invention preferably includes the following steps: firstly, solvent extraction, followed by adsorption with a solid complexing agent, resulting in a refined Fischer-Tropsch synthetic oil with an oxygen-containing compound content of less than 10 ppm; more preferably, the polar solvent used in the solvent extraction is a mixture of a low-boiling-point organic oxygen-containing compound and water, wherein the low-boiling-point organic oxygen-containing compound is at least one selected from trifluoroethanol, acetic acid, trifluoroacetic acid, n-propanol, and isopropanol, and the content of the low-boiling-point organic oxygen-containing compound in the polar solvent is ≥90 wt%; more preferably, the solid complexing agent is at least one selected from aluminum trichloride, aluminum tribromide, and ferric chloride.

[0016] In the preparation method of the polyα-olefin pour point depressant of the present invention, preferably, the metallocene catalyst in the metallocene catalytic system is selected from diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia dichloride, isopropylidene(cyclopentadiene)(9-fluorenyl)zirconia dichloride, rac-vinylbisindenylzirconia dichloride, rac-dimethylsilylbisindenylzirconia dichloride, 2-(2,3,4,5-tetramethylcyclopentadiene)-4,6-di-tert-butylphenoxytitanium dichloride, and 2-(2,3,4,5-tetramethylcyclopentadiene)-4-tert-butyl-6-triphenylmethylphenoxytitanium dichloride.

[0017] The method for preparing the polyα-olefin pour point depressant of the present invention preferably uses a boron agent as the activator in the metallocene catalytic system. More preferably, the boron agent is selected from at least one of Ph3CB(C6F5)4, B(C6F5)3, and Ph3CB[(CF3)2C6H3]4.

[0018] In the preparation method of the polyα-olefin pour point depressant of the present invention, it is preferred that the co-catalyst in the metallocene catalytic system is triisobutylaluminum.

[0019] In the preparation method of the polyα-olefin pour point depressant of the present invention, preferably, the molar ratio of the metallocene catalyst to the mixed hydrocarbon components of the raw materials in the metallocene catalytic system is 1:2×10. 5 ~4.5×10 5 The molar ratio of aluminum in the co-catalyst to the transition metal in the metallocene catalyst is 10–100:1, and the molar ratio of boron in the activator to the transition metal in the metallocene catalyst is 1–3:1.

[0020] The preferred method for preparing the polyα-olefin pour point depressant of the present invention is as follows: the polymerization conditions are: temperature 30-100℃, time 1-4h.

[0021] Therefore, the present invention also provides a polyα-olefin pour point depressant, which is prepared by the above preparation method and is added to Group I, Group II or Group III lubricating oil base oil at an amount of 0.1 wt% to 1 wt%.

[0022] The preparation method of the polyα-olefin pour point depressant provided by the present invention specifically includes the following steps:

[0023] Step 1: The Fischer-Tropsch synthetic oil is cut, refined, and oxygen-containing compounds are removed to obtain a mixed hydrocarbon component with an oxygen-containing compound content of less than 10 ppm and an average carbon number of 10.2 to 16.5.

[0024] Step 2: Using a bridged metallocene as a catalyst, a mixed hydrocarbon component with an average carbon number of 10.2 to 16.5 is polymerized in a high-pressure reactor, and the molecular weight of poly-α-olefin is adjusted by controlling the hydrogen partial pressure.

[0025] Step 3: After the reaction is completed, the catalyst and unreacted monomers are separated by post-treatment such as water washing, filtration, and distillation.

[0026] Step 4: Add the obtained pour point depressant to Group I, II, and III lubricating oil base oils to test its pour point depressing effect.

[0027] The preparation method provided by this invention uses abundant Fischer-Tropsch synthetic oil as raw material, enabling the production of high-value-added products and improving the economics of processing schemes primarily focused on fuel oil production through Fischer-Tropsch synthesis. Furthermore, due to the single-center, directional polymerization capability and high polymerization activity of metallocene catalysts, not only is the catalyst dosage small and the catalyst separation process simple, but the overall technology is also environmentally friendly. Moreover, it synthesizes pour point depressants with controllable molecular weight and narrow molecular weight distribution, showing significant pour point reduction effects on Group I, Group II, and Group III lubricating oil base oils. The pour point depressant significantly lowers the pour point of Group I, Group II, and Group III lubricating oil base oils, with a pour point reduction of over 18°C ​​for Group I and Group II base oils and over 20°C for Group III base oils.

[0028] In summary, the beneficial effects of this invention are as follows:

[0029] The preparation method has advantages such as high polymerization activity, small catalyst dosage, simple post-processing, and environmentally friendly process; the prepared pour point depressant has the characteristics of moderate molecular weight, narrow molecular weight distribution, and good pour point depressing effect. Detailed Implementation

[0030] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods without specific conditions in the following embodiments are generally performed under conventional conditions, and percentages not specified are by weight. Unless otherwise specified, all Fischer-Tropsch synthetic oils and mixed hydrocarbon components used in all embodiments are commercially available. Raw materials with different average carbon numbers can be obtained by temperature-controlled fractionation.

[0031] The preparation method of the poly-α-olefin pour point depressant provided by the present invention includes the following steps: cutting and refining Fischer-Tropsch synthetic oil to obtain a mixed hydrocarbon component, wherein the average carbon number of the α-olefin in the mixed hydrocarbon component is 10.2 to 16.5, and then polymerizing it under the catalysis of a metallocene catalytic system to obtain the poly-α-olefin pour point depressant.

[0032] Specifically, the metallocene catalytic system is bridged to the metallocene catalytic system; Fischer-Tropsch synthesis oil is obtained from high-temperature or low-temperature Fischer-Tropsch synthesis reactions.

[0033] Specifically, the preparation method of this invention uses abundant Fischer-Tropsch synthetic oil as raw material, which can be used to produce high value-added products, improving the economics of processing schemes dominated by Fischer-Tropsch synthesis for fuel oil production. Furthermore, the pour point depressant prepared by the method of this invention has advantages such as moderate molecular weight and narrow molecular weight distribution, and exhibits significant pour point depressing effect.

[0034] In some embodiments, preferably, hydrogen gas is introduced during the polymerization process to adjust the molecular weight, and the hydrogen partial pressure is controlled to be 0.1-1 MPa, to obtain a polyα-olefin pour point depressant with a weight-average molecular weight of 10,000-150,000 and a molecular weight distribution of 1.5-3.

[0035] In some embodiments, preferably, the Fischer-Tropsch synthetic oil is a hydrocarbon mixture with a boiling range of 50-380°C and an average carbon number of 6-25; the boiling range of the mixed hydrocarbon component is 80-340°C. For the above-mentioned boiling range of the Fischer-Tropsch synthetic oil, the initial boiling point is 50°C and the final boiling point is 380°C. Fischer-Tropsch synthetic oils with an initial boiling point greater than 50°C and a final boiling point less than 380°C are included in the above range. Similarly, for the above-mentioned boiling range of the mixed hydrocarbon component, the initial boiling point is 80°C and the final boiling point is 340°C. Fischer-Tropsch synthetic oils with an initial boiling point greater than 80°C and a final boiling point less than 340°C are included in the above range.

[0036] In some embodiments, preferably, the refining process includes the following steps: first solvent extraction, followed by adsorption with a solid complexing agent, resulting in a refined Fischer-Tropsch synthetic oil with an oxygen-containing compound content of less than 10 ppm; more preferably, the polar solvent used in the solvent extraction is a mixture of a low-boiling-point organic oxygen-containing compound and water, wherein the low-boiling-point organic oxygen-containing compound is at least one selected from trifluoroethanol, acetic acid, trifluoroacetic acid, n-propanol, and isopropanol, and the content of the low-boiling-point organic oxygen-containing compound in the polar solvent is ≥90 wt%; more preferably, the solid complexing agent is at least one selected from aluminum trichloride, aluminum tribromide, and ferric chloride.

[0037] In some embodiments, preferably, the metallocene catalyst in the metallocene catalytic system is selected from diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia, isopropylidene(cyclopentadiene)(9-fluorenyl)zirconia, rac-vinylbisindylzirconia, rac-dimethylsilylbisindylzirconia, 2-(2,3,4,5-tetramethylcyclopentadiene)-4,6-di-tert-butylphenoxytitanium chloride, and 2-(2,3,4,5-tetramethylcyclopentadiene)-4-tert-butyl-6-triphenylmethylphenoxytitanium chloride.

[0038] In some embodiments, preferably, the activator in the metallocene catalytic system is a boron agent, and more preferably, the boron agent is selected from at least one of Ph3CB(C6F5)4, B(C6F5)3, and Ph3CB[(CF3)2C6H3]4.

[0039] In some embodiments, preferably, the co-catalyst in the metallocene catalytic system is triisobutylaluminum.

[0040] In some embodiments, preferably, in the metallocene catalytic system, the molar ratio of the metallocene catalyst to the mixed hydrocarbon components of the feedstock is 1:2×10. 5 ~4.5×10 5 The molar ratio of aluminum in the co-catalyst to the transition metal in the metallocene catalyst is 10–100:1, and the molar ratio of boron in the activator to the transition metal in the metallocene catalyst is 1–3:1.

[0041] In some embodiments, preferably, the polymerization conditions are: temperature 30–100°C, time 1–4 hours.

[0042] The present invention provides a polyα-olefin pour point depressant, which is prepared by the above-described method and is added to Group I, Group II or Group III lubricating oil base oil at a rate of 0.1 wt% to 1 wt%.

[0043] The preparation method of the polyα-olefin pour point depressant provided by the present invention includes the following steps:

[0044] (1) The raw material cutting and refining method is carried out according to the following steps:

[0045] Fischer-Tropsch synthetic oil (C6-C) 25 Distillation is carried out at a range of 50℃-380℃, and the distillation range of the cut fraction is controlled at 80℃-340℃ to obtain a mixed hydrocarbon component with an average carbon number of 10.2-16.5. The mixed hydrocarbon component is then subjected to a combination of liquid-liquid extraction and complexation purification process to deeply remove oxygen-containing compounds from the fraction. After purification, the oxygen-containing compound content in the raw material is less than 10ppm.

[0046] The polar solvent used in the liquid-liquid extraction is a mixture of a low-boiling-point organic oxygen-containing compound and water. The low-boiling-point organic oxygen-containing compound is at least one of trifluoroethanol, acetic acid, trifluoroacetic acid, n-propanol, and isopropanol. The content of the low-boiling-point organic oxygen-containing compound in the polar solvent is ≥90wt%.

[0047] The complexing agent used for complexation purification is at least one of aluminum trichloride, aluminum tribromide, and ferric chloride.

[0048] The method for calculating the average carbon number of the mixed hydrocarbon components:

[0049] Average carbon number = (C6*6*wt% + C8*8*wt% + ... + C25*25wt%) / ∑X i n (i = 6, n = 25).

[0050] (2) The olefin polymerization and post-processing method is carried out according to the following steps:

[0051] 1) Before the polymerization begins, clean the reactor with 300ml of purified cyclohexane at a temperature of 100℃ for 0.5h-1h. After releasing the cyclohexane, purge the polymerization reactor with high-purity nitrogen to ensure that air and trace amounts of water are removed from the polymerization reactor.

[0052] 2) After purging with nitrogen, the mixture is cooled to the predetermined reaction conditions using circulating water. 200g of mixed hydrocarbon components, co-catalyst, activator and main catalyst are added. Stirring is started and the reaction temperature is set. The reaction temperature is controlled by the cooling system. After a certain reaction time, the reaction is stopped, cooled and vented. The product is transferred to a 500mL round-bottom flask and terminated with 10% acidified ethanol.

[0053] 3) After ethanol termination, the product was washed with water and separated into layers. White clay was added to the oil phase for adsorption, and the adsorption temperature was controlled at 60℃~80℃ for 0.5h. The product was obtained by filtration and the oligomer components below 300℃ were distilled off. The product was then tested.

[0054] The cocatalyst is a commercially available triisobutylaluminum toluene solution with a concentration of 1.0 mmol / ml. The activator, boron agent, and metallocene are both solids, which are dissolved in toluene solution in advance for use. A fixed amount of boron agent and metallocene are taken into 20 ml of toluene solution each time according to the experimental needs.

[0055] (3) The pour point depressant was tested and analyzed.

[0056] Pour point depressants were added to Group I, Group II, and Group III lubricating oil base oils at a ratio of 0.1% to 1%, with a blending temperature of 120℃ and a blending time of 8 hours. The pour point of the lubricating oil base oil was measured before and after the addition of the pour point depressant. The pour point reduction margin of the lubricating oil base oil refers to the difference between the pour point measured after the addition of the pour point depressant and the pour point measured without the addition of the pour point depressant.

[0057] Note that all raw materials and catalysts used are stored in an anhydrous and oxygen-free glove box. Sampling operations are also carried out separately in the glove box, and a gas cylinder sampler is used for sampling.

[0058] The main raw material for the following examples and comparative examples, Fischer-Tropsch synthetic oil, was sourced from Ningxia Coal Industry Co., Ltd. of China Energy Investment Corporation, and was of industrial grade; the lubricating oil base oil was purchased from the market and was of grades HVIP6, U6, and HVI150. Bridge-linked metallocene: diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia, isopropylidene(cyclopentadiene)(9-fluorenyl)zirconia, rac-vinylbisindylzirconia, rac-dimethylsilylbisindylzirconia, 98% purity, purchased from Bailingwei Chemical Technology Co., Ltd.; 2-(2,3,4,5-tetramethylcyclopentadiene)-4,6-di-tert-butylphenoxytitanium dichloride, 2-(2,3,4,5-tetramethylcyclopentadiene)-4-tert-butyl-6-triphenylmethylphenoxytitanium dichloride (Reference: Synthesis Zhang Y, Mu Y. Highly efficient one-step direct synthesis of monocyclopentadienyltitanium complexes[J]. Organometallics, 2006, 25(3):631-634).

[0059] Evaluation and analysis methods:

[0060] The pour point of the oil was determined using the analytical method specified in GB / T3535; the composition distribution and fraction analysis of the product were determined according to the method specified in ASTM2887; and the weight-average molecular weight and its distribution of the pour point depressant were determined according to SHT1759-1.

[0061] The refined mixed hydrocarbon components used in the following examples were prepared according to the following preparation method. Specifically, the mixed hydrocarbon components were prepared from Fischer-Tropsch synthetic oil, including the following steps:

[0062] (1) Oil distillation, cutting, and refining:

[0063] Fischer-Tropsch synthetic oil (C6-C) 25 Distillation is performed on the fraction with a distillation range of 50℃-380℃. The distillation range of the fraction is controlled to be 80℃-340℃ to obtain a mixed hydrocarbon component. The average carbon number of the mixed hydrocarbon component is 10.2-16.5 (various mixed hydrocarbon components with different average carbon numbers are obtained by fine-tuning the distillation range). The mixed hydrocarbon component is then subjected to a combination of liquid-liquid extraction (the solvent is a mixture of trifluoroethanol and water, with a trifluoroethanol content of 95wt%) and complexation purification (the complexing agent is aluminum trichloride) to deeply remove oxygen-containing compounds from the fraction. After purification, the oxygen-containing compound content in the raw material is less than 10ppm.

[0064] Example 1

[0065] Polymerization was carried out using refined mixed hydrocarbon components as raw materials. First, the reactor was pretreated, and then the polymerization reaction began: 200g of the mixed hydrocarbon component with an average carbon number of 10.2 and 35μmol of triisobutylaluminum were taken from a glove box and added to the polymerization reactor. Stirring and heating were initiated, with a heating rate controlled at 2℃ / min. When the temperature reached 30℃, a 20ml toluene solution containing 3.49μmol of diphenylmethylene (cyclopentadiene)(9-fluorenyl)zirconium dichloride and 3.5μmol of Ph3CB(C6F5)4 was added. The reaction temperature was controlled at 30℃, and the hydrogen partial pressure at 0.1MPa. The reaction was carried out for 2 hours, after which stirring was stopped, and the material was discharged into 50ml of acidified ethanol (10%) to terminate the polymerization reaction. After water washing and separation, the mixture was filtered through bleaching clay adsorption, followed by vacuum distillation. The fraction distilled off below 300℃ was collected.

[0066] Add 0.04g of the product to 40g of Group II base oil (HVIP6), mix in a beaker at 60℃ for 1h, and determine the pour point of the base oil before and after adding the pour point depressant.

[0067] Example 2

[0068] Using refined mixed hydrocarbon components as raw materials, the same polymerization method as in Example 1 was employed, with the following differences: the average carbon number of the added mixed hydrocarbon components was 16.5, the amount of triisobutylaluminum added was 50 μmol, the temperature was raised to 50°C, and 20 ml of toluene solution containing 0.96 μmol isopropylidene (cyclopentadiene)(9-fluorenyl)zirconium dichloride and 2.5 μmol B(C6F5)3 was added. The reaction temperature was controlled at 50°C, the hydrogen partial pressure was 0.3 MPa, and the reaction was carried out for 1 h. 0.1 g of the product was added to 40 g of Group III base oil (U6).

[0069] Example 3

[0070] Using refined mixed hydrocarbon components as raw materials, the same polymerization method as in Example 1 was employed, with the following differences: the average carbon number of the added mixed hydrocarbon components was 11.5, the amount of triisobutylaluminum added was 20 μmol, the temperature was raised to 70°C, and 20 ml of toluene solution containing 1.55 μmol of rac-vinylbisindenylzirconium dichloride and 4.5 μmol of Ph3CB[(CF3)2C6H3]4 was added. The reaction temperature was controlled at 70°C, the hydrogen partial pressure was 0.5 MPa, and the reaction was carried out for 1.5 h. 0.2 g of the product was added to 40 g of Group I base oil (HVI150).

[0071] Example 4

[0072] Using refined mixed hydrocarbon components as raw materials, the same polymerization method as in Example 1 was employed, with the following differences: the average carbon number of the added mixed hydrocarbon components was 12.5, the amount of triisobutylaluminum added was 50 μmol, the temperature was raised to 80°C, and 20 ml of toluene solution containing 1.63 μmol of rac-dimethylsilylbisindenylzirconium dichloride and 4.5 μmol of Ph3CB(C6F5)4 was added. The reaction temperature was controlled at 80°C, the hydrogen partial pressure at 0.7 MPa, and the reaction was carried out for 2 h. 0.32 g of the product was then added to 40 g of Group II base oil (HVIP6).

[0073] Example 5

[0074] Using refined mixed hydrocarbon components as raw materials, the same polymerization method as in Example 1 was employed, with the following differences: the average carbon number of the added mixed hydrocarbon components was 13.6, the amount of triisobutylaluminum added was 75 μmol, the temperature was raised to 90°C, and 20 ml of toluene solution containing 2.11 μmol of 2-(2,3,4,5-tetramethylcyclopentadiene)-4,6-di-tert-butylphenoxytitanium dichloride and 6 μmol of Ph3CB[(CF3)2C6H3]4 was added. The reaction temperature was controlled at 90°C, the hydrogen partial pressure at 1.0 MPa, and the reaction was carried out for 3 h. 0.4 g of the product was added to 40 g of Group III base oil (U6).

[0075] Example 6

[0076] Using refined mixed hydrocarbon components as raw materials, the same polymerization method as in Example 1 was employed, with the following differences: the average carbon number of the added mixed hydrocarbon components was 14.5, the amount of triisobutylaluminum added was 100 μmol, the temperature was raised to 100 °C, and 20 ml of toluene solution containing 1.09 μmol of 2-(2,3,4,5-tetramethylcyclopentadiene)-4-tert-butyl-6-triphenylmethylphenoxytitanium dichloride and 1.5 μmol of Ph3CB[(CF3)2C6H3]4 was added. The reaction temperature was controlled at 100 °C, the hydrogen partial pressure at 0.9 MPa, and the reaction was carried out for 4 h. 0.2 g of the product was added to 40 g of Group I base oil (HVI150).

[0077] Key process parameters and product performance of the polymerization process are listed in Appendix 1.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that the average carbon number of the mixed hydrocarbon components is 8.6. 0.04g of the product was added to 40g of Group II base oil (HVIP6), and the mixture was blended in a beaker at 60°C for 1 hour. The pour point of the base oil before and after the addition of the pour point depressant was measured.

[0080] Comparative Example 2

[0081] The difference from Example 2 is that the average carbon number of the mixed hydrocarbon components is 17.8. 0.1g of the product was added to 40g of Group III base oil (U6).

[0082] Comparative Example 3

[0083] The difference from Example 3 is that the catalytic system used is the Ziegler-Natta catalytic system. 0.2% triisobutylaluminum was added, the temperature was raised to 70°C, and 0.6g of TiCl3 (0.3% of the raw material mass ratio) was added. The reaction temperature was controlled at 70°C, and the reaction was carried out for 1.5 hours. 0.2g of the product was then added to 40g of Group I base oil (HVI150).

[0084] Table 1

[0085]

[0086]

[0087] As shown in Table 1, the pour point depressant prepared by the method of this invention has good pour point depressing effects on Group I, Group II, and Group III lubricating oil base oils. When the amount of pour point depressant added is in the range of 0.1% to 1%, the pour point depressing range for Group I and Group II lubricating oil base oils is higher than 18°C, and the pour point depressing range for Group III lubricating oil base oil is higher than 20°C. A comparison between Comparative Examples 1-2 and Examples 1-2 shows that when the carbon number distribution of the mixed hydrocarbon components exceeds 10.2 to 16.5, the pour point depressing effect of the obtained product is poor, only reducing the temperature by 6°C and 9°C respectively. Comparative Example 3 shows that when using a Zn catalytic system, the catalyst dosage reaches 0.3%.

[0088] As can be seen from the above, the preparation method provided by this invention uses abundant Fischer-Tropsch synthetic oil as raw material, which can be used to produce high value-added products and improve the economic efficiency of the processing scheme dominated by Fischer-Tropsch synthesis for fuel oil production. Furthermore, because metallocene catalysts have single-center, strong directional polymerization ability and high polymerization activity, they not only require a small amount of catalyst and have a simple catalyst separation process, but also have an overall environmentally friendly technology. Moreover, they synthesize pour point depressants with controllable molecular weight and narrow molecular weight distribution, showing significant pour point depressing effects on Group I, Group II, and Group III lubricating oil base oils. The pour point depressants significantly reduce the pour point of Group I, Group II, and Group III lubricating oil base oils, with a pour point reduction of more than 18°C ​​for Group I and Group II base oils and more than 20°C for Group III base oils.

[0089] In summary, the beneficial effects of this invention are as follows:

[0090] The preparation method has advantages such as high polymerization activity, small catalyst dosage, simple post-processing, and environmentally friendly process; the prepared pour point depressant has the characteristics of moderate molecular weight, narrow molecular weight distribution, and good pour point depressing effect.

[0091] 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 present invention.

Claims

1. A method for preparing a polyα-olefin pour point depressant, characterized in that, Includes the following steps: The Fischer-Tropsch synthetic oil is distilled, cut, and refined to obtain a mixed hydrocarbon component. The average carbon number of the α-olefin in the mixed hydrocarbon component is 10.2~16.

5. Then, it is polymerized under the catalysis of a metallocene catalytic system to obtain the polyα-olefin pour point depressant. During the polymerization process, hydrogen gas is introduced to adjust the molecular weight, and the hydrogen partial pressure is controlled at 0.1~1MPa to obtain a polyα-olefin pour point depressant with a weight-average molecular weight of 1~150,000 and a molecular weight distribution of 1.5~3. The Fischer-Tropsch synthetic oil is a mixture of hydrocarbons with a distillation range of 50-380℃ and a carbon number of 6-25; the distillation range of the mixed hydrocarbon components is 80-340℃. The refined Fischer-Tropsch synthetic oil contains less than 10 ppm of oxygenated compounds.

2. The preparation method according to claim 1, characterized in that, The refining process includes the following steps: first, solvent extraction is used, followed by adsorption with a solid complexing agent, and the oxygen content in the refined Fischer-Tropsch synthetic oil is less than 10 ppm.

3. The preparation method according to claim 1, characterized in that, The metallocene catalyst in the metallocene catalytic system is selected from diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconia dichloride, isopropylidene (cyclopentadiene) (9-fluorenyl)zirconia dichloride, rac-vinylbisindylzirconia dichloride, rac-dimethylsilylbisindylzirconia dichloride, 2-(2,3,4,5-tetramethylcyclopentadiene)-4,6-di-tert-butylphenoxytitanium dichloride, and 2-(2,3,4,5-tetramethylcyclopentadiene)-4-tert-butyl-6-triphenylmethylphenoxytitanium dichloride.

4. The preparation method according to claim 1, characterized in that, The activator in the metallocene catalytic system is a boron agent.

5. The preparation method according to claim 1, characterized in that, The co-catalyst in the metallocene catalytic system is triisobutylaluminum.

6. The preparation method according to claim 1, characterized in that, In the metallocene catalytic system, the molar ratio of aluminum in the co-catalyst to the transition metal in the metallocene catalyst is 10~100:1, and the molar ratio of boron in the activator to the transition metal in the metallocene catalyst is 1~3:

1.

7. The preparation method according to claim 1, characterized in that, The polymerization conditions are: temperature 30~100℃, time 1h~4h.

8. The preparation method according to claim 2, characterized in that, The polar solvent used in the solvent extraction is a mixture of a low-boiling-point organic oxygen-containing compound and water. The low-boiling-point organic oxygen-containing compound is at least one of trifluoroethanol, acetic acid, trifluoroacetic acid, n-propanol, and isopropanol. The content of the low-boiling-point organic oxygen-containing compound in the polar solvent is ≥90wt%.

9. The preparation method according to claim 2, characterized in that, The solid complexing agent is at least one of aluminum trichloride, aluminum tribromide, and ferric chloride.

10. The preparation method according to claim 4, characterized in that, The boron agent is selected from at least one of Ph3CB(C6F5)4, B(C6F5)3, and Ph3CB[(CF3)2C6H3]4.

11. A polyα-olefin pour point depressant, characterized in that, Prepared by the preparation method according to any one of claims 1-10, and added to Group I, Group II or Group III lubricating oil base oil at an amount of 0.1 wt% to 1 wt%.

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