Low-pour-point high-viscosity metallocene PAO base oil and preparation method thereof

Abstract

The invention provides low-pour-point high-viscosity metallocene PAO base oil and a preparation method thereof, and the preparation method comprises the following steps: (1) taking naphtha fraction generated by coal indirect liquefaction as a raw material, and carrying out single carbon cutting treatment to obtain olefin with a single carbon atom number and alkane thereof; (2) performing oxide removal treatment on olefin and alkane with single carbon atom number or a mixture of olefin and alkane with single carbon atom number; and (3) under the catalysis of a metallocene catalyst, carrying out polymerization reaction on the mixture subjected to oxide removal treatment, quenching the obtained product, purifying, and carrying out hydrogenation saturation to obtain the PAO base oil. According to the method disclosed by the invention, the molecular structure of the product can be controlled, the pour point of the metallocene PAO product is reduced, the high-viscosity metallocene PAO product is prepared, and the performance index of the product is controllable.

Description

Technical Field

[0001] The invention belongs to the technical field of metallocene PAO base oil preparation, and in particular relates to a low pour point and high viscosity metallocene PAO base oil and a preparation method thereof. Background Art

[0002] Polyalphaolefin (PAO) is a kind of synthetic base oil, a synthetic hydrocarbon lubricant prepared by chemical synthesis. Pour point refers to the lowest temperature at which a cooled sample can flow under specified test conditions. It is a conventional indicator for measuring the low-temperature fluidity of lubricants. Viscosity refers to the resistance of a fluid to flow. It is a physical quantity that measures the viscosity of a fluid. The VI value represents a conventional value of the property that the viscosity of an oil changes with temperature. The higher the viscosity index, the smaller the viscosity of the oil changes with temperature, and vice versa.

[0003] 200580046574.1 discloses the use of a 1-decene / 1-dodecene olefin mixture for preparing a high-viscosity polyalphaolefin (PAO) having a viscosity (ASTM D-445) of about 40 to about 100 cSt at 100°C and a number average molecular weight of about 1200 to 4000. The high-viscosity polyalphaolefin is particularly useful as a lubricant base oil, but the product has a high pour point, which is not conducive to use in a low-temperature environment.

[0004] 201610392063.5 discloses a method for preparing a low-viscosity metallocene PAO base oil. The method adopts a dual metallocene-chain shuttling agent catalytic system to synthesize low-viscosity PAO, while reducing the selectivity of dimers in the product to achieve the purpose of increasing the yield of lubricant base oil components, avoiding the disadvantage of using hydrogen as a molecular weight regulator so that part of the raw materials are saturated into alkanes. However, this method cannot be used to produce high-viscosity metallocene PAO products.

[0005] 201510881163.X discloses a method for preparing PAO from Fischer-Tropsch synthetic oil products, which uses light oil generated by indirect liquefaction of coal as raw material, undergoes intermittent polymerization reaction and fixed-bed hydrofining to obtain a base oil PAO with excellent performance. This method only explores feasibility, and the quality of the prepared PAO is not high, and it is difficult to meet the requirements for commercial sales. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the present invention provides a method for producing a low pour point and high viscosity metallocene PAO base oil.

[0007] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a low pour point and high viscosity metallocene PAO base oil, comprising the following steps:

[0009] (1) using the naphtha fraction generated by indirect coal liquefaction as a raw material to perform single carbon cutting treatment to obtain olefins and alkanes having a single carbon atom number;

[0010] (2) removing oxides from olefins and alkanes having a single carbon number, or mixtures thereof;

[0011] (3) The mixture after the oxide removal treatment is polymerized under the catalysis of a metallocene catalyst, and the obtained product is quenched, purified, and hydrogenated to obtain a PAO base oil.

[0012] In a specific embodiment of the preparation method of the present invention, the distillation range of the naphtha fraction generated by the indirect liquefaction of coal in step (1) is IBP-220°C, for example, 60°C, 100°C, 150°C, 200°C.

[0013] In some specific embodiments, the single carbon cutting treatment in step (1) is to distill the naphtha fraction generated by indirect coal liquefaction to obtain a series of olefins and alkanes with a single carbon atom number; for example, a C5-C12 mixed liquid can be obtained, that is, a mixed liquid of pentene and pentane, a mixed liquid of hexene and hexane, heptene and heptane, etc. Specifically, a mixed liquid of pentene and pentane is obtained at a cutting temperature of 30 to 36°C; a mixed liquid of hexene and hexane is obtained at a cutting temperature of 63 to 69°C; a mixed liquid of heptene and heptane is obtained at a cutting temperature of 90 to 98°C; a mixed liquid of octene and octane is obtained at a cutting temperature of 121 to 125°C; a mixed liquid of nonene and nonane is obtained at a cutting temperature of 145 to 151°C; a mixed liquid of decene and decane is obtained at a cutting temperature of 170 to 174°C; a mixed liquid of undecene and undecane is obtained at a cutting temperature of 192 to 196°C; and a mixed liquid of dodecene and dodecane is obtained at a cutting temperature of 213 to 216°C.

[0014] In some specific embodiments, the content of olefins and alkanes with a single carbon number obtained by single carbon cutting is ≥ 99wt%, for example, the content of pentene and pentane obtained at a single carbon cutting temperature of 30-36° C. is ≥ 99wt%. In some more specific embodiments, the content of olefins is 20-80wt%, for example, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%.

[0015] The preparation method of the present invention obtains olefins with a single carbon number Cn (n=5, 6, 7, 8, 9, 10, 11 or 12) and corresponding alkanes by single carbon cutting at a specific temperature; in some specific embodiments, the reactants participating in the following polymerization reaction can be alkanes or olefins with a single carbon number Cn treated as above, or a mixture of certain Cn+1 alkenes and their Cn+1 alkanes. The product treated by single carbon cutting in the preparation method of the present invention is more suitable for metallocene catalyst polymerization, the quality of the polymerization product is controllable, and the problem of more impurities and poor regularity in wide-fraction raw materials is avoided.

[0016] In step (2) of the preparation method of the present invention, the deoxidation treatment is carried out by countercurrent extraction of the composite extraction solvent and the single carbon mixture; in some specific embodiments, the composite extraction solvent is selected from two or more of ester compounds, glycol compounds, amide compounds, pyrrolidone compounds, and diol compounds, for example, propylene glycol and N-methylpyrrolidone composite extractant, ethylene glycol and dibutyl phthalate, N,N-dimethylformamide and diethyl phthalate.

[0017] In some specific embodiments, the metallocene catalyst in step (3) comprises a main catalyst and an auxiliary agent, wherein the main catalyst is a complex of a transition metal element of group IVB, and the auxiliary agent is an organic boron compound and / or an alkyl aluminum. Specifically, the ratio of the molar amount of the transition metal element of group IVB in the main catalyst to the molar amount of the olefin in the naphtha fraction (for example, Zr / α-olefin) is 1×10 -4 ~5×10 -5 The molar ratio of the added alkyl aluminum to the main catalyst (for example, Al / Zr) is 40 to 200, and the molar ratio of the added organic boron compound to the main catalyst (for example, B / Zr) is 0.5 to 2.0.

[0018] In some more specific embodiments, the main catalyst is a bridged metallocene catalyst; the bridged metallocene catalyst is selected from one or more of rac-vinyl bridged bis-indenyl zirconium dichloride, rac-ethylene bis(4,5,6,7-tetrahydro-1-indenyl)] zirconium dichloride, rac-dimethylsilyl bridged bis-indenyl zirconium dichloride or rac dimethylsilyl bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride.

[0019] In the preparation method of the present invention, the polymerization reaction in step (3) is carried out under anhydrous and oxygen-free conditions and at a reaction temperature of 30 to 150° C. for 0.1 to 5 hours.

[0020] In some specific embodiments, alcohols, water or acids are added to the product obtained by the polymerization reaction for quenching. Preferably, clay or diatomaceous earth is added to the quenched product to remove the catalyst metal and boride therein; the reaction temperature of the hydrogenation is 100-300° C., and the reaction pressure is 2-6 MPa.

[0021] In a second aspect, the present invention provides a low pour point and high viscosity metallocene PAO base oil, which is prepared by the above preparation method.

[0022] In some specific embodiments, the metallocene PAO base oil has a viscosity of 40 to 1000 cSt at 100°C and a pour point of -21 to -60°C.

[0023] The above technical solution has the following technical effects:

[0024] The preparation method of the present invention uses naphtha fractions generated by indirect liquefaction of coal containing α-olefins as a raw material, and obtains olefins and alkanes with a single carbon atom number through single carbon cutting treatment, so that the polymerization process can control the molecular structure in the product oil, reduce the pour point of the metallocene PAO product, prepare a high-viscosity metallocene PAO product, and the product performance indicators are controllable. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0026] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0027] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0028] 1-Decene: purchased from INEOS, purity>96%;

[0029] 1-Dodecene: purchased from INEOS, purity>92%.

[0030] The components of the naphtha fraction (distillation range is IBP-220° C.) generated by indirect liquefaction of the raw material-coal used in the following examples and comparative examples of the present invention are shown in Table 1 below:

[0031] Table 1

[0032] Element α-Olefin (wt%) Normal alkanes (wt%) Other hydrocarbons (wt%) Oxygen-containing compounds (wt%) Naphtha 51.2 31.5 14.8 2.5

[0033] The evaluation methods of the products obtained in the following embodiments and comparative examples are as follows:

[0034] Viscosity: GB / T 256;

[0035] Pour point: GB / T 3535;

[0036] Single carbon content: gas chromatography analysis.

[0037] Example 1

[0038] (1) performing single carbon cutting on naphtha generated by indirect coal liquefaction by distillation to obtain a mixed solution of octene and octane (with a single carbon content greater than 99%) at 121-125° C.;

[0039] (2) removing oxides by countercurrent removal from a mixed solution of octene and octane and a composite extractant of propylene glycol and N-methylpyrrolidone;

[0040] (3) High-purity nitrogen was used to remove dissolved oxygen, and molecular sieves were used to remove trace water. The reaction was carried out in a glove box. 500 g of the mixture was weighed and placed in a 1000 ml flask with mechanical stirring. All openings were sealed and connected to a double-row pipeline. The air in the pipeline was evacuated and replaced with high-purity nitrogen three times to keep the reaction under an inert atmosphere.

[0041] The mixture was heated in an oil bath to 50°C, and a pre-prepared metallocene catalyst (rac-vinyl bridged bisindenyl zirconium dichloride, with a molar ratio of Zr / α-olefin of 8×10 -5 ) and MAO and boron salt additive solution (where Al / Zr is 100, B / Zr is 1.2) were polymerized for 2 hours, ethanol was added to quench, and then 2% white clay was added to remove the catalyst metal and boride residues; then stirred at 120°C for 2 hours, filtered, and the unreacted α-olefins and alkanes were removed by actual boiling point. Hydrogenation saturation was carried out at 200°C and 4MPa to obtain PAO base oil.

[0042] Example 2

[0043] The difference between this embodiment and embodiment 1 lies in step (1), i.e., fractionating naphtha by distillation to obtain a mixed solution of decene and decane (with a single carbon content greater than 99%) at 170-174°C, and using oil bath heating to raise the temperature to 140°C during the polymerization process.

[0044] Example 3

[0045] (1) performing single carbon cutting on naphtha generated by indirect coal liquefaction by distillation to obtain a mixed solution of decene and decane (with a single carbon content greater than 99%) at 170-174° C.;

[0046] (2) removing oxides by countercurrent removal from a mixed solution of decene and decane and a composite extractant of propylene glycol and N-methylpyrrolidone;

[0047] (3) High-purity nitrogen was used to remove dissolved oxygen, and molecular sieves were used to remove trace water. The reaction was carried out in a glove box. 500 g of the mixture was weighed and placed in a 1000 ml flask with mechanical stirring. All openings were sealed and connected to a double-row pipeline. The air in the pipeline was evacuated and replaced with high-purity nitrogen three times to keep the reaction under an inert atmosphere.

[0048] The oil bath was heated to 70 °C, and the pre-prepared metallocene catalyst (rac dimethylsilylbis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, Zr / α-olefin molar ratio was 8×10 -5 ) and MAO and boron salt additive solution (where Al / Zr is 120, B / Zr is 1.2) were polymerized for 2 hours, ethanol was added to quench, and then 2% white clay was added to remove the catalyst metal and boride residues; then stirred at 120°C for 2 hours, filtered, and the unreacted α-olefins and alkanes were removed by actual boiling point. Hydrogenation saturation was carried out at 200°C and 4MPa to obtain PAO base oil.

[0049] Example 4

[0050] (1) performing single carbon cutting on naphtha generated by indirect coal liquefaction by distillation to obtain a mixed solution of hexene and hexane (with a single carbon content greater than 99%) at 62-69° C., and a mixed solution of dodecene and dodecane (with a single carbon content greater than 99%) at 213-216° C.;

[0051] (2) removing oxides from the mixed solution of hexene and hexane, the mixed solution of dodecene and dodecane, and a composite extractant (propylene glycol and N-methylpyrrolidone composite extractant) by countercurrent removal;

[0052] (3) High-purity nitrogen was used to remove dissolved oxygen, and molecular sieves were used to remove trace water. The reaction was carried out in a glove box. 500 g of the mixture was weighed and placed in a 1000 ml flask with mechanical stirring. All openings were sealed and connected to a double-row pipeline. The air in the pipeline was evacuated and replaced with high-purity nitrogen three times to keep the reaction under an inert atmosphere.

[0053] The oil bath was heated to 70 °C, and the pre-prepared metallocene catalyst (rac dimethylsilylbis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, Zr / α-olefin molar ratio was 8×10 -5) and MAO and boron salt additive solution (where Al / Zr is 120, B / Zr is 1.2) were polymerized for 2 hours, ethanol was added to quench, and then 2% white clay was added to remove the catalyst metal and boride residues; then stirred at 120°C for 2 hours, filtered, and the unreacted α-olefins and alkanes were removed by actual boiling point. Hydrogenation saturation was carried out at 200°C and 4MPa to obtain PAO base oil.

[0054] Example 5

[0055] (1) performing single carbon cutting on naphtha generated by indirect coal liquefaction by distillation, obtaining a mixed solution of octene and octane (with a single carbon content greater than 99%) at 121-125° C., obtaining a mixed solution of decene and decane (with a single carbon content greater than 99%) at 170-174° C., and obtaining a mixed solution of dodecene and dodecane (with a single carbon content greater than 99%) at a cutting temperature of 213-216° C.;

[0056] (2) removing oxides from the mixed solution of octene and octane, the mixed solution of decene and decane, and the mixed solution of dodecene and dodecane with a composite extractant (propylene glycol and N-methylpyrrolidone composite extractant) in a countercurrent removal manner;

[0057] (3) High-purity nitrogen was used to remove dissolved oxygen, and molecular sieves were used to remove trace water. The reaction was carried out in a glove box. 500 g of the mixture was weighed and placed in a 1000 ml flask with mechanical stirring. All openings were sealed and connected to a double-row pipeline. The air in the pipeline was evacuated and replaced with high-purity nitrogen three times to keep the reaction under an inert atmosphere.

[0058] The oil bath was heated to 95 °C, and the pre-prepared metallocene catalyst (rac dimethylsilylbis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, with a Zr / α-olefin molar ratio of 8×10 -5 ) and MAO and boron salt additive solution (where Al / Zr is 120, B / Zr is 1.2) were polymerized for 2 hours, ethanol was added to quench, and then 2% white clay was added to remove the catalyst metal and boride residues; then stirred at 120°C for 2 hours, filtered, and the unreacted α-olefins and alkanes were removed by actual boiling point. Hydrogenation saturation was carried out at 200°C and 4MPa to obtain PAO base oil.

[0059] The viscosity, pour point and other tests were performed on the PAO base oil obtained above. The test results are shown in Table 2 below;

[0060] Table 2

[0061]

[0062]

[0063] From the test data in Table 2 above, it can be seen that it is completely feasible to prepare metallocene PAO using coal-based α-olefins. Through single carbon cutting and deoxidation followed by homopolymerization or copolymerization, metallocene PAO products with a viscosity of 40 to 1000 cSt at 100°C and a pour point of -21 to -60°C can be stably prepared.

Claims

1. A method for preparing a low pour point high viscosity metallocene PAO base oil, characterized in that: The following steps are involved: (1) using the naphtha fraction generated by indirect coal liquefaction as a raw material to perform single carbon cutting treatment to obtain olefins and alkanes having a single carbon atom number; (2) removing oxides from olefins and alkanes having a single carbon number, or mixtures thereof; (3) The mixture after the oxide removal treatment is polymerized under the catalysis of a metallocene catalyst, and the obtained product is quenched, purified, and hydrogenated to obtain a PAO base oil.

2. The preparation method according to claim 1, characterized in that: The distillation range of the naphtha fraction generated by the indirect liquefaction of coal in step (1) is IBP-220°C.

3. The preparation method according to claim 2, characterized in that: The single carbon cutting process is to obtain olefins and alkanes having a single carbon number after distilling the naphtha fraction generated by indirect coal liquefaction.

4. The preparation method according to claim 3, characterized in that: The content of olefins and alkanes with a single carbon number obtained by the single carbon cutting process is ≥ 99wt%; Wherein, the content of the olefin is 20-80wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step (2), deoxidation treatment is performed by countercurrent extraction of the composite extraction solvent and the single carbon mixture; The composite extraction solvent is selected from two or more of ester compounds, glycol compounds, amide compounds, pyrrolidone compounds or diol compounds.

6. The preparation method according to any one of claims 1 to 5, characterized in that In step (3), the metallocene catalyst comprises a main catalyst and an auxiliary agent, wherein the main catalyst is a complex of a transition metal element of Group IVB, and the auxiliary agent is an organic boride and / or an alkyl aluminum.

7. The preparation method according to claim 6, characterized in that: The main catalyst adopts a bridged metallocene catalyst; the bridged metallocene catalyst is selected from one or more of rac-vinyl bridged bis-indenyl zirconium dichloride, rac-ethylene bis(4,5,6,7-tetrahydro-1-indenyl)] zirconium dichloride, rac-dimethylsilyl bridged bis-indenyl zirconium dichloride or rac dimethylsilyl bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride.

8. The preparation method according to any one of claims 1 to 7, characterized in that The polymerization reaction is carried out under anhydrous and oxygen-free conditions and at a reaction temperature of 30 to 150° C. for 0.1 to 5 hours; Preferably, alcohols, water or acids are added to the product obtained by the polymerization reaction for quenching. Preferably, clay or diatomaceous earth is added to the quenched product to remove the catalyst metal and boride therein; The reaction temperature of the hydrogenation is 100-300° C., and the reaction pressure is 2-6 MPa.

9. A low pour point high viscosity metallocene PAO base oil, characterized in that: The method is prepared by any one of claims 1 to 8.

10. The metallocene PAO base oil according to claim 9, characterized in that The metallocene PAO base oil has a viscosity of 40 to 1000 cSt at 100°C and a pour point of -21 to -60°C.

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