A method for preparing low-viscosity PAO lubricant base oil from Fischer-Tropsch synthesis intermediate oil

Abstract

The present invention provides a method for preparing a low-viscosity PAO lubricant base oil from a Fischer-Tropsch intermediate oil. The method comprises: deoxygenating the Fischer-Tropsch intermediate oil, fractionating the resulting deoxygenated Fischer-Tropsch intermediate oil, and mixing the resulting low-temperature distillate and the intermediate-temperature distillate with a polymerization catalyst, optionally containing a portion of the previously removed Fischer-Tropsch oxygenates, to carry out a polymerization reaction. The method improves the quality and diversity of the feedstock for PAO production, enables multi-dimensional matching between product, feedstock, and conditions through flexible product-oriented modulation, and allows for the reuse of oxygenates in the feedstock.

Description

Technical Field

[0001] The present invention belongs to the field of Fischer-Tropsch synthesis product processing, and relates to a method for preparing PAO lubricant base oil from an intermediate oil product of indirect coal liquefaction, and specifically relates to a method for preparing low-viscosity PAO lubricant base oil from an intermediate oil product of Fischer-Tropsch synthesis. Background Art

[0002] With the advancement of global industry, manufacturing technology, and environmental protection requirements, lubricants are facing increasingly demanding operating conditions across various sectors. Demand for high-quality synthetic lubricants with longer drain intervals, improved lubrication performance, and energy-saving and environmentally friendly properties will continue to rise. PAO (polyalphaolefin), a Group IV synthetic lubricant base oil, is highly favored in the high-end lubricant market due to its regular molecular structure, excellent viscosity-temperature performance, low-temperature fluidity, high-temperature oxidation resistance, low volatility, and cleanliness.

[0003] In my country, α-olefins for PAO production are primarily obtained through paraffin cracking, while overseas, α-olefins are primarily obtained through ethylene oligomerization. This process offers significant advantages over the Chinese paraffin cracking method, but there are currently no ethylene oligomerization production facilities in China, and its production technology has long been monopolized by a few foreign chemical companies. Due to the complex composition, wide distillation range, and relatively low α-olefin content of the raw materials produced by the paraffin cracking method, the quality of the resulting PAO products remains significantly lower than that of overseas products, resulting in my country's long-term reliance on imports for high-quality PAO base oils.

[0004] Indirect coal liquefaction (CTL) is a technology that uses syngas (a mixture of CO and H₂) to produce liquid hydrocarbons, primarily through Fischer-Tropsch synthesis, using catalysts and suitable conditions. Based on my country's energy resources, companies such as Ningxia Coal Company of the State Energy Group, Yitai Group, Lu'an Group, Yankuang Group, and Future Energy have completed and commissioned million-ton-scale coal-based Fischer-Tropsch liquefaction (FTSL) projects. α-olefins in FTSL intermediates account for nearly 70% of the liquid phase, with the remainder consisting of normal alkanes and oxygenates, primarily alcohols. After separation, the appropriate fractions can be used to produce PAOs. FTSL intermediates can improve the quality and diversity of PAO feedstock in my country, addressing the current situation of low-quality and limited raw material availability. Using FTSL intermediates to produce PAO base oils can improve the quality of PAO base oils, filling the gap in my country's production of high-quality PAO lubricant base oils, reducing reliance on imports, ensuring energy security, and promoting the healthy and stable development of the coal-to-liquids industry, creating significant economic and social value.

[0005] CN105062555B and CN105885929B each disclose a method for preparing a low-viscosity metallocene PAO base oil. The method uses a coal-based α-olefin fraction (80°C-240°C) from which oxygenates have been removed as a raw material, and a metallocene catalyst solution is added to carry out a polymerization reaction to obtain a low-viscosity PAO lubricant base oil. The patents use metallocene as a catalyst, but the technology is immature and the catalyst is expensive, and the raw material adaptability is weak, making it difficult to implement in actual production processes. Furthermore, in the actual reaction process, the oxygenates in the raw materials are non-ideal components that significantly affect the reaction conversion rate and product yield, so they must be removed in advance, thereby increasing equipment investment costs and wasting resources.

[0006] CN104152176B discloses a method for producing poly-α-olefin synthetic oil using coal-based feedstocks. This method involves separating the crude α-olefin product produced in an indirect coal liquefaction process into α-olefin components with a distillation range of 80°C-275°C and a carbon number of C5-C12. These components are then polymerized in the presence of a catalyst such as AlCl3 or its alcohol complexes to produce a product with a viscosity index greater than 145. The coal-based α-olefin feedstock in this patent contains isomeric and aromatic components and is not a typical coal indirect liquefaction feedstock. Therefore, the comprehensive application of oxygen-containing compounds in the feedstock is not addressed.

[0007] CN105368489B discloses a method for preparing PAO from Fischer-Tropsch oil products. This method uses light oil produced by indirect coal liquefaction as the raw material. The polymerization reaction is performed at a pressure of 10.0-15.0 MPa and a temperature of 300-400°C using a Lewis acid catalyst. The PAO product is obtained through batch polymerization and fixed-bed hydrofining. However, the reaction conditions are harsh, the equipment requirements are too high, and the resulting product brand is relatively limited, which cannot meet market demand.

[0008] In summary, the existing methods for preparing poly-α-olefin synthetic oil using coal-based raw materials all have many shortcomings. Summary of the Invention

[0009] To address the aforementioned issues in the prior art, the present invention provides a method for preparing a low-viscosity PAO lubricant base oil from a Fischer-Tropsch synthesis intermediate oil. This method allows for flexible adjustment of the composition of the reaction feedstock and catalyst based on product requirements to produce a low-viscosity PAO lubricant base oil product. It also allows for the reuse of oxygenated compounds in the feedstock, is environmentally friendly, and significantly reduces energy consumption.

[0010] The present invention provides a method for preparing a low-viscosity PAO lubricant base oil from a Fischer-Tropsch synthesis intermediate oil product, comprising:

[0011] (1) deoxygenating the Fischer-Tropsch synthesis intermediate oil to obtain a Fischer-Tropsch oxygenated compound and a deoxygenated Fischer-Tropsch synthesis intermediate oil;

[0012] (2) fractionating the deoxygenated Fischer-Tropsch synthesis intermediate oil to obtain a low-temperature distillate, a medium-temperature distillate, and a high-temperature distillate;

[0013] (3) using an additive, or a mixture of the additive and a portion of the Fischer-Tropsch oxygenate as a polymerization catalyst, mixing the low-temperature distillate oil and the medium-temperature distillate oil, adding the polymerization catalyst thereto to carry out a polymerization reaction, and post-treating the reaction product to obtain a polymer product to be hydrogenated and a recycled catalyst, wherein the additive comprises AlCl3 and / or FeCl3, and optionally at least one oxygenate selected from the following: alcohol, aldehyde, ketone, acid or ether; wherein the polymerization catalyst contains more than 5 wt% of the oxygenate;

[0014] (4) subjecting the to-be-hydrogenated polymer product to a hydrorefining reaction to obtain a crude polymer oil product;

[0015] (5) fractionating the crude polymerized oil product to obtain the low-viscosity PAO lubricant base oil.

[0016] The exemplary technical solutions provided by the present invention can achieve the following beneficial effects, but are not limited thereto:

[0017] 1. Improve the quality and diversity of raw materials for PAO production to make up for the current situation of low quality and single variety of domestic raw materials;

[0018] 2. Achieve flexible adjustments based on product orientation and form a multi-dimensional match between products, raw materials and conditions;

[0019] 3. Effectively utilizing oxygen-containing compounds in Fischer-Tropsch synthesis intermediate oils, such as Fischer-Tropsch light oil, to prepare polymerization catalysts can improve economic and ecological benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are a part of the specification and provide further explanation of the present invention together with the specific embodiments, but are not intended to limit the scope of protection of the present invention.

[0021] Figure 1 The following is an exemplary process flow chart for preparing low-viscosity PAO lubricant base oil from coal indirect liquefaction products according to the present invention.

[0022] Description of the reference numerals is as follows:

[0023] 1. Fischer-Tropsch intermediate oil; 2. Fischer-Tropsch oxygenates; 3. Deoxygenated Fischer-Tropsch intermediate oil; 4. Extracted oxygenates; 5. Additives; 6. Low-temperature distillate oil; 7. Medium-temperature distillate oil; 8. High-temperature distillate oil; 9. Low-viscosity PAO lubricant base oil;

[0024] I, deoxygenation unit; II, polymerization catalyst preparation unit; III, raw material fractionation unit; IV, storage unit; V, tank reactor 1; VI, tank reactor 2; VII, post-processing unit; VIII, hydrofining unit; IX, product distillation unit. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are described in detail below. The specific embodiments described herein are only used to illustrate and explain the present invention, but are not used to limit the present invention.

[0026] Herein, unless otherwise specified, the term "a portion" refers to any value within the range of greater than 0% and less than 100% relative to the total amount of the object it modifies.

[0027] In this document, unless otherwise specified, the term "low viscosity" means a viscosity less than or equal to 10 mm at 100°C. 2 / s.

[0028] In one embodiment, the present invention relates to a method for preparing a low-viscosity PAO lubricant base oil from a Fischer-Tropsch intermediate oil product, comprising:

[0029] (1) deoxygenating the Fischer-Tropsch synthesis intermediate oil to obtain a Fischer-Tropsch oxygenated compound and a deoxygenated Fischer-Tropsch synthesis intermediate oil;

[0030] (2) fractionating the deoxygenated Fischer-Tropsch synthesis intermediate oil to obtain a low-temperature distillate, a medium-temperature distillate, and a high-temperature distillate;

[0031] (3) using an additive or a mixture of the additive and a portion of the oxygen-containing compound as a polymerization catalyst, mixing the low-temperature distillate oil and the medium-temperature distillate oil, adding the polymerization catalyst thereto, conducting a polymerization reaction, and post-treating the reaction product to obtain a polymer product to be hydrogenated and a recycled catalyst, wherein the additive comprises AlCl3 and / or FeCl3, and optionally at least one oxygen-containing compound selected from the group consisting of an alcohol, an aldehyde, a ketone, an acid, or an ether; wherein the polymerization catalyst contains 5 wt% or more of the oxygen-containing compound;

[0032] (4) subjecting the to-be-hydrogenated polymer product to a hydrorefining reaction to obtain a crude polymer oil product;

[0033] (5) fractionating the crude polymerized oil product to obtain the low-viscosity PAO lubricant base oil.

[0034] In some embodiments, in step (1), the Fischer-Tropsch synthesis middle oil product is Fischer-Tropsch light oil, with a distillation range less than 350 °C, preferably less than 280 °C. Preferably, the Fischer-Tropsch light oil contains 0.1 wt% - 10 wt% of Fischer-Tropsch oxygenates. In this article, the Fischer-Tropsch oxygenates include one or more of C1-C12 alcohols, aldehydes, ketones, acids, or ether oxygenates.

[0035] In some embodiments, in step (1), the deoxygenation can be carried out by a method conventional in the art. For example, any one selected from extraction, physical adsorption, chemical adsorption, or hydrogenation methods can be used for the deoxygenation.

[0036] In some embodiments, in step (2), the fractionation can be carried out by means conventional in the art. For example, atmospheric distillation and vacuum distillation can be used for the fractionation. The operating conditions of the atmospheric distillation and vacuum distillation are conventional operating conditions in the art. For example, the vacuum degree of the vacuum distillation can be 10 - 150 torr (such as 50 - 150 torr, 80 - 150 torr).

[0037] In this article, the low-temperature fraction oil, medium-temperature fraction oil, and high-temperature fraction oil in step (2) are fraction oils with an end boiling point < 125 °C (< C8), fraction oils with an end boiling point between 126 - 216 °C (C8 - C12), and fraction oils with an end boiling point between 217 - 280 °C (C13 - C14), respectively.

[0038] In the present invention, a complex polymerization catalyst is prepared by complexing oxygenates with acidic AlCl3 and FeCl3, which can reduce the acidity of the catalyst, thereby contributing to obtaining a PAO lubricant base oil product with a low viscosity but a high viscosity index. In some embodiments, in step (3), according to the actual requirements of the product viscosity, at least one additional oxygenate selected from alcohols, aldehydes, ketones, acids, or ethers (which may be the same as or different from the Fischer-Tropsch oxygenates obtained in step (1)) can be flexibly added or not added to the additive, so as to adjust the composition of the catalyst at any time during the production process, contributing to obtaining different low-viscosity PAO lubricant base oil products.

[0039] In some preferred embodiments, the alcohol includes n-propanol, n-butanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, 2,2-dimethylbutanol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, trimethylolpropane, glycerol, pentaerythritol, 2-phenyl-2-propanol. In some preferred embodiments, the aldehyde includes propionaldehyde and butyraldehyde. In some preferred embodiments, the ketone includes acetone and butanone. In some preferred embodiments, the acid is acetic acid. In some preferred embodiments, the ether is diethyl ether.

[0040] The inventors have observed that as the oxygenate content in the polymerization catalyst increases, the resulting product viscosity decreases. Therefore, depending on the needs of the production process, a portion of the previously separated Fischer-Tropsch oxygenate can be mixed with the additive to prepare the polymerization catalyst, thereby reducing the need for external oxygenates to a certain extent.

[0041] In some embodiments, in step (3), the additive comprises 20 wt% to 60 wt% of AlCl3 or 0 wt% to 100 wt% of FeCl3.

[0042] In some embodiments, in step (3), the additive comprises 0%-80wt% (e.g., 0wt%, 40wt%, 50wt%, 60wt%, 80wt%) of an oxygen-containing compound. In some preferred embodiments, the oxygen-containing compound contained in the additive can be selected from n-pentanol, isopentanol, n-hexanol, isohexanol, propionaldehyde, butyraldehyde, acetone, and butanone.

[0043] In some embodiments, in step (3), the polymerization catalyst comprises 0 wt%-60 wt% of AlCl3 or 0 wt%-100 wt% of FeCl3, and the content of both is not 0 wt% at the same time.

[0044] In some embodiments, in step (3), the polymerization catalyst contains 5 wt% to 90 wt%, preferably 5 wt% to 85 wt% of an oxygen-containing compound.

[0045] In some embodiments, in step (3), the low-temperature distillate oil and the medium-temperature distillate oil are polymerized under the following conditions: the reaction temperature is 60°C-180°C (e.g., 80°C-160°C), and the reaction pressure is 0-1.0 MPa (e.g., 0.1-1.0 MPa).

[0046] In some embodiments, in step (3), the amount of the polymerization catalyst added is 0.1 wt% to 12 wt% (e.g., 2 wt% to 12 wt%, 3 wt% to 12 wt%, 3.5 wt% to 10 wt%) relative to the sum of the mass of the low-temperature distillate oil and the medium-temperature distillate oil. In some embodiments, in step (3), the mass ratio of the low-temperature distillate oil to the medium-temperature distillate oil is 0:1 to 20:1 (e.g., 0.05:1 to 15:1, 0.08:1 to 12:1, 0.1:1 to 10:1).

[0047] In some embodiments, in step (3), the post-treatment includes: filtration (to recover the catalyst), alkali washing and optional water washing. In some preferred embodiments, 1wt%-10wt% (e.g., 5wt%-10wt%, 5wt%-8wt%) of NaOH aqueous solution or Ca(OH)2 powder can be used for the alkali washing, the temperature of the alkali washing is 40°C-350°C (e.g., 50°C-350°C, 60°C-320°C), and the time of the alkali washing is 0.5-8h (e.g., 1-7h, 1-6h). In some preferred embodiments, the solution after the alkali washing is washed to neutrality by the water washing.

[0048] In some embodiments, in step (3), the recycled catalyst can be recycled back into the polymerization reaction for repeated use.

[0049] In some embodiments, in step (4), the hydrofining reaction is a fixed-bed hydrofining reaction. In some preferred embodiments, the polymer product to be hydrogenated is heated and then introduced from the top of the fixed bed. The hydrogen and the polymer product to be hydrogenated are fully mixed and reacted in the catalyst bed, and then separated by an oil-gas separator, and the obtained polymerized crude oil product is discharged from the bottom. In some preferred embodiments, the fixed-bed hydrofining reaction is carried out under the following conditions: reaction pressure of 4-12 MPa (e.g., 5-10 MPa), reaction temperature of 250°C-360°C (e.g., 280°C-350°C), and space velocity of 1.0-2.0 h -1 Preferably, the catalyst for the fixed-bed hydrotreating reaction is a Ni-Mo catalyst.

[0050] In this article, the low viscosity PAO lubricant base oil is a low viscosity PAO lubricant base oil with a viscosity of 10 mm at 100 ° C. 2 In some embodiments, in step (6), the low viscosity PAO lubricant base oil may include, but is not limited to, PAO4, PAO6, PAO8, and PAO10.

[0051] The exemplary embodiments of the present invention are described below in further detail, but the protection scope of the present invention is not limited thereto.

[0052] The oxygenates in the Fischer-Tropsch middle distillates are removed by any one method selected from extraction, physical adsorption, chemical adsorption or hydrogenation to obtain Fischer-Tropsch oxygenates and deoxygenated Fischer-Tropsch synthesis middle distillates. Among them, the deoxygenated Fischer-Tropsch synthesis middle distillates are subjected to atmospheric distillation and vacuum distillation (for example, the vacuum degree can be 10-150 torr) under conventional conditions to obtain a low-temperature distillate oil with an end boiling point < 125 °C (<C8), a medium-temperature distillate oil with an end boiling point between 126-216 °C (C8-C12), and a high-temperature distillate oil with an end boiling point between 217-280 °C (C13-C14); A part of the optional Fischer-Tropsch oxygenates is mixed with additives (the content of AlCl3 is 0 wt%-60 wt%, the content of FeCl3 is 0 wt%-100 wt%, and the contents of the two are not zero at the same time; the content of oxygenates is 0 wt%-80 wt%) to obtain a polymerization catalyst (which may contain 5 wt%-90 wt% of oxygenates).

[0053] The low-temperature distillate oil and the medium-temperature distillate oil are mixed with the polymerization catalyst, and a polymerization reaction is carried out under the conditions of a reaction temperature of 60-180 °C and a reaction pressure of 0-1.0 MPa. The reaction product is subjected to post-treatments such as filtration (to recover the recycled catalyst), caustic washing, and optional water washing to obtain a hydrogenation polymerization product to be treated and a recycled catalyst; Preferably, the recycled catalyst can be reused in the polymerization reaction.

[0054] The hydrogenation polymerization product to be treated is placed in a fixed-bed hydrogenation reactor, under the conditions of a reaction pressure of 4-12 MPa, a reaction temperature of 250-360 °C, a space velocity of 1.0-2.0 h -1 -1, and the catalyst is a Ni-Mo series catalyst (the metal content in the catalyst is 15 wt%-40 wt% (where the Ni content is greater than 3 wt% and the Mo content is greater than 14 wt%), and the rest is an alumina carrier), a hydrorefining reaction is carried out to obtain a stable crude polymerization oil product. Specifically, during the hydrorefining process, the hydrogenation polymerization product to be treated is heated and then enters from the top of the fixed bed. After hydrogen and the material are fully mixed and reacted in the catalyst bed layer, they are separated by an oil-gas separator, and the finished product is discharged from the bottom. The finished product can enter the finished product tank through a pressure regulating valve. The stable crude polymerization oil product is fractionated by a conventional method known in the art to obtain a low-viscosity PAO lubricant base oil.

[0055] The exemplary technical solutions of the present invention can be described by the following numbered paragraphs:

[0056] 1. A method for preparing a low-viscosity PAO lubricant base oil from Fischer-Tropsch synthesis middle distillates, comprising:

[0057] (1) deoxygenating the Fischer-Tropsch synthesis intermediate oil to obtain a Fischer-Tropsch oxygenated compound and a deoxygenated Fischer-Tropsch synthesis intermediate oil;

[0058] (2) fractionating the deoxygenated Fischer-Tropsch synthesis intermediate oil to obtain a low-temperature distillate, a medium-temperature distillate, and a high-temperature distillate;

[0059] (3) using an additive, or a mixture of the additive and a portion of the Fischer-Tropsch oxygenate as a polymerization catalyst, mixing the low-temperature distillate oil and the medium-temperature distillate oil, adding the polymerization catalyst thereto to carry out a polymerization reaction, and post-treating the reaction product to obtain a polymer product to be hydrogenated and a recycled catalyst, wherein the additive comprises AlCl3 and / or FeCl3, and optionally at least one oxygenate selected from the following: alcohol, aldehyde, ketone, acid or ether; wherein the polymerization catalyst contains more than 5 wt% of the oxygenate;

[0060] (4) subjecting the to-be-hydrogenated polymer product to a hydrorefining reaction to obtain a crude polymer oil product;

[0061] (5) fractionating the crude polymerized oil product to obtain the low-viscosity PAO lubricant base oil.

[0062] 2. The method as described in paragraph 1, wherein, in step (1), the Fischer-Tropsch synthesis intermediate oil product is Fischer-Tropsch light oil, and its distillation range is less than 350°C.

[0063] 3. The method of paragraph 2, wherein the Fischer-Tropsch light oil contains 0.1 wt% to 10 wt% of Fischer-Tropsch oxygenates.

[0064] 4. The method according to any one of paragraphs 1 to 3, wherein in step (1), the deoxygenation is carried out by any one selected from extraction, physical adsorption, chemical adsorption or hydrogenation.

[0065] 5. The method according to any one of paragraphs 1 to 4, wherein, in step (2), the fractionation is performed by atmospheric distillation and reduced pressure distillation.

[0066] 6. The method of any one of paragraphs 1 to 5, wherein in step (3), the alcohol comprises n-propanol, n-butanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, 2,2-dimethylbutanol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, trimethylolpropane, glycerol, pentaerythritol, 2-phenyl-2-propanol; the aldehyde comprises propionaldehyde and butyraldehyde; the ketone comprises acetone and butanone; the acid is acetic acid; and the ether is diethyl ether.

[0067] 7. The method of any one of paragraphs 1 to 6, wherein, in step (3), the additive comprises 20 wt% to 60 wt% of AlCl3 or 0 wt% to 100 wt% of FeCl3.

[0068] 8. The method of any one of paragraphs 1 to 7, wherein in step (3), the additive comprises 0% to 80 wt% of an oxygen-containing compound.

[0069] 9. The method of paragraph 8, wherein, in step (3), the oxygen-containing compound contained in the additive is selected from n-pentanol, isopentanol, n-hexanol, isohexanol, propionaldehyde, butyraldehyde, acetone, and butanone.

[0070] 10. The method of any one of paragraphs 1 to 9, wherein in step (3), the polymerization catalyst comprises 0 wt% to 60 wt% of AlCl3 or 0 wt% to 100 wt% of FeCl3, and the content of both is not 0 wt%.

[0071] 11. The method of any one of paragraphs 1 to 10, wherein in step (3), the polymerization catalyst contains 5 wt% to 90 wt% of an oxygen-containing compound.

[0072] 12. The method of any one of paragraphs 1 to 11, wherein in step (3), the low-temperature distillate oil and the medium-temperature distillate oil are polymerized under the following conditions: a reaction temperature of 60° C. to 180° C. and a reaction pressure of 0 to 1.0 MPa.

[0073] 13. The method as described in any one of paragraphs 1 to 12, wherein in step (3), the amount of the polymerization catalyst added is 0.1 wt% to 12 wt% relative to the mass of the Fischer-Tropsch synthesis intermediate oil product.

[0074] 14. The method according to any one of paragraphs 1 to 13, wherein in step (3), the mass ratio of the low temperature distillate oil to the medium temperature distillate oil is 0:1 to 20:1

[0075] 15. The method of any one of paragraphs 1 to 14, wherein in step (3), the post-treatment comprises: filtration, alkaline washing, and optionally water washing.

[0076] 16. The method of paragraph 15, wherein, in step (3), 1 wt%-10 wt% of NaOH aqueous solution or Ca(OH)2 powder is used for the alkali washing, the alkali washing temperature is 40°C-350°C, and the alkali washing time is 0.5-8h.

[0077] 17. The method according to paragraph 15 or 16, wherein in step (3), the alkali-washed solution is washed to neutrality by the water washing.

[0078] 18. The method of any one of paragraphs 1 to 17, wherein in step (3), the recycled catalyst is recycled back into the polymerization reaction for reuse.

[0079] 19. The method of any one of paragraphs 1 to 18, wherein in step (4), the hydrofining reaction is a fixed-bed hydrofining reaction.

[0080] 20. The method of paragraph 19, wherein the polymer product to be hydrogenated is heated and then introduced into the fixed bed from the top, hydrogen and the polymer product to be hydrogenated are fully mixed and reacted in the catalyst bed, and then separated by an oil-gas separator, and the obtained crude polymer oil product is discharged from the bottom.

[0081] 21. The method of paragraph 19 or 20, wherein the fixed bed hydrofining reaction is carried out under the following conditions: reaction pressure of 4-12 MPa, reaction temperature of 250°C-360°C, space velocity of 1.0-2.0 h -1 .

[0082] 22. The method of any one of paragraphs 19 to 21, wherein the catalyst for the fixed-bed hydrotreating reaction is a Ni-Mo catalyst.

[0083] 23. The method of any one of paragraphs 1 to 22, wherein in step (6), the low viscosity PAO lubricant base oil comprises PAO4, PAO6, PAO8, or PAO10.

[0084] Example

[0085] Unless otherwise specified, the reagents, materials and devices involved in the following examples are all commercially available in the art; the conventional operations involved in the following examples can be found in patents, patent applications and publications disclosed in the art (for example, He Yongde, ed., "Modern Coal Chemical Technology Handbook", Chemical Industry Press, 2003, but not limited thereto).

[0086] The PAO lubricant base oil performance test method in the present invention is as follows:

[0087] Determination of kinematic viscosity of petroleum products: GB / T 265

[0088] Calculation method for viscosity index of petroleum products: GB / T 1995

[0089] Determination of pour point of petroleum products: GB / T 3535

[0090] Determination of flash point of lubricating oil: GB / T 3536-2008.

[0091] The properties of the Fischer-Tropsch light oil used as a raw material in the following examples are shown in the following table:

[0092]

[0093] Example 1

[0094] The Fischer-Tropsch light oil is subjected to an extraction tower extraction method (the extraction agent is sulfolane with a volume ratio of 1: 1 and the extraction time is 2h) to remove oxygenated compounds to obtain Fischer-Tropsch oxygenated compounds and deoxygenated Fischer-Tropsch light oil. Next, the deoxygenated Fischer-Tropsch light oil is subjected to atmospheric distillation (tower top temperature 110°C, tower bottom temperature 230°C, tower plate number 50) and vacuum distillation (vacuum degree is 100torr, tower top temperature 150°C, tower bottom temperature 220°C, tower plate number 50) to obtain low-temperature distillate oil and medium-temperature distillate oil. 20wt% of the obtained Fischer-Tropsch oxygenated compounds are mixed with additives to obtain a polymerization catalyst. The amount of AlCl3 added in the additive is 60wt%, and the amount of n-hexanol added is 40wt%. The amount of oxygenated compounds in the obtained polymerization catalyst is 50wt%.

[0095] A low-temperature distillate oil and a medium-temperature distillate oil were mixed in a mass ratio of 0.1:1, and then 10 wt% (relative to the total mass of the low-temperature distillate oil and the medium-temperature distillate oil) of the above-mentioned polymerization catalyst was added thereto. A polymerization reaction was carried out at a reaction temperature of 160° C. and a reaction pressure of 0.1 MPa. The reaction product was filtered to recover the catalyst, and then alkali-washed with a 5 wt% NaOH aqueous solution at 60° C. for 1 hour, and then washed with water until neutral, to obtain a polymerization product to be hydrogenated and a recycled catalyst.

[0096] The polymer product to be hydrogenated is placed in a fixed bed hydrogenation reactor at a reaction pressure of 10.0 MPa, a reaction temperature of 350°C, and a space velocity of 1 h -1 , a hydrorefining reaction was carried out under the conditions of a Ni-Mo catalyst (wherein the Ni content was 3wt%, the Mo content was 24wt%, and the rest was an aluminum oxide carrier) to obtain a crude polymer oil product with stable properties. Thereafter, a true boiling point apparatus was used for fractional distillation under a vacuum degree of 10 torr to obtain a distillate oil with a temperature greater than 340°C, which is the PAO-10 lubricant base oil product. The specific results are shown in Table 1.

[0097] Example 2

[0098] The Fischer-Tropsch light oil is subjected to conventional physical adsorption methods in the art (the adsorbent is aluminum oxide, and the adsorption time is 2 hours) to remove oxygenated compounds to obtain Fischer-Tropsch oxygenated compounds and deoxygenated Fischer-Tropsch light oil. Next, the deoxygenated Fischer-Tropsch light oil is subjected to atmospheric distillation (tower top temperature 110°C, tower bottom temperature 230°C, tower plate number 50) and reduced pressure distillation (vacuum degree is 100 torr, tower top temperature 150°C, tower bottom temperature 220°C, tower plate number 50) to obtain low-temperature distillate oil and medium-temperature distillate oil. 25wt% of the obtained Fischer-Tropsch oxygenated compounds are mixed with additives to obtain a polymerization catalyst. The amount of AlCl3 added in the additive is 50wt%, the amount of propionaldehyde added is 50wt%, and the amount of oxygenated compounds added in the obtained polymerization catalyst is 60wt%.

[0099] Low-temperature distillate oil and medium-temperature distillate oil are mixed in a mass ratio of 0.8:1, and then 8 wt% (relative to the total mass of the low-temperature distillate oil and the medium-temperature distillate oil) of the above-mentioned polymerization catalyst is added thereto. A polymerization reaction is carried out at a reaction temperature of 140°C and a reaction pressure of 0.3 MPa. The reaction product is filtered to recover the catalyst and treated with alkali washing with Ca(OH)2 powder at 280°C for 6 hours to obtain a polymerization product to be hydrogenated and a recycled catalyst.

[0100] The polymer product to be hydrogenated is placed in a fixed bed hydrogenation reactor at a reaction pressure of 8.0 MPa, a reaction temperature of 320°C, and a space velocity of 1.5 h -1 , a hydrorefining reaction was carried out under the conditions of a Ni-Mo catalyst (wherein the Ni content was 3wt%, the Mo content was 23wt%, and the rest was an aluminum oxide carrier) to obtain a crude polymer oil product with stable properties. Thereafter, a true boiling point apparatus was used for fractional distillation under a vacuum degree of 10 torr to obtain a distillate oil with a temperature greater than 330°C, which is the PAO-8 lubricant base oil product. The specific results are shown in Table 1.

[0101] Example 3

[0102] The Fischer-Tropsch light oil is subjected to chemical adsorption (the adsorbent is a microporous molecular sieve and the adsorption time is 1.5h) to remove oxygenated compounds to obtain Fischer-Tropsch oxygenated compounds and deoxygenated Fischer-Tropsch light oil. Next, the deoxygenated Fischer-Tropsch light oil is subjected to atmospheric distillation (tower top temperature 115°C, tower bottom temperature 240°C, tower plate number 50) and vacuum distillation (vacuum degree is 150torr, tower top temperature 160°C, tower bottom temperature 228°C, tower plate number 52) to obtain low-temperature distillate oil and medium-temperature distillate oil. 30wt% of the obtained Fischer-Tropsch oxygenated compounds are mixed with additives to obtain a polymerization catalyst. The amount of AlCl3 added to the additive is 20wt%, and the amount of butanone added is 80wt%. The amount of oxygenated compounds added to the obtained polymerization catalyst is 84.60wt%.

[0103] Low-temperature distillate oil and medium-temperature distillate oil are mixed in a mass ratio of 2:1, and then 6.2 wt% (relative to the total mass of the low-temperature distillate oil and the medium-temperature distillate oil) of the above-mentioned polymerization catalyst is added thereto. A polymerization reaction is carried out at a reaction temperature of 120°C and a reaction pressure of 0.5 MPa. The reaction product is filtered to recover the catalyst and treated with alkali washing with Ca(OH)2 powder at 320°C for 4 hours to obtain a polymerization product to be hydrogenated and a recycled catalyst.

[0104] The polymer product to be hydrogenated is placed in a fixed bed hydrogenation reactor at a reaction pressure of 6.5 MPa, a reaction temperature of 300°C, and a space velocity of 1.8 h -1 , a Ni-Mo catalyst (wherein the Ni content is 3.2wt%, the Mo content is 27wt%, and the rest is an aluminum oxide carrier) was used for a hydrorefining reaction to obtain a crude polymer oil product with stable properties. Thereafter, a true boiling point apparatus was used for fractionation under a vacuum degree of 10 torr to obtain a distillate oil with a temperature greater than 320°C, which is the PAO-6 lubricant base oil product. The specific results are shown in Table 1.

[0105] Example 4

[0106] The Fischer-Tropsch light oil is subjected to an extraction method (the extraction agent is methanol in a volume ratio of 1:1, and the extraction time is 1.5 hours) to remove oxygenated compounds to obtain Fischer-Tropsch oxygenated compounds and deoxygenated Fischer-Tropsch light oil. Next, the deoxygenated Fischer-Tropsch light oil is subjected to atmospheric distillation (tower top temperature 108°C, tower bottom temperature 225°C, tower plate number 40) and vacuum distillation (vacuum degree 80 torr, tower top temperature 155°C, tower bottom temperature 206°C, tower plate number 55) to obtain low-temperature distillate oil and medium-temperature distillate oil. 5wt% of the obtained Fischer-Tropsch oxygenated compounds are mixed with the additive FeCl3 to obtain a polymerization catalyst. The amount of FeCl3 added to the obtained polymerization catalyst is 95wt%, and the amount of oxygenated compounds added is 5wt%.

[0107] A low-temperature distillate oil and a medium-temperature distillate oil were mixed in a mass ratio of 10:1, and then 3.8 wt% (relative to the total mass of the low-temperature distillate oil and the medium-temperature distillate oil) of the above-mentioned polymerization catalyst was added thereto. A polymerization reaction was carried out at a reaction temperature of 80° C. and a reaction pressure of 1 MPa. The reaction product was filtered to recover the catalyst, and then alkali-washed with an 8 wt% NaOH aqueous solution at 80° C. for 1 hour and then washed with water until neutral to obtain a polymerization product to be hydrogenated and a recycled catalyst.

[0108] The polymer product to be hydrogenated is placed in a fixed bed hydrogenation reactor at a reaction pressure of 5 MPa, a reaction temperature of 280°C, and a space velocity of 2.0 h -1, a hydrogenation refining reaction was carried out under the conditions of a Ni-Mo catalyst (wherein the Ni content was 3.2wt%, the Mo content was 27wt%, and the rest was an aluminum oxide carrier) to obtain a crude polymer oil product with stable properties. Thereafter, a true boiling point apparatus was used for fractional distillation under a vacuum degree of 50 torr to obtain a distillate oil with a temperature greater than 310°C, which is the PAO-4 lubricant base oil product. The specific results are shown in Table 1.

[0109] Table 1 Analysis results of the products of each embodiment

[0110] Example Brand <![CDATA[Viscosity at 100 °C, mm 2 / s]]> Viscosity Index Pour point / ℃ Example 1 PAO-10 10.2 139 <-50 Example 2 PAO-8 7.9 136 <-50 Example 3 PAO-6 6.3 130 <-50 Example 4 PAO-4 4.4 125 <-50

Claims

1. A method for preparing a low-viscosity PAO lubricant base oil from a Fischer-Tropsch intermediate oil product, comprising: (1) deoxygenating a Fischer-Tropsch synthesis intermediate oil product to obtain a Fischer-Tropsch oxygenate and a deoxygenated Fischer-Tropsch synthesis intermediate oil product, wherein the Fischer-Tropsch synthesis intermediate oil product is a Fischer-Tropsch light oil having a distillation range of less than 350° C., and the Fischer-Tropsch light oil contains 0.1 wt % to 10 wt % of the Fischer-Tropsch oxygenate; (2) fractionating the deoxygenated Fischer-Tropsch synthesis intermediate oil to obtain a low-temperature distillate, a medium-temperature distillate, and a high-temperature distillate; (3) using an additive, or a mixture of the additive and a portion of the Fischer-Tropsch oxygenate as a polymerization catalyst, mixing the low-temperature distillate oil and the medium-temperature distillate oil, adding the polymerization catalyst thereto to carry out a polymerization reaction, and post-treating the reaction product to obtain a polymer product to be hydrogenated and a recycled catalyst, wherein the additive comprises AlCl3 and / or FeCl3, and at least one oxygenate selected from the following: alcohol, aldehyde, ketone, acid or ether; wherein the polymerization catalyst contains more than 5 wt% of the oxygenate; (4) subjecting the to-be-hydrogenated polymer product to a hydrorefining reaction to obtain a crude polymer oil product; (5) fractionating the crude polymerized oil product to obtain the low-viscosity PAO lubricant base oil.

2. The method according to claim 1, wherein In step (1), the deoxygenation is carried out by any one method selected from extraction, physical adsorption, chemical adsorption or hydrogenation.

3. The method according to claim 1, wherein In step (2), the fractionation is carried out by atmospheric distillation and reduced pressure distillation.

4. The method according to any one of claims 1 to 3, wherein In step (3), the alcohol includes n-propanol, n-butanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, 2,2-dimethylbutanol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, trimethylolpropane, glycerol, pentaerythritol or 2-phenyl-2-propanol; the aldehyde includes propionaldehyde or butyraldehyde; the ketone includes acetone or butanone; the acid is acetic acid; and the ether is diethyl ether.

5. The method according to any one of claims 1 to 3, wherein In step (3), the additive comprises 20 wt% to 60 wt% of AlCl3.

6. The method according to any one of claims 1 to 3, wherein In step (3), the additive comprises 40% to 80 wt% of an oxygen-containing compound.

7. The method according to claim 6, wherein: In step (3), the oxygen-containing compound contained in the additive is selected from n-pentanol, isopentanol, n-hexanol, isohexanol, propionaldehyde, butyraldehyde, acetone or butanone.

8. The method according to any one of claims 1 to 3, wherein In step (3), the polymerization catalyst contains 5 wt% to 90 wt% of an oxygen-containing compound.

9. The method according to any one of claims 1 to 3, wherein In step (3), the low-temperature distillate oil and the medium-temperature distillate oil are subjected to polymerization reaction under the following conditions: reaction temperature is 60° C.-180° C., and reaction pressure is 0-1.0 MPa.

10. The method according to any one of claims 1 to 3, wherein In step (3), the amount of the polymerization catalyst added is 0.1 wt% to 12 wt% relative to the sum of the mass of the low-temperature distillate oil and the medium-temperature distillate oil.

11. The method according to any one of claims 1 to 3, wherein In step (3), the mass ratio of the low-temperature distillate oil to the medium-temperature distillate oil is 0.1:1 to 20:

1.

12. The method according to any one of claims 1 to 3, wherein In step (3), the post-treatment includes: filtration and alkali washing.

13. The method of claim 12, wherein: In step (3), the post-treatment further includes water washing.

14. The method of claim 12, wherein: In step (3), 1 wt% to 10 wt% NaOH aqueous solution is used for the alkali washing, the temperature of the alkali washing is 40° C. to 350° C., and the time of the alkali washing is 0.5 to 8 h.

15. The method of claim 13, wherein: In step (3), the alkali-washed solution is washed to neutrality by water washing.

16. The method according to any one of claims 1 to 3, wherein In step (3), the recycled catalyst is recycled back into the polymerization reaction for repeated use.

17. The method according to any one of claims 1 to 3, wherein In step (4), the hydrofining reaction is a fixed-bed hydrofining reaction.

18. The method of claim 17, wherein: The polymer product to be hydrogenated is heated and then enters from the top of the fixed bed. The hydrogen and the polymer product to be hydrogenated are fully mixed and reacted in the catalyst bed. The mixture is then separated by an oil-gas separator and the obtained crude polymer oil product is discharged from the bottom.

19. The method of claim 18, wherein: The fixed bed hydrofining reaction is carried out under the following conditions: reaction pressure of 4-12 MPa, reaction temperature of 250°C-360°C, space velocity of 1.0-2.0 h -1 .

20. The method according to claim 18 or 19, wherein The catalyst for the fixed-bed hydrotreating reaction is a Ni-Mo catalyst.

21. The method of any one of claims 1 to 3, wherein: In step (6), the low-viscosity PAO lubricant base oil includes PAO4, PAO6, PAO8 or PAO10.

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