Separation system of poly-alpha-olefin reaction product and process for separating poly-alpha-olefin

Abstract

The invention provides a separation system of a poly-alpha-olefin reaction product and a process for separating poly-alpha-olefin. The poly-alpha-olefin reaction product is a poly-alpha-olefin product system obtained by carrying out polymerization reaction on raw materials comprising a BF3 gas catalyst and alpha-olefin and BF3 gas after the polymerization reaction; the separation system comprises a fractionating tower, a compressor, an alkaline washing tower and a water washing tower, the fractionating tower is used for fractionating the poly-alpha-olefin product system to obtain first BF3 gas and crude poly-alpha-olefin liquid; the compressor is used for compressing the first BF3 gas and the BF3 gas after the polymerization reaction to obtain second BF3 gas; the alkaline washing tower is used for carrying out alkaline washing on the crude poly-alpha-olefin liquid to obtain poly-alpha-olefin liquid subjected to alkaline washing; the water washing tower is used for washing the poly-alpha-olefin liquid subjected to alkali washing to obtain poly-alpha-olefin. The separation system can effectively shorten the separation process of the poly-alpha-olefin reaction product and improve the separation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of separation of poly-alpha-olefin reaction products, and in particular to a separation system of poly-alpha-olefin reaction products and a process for separating poly-alpha-olefin. Background Art

[0002] Polyalphaolefin (PAO) has a regular chemical structure, and has the characteristics of high viscosity index, low pour point, low low-temperature viscosity and excellent thermal oxidation stability, making it an ideal synthetic base oil. At present, the catalytic system in the synthesis of polyalphaolefin (PAO) base oil in China mostly uses AlCl3 as a catalyst, so there are problems such as large solid waste emissions.

[0003] The main method for producing PAO in foreign industry is olefin polymerization. This process uses ethylene and other low molecular weight olefins as raw materials to produce PAO by polymerization of 1-decene intermediates. In addition to the different operating conditions and specific process due to the use of different catalyst systems, the production process of PAO can be roughly divided into: (1) polymerization of ethylene and other low molecular weight olefins into α-olefins (C4~C 30 ) and separation; (2) further polymerizing the main raw material 1-decene (content of about 25%), and saturating the polymer by hydrogenation to obtain PAO base oil. Domestically, wax cracking α-olefins are mainly used as raw materials, and the polymerization method is usually trimerization or tetramerization. The obtained crude polymer liquid is refined with white clay and lime to remove impurities such as colloids and residual catalysts, and then after atmospheric and vacuum refining and hydrogenation refining, various specifications of PAO products are obtained.

[0004] The U.S. patent application with the patent application publication number US3763244A provides a method for catalyzing conventional α-olefins (C6~C 16 ) A method for preparing a low pour point lubricating oil. The U.S. patent application with a patent application publication number of US3742082A provides a method for synthesizing olefin polymers from α-olefins using BF3 as a catalyst and phosphoric acid or water as a co-catalyst. In the above patents, water or water and other substances are used as co-catalysts, which easily leads to corrosion problems, thereby greatly increasing the investment cost of the device. The U.S. patent application with a patent application publication number of US4227027A recovers boron trifluoride by adding a polyol containing more than two hydrocarbon groups, but this method easily introduces impurities, thereby causing catalyst accumulation. The U.S. patent application with a patent application publication number of US6410812B1 uses alcohols such as butanol for complex separation and recovers BF3 in the flash gas at the top of the flash tank, but this method is very likely to cause excessive accumulation of BF3 complexes.

[0005] At present, in the technical scheme of using BF3 to synthesize low-viscosity PAO lubricating oil, it is necessary to add water or alcohol co-catalyst during the polymerization reaction. The addition of alcohol catalyst not only makes the catalyst and product fractionation process overly complicated, but also has poor separation effect. There are also problems such as corrosion aggravation caused by the addition of water. The Chinese patent application with patent application publication number CN115678600A provides a method for stripping the polymerization product using an inert gas, but the stripping of the inert gas will make the recovery, purification and reuse of BF3 more difficult. Therefore, it is urgent to develop a separation and treatment method for the reaction product of continuous production of poly-alpha-olefins. Summary of the invention

[0006] The main purpose of the present invention is to provide a separation system for poly-α-olefin reaction products and a process for separating poly-α-olefins, so as to solve the problems of long separation process and poor separation effect of poly-α-olefin reaction products in the prior art.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a separation system for polyα-olefin reaction products is provided, wherein the polyα-olefin reaction product is a polyα-olefin product system and BF3 gas obtained by subjecting raw materials including a BF3 gas catalyst and an α-olefin to a polymerization reaction; the separation system is used to separate the polyα-olefin reaction product; the separation system comprises: a fractionation tower, a compressor, an alkali washing tower and a water washing tower, the fractionation tower having a fractionation tower body inlet, a fractionation tower top outlet and a fractionation tower bottom outlet, the fractionation tower inlet is used to introduce the polyα-olefin product system, the fractionation tower is used to fractionate the polyα-olefin product system to obtain a first BF3 gas and a crude polyα-olefin liquid; the compressor has a compressor inlet and a compressor outlet, the compressor inlet is connected to the fractionation tower top outlet, and the compressor outlet is connected to the compressor outlet. The compressor is used for compressing the first BF3 gas and the BF3 gas after the polymerization reaction to obtain the second BF3 gas; the second BF3 gas is used as the BF3 gas catalyst for the polymerization reaction; the alkali washing tower has an alkali washing tower top inlet, an alkali washing tower top outlet, an alkali washing tower bottom inlet and an alkali washing tower bottom outlet, the alkali washing tower top inlet is connected to the alkali liquid source, the fractionation tower bottom inlet is connected to the crude poly-α-olefin liquid, the alkali washing tower is used for alkali washing the crude poly-α-olefin liquid to obtain the alkali-washed poly-α-olefin liquid and the waste alkali liquid; the water washing tower has a water washing tower top inlet, a water washing tower top outlet, a water washing tower bottom inlet and a water washing tower bottom outlet, the water washing tower top inlet is connected to the water washing liquid source, the alkali washing tower bottom inlet is connected to the alkali-washed poly-α-olefin liquid, the water washing tower is used for water washing the alkali-washed poly-α-olefin liquid to obtain the poly-α-olefin and waste water.

[0008] Furthermore, the distillation tower is a packed tower, the packing in the distillation tower is a random packing or a structured packing, the number of theoretical plates of the distillation tower is 2 to 10; the whole tower pressure drop of the distillation tower is ≤5kPa; and / or the distillation tower includes two packed beds, and the poly-α-olefin reaction product is arranged between the packed beds.

[0009] Furthermore, the top of the distillation tower is condensed by an inserted coil, and a refrigerant medium is introduced into the inserted coil for temperature control; and / or the temperature of the refrigerant medium is -8 to 0°C; and / or the top temperature of the distillation tower is 2 to 8°C; and / or the top pressure of the distillation tower is 0.15 to 0.4 MPa (G); and / or the separation system also includes a feed heat exchanger, which is used for performing a first heat exchange on the poly-α-olefin reaction product, and the outlet temperature of the feed heat exchanger is 115 to 130°C; and / or a distillation tower reboiler is provided at the bottom of the distillation tower, and the distillation tower reboiler is used to provide a heat source to the distillation tower, and the bottom temperature of the distillation tower is 200 to 250°C.

[0010] Furthermore, a feed heat exchanger, an air cooler and a water cooler are sequentially arranged on the connecting pipelines of the fractionation tower and the alkali washing tower, and the feed heat exchanger, the air cooler and the water cooler are used to perform a second heat exchange, air cooling and water cooling on the crude poly-alpha-olefin liquid in sequence.

[0011] Furthermore, a booster pump is provided on the connecting pipeline between the fractionation tower and the feed heat exchanger, and the booster pump is used to increase the pressure of the crude poly-alpha-olefin liquid.

[0012] Furthermore, the alkali washing tower is a packed tower, the packing in the alkali washing tower is a random packing or a structured packing, the theoretical number of plates of the alkali washing tower is 2 to 10, and the whole tower pressure drop of the alkali washing tower is ≤5kPa.

[0013] Furthermore, the water washing tower is a packed tower, the packing in the water washing tower is a random packing or a structured packing, the theoretical number of plates of the water washing tower is 2 to 10, and the whole tower pressure drop of the water washing tower is ≤5kPa.

[0014] According to another aspect of the present invention, there is provided a process for separating poly-α-olefins using the above-mentioned separation system, the process comprising: subjecting a raw material including a BF3 gas catalyst and an α-olefin to a polymerization reaction to obtain a poly-α-olefin product system and the BF3 gas after the polymerization reaction as a poly-α-olefin reaction product; fractionating the poly-α-olefin product system to obtain a first BF3 gas and a crude poly-α-olefin liquid; mixing the first BF3 gas and the BF3 gas after the polymerization reaction and compressing them to obtain a second BF3 gas; sequentially subjecting the crude poly-α-olefin liquid to alkali washing and water washing to obtain a poly-α-olefin; and using the second BF3 gas as a catalyst for the polymerization reaction.

[0015] Further, the temperature of the poly-α-olefin product system is 20-60°C, the pressure of the poly-α-olefin product system is 0.2-0.5 MPa(G); and / or the pressure of the second BF3 gas is 0.2-0.6 MPa(G); and / or the temperature of the crude poly-α-olefin liquid is 20-60°C.

[0016] Further, the crude poly-α-olefin liquid is alkali-washed with alkali liquid to obtain alkali-washed poly-α-olefin, wherein the alkali liquid comprises an alkaline solution and a first deionized water; the volume ratio of the alkaline solution to the first deionized water is 1:10 to 1:20; the volume ratio of the alkali liquid to the crude poly-α-olefin liquid is 1:10 to 1:20; and / or, the alkali-washed poly-α-olefin is washed with a water washing liquid, the water washing liquid comprises a second deionized water, and the volume ratio of the second deionized water to the alkali-washed poly-α-olefin is 1:10 to 1:20.

[0017] By applying the technical scheme of the present invention, the separation system of the polyα-olefin reaction product provided by the present invention can effectively shorten the separation process of the polyα-olefin reaction product and improve the separation effect of the polyα-olefin reaction product, especially for the separation process of the polyα-olefin reaction product in the continuous production process of polyα-olefin using BF3 gas as a catalyst. The first BF3 gas and the crude polyα-olefin liquid can be effectively separated from the polyα-olefin product system by a fractionation tower. By recovering the BF3 gas after the polymerization reaction and the unreacted first BF3 gas in the separation system and passing it into the compressor by pressure control, it can be used as a catalyst for polymerization reaction, thereby improving the utilization rate of BF3 gas and reducing the consumption of catalyst, thereby reducing production costs. By adopting a countercurrent contact method and using an alkali washing tower and a water washing tower to further treat the crude polyα-olefin liquid in turn, the BF3 remaining in the crude polyα-olefin liquid can be removed, and most of the waste alkali liquid after alkali washing and the waste water after water washing can be recycled, thereby saving the system operation cost. In addition, the polyα-olefin obtained by the separation system of the present invention can be used as a raw material for subsequent oil processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A schematic diagram of a separation system for poly-alpha-olefin reaction products of the present application is shown.

[0020] The above drawings include the following reference numerals:

[0021] 1. Distillation tower; 2. Compressor; 3. Alkali washing tower; 4. Water washing tower; 5. Feed heat exchanger; 6. Distillation tower reboiler; 7. Air cooler; 8. Water cooler; 9. Temperature control valve group A; 10. Temperature control valve group B; 11. Pressure control valve group C; 12. Pressure control valve group D; 13. Temperature control valve group E; 14. Liquid level control valve group F; 15. Liquid level control valve group G; 16. Flow control valve group H; 17. Flow control valve group I; 18. Interface control valve group J; 19. Flow control valve group K; 20. Flow control valve group L; 21. Interface control valve group M; 22. Flow control valve group N. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As analyzed in the background technology of this application, the prior art has the problem of long separation process and poor separation effect of poly-α-olefin reaction products. In order to solve the above problems, this application provides a separation system for poly-α-olefin reaction products and a process for separating poly-α-olefins.

[0024] In a typical embodiment of the present application, a separation system for poly-α-olefin reaction products is provided, wherein the poly-α-olefin reaction products are a poly-α-olefin product system obtained by polymerizing a raw material including a BF3 gas catalyst and an α-olefin and a BF3 gas after the polymerization reaction; the separation system is used to separate the poly-α-olefin reaction products; Figure 1 As shown, the separation system comprises: a fractionation tower 1, a compressor 2, an alkali washing tower 3 and a water washing tower 4, the fractionation tower 1 has a fractionation tower body inlet, a fractionation tower top outlet and a fractionation tower bottom outlet, the fractionation tower inlet is used to introduce a poly-α-olefin product system, the fractionation tower 1 is used to fractionate the poly-α-olefin product system to obtain a first BF3 gas and a crude poly-α-olefin liquid; the compressor 2 has a compressor inlet and a compressor outlet, the compressor inlet is connected to the fractionation tower top outlet, the compressor 2 is used to compress the first BF3 gas and the BF3 gas after the polymerization reaction to obtain a second BF3 gas; the second BF3 gas is used as BF3 in the polymerization reaction 3 gas catalyst; alkali washing tower 3 has an alkali washing tower top inlet, an alkali washing tower top outlet, an alkali washing tower bottom inlet and an alkali washing tower bottom outlet, the alkali washing tower top inlet is connected to the alkali liquid source, the fractionation tower bottom inlet is connected to the crude poly-α-olefin liquid, and the alkali washing tower 3 is used to alkali wash the crude poly-α-olefin liquid to obtain alkali-washed poly-α-olefin liquid and waste alkali liquid; water washing tower 4 has a water washing tower top inlet, a water washing tower top outlet, a water washing tower bottom inlet and a water washing tower bottom outlet, the water washing tower top inlet is connected to the water washing liquid source, the alkali washing tower bottom inlet is connected to the alkali-washed poly-α-olefin liquid, and the water washing tower 4 is used to wash the alkali-washed poly-α-olefin liquid to obtain poly-α-olefin and waste water.

[0025] The separation system of polyalpha-olefin reaction products provided by the present invention can effectively shorten the separation process of polyalpha-olefin reaction products and improve the separation effect of polyalpha-olefin reaction products, especially for the separation process of polyalpha-olefin reaction products in the continuous production process of polyalpha-olefin using BF3 gas as a catalyst. The first BF3 gas and crude polyalpha-olefin liquid can be effectively separated from the polyalpha-olefin product system by the fractionation tower 1. By recovering the BF3 gas after the polymerization reaction and the unreacted first BF3 gas in the separation system and passing it into the compressor 2 by pressure control, it can be used as a catalyst for polymerization reaction, thereby improving the utilization rate of BF3 gas and reducing the consumption of catalyst, thereby reducing production costs. By adopting a countercurrent contact method and using an alkali washing tower 3 and a water washing tower 4 to further treat the crude polyalpha-olefin liquid in turn, the BF3 remaining in the crude polyalpha-olefin liquid can be removed, and most of the waste alkali liquid after alkali washing and the waste water after water washing can be recycled, thereby saving the system operation cost. In addition, the polyalpha-olefin obtained by the separation system of the present invention can be used as a raw material for subsequent oil processing.

[0026] In one embodiment of the present application, the distillation tower 1 is a packed tower, the packing in the distillation tower 1 is a random packing or a structured packing, the number of theoretical plates of the distillation tower 1 is 2 to 10; the full-tower pressure drop of the distillation tower 1 is ≤5 kPa; and / or the distillation tower 1 includes two packed beds, and the poly-α-olefin reaction product is arranged between the packed beds.

[0027] It is preferred that the fractionation tower 1 has two packed beds and uses the above-mentioned packing, and the poly-α-olefin reaction product is arranged between the two packed beds, which helps to achieve a more refined and more complete separation of the poly-α-olefin reaction product. It is preferred that the theoretical plate number and the full tower pressure drop of the fractionation tower 1 are within the above ranges, which helps to reduce energy consumption and operating costs, and also helps to maintain the stability and continuity of the entire process.

[0028] In one embodiment of the present application, the top of the distillation tower 1 is condensed by an inserted coil, and a refrigerant medium is introduced into the inserted coil for temperature control; and / or, the temperature of the refrigerant medium is -8 to 0°C; and / or, the top temperature of the distillation tower 1 is 2 to 8°C; and / or, the top pressure of the distillation tower 1 is 0.15 to 0.4 MPa (G); and / or, the separation system also includes a feed heat exchanger 5, which is used for performing a first heat exchange on the poly-α-olefin reaction product, and the outlet temperature of the feed heat exchanger 5 is 115 to 130°C; and / or, a distillation tower reboiler 6 is provided at the bottom of the distillation tower 1, and the distillation tower reboiler 6 is used to provide a heat source to the distillation tower 1, and the bottom temperature of the distillation tower 1 is 200 to 250°C.

[0029] Preferably, the top of the fractionation tower 1 is condensed by inserting a coil, and a refrigerant medium in the above temperature range is introduced into the inserting coil, which helps to accurately control the top temperature of the fractionation tower 1, thereby facilitating the effective recovery of BF3 gas, thereby reducing the loss of the catalyst. Preferably, the top temperature and top pressure of the fractionation tower 1 are controlled within the above range, which helps to maintain the operational stability of the entire fractionation process, thereby improving the separation effect of the polyalphaolefin reaction product. The above-mentioned feed heat exchanger 5 is used and the outlet temperature of the feed heat exchanger 5 is preferably controlled within the above range, which helps to heat the polyalphaolefin reaction product, thereby making it easier to separate the BF3 gas from the liquid, thereby improving its separation efficiency. The above-mentioned fractionation tower reboiler 6 is used to provide a heat source to the fractionation tower 1, which helps to keep the bottom temperature of the fractionation tower 1 within the above range, thereby helping to further improve the separation effect of the first BF3 gas and the crude polyalphaolefin liquid.

[0030] In one embodiment of the present application, a feed heat exchanger 5, an air cooler 7 and a water cooler 8 are sequentially arranged on the connecting pipelines of the distillation tower 1 and the alkali washing tower 3. The feed heat exchanger 5, the air cooler 7 and the water cooler 8 are used to perform a second heat exchange, air cooling and water cooling on the crude poly-α-olefin liquid in sequence.

[0031] It is preferred to use the above-mentioned feed heat exchanger 5, air cooler 7 and water cooler 8 to perform the second heat exchange, air cooling and water cooling on the crude poly-α-olefin liquid in sequence, which helps to further control the temperature of the crude poly-α-olefin liquid, so that the temperatures of the second heat exchange, air cooling and water cooling are reduced in sequence, thereby facilitating subsequent alkali washing and water washing.

[0032] In one embodiment of the present application, a booster pump is provided on the connecting pipeline between the fractionation tower 1 and the feed heat exchanger 5 , and the booster pump is used to increase the pressure of the crude poly-α-olefin liquid.

[0033] The booster pump is provided to facilitate the crude poly-α-olefin liquid output from the bottom outlet of the fractionation tower 1 to be passed into the feed heat exchanger 5 for subsequent heat exchange process.

[0034] In one embodiment of the present application, the alkali washing tower 3 is a packed tower, the packing in the alkali washing tower 3 is a random packing or a structured packing, the theoretical number of plates of the alkali washing tower 3 is 2 to 10, and the full tower pressure drop of the alkali washing tower 3 is ≤5 kPa.

[0035] It is preferred to use an alkali washing tower 3 with the above-mentioned filler, and control the theoretical plate number and the full-tower pressure drop of the alkali washing tower 3 within the above-mentioned range, which helps to achieve sufficient contact between the crude poly-α-olefin liquid entering from the bottom inlet of the tower and the alkali solution entering from the top inlet of the tower through full-tower countercurrent contact, thereby better removing the residual BF3 in the crude poly-α-olefin liquid, and further improving the purity and quality of the poly-α-olefin product.

[0036] In one embodiment of the present application, the water washing tower 4 is a packed tower, the packing in the water washing tower 4 is a random packing or a structured packing, the theoretical number of plates of the water washing tower 4 is 2 to 10, and the full tower pressure drop of the water washing tower 4 is ≤5 kPa.

[0037] It is preferred to use a water washing tower 4 with the above-mentioned filler, and control the theoretical plate number and the full-tower pressure drop of the water washing tower 4 within the above-mentioned range, which helps to achieve full contact between the alkali-washed poly-α-olefin liquid entering from the bottom inlet of the tower and the water washing liquid entering from the top inlet of the tower through full-tower countercurrent contact, thereby helping to remove the alkali liquid carried in the alkali-washed poly-α-olefin liquid, thereby further improving the purity and quality of the poly-α-olefin.

[0038] In another typical embodiment of the present application, a process for separating poly-α-olefins using the above-mentioned separation system is provided, and the process comprises: subjecting a raw material including a BF3 gas catalyst and an α-olefin to a polymerization reaction to obtain a poly-α-olefin product system and the BF3 gas after the polymerization reaction as a poly-α-olefin reaction product; fractionating the poly-α-olefin product system to obtain a first BF3 gas and a crude poly-α-olefin liquid; mixing the first BF3 gas and the BF3 gas after the polymerization reaction and compressing them to obtain a second BF3 gas; sequentially subjecting the crude poly-α-olefin liquid to alkali washing and water washing to obtain a poly-α-olefin; and using the second BF3 gas as a catalyst for the polymerization reaction.

[0039] The process for separating polyα-olefin from polyα-olefin reaction products provided by the present invention can effectively shorten the separation process of polyα-olefin reaction products and improve the separation effect of polyα-olefin reaction products, especially for the separation process of polyα-olefin reaction products in the continuous production process of polyα-olefin using BF3 gas as a catalyst. By fractionating the polyα-olefin product system, the first BF3 gas and the crude polyα-olefin liquid can be effectively separated. By recovering the BF3 gas after the polymerization reaction and the first BF3 gas that did not react during the separation process, the gas can be used as a catalyst for the polymerization reaction, thereby improving the utilization rate of the BF3 gas. By further treating the crude polyα-olefin liquid in a combination of alkali washing and water washing, the residual BF3 can be removed, and most of the waste alkali liquid after alkali washing and the waste water after water washing can be recycled, thereby saving process costs, and the polyα-olefin finally obtained can be used as a raw material for subsequent oil processing.

[0040] In one embodiment of the present application, the temperature of the polyα-olefin product system is 20-60°C, and the pressure of the polyα-olefin product system is 0.2-0.5 MPa(G); and / or, the pressure of the second BF3 gas is 0.2-0.6 MPa(G); and / or, the temperature of the crude polyα-olefin liquid is 20-60°C.

[0041] It is preferred to control the temperature and pressure of the poly-alpha-olefin product system within the above ranges, which helps to more effectively separate the first BF3 gas and the crude poly-alpha-olefin liquid from the poly-alpha-olefin product system. It is preferred that the pressure of the second BF3 gas is within the above range, which helps the second BF3 gas to act as a catalyst for polymerization reaction, thereby improving the reaction efficiency of the polymerization reaction. It is preferred to control the temperature of the crude poly-alpha-olefin liquid within the above range, which helps to further remove the residual BF3 gas in the crude poly-alpha-olefin liquid during the alkali washing process, thereby improving the purity and quality of the poly-alpha-olefin.

[0042] In one embodiment of the present application, the crude poly-α-olefin liquid is alkali-washed with alkali liquid to obtain the alkali-washed poly-α-olefin, wherein the alkali liquid comprises an alkaline solution and a first deionized water solution; the volume ratio of the alkaline solution to the first deionized water solution is 1:10 to 1:20; the volume ratio of the alkali liquid to the crude poly-α-olefin liquid is 1:10 to 1:20; and / or, the alkali-washed poly-α-olefin is washed with a water washing solution, the water washing solution comprises a second deionized water solution, and the volume ratio of the second deionized water solution to the alkali-washed poly-α-olefin is 1:10 to 1:20.

[0043] Preferably, the crude poly-α-olefin liquid is alkali-washed by the alkali solution, and the volume ratio of the alkaline solution to the first desalted water in the alkali solution, the volume ratio of the alkali solution to the crude poly-α-olefin liquid, and the type of the first desalted water are controlled within the above range, which helps to effectively remove the BF3 gas remaining in the crude poly-α-olefin liquid, thereby improving the neutralization efficiency, and further improving the purity and quality of the poly-α-olefin. Preferably, the poly-α-olefin after alkali washing is washed with water, and the volume ratio of the second desalted water to the poly-α-olefin after alkali washing is controlled within the above range, which helps to fully wash the alkali solution in the crude poly-α-olefin liquid after alkali washing, thereby further improving the purity and quality of the poly-α-olefin.

[0044] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0045] Example 1

[0046] use Figure 1 The poly-α-olefin reaction product separation system is used to separate the poly-α-olefin reaction product to obtain poly-α-olefin.

[0047] A poly-α-olefin product system and a BF3 gas after the polymerization reaction are polymerized to obtain a poly-α-olefin product system and a BF3 gas as a poly-α-olefin reaction product. The properties of the poly-α-olefin product system are shown in Table 1. According to the ASTM D86 curve, the poly-α-olefin product system has a volume percentage of 0%, 5%, 10%, 30%, 50%, 70%, 90%, 95% and 100% of the collected condensate at distillation temperatures of 62°C, 117°C, 143°C, 225°C, 357°C, 421°C, 483°C, 505°C and 527°C, respectively.

[0048] Table 1

[0049]

[0050] The poly-α-olefin product system is heated to 121°C by the first heat exchange in the feed heat exchanger 5 of the fractionation tower 1, and then enters the fractionation tower 1 from the inlet of the fractionation tower body for fractionation to obtain the first BF3 gas and the crude poly-α-olefin liquid. The fractionation tower 1 includes two sections of packed beds, and the poly-α-olefin product system enters the middle of the two sections of packed beds. The top of the fractionation tower 1 is condensed by inserting coils, and the condensed liquid flows back into the tower. The inserted coil uses a -5°C cold coal medium to cool the top of the fractionation tower to 4°C. An electrically heated fractionation tower reboiler 6 is set at the bottom of the fractionation tower 1 to make the bottom temperature of the fractionation tower 1 reach 211°C. Among them, the top pressure of the distillation tower 1 is 0.15MPa (G), a temperature control valve group A9 is arranged between the tube side outlet of the feed heat exchanger 5 and the shell side bypass, a temperature control valve group B10 is arranged between the top of the distillation tower 1 and the top refrigerant medium, a pressure control valve group C11 is arranged between the top of the distillation tower 1 and the liquid separation tank connected to the inlet and outlet of the compressor 2, a temperature control valve group E13 is arranged between the bottom of the distillation tower 1 and the distillation tower reboiler 6, and a liquid level control valve group F14 is arranged between the bottom liquid level of the distillation tower 1 and the outlet of the bottom pump of the distillation tower.

[0051] The top gas of distillation tower 1 (first BF3 gas) is mixed with the BF3 gas produced by the polymerization reaction and then enters compressor 2 from the compressor inlet for compression to obtain a second BF3 gas. The second BF3 gas is pressurized to 0.35 MPa (G) and then enters the polymerization reactor as a catalyst gas for polymerization reaction, wherein a pressure control valve group D12 is arranged between the outlet and the outlet return line of the circulating gas compressor complete set in compressor 2.

[0052] The crude poly-α-olefin liquid output from the bottom outlet of the fractionation tower 1 is boosted to 0.45MPa(G) by the bottom pump (boosting pump) of the fractionation tower 1, and then cooled to 141°C by the feed heat exchanger 5, cooled to 50°C by the air cooler 7, and cooled to 40°C by the water cooler 8 in sequence, and enters the alkali washing tower 3 from the bottom inlet of the alkali washing tower, and the alkali solution enters the alkali washing tower 3 from the top inlet of the alkali washing tower, and adopts a full tower countercurrent contact operation mode, and the alkali solution is used to neutralize the BF3 remaining in the crude poly-α-olefin liquid to obtain the alkali-washed poly-α-olefin liquid and the waste alkali solution. The alkali-washed poly-α-olefin liquid is output from the top outlet of the alkali washing tower, and the waste alkali solution is boosted by the bottom pump of the alkali washing tower and divided into two paths, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to the feed pipeline of the alkali washing tower 3 and mixed with the pre-configured alkali solution. Among them, the alkali washing tower 3 is a packed tower, and the packing in the alkali washing tower adopts random packing. The theoretical number of plates of the alkali washing tower 3 is 2, the pressure drop of the whole tower of the alkali washing tower 3 is 5kPa, the pressure of the alkali liquid is 0.35MPa(G), and the alkali liquid includes NaOH solution and the first desalted water; the volume ratio of the NaOH solution to the first desalted water is 1:10, and the volume ratio of the alkali liquid to the crude poly-α-olefin liquid is 1:10. The alkali liquid and the first desalted water are mixed and enter the alkali liquid buffer tank. A liquid level control valve group G15 is set between the liquid level of the alkali liquid buffer tank and the fresh alkali liquid, and a flow control valve group H16 is set between the alkali liquid and the desalted water. A flow control valve group I17 is set between the alkali liquid feed and the crude poly-α-olefin liquid feed to control the flow ratio of the alkali liquid and the crude poly-α-olefin liquid feed, and an interface control valve group J18 is set between the bottom interface of the alkali washing tower 3 and the waste alkali liquid at the outlet of the bottom pump of the alkali washing tower 3 to the wastewater treatment. A flow control valve group K19 is provided at the outlet of the bottom pump of the alkali washing tower 3 for circulating the waste alkali liquid.

[0053] The poly-α-olefin liquid after alkali washing enters the water washing tower 4 from the bottom inlet of the water washing tower, and the second desalted water enters from the top inlet of the water washing tower. The operation mode of full tower countercurrent contact is adopted, and the alkali liquid in the poly-α-olefin liquid after alkali washing is fully washed by the second desalted water to obtain poly-α-olefin and wastewater. The poly-α-olefin is output from the water washing tower outlet at the top of the water washing tower 4 and sent to the downstream oil processing unit as raw materials. The alkali-containing wastewater is boosted by the bottom pump of the water washing tower and divided into two paths, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to mix with fresh desalted water. Among them, water washing tower 4 is a packed tower, and the packing in water washing tower 4 adopts random packing. The theoretical number of tower plates of water washing tower 4 is 2, the full tower pressure drop of water washing tower 4 is 5kPa, the volume ratio of the second desalted water and the poly-α-olefin after alkali washing is 1:10, and a flow control valve group L20 is arranged between the second desalted water and the poly-α-olefin after alkali washing, and an interface control valve group M21 is arranged between the bottom interface of water washing tower 4 and the wastewater at the outlet of the bottom pump of water washing tower to wastewater treatment, and a flow control valve group N22 is arranged for the circulating wastewater liquid at the outlet of the bottom pump of water washing tower 4.

[0054] Example 2

[0055] The difference from Example 1 is that the polyalphaolefin product system is heated to 115°C by the first heat exchange in the feed heat exchanger 5 of the fractionation tower 1 and then enters the fractionation tower 1 from the inlet of the fractionation tower body for fractionation to obtain the first BF3 gas and the crude polyalphaolefin liquid. The fractionation tower 1 includes two sections of packed beds, and the polyalphaolefin product system enters the middle of the two sections of packed beds. The top of the fractionation tower 1 is condensed by inserting a coil, and the condensed liquid flows back into the tower. The inserted coil uses a -8°C cold coal medium to cool the top temperature of the fractionation tower to 2°C. An electrically heated fractionation tower reboiler 6 is arranged at the bottom of the fractionation tower 1 to make the bottom temperature of the fractionation tower 1 reach 200°C. Among them, the top pressure of the fractionation tower 1 is 0.15MPa(G), the temperature of the polyalphaolefin product system is 20°C, and the pressure is 0.2MPa(G).

[0056] The top gas of distillation tower 1 (first BF3 gas) is mixed with the BF3 gas produced by the polymerization reaction and then enters compressor 2 from the compressor inlet for compression to obtain the second BF3 gas. The second BF3 gas is pressurized to 0.2MPa (G) and then enters the polymerization reactor as a catalyst gas for polymerization reaction.

[0057] The crude poly-α-olefin liquid output from the bottom outlet of the fractionation tower 1 is boosted to 0.45MPa(G) by the bottom pump (boosting pump) of the fractionation tower 1, and then cooled to 141°C by the feed heat exchanger 5, cooled to 50°C by the air cooler 7, and cooled to 40°C by the water cooler 8 in sequence, and enters the alkali washing tower 3 from the bottom inlet of the alkali washing tower, and the alkali solution enters the alkali washing tower 3 from the top inlet of the alkali washing tower, and adopts a full tower countercurrent contact operation mode, and the alkali solution is used to neutralize the BF3 remaining in the crude poly-α-olefin liquid to obtain the alkali-washed poly-α-olefin liquid and the waste alkali solution. The alkali-washed poly-α-olefin liquid is output from the top outlet of the alkali washing tower, and the waste alkali solution is boosted by the bottom pump of the alkali washing tower and divided into two paths, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to the feed pipeline of the alkali washing tower 3 and mixed with the pre-configured alkali solution. Among them, the alkali washing tower 3 is a packed tower, and the packing adopts regular packing. The theoretical number of plates of the alkali washing tower 3 is 6, the full tower pressure drop of the alkali washing tower 3 is 4 kPa, the pressure of the alkali solution is 0.35 MPa (G), and the alkali solution includes NaOH solution and the first desalted water; the volume ratio of the NaOH solution and the first desalted water is 1:15, and the volume ratio of the alkali solution and the crude poly-α-olefin liquid is 1:15.

[0058] The poly-α-olefin liquid after alkali washing enters the water washing tower 4 from the bottom inlet of the water washing tower, and the second desalted water enters from the top inlet of the water washing tower. The operation mode of full tower countercurrent contact is adopted, and the alkali solution in the poly-α-olefin liquid after alkali washing is fully washed by the second desalted water to obtain poly-α-olefin and wastewater. The poly-α-olefin is output from the water washing tower outlet at the top of the water washing tower 4 and sent to the downstream oil processing unit as a raw material. The alkali-containing wastewater is divided into two paths after being pressurized by the bottom pump of the water washing tower, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to mix with fresh desalted water. Among them, the water washing tower 4 is a packed tower, and the packing adopts regular packing. The theoretical number of plates of the water washing tower 4 is 6, and the full tower pressure drop of the water washing tower 4 is 4kPa. The volume ratio of the second desalted water and the poly-α-olefin after alkali washing is 1:15.

[0059] Example 3

[0060] The difference from Example 1 is that the poly-α-olefin product system is heated to 130°C by the first heat exchange in the feed heat exchanger 5 of the fractionation tower 1 and then enters the fractionation tower 1 from the inlet of the fractionation tower body for fractionation to obtain the first BF3 gas and the crude poly-α-olefin liquid. The fractionation tower 1 includes two sections of packed beds, and the poly-α-olefin product system enters the middle of the two sections of packed beds. The top of the fractionation tower 1 is condensed by inserting a coil, and the condensed liquid flows back into the tower. The inserted coil uses a 0°C cold coal medium to cool the top temperature of the fractionation tower to 8°C. The bottom of the fractionation tower 1 is provided with an electrically heated fractionation tower reboiler 6 to make the bottom temperature of the fractionation tower 1 reach 250°C. Among them, the top pressure of the fractionation tower 1 is 0.4MPa(G), the temperature of the poly-α-olefin product system is 60°C, and the pressure is 0.5MPa(G).

[0061] The top gas of distillation tower 1 (first BF3 gas) is mixed with the BF3 gas produced by the polymerization reaction and then enters compressor 2 from the compressor inlet for compression to obtain the second BF3 gas. The second BF3 gas is pressurized to 0.5MPa (G) and then enters the polymerization reactor as a catalyst gas.

[0062] The crude poly-α-olefin liquid output from the bottom outlet of the fractionation tower 1 is boosted to 0.45MPa(G) by the bottom pump (boosting pump) of the fractionation tower 1, and then cooled to 141°C by the feed heat exchanger 5, cooled to 50°C by the air cooler 7, and cooled to 40°C by the water cooler 8 in sequence, and enters the alkali washing tower 3 from the bottom inlet of the alkali washing tower, and the alkali solution enters the alkali washing tower 3 from the top inlet of the alkali washing tower, and adopts a full tower countercurrent contact operation mode, and the alkali solution is used to neutralize the BF3 remaining in the crude poly-α-olefin liquid to obtain the alkali-washed poly-α-olefin liquid and the waste alkali solution. The alkali-washed poly-α-olefin liquid is output from the top outlet of the alkali washing tower, and the waste alkali solution is boosted by the bottom pump of the alkali washing tower and divided into two paths, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to the feed pipeline of the alkali washing tower 3 and mixed with the pre-configured alkali solution. Among them, the theoretical number of plates of the alkali washing tower 3 is 10, the full tower pressure drop of the alkali washing tower 3 is 3 kPa, the pressure of the alkali solution is 0.35 MPa (G), and the alkali solution includes NaOH solution and the first desalted water; the volume ratio of the NaOH solution to the first desalted water is 1:20, and the volume ratio of the alkali solution to the crude poly-α-olefin liquid is 1:20.

[0063] The poly-α-olefin liquid after alkali washing enters the water washing tower 4 from the bottom inlet of the water washing tower, and the second desalted water enters from the top inlet of the water washing tower. The operation mode of full tower countercurrent contact is adopted, and the alkali liquid in the poly-α-olefin liquid after alkali washing is fully washed by the second desalted water to obtain poly-α-olefin and wastewater. The poly-α-olefin is output from the water washing tower outlet at the top of the water washing tower 4 and sent to the downstream oil processing unit as a raw material. The alkali-containing wastewater is divided into two paths after being pressurized by the bottom pump of the water washing tower, one path (20%) is sent to wastewater treatment, and the other path (80%) is circulated to mix with fresh desalted water. Among them, the theoretical number of plates of the water washing tower 4 is 10, the full tower pressure drop of the water washing tower 4 is 3kPa, and the volume ratio of the second desalted water to the poly-α-olefin after alkali washing is 1:20.

[0064] Example 4

[0065] The difference from Example 1 is that the top of the distillation tower 1 is condensed by inserting a coil, the top temperature of the distillation tower 1 is 8°C, the bottom temperature is 250°C, the top pressure is 0.4 MPa (G), and finally poly-α-olefin and wastewater are obtained.

[0066] Example 5

[0067] The difference from Example 1 is that the top of the distillation tower 1 is condensed by an inserted coil, the top temperature of the distillation tower 1 is 10°C, the bottom temperature is 280°C, the top pressure is 0.5 MPa (G), and finally poly-α-olefin and wastewater are obtained.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that the polyα-olefin product system is fractionated by a flash tower to obtain a first BF3 gas and a crude polyα-olefin liquid, and finally polyα-olefin and waste water are obtained, wherein the top pressure of the flash tower is 0.15 MPa (G) and the feed temperature is 180°C.

[0070] Test method:

[0071] The mass flow rate of the polyα-olefin in the above embodiments and comparative examples, the mass flow rate of the polyα-olefin in the polyα-olefin reaction product, the mass flow rate of the first BF3 gas, and the mass flow rate of the BF3 gas in the polyα-olefin reaction product were counted by a flow meter to obtain the yield of the polyα-olefin and the yield of the first BF3 gas. The results are shown in Table 2. The yield of the polyα-olefin = the mass flow rate of the polyα-olefin / the mass flow rate of the polyα-olefin in the polyα-olefin reaction product, the yield of the first BF3 gas = the mass flow rate of the first BF3 gas / the mass flow rate of the BF3 gas in the polyα-olefin reaction product.

[0072] Table 2

[0073]

[0074]

[0075] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0076] The separation system of polyalpha-olefin reaction products provided by the present invention can effectively shorten the separation process of polyalpha-olefin reaction products and improve the separation effect of polyalpha-olefin reaction products, especially for the separation process of polyalpha-olefin reaction products in the continuous production process of polyalpha-olefin using BF3 gas as a catalyst. The first BF3 gas and crude polyalpha-olefin liquid can be effectively separated from the polyalpha-olefin product system by a fractionation tower. By recovering the BF3 gas after the polymerization reaction and the unreacted first BF3 gas in the separation system and passing it into a compressor by pressure control, it can be used as a catalyst for polymerization reaction, thereby improving the utilization rate of BF3 gas and reducing the consumption of catalyst, thereby reducing production costs. By adopting a countercurrent contact method and using an alkali washing tower and a water washing tower to further treat the crude polyalpha-olefin liquid in turn, the BF3 remaining in the crude polyalpha-olefin liquid can be removed, and most of the waste alkali liquid after alkali washing and the waste water after water washing can be recycled, thereby saving the system operation cost. In addition, the polyalpha-olefin obtained by the separation system of the present invention can be used as a raw material for subsequent oil processing.

[0077] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A separation system for poly-alpha-olefin reaction products, characterized in that: The poly-α-olefin reaction product is a poly-α-olefin product system obtained by polymerizing a raw material including a BF3 gas catalyst and an α-olefin and a BF3 gas after the polymerization reaction; The separation system is used to separate the poly-alpha-olefin reaction product; The separation system comprises: A fractionation tower (1) has a fractionation tower body inlet, a fractionation tower top outlet and a fractionation tower bottom outlet, wherein the fractionation tower body inlet is used to introduce the poly-α-olefin product system, and the fractionation tower (1) is used to fractionate the poly-α-olefin product system to obtain a first BF3 gas and a crude poly-α-olefin liquid; A compressor (2) having a compressor inlet and a compressor outlet, wherein the compressor inlet is connected to the outlet of the top of the fractionation tower, and the compressor (2) is used to compress the first BF3 gas and the BF3 gas after the polymerization reaction to obtain a second BF3 gas; and the second BF3 gas is used as a BF3 gas catalyst for the polymerization reaction; An alkali washing tower (3) is provided with an alkali washing tower top inlet, an alkali washing tower top outlet, an alkali washing tower bottom inlet and an alkali washing tower bottom outlet, wherein the alkali washing tower top inlet is connected to an alkali liquid source, and the fractionation tower bottom inlet is connected to the crude poly-α-olefin liquid. The alkali washing tower (3) is used to perform alkali washing on the crude poly-α-olefin liquid to obtain alkali-washed poly-α-olefin liquid and waste alkali liquid; The water washing tower (4) has a water washing tower top inlet, a water washing tower top outlet, a water washing tower bottom inlet and a water washing tower bottom outlet. The water washing tower top inlet is connected to a water washing liquid source, and the alkali washing tower bottom inlet is connected to the alkali washed poly-α-olefin liquid. The water washing tower (4) is used to wash the alkali washed poly-α-olefin liquid with water to obtain poly-α-olefin and wastewater.

2. The separation system according to claim 1, characterized in that: The fractionation tower (1) is a packed tower, the packing in the fractionation tower (1) is a random packing or a structured packing, the number of theoretical plates of the fractionation tower (1) is 2 to 10; the whole tower pressure drop of the fractionation tower (1) is ≤5 kPa; and / or the fractionation tower (1) comprises two packed bed layers, and the poly-α-olefin reaction product is arranged between the packed bed layers.

3. The separation system according to claim 1 or 2, characterized in that: The top of the fractionation tower (1) is condensed by inserting a coil, and a refrigerant is introduced into the inserting coil for temperature control; and / or the temperature of the refrigerant is -8 to 0°C; and / or the top temperature of the fractionation tower (1) is 2 to 8°C; and / or the top pressure of the fractionation tower (1) is 0.15 to 0.4 MPa(G); And / or, the separation system further comprises a feed heat exchanger (5), the feed heat exchanger (5) is used to perform a first heat exchange on the poly-α-olefin reaction product, and the outlet temperature of the feed heat exchanger (5) is 115-130° C.; And / or, a fractionation tower reboiler (6) is provided at the bottom of the fractionation tower (1), and the fractionation tower reboiler (6) is used to provide a heat source to the fractionation tower (1), and the bottom temperature of the fractionation tower (1) is 200-250°C.

4. The separation system according to any one of claims 1 to 3, characterized in that: A feed heat exchanger (5), an air cooler (7) and a water cooler (8) are also sequentially arranged on the connecting pipeline between the fractionation tower (1) and the alkali washing tower (3); the feed heat exchanger (5), the air cooler (7) and the water cooler (8) are used to perform a second heat exchange, air cooling and water cooling on the crude poly-α-olefin liquid in sequence.

5. The separation system according to claim 4, characterized in that: A booster pump is provided on the connecting pipeline between the fractionation tower (1) and the feed heat exchanger (5), and the booster pump is used to increase the pressure of the crude poly-α-olefin liquid.

6. The separation system according to any one of claims 1 to 5, characterized in that The alkali washing tower (3) is a packed tower. The packing in the alkali washing tower (3) is a random packing or a structured packing. The number of theoretical plates of the alkali washing tower (3) is 2 to 10. The full tower pressure drop of the alkali washing tower (3) is ≤5 kPa.

7. The separation system according to any one of claims 1 to 6, characterized in that The water washing tower (4) is a packed tower. The packing in the water washing tower (4) is a random packing or a structured packing. The number of theoretical plates of the water washing tower (4) is 2 to 10. The full tower pressure drop of the water washing tower (4) is ≤5 kPa.

8. A process for separating poly-α-olefins using the separation system according to any one of claims 1 to 7, characterized in that: The process comprises: A raw material including a BF3 gas catalyst and an α-olefin is polymerized to obtain a poly-α-olefin product system and a BF3 gas after the polymerization reaction as a poly-α-olefin reaction product; fractionating the poly-alpha-olefin product system to obtain a first BF3 gas and a crude poly-alpha-olefin liquid; The first BF3 gas and the BF3 gas after the polymerization reaction are mixed and compressed to obtain a second BF3 gas; The crude poly-alpha-olefin liquid is sequentially subjected to alkali washing and water washing to obtain poly-alpha-olefin; The second BF3 gas is used as a catalyst for the polymerization reaction.

9. The process according to claim 8, characterized in that The temperature of the poly-α-olefin product system is 20-60°C, and the pressure of the poly-α-olefin product system is 0.2-0.5 MPa(G); and / or the pressure of the second BF3 gas is 0.2-0.6 MPa(G); and / or the temperature of the crude poly-α-olefin liquid is 20-60°C.

10. The process according to claim 8 or 9, characterized in that The crude poly-α-olefin liquid is subjected to alkali washing by alkali solution to obtain alkali-washed poly-α-olefin, wherein the alkali solution comprises an alkaline solution and a first desalted water; the volume ratio of the alkaline solution to the first desalted water is 1:10 to 1:20; the volume ratio of the alkali solution to the crude poly-α-olefin liquid is 1:10 to 1:20; And / or, the alkali-washed poly-α-olefin is washed with a washing liquid, the washing liquid comprises a second desalted water, and the volume ratio of the second desalted water to the alkali-washed poly-α-olefin is 1:10 to 1:20.

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