Method for separating alpha-olefin from Fischer-Tropsch synthesis naphtha and alpha-olefin product

Abstract

The invention provides a method for separating alpha-olefin from Fischer-Tropsch synthesis naphtha and an alpha-olefin product, and belongs to the field of petrochemical industry. The method comprises the following steps: deacidifying and washing Fischer-Tropsch synthesis naphtha in sequence to obtain deacidified oil; the deacidified oil is pre-cut, and C5-C9 fraction sections are obtained; extracting and deoxidizing the C5-C9 fraction sections to obtain deoxidized oil; carrying out rectification cutting on the deoxidized oil to respectively obtain a C6 fraction, a C7 fraction and a C8 fraction; sequentially carrying out first extractive distillation, first precise distillation and first adsorption deoxidation on the C6 fraction; sequentially carrying out second extractive distillation, second precise distillation and second adsorption deoxidation on the C7 fraction; and sequentially carrying out etherification reaction, secondary rectification cutting and third adsorption deoxidation on the C8 fraction. By adopting the method, a high-purity alpha-olefin product can be separated.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and in particular, relates to a method for separating alpha-olefins from Fischer-Tropsch synthesis naphtha and alpha-olefin products. Background Art

[0002] α-Olefin is one of the important polymerization monomers and is widely used in the fields of synthetic polyethylene, synthetic rubber, synthetic aldehyde, synthetic ketone, synthetic plastic, synthetic resin, synthetic fiber, synthetic rubber and synthetic medicine. α-Olefins such as 1-hexene, 1-heptene, 1-octene, 1-nonene, etc. Fischer-Tropsch synthesis naphtha has the advantage of being rich in α-olefins (content> 50%), which is conducive to obtaining long-chain olefins with high added value. However, the components of Fischer-Tropsch synthesis naphtha are complex. In addition to α-olefins, it also contains isomers of α-olefins, organic acids, and oxygen-containing compounds such as alcohols, aldehydes, ketones, and esters. The presence of these substances will directly affect the purity of the final α-olefins. Specifically, the boiling points of isomers and α-olefins are similar. For example, the C8 raw material after cutting Fischer-Tropsch synthesis naphtha contains 2-methyl-1-heptene, whose boiling point is close to that of 1-octene, and it is difficult to remove it by distillation, resulting in a decrease in the purity of the 1-octene product. The presence of organic acids will seriously corrode oil pipelines and equipment, affecting oil quality; oxygen-containing compounds will react with acid catalysts for complexation or substitution, resulting in catalyst deactivation, which will affect the subsequent polymerization of α-olefins. Therefore, before the α-olefin polymerization process, isomers, organic acids and oxygen-containing compounds in Fischer-Tropsch naphtha need to be removed, and it is necessary to provide a method that can effectively improve the purity of α-olefin products. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for separating α-olefins from Fischer-Tropsch naphtha and α-olefin products, so as to solve the problem in the prior art that isomers, organic acids and oxygen-containing compounds in Fischer-Tropsch naphtha are not completely removed, thus affecting the purity of the α-olefin products.

[0004] In order to achieve the above object, according to one aspect of the present invention, there is provided a method for separating α-olefins from Fischer-Tropsch naphtha, comprising the following steps:

[0005] S1, deacidifying Fischer-Tropsch synthesis naphtha to obtain deacidified oil;

[0006] S2, pre-cutting the deacidified oil to obtain a C5-C9 fraction;

[0007] S3, extracting and deoxygenating the C5-C9 fractions to obtain deoxygenated oil;

[0008] S4, distilling and cutting the deoxygenated oil to obtain a C6 fraction, a C7 fraction and a C8 fraction respectively;

[0009] S5, sequentially subjecting the C6 fraction to a first extractive distillation, a first precise distillation and a first adsorptive deoxygenation to obtain a 1-hexene product;

[0010] S6, sequentially subjecting the C7 fraction to a second extractive distillation, a second precise distillation, and a second adsorptive deoxygenation to obtain a 1-heptene product;

[0011] S7, sequentially subjecting the C8 fraction to etherification reaction, secondary distillation cutting and third adsorption deoxygenation to obtain a 1-octene product.

[0012] Furthermore, S1 includes:

[0013] The Fischer-Tropsch synthesis naphtha is mixed with alkali solution in a deacidification tank, and after deacidification, deacidified oil is obtained; the deacidified oil is washed with water in a deacidification water washing tower to obtain deacidified oil;

[0014] Preferably, the alkaline substance in the alkali solution includes at least one of potassium hydroxide, sodium hydroxide, sodium carbonate and potassium carbonate, and the mass concentration of the alkaline substance in the alkali solution is 2% to 8%;

[0015] Preferably, the acid value of the deacidified oil is less than 0.05 mg KOH / g.

[0016] Further, the pre-cutting includes a first pre-cutting and a second pre-cutting; S2 includes:

[0017] The deacidified oil is fed into the C4 tower, and after the first pre-cutting, a C4 fraction is obtained at the top of the C4 tower, and a C4+ fraction section is obtained at the bottom of the tower; the C4+ fraction section is fed into the C9 tower, and after the second pre-cutting, a C5-C9 fraction section is obtained at the top of the C9 tower, and a C9+ fraction section is obtained at the bottom of the tower;

[0018] Further, the number of plates of the C4 tower is 35 to 55, the reflux ratio is 2 to 10, the tower top temperature is 35 to 50° C., and the pressure is 0.3 to 0.5 MPa;

[0019] Furthermore, the number of plates of the C9 tower is 30 to 60, the reflux ratio is 1 to 20, and the tower bottom temperature is 170 to 175°C.

[0020] Furthermore, S3 includes:

[0021] Feeding the C5-C9 fraction into the extraction deoxygenation tower in reverse contact with the first extraction deoxygenator, and obtaining deoxygenated oil and oxygen-containing extractant after extraction deoxygenation;

[0022] Preferably, the first extractive deoxidant comprises at least one of 1,2-propylene glycol, cyclopentane sulfone, butyl acetate, acetonitrile, dimethyl sulfoxide, 1,4-butanediol, ethanolamine, 1-methyl-2-pyrrolidone, and glycerol;

[0023] More preferably, the first extracting deoxidizing agent is a mixed system of 1,4-butanediol and glycerol or sulfolane, wherein the volume ratio of 1,4-butanediol to glycerol or sulfolane is (1-8):1;

[0024] Preferably, the number of plates of the extractive deoxygenation tower is 20 to 100, the reflux ratio is 1 to 20, and the temperature of the extractive deoxygenation tower is 30 to 50° C. Preferably, S3 further comprises: feeding the oxygenate-containing extractant to an extractant recovery tower for regeneration treatment to obtain a recovered extractant; returning the recovered extractant to the extractive deoxygenation tower;

[0025] Preferably, the top temperature of the extractant recovery tower is 90-150°C, the bottom temperature is 120-200°C, and the pressure is 10-70 kPa;

[0026] Preferably, the mass ratio of the first extracting deoxidant to the C5-C9 fraction is (1-5):1.

[0027] Further, the distillation cutting includes a first distillation cutting, a second distillation cutting, a third distillation cutting and a fourth distillation cutting; S4 includes:

[0028] S41, feeding the deoxygenated oil into the C5 tower, and after the first distillation and cutting, obtaining a C5 fraction at the top of the C5 tower and a C6-C9 fraction section at the bottom of the tower;

[0029] S42, feeding the C6-C9 fraction segment into the C6 tower, and after the second distillation cutting, obtaining the C6 fraction at the top of the C6 tower and obtaining the C7-C9 fraction segment at the bottom of the tower;

[0030] S43, feeding the C7-C9 fraction segment into the C7 tower, and after the third distillation cutting, obtaining the C7 fraction at the top of the C7 tower and obtaining the C8-C9 fraction segment at the bottom of the tower;

[0031] S44, feeding the C8-C9 fraction segment into the C8 tower, and after the fourth distillation cutting, obtaining the C8 fraction at the top of the C8 tower and the C9 fraction at the bottom of the tower;

[0032] Preferably, the number of plates of the C5 tower is 20 to 60, the reflux ratio is 3 to 15, the top pressure is 0.1 to 0.2 MPa, the top temperature is 55 to 70° C., and the bottom temperature is 105 to 130° C.;

[0033] Preferably, the number of plates of the C6 tower is 20 to 60, the reflux ratio is 2 to 15, the top temperature is 50 to 70°C, and the bottom temperature is 110 to 130°C;

[0034] Preferably, the number of plates of the C7 tower is 20 to 50, the reflux ratio is 1 to 15, the top temperature is 90 to 100° C., and the bottom temperature is 120 to 140° C.;

[0035] Preferably, the number of plates of the C8 tower is 20 to 50, the reflux ratio is 1 to 15, the top temperature is 110 to 120°C, and the bottom temperature is 185 to 210°C.

[0036] Furthermore, S5 includes:

[0037] S51, feeding the C6 fraction into a first extractive distillation tower to contact with a first extractant in a reverse direction, and after the first extractive distillation, obtaining an alkane-rich component at the top of the first extractive distillation tower, and obtaining a mixture containing the extractant and C6-rich olefins at the bottom of the tower;

[0038] S52, feeding a mixture containing an extractant and C6 olefin-rich components into a first extractant regeneration tower, and obtaining a first regenerated extractant at the top of the first extractant regeneration tower after regeneration treatment, and obtaining a C6 olefin-rich component at the bottom of the tower;

[0039] S53, returning the first regenerated extractant to the first extractive distillation tower, feeding the C6 olefin-rich component to the first precision distillation tower, and obtaining a crude 1-hexene product at the top of the first precision distillation tower after the first precision distillation;

[0040] S54, feeding the crude 1-hexene product into a first adsorption deoxygenation tower, and obtaining a 1-hexene product after first adsorption deoxygenation;

[0041] Preferably, the first extractive distillation tower has a plate number of 90 to 130, a reflux ratio of 5 to 20, a tower top temperature of 65 to 70° C., and a tower bottom temperature of 140 to 190° C.;

[0042] Preferably, the number of plates of the first extractant regeneration tower is 30 to 50, the reflux ratio is 3 to 10, the top temperature is 60 to 68° C., and the bottom temperature is 200 to 230° C.;

[0043] Preferably, the number of plates of the first precision distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 60-65°C, and the bottom temperature is 65-85°C;

[0044] Preferably, the volume ratio of the first extractant to the C6 fraction is (5-20):1.

[0045] Furthermore, S6 includes:

[0046] S61, feeding the C7 fraction into a second extractive distillation tower to contact with a second extractant in a reverse direction, and obtaining an alkane-rich component at the top of the second extractive distillation tower after the second extractive distillation, and obtaining a mixture containing the extractant and C7 olefin-rich components at the bottom of the tower;

[0047] S62, feeding a mixture containing an extractant and C7 olefin-rich components into a second extractant regeneration tower, and obtaining a second regenerated extractant at the top of the second extractant regeneration tower after regeneration treatment, and obtaining a C7 olefin-rich component at the bottom of the tower;

[0048] S63, circulating the second regenerated extractant back to the second extractive distillation tower, feeding the C7 olefin-rich component to the second precision distillation tower, and obtaining a crude 1-heptene product at the top of the second precision distillation tower after the second precision distillation;

[0049] S64, feeding the crude 1-heptene product into a second adsorption deoxygenation tower, and obtaining a 1-heptene product after the second adsorption deoxygenation;

[0050] Preferably, the second extractive distillation tower has a plate number of 90 to 130, a reflux ratio of 5 to 20, a tower top temperature of 95 to 100° C., and a tower bottom temperature of 160 to 200° C.;

[0051] Preferably, the number of plates of the second extractant regeneration tower is 30 to 50, the reflux ratio is 3 to 10, the top temperature is 90 to 98° C., and the bottom temperature is 210 to 240° C.;

[0052] Preferably, the number of plates of the second precision distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 90-96°C, and the bottom temperature is 115-125°C;

[0053] Preferably, the first extractant and the second extractant both include a main extractant and a secondary extractant, wherein the main extractants of the first extractant and the second extractant are each independently selected from at least one of dimethyl phthalate, morpholine, ethanolamine, N-formylmorpholine, butyl acetate, γ-butyrolactone, and ε-caprolactone, and the secondary extractants of the first extractant and the second extractant are each independently selected from at least one of water, N,N-dimethylformamide, and N-methylpyrrolidone;

[0054] Preferably, in the first extractant and the second extractant, the mass ratio of the main extractant to the secondary extractant is independently (2-10):1;

[0055] Preferably, the volume ratio of the second extractant to the C7 fraction is (5-20):1.

[0056] Further, the secondary distillation cutting includes a first distillation cutting and a second distillation cutting; S7 includes:

[0057] S71, feeding the C8 fraction into a reactor to undergo an etherification reaction with a low-carbon alcohol to obtain an etherified product;

[0058] S72, feeding the etherification product to a light-removing tower for a first distillation and cutting to remove light components, and then feeding the product to a heavy-removing tower for a second distillation and cutting to remove heavy components, and obtaining a crude 1-octene product at the top of the heavy-removing tower;

[0059] S73, feeding the crude 1-octene product into a third adsorption deoxygenation tower, and obtaining a 1-octene product after the third adsorption deoxygenation;

[0060] Preferably, the low-carbon alcohol is one or more of methanol, ethanol, and propanol, more preferably methanol;

[0061] Preferably, the catalyst for the etherification reaction is an ion exchange resin;

[0062] Preferably, the number of plates of the light-removal tower is 110-140, the reflux ratio is 10-40, the top temperature is 116-119°C, and the bottom temperature is 120-130°C;

[0063] Preferably, the number of plates of the deweighting tower is 110-140, the reflux ratio is 10-40, the top temperature is 117-120°C, and the bottom temperature is 125-135°C;

[0064] Preferably, the C8 fraction comprises 0.2 to 0.8% of 2-methyl-1-heptene in terms of mass percentage;

[0065] More preferably, the molar ratio of 2-methyl-1-heptene to lower alcohol is 1:(1.5-8).

[0066] Furthermore, the first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower each include two parallel adsorption towers, each of which is loaded with an adsorbent, one of which is used for adsorption deoxygenation, and the other is used for regenerating the adsorbent, and the two adsorption towers are used alternately;

[0067] Preferably, the regeneration of the adsorbent comprises: using high-temperature hot nitrogen to purge and regenerate the adsorbent, the temperature of the high-temperature hot nitrogen being 250-300° C.;

[0068] Preferably, the temperature of the first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower during the adsorption deoxygenation process is 20° C. to 60° C., and the pressure is 10 kPa to 50 kPa;

[0069] Preferably, the adsorbent is a molecular sieve, and the molecular sieve includes at least one of 4A molecular sieve, 5A molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-34 molecular sieve, 13X molecular sieve, Y-type molecular sieve, and MCM-22 molecular sieve.

[0070] The second aspect of the present invention provides an α-olefin product, which is produced by the method provided by the first aspect, and includes a 1-hexene product, a 1-heptene product and a 1-octene product.

[0071] Furthermore, the purity of the 1-hexene product is ≥99%, the purity of the 1-heptene product is ≥99%, and the purity of the 1-octene product is ≥98%.

[0072] By applying the technical solution of the present invention, isomers, organic acids and oxygen-containing compounds in oil products can be removed to the maximum extent through the cooperation of deacidification, pre-cutting, extraction deoxygenation, distillation cutting and adsorption deoxygenation, etc. Specifically, the content of oxygen-containing compounds in oil products can be reduced to below 5ppm, meeting the requirements of polymerization grade indicators, and finally effectively separating high-purity α-olefin products, such as 1-hexene products, 1-heptene products and 1-octene products. In addition, the present invention reasonably prepares corresponding fine separation and purification steps according to different carbon number fractions, which can not only further remove oxygen-containing compounds, but also realize the reasonable and efficient utilization of each fraction, and effectively reduce energy consumption and production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 The present invention is a process flow chart for separating α-olefins from Fischer-Tropsch naphtha according to one embodiment of the present invention.

[0074] Description of reference numerals:

[0075] 1. Deacidification tank; 2. Deacidification water washing tower; 3. C4 tower; 4. C9 tower; 5. Extraction deoxygenation tower; 6. Extraction agent recovery tower; 7. C5 tower; 8. C6 tower; 9. C7 tower; 10. C8 tower; 11. First extraction distillation tower; 12. First extraction agent regeneration tower; 13. First precision distillation tower; 14. First adsorption deoxygenation tower; 15. Second extraction distillation tower; 16. Second extraction agent regeneration tower; 17. Second precision distillation tower; 18. Second adsorption deoxygenation tower; 19. Reactor; 20. Light removal tower; 21. Heavy removal tower; 22. Third adsorption deoxygenation tower; 101-Alkali solution inlet; 102, Fischer-Tropsch synthesis naphtha inlet; 103, First extraction agent inlet; 104, Second extraction agent inlet; 105, 1-hexene product outlet; 106, 1-heptene product outlet; 107, 1-octene product outlet; 108, Low-carbon alcohol inlet. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0077] As described in the background of the present invention, the prior art has the problem that the isomers, organic acids and oxygen-containing compounds in the Fischer-Tropsch synthesis naphtha are not completely removed, which affects the purity of the α-olefin product. In order to solve the above problem, in a typical embodiment of the present invention, a method for separating α-olefins from the Fischer-Tropsch synthesis naphtha is provided, comprising the following steps:

[0078] S1, deacidifying Fischer-Tropsch synthesis naphtha to obtain deacidified oil;

[0079] S2, pre-cutting the deacidified oil to obtain a C5-C9 fraction;

[0080] S3, extracting and deoxygenating the C5-C9 fractions to obtain deoxygenated oil;

[0081] S4, distilling and cutting the deoxygenated oil to obtain a C6 fraction, a C7 fraction and a C8 fraction respectively;

[0082] S5, sequentially subjecting the C6 fraction to a first extractive distillation, a first precise distillation and a first adsorptive deoxygenation to obtain a 1-hexene product;

[0083] S6, sequentially subjecting the C7 fraction to a second extractive distillation, a second precise distillation, and a second adsorptive deoxygenation to obtain a 1-heptene product;

[0084] S7, sequentially subjecting the C8 fraction to etherification reaction, secondary distillation cutting and third adsorption deoxygenation to obtain a 1-octene product.

[0085] The Fischer-Tropsch synthesis naphtha of the present invention refers to naphtha produced by the Fischer-Tropsch synthesis process, which is mainly composed of hydrocarbons from C5 to C11. Among them, Fischer-Tropsch synthesis is a chemical process for converting synthesis gas (mainly composed of carbon monoxide and hydrogen) into liquid fuels and other hydrocarbon products, and is widely used in coal-to-oil, natural gas-to-oil and other processes.

[0086] First, the purpose of deacidification of Fischer-Tropsch naphtha is to remove acidic substances (organic acids, etc.) in the oil.

[0087] Next, the deacidified oil is pre-cut, and the pre-cutting can separate the fractions with different carbon numbers in advance, such as the C5-fraction segment and the C9+fraction segment, so that a purer C5-C9 fraction segment can be provided for the subsequent fine separation and purification, reducing the processing volume of the subsequent fine separation and purification, and effectively avoiding the fluctuation of the system pressure during operation, reducing the load of the subsequent tower, and also helping to improve the purity and yield of the target product. In addition, the separated C5-fraction and C9+fraction segments can be used as raw materials for other chemical products. The C5-fraction can be used in the process of naphtha cracking to produce ethylene, and react with ethylene to increase the production of propylene. For example, the C4 fraction can be used to prepare butadiene, etc. The C9+fraction segment can be used as a raw material for solvent oil or lubricating oil base oil. By pre-cutting and rationally utilizing these by-products, the economic benefits and resource utilization of the entire process can be further increased.

[0088] Subsequently, the C5-C9 fraction is subjected to extractive deoxygenation to remove oxygen-containing compounds therein and obtain deoxygenated oil.

[0089] After the extraction and deoxygenation, the deoxygenated oil is distilled and cut to separate the C5 fraction, C6 fraction, C7 fraction, C8 fraction and C9 fraction, which can be further processed according to actual needs. For example, the C5 fraction can be used to produce n-hexanol, as an additive for high-octane gasoline, and as a raw material for organic synthesis.

[0090] For C6 fraction, C7 fraction, C8 fraction, the present invention reasonably prepares corresponding fine separation and purification steps according to different carbon number fractions to obtain high-purity 1-hexene products, 1-heptene products and 1-octene products. Specifically, the C6 fraction and the C7 fraction are each subjected to extractive distillation, precise distillation and adsorption deoxygenation, and the alkane components and oxygen-containing compounds therein are removed to the maximum extent through the cooperation of extractive distillation, precise distillation and adsorption deoxygenation, thereby obtaining high-purity 1-hexene products and 1-heptene products. The C8 fraction is sequentially subjected to etherification reaction, secondary distillation cutting and third adsorption deoxygenation, wherein the isomers (such as 2-methyl-1-heptene) in the C8 fraction are converted into ether compounds through etherification reaction, and then the ether compounds and oxygen-containing compounds formed therein are further removed through secondary distillation cutting and third adsorption deoxygenation to obtain a high-purity 1-octene product.

[0091] The present invention cooperates with each other through the steps of deacidification, pre-cutting, extraction deoxygenation, distillation cutting and adsorption deoxygenation to remove isomers, organic acids and oxygen-containing compounds in oil products to the maximum extent, specifically reducing the content of oxygen-containing compounds in oil products to below 5ppm, meeting the requirements of polymerization grade indicators, and finally effectively separating high-purity α-olefin products, such as 1-hexene products, 1-heptene products and 1-octene products. In addition, the present invention reasonably prepares corresponding fine separation and purification steps according to different carbon number fractions, realizes the reasonable and efficient utilization of each fraction, and effectively reduces energy consumption and production costs.

[0092] The present invention can use alkaline substances to achieve deacidification. In some embodiments, S1 includes: mixing Fischer-Tropsch synthesis naphtha with alkali solution in a deacidification tank, and obtaining deacidified oil after deacidification; washing the deacidified oil in a deacidification water washing tower to obtain deacidified oil. The alkaline substance in the alkali solution includes at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, and potassium carbonate, and the mass concentration of the alkaline substance in the alkali solution is 2% to 8%. The deacidified oil is then washed with water to further remove residual acidic and alkaline substances to ensure that the acid value of the deacidified oil is less than 0.05 mg KOH / g.

[0093] Pre-cutting is essentially to cut off the C5- fraction and the C9+ fraction segment, thereby obtaining a C5-C9 fraction segment. In some embodiments, pre-cutting includes a first pre-cutting and a second pre-cutting; S2 includes: feeding the deacidified oil into the C4 tower, and after the first pre-cutting, obtaining a C4 fraction at the top of the C4 tower and a C4+ fraction segment at the bottom of the tower, to prevent the lighter components from affecting the tower pressure and operational stability of the subsequent process; allowing the C4+ fraction segment to enter the C9 tower, and after the second pre-cutting, obtaining a C5-C9 fraction segment at the top of the C9 tower and a C9+ fraction segment at the bottom of the tower, to reduce the load of the subsequent process segments. The first pre-cutting and the second pre-cutting utilize the difference in volatility of different fractions at different temperatures to achieve separation through a distillation process. In the first pre-cutting process of the C4 tower, the relatively low-boiling-point C4 fraction is separated at the top of the tower, while the relatively high-boiling-point C4+ fraction segment is separated at the bottom of the tower; in the second pre-cutting process of the C9 tower, the relatively low-boiling-point C5-C9 fraction segment is separated at the top of the tower, while the relatively high-boiling-point C9+ fraction segment is separated at the bottom of the tower.

[0094] The present invention does not limit the specific types of C4 tower and C9 tower, which can be conventional petrochemical equipment in the art for separating C4 fraction and C9+ fraction. In some preferred embodiments, the number of plates of C4 tower is 35-55, the reflux ratio is 2-10, the top temperature is 35-50°C, and the pressure is 0.3-0.5MPa. The number of plates of C9 tower is 30-60, the reflux ratio is 1-20, and the bottom temperature is 170-175°C. Among them, the number of plates refers to the number of plates required in C4 tower and C9 tower under ideal conditions. By limiting the number of plates, effective separation is achieved; the reflux ratio refers to the ratio of the amount of liquid refluxed from the top of the tower to the bottom of the tower to the amount of steam rising from the bottom of the tower to the top of the tower. The reflux ratio will affect the separation efficiency and output. The larger the reflux ratio, the more times the material in the tower is circulated, and the better the separation effect. The feed position of C4 tower is the middle of the tower, and the feed position of C9 tower is the middle of the tower. That is to say, the deacidified oil and C4+ fraction segments enter the C4 tower and C9 tower from the middle of the C4 tower and C9 tower respectively.

[0095] In some embodiments, S3 includes: feeding the C5-C9 fraction into the extractive deoxygenation tower and contacting it with the first extractive deoxygenator in reverse, and obtaining deoxygenated oil and oxygen-containing extractant after extractive deoxygenation. The oxygen-containing compounds therein are removed by reverse contacting the C5-C9 fraction with the first extractive deoxygenator. The first extractive deoxygenator can be one or more of 1,2-propylene glycol, cyclopentane sulfone, butyl acetate, acetonitrile, dimethyl sulfoxide, 1,4-butanediol, ethanolamine, 1-methyl-2-pyrrolidone, and glycerol. The preferred system is a mixed system of 1,4-butanediol and glycerol or cyclopentane sulfone, that is, it can be a mixed system of 1,4-butanediol and glycerol, or it can be a mixed system of 1,4-butanediol and cyclopentane sulfone, wherein the volume ratio of 1,4-butanediol to glycerol or cyclopentane sulfone is (1-8):1. The mass ratio of the first extractive deoxygenator to the C5-C9 fraction is (1-5):1.

[0096] The present invention does not limit the specific type of the extractive deoxygenation tower, which can be a conventional extractive deoxygenation tower in the art. In some preferred embodiments, the number of plates of the extractive deoxygenation tower is 20 to 100, the reflux ratio is 1 to 20, the top temperature of the extractive deoxygenation tower is 30 to 50°C, and the bottom temperature is 30 to 50°C. The feeding position of the C5 to C9 fraction section of the extractive deoxygenation tower is the bottom of the tower, that is, the C5 to C9 fraction section enters the extractive deoxygenation tower through the bottom side of the extractive deoxygenation tower, and the first extractive deoxygenation agent enters the extractive deoxygenation tower from the top side of the extractive deoxygenation tower, thereby achieving reverse contact between the two. After extractive deoxygenation, the deoxygenated oil is discharged from the top of the extractive deoxygenation tower, and the oxygen-containing extractant is discharged from the bottom of the extractive deoxygenation tower.

[0097] The oxygenate-containing extractant is an extractant containing oxygen-containing compounds, which is regenerated to obtain a recovered extractant, and then recycled back to the extractive deoxygenation tower to achieve efficient utilization of resources. In some embodiments, S3 further includes: feeding the oxygenate-containing extractant to the extractive agent recovery tower for regeneration to obtain a recovered extractant; and returning the recovered extractant to the extractive deoxygenation tower.

[0098] In order to achieve the recovery and reuse of the extractant, in some embodiments, the top temperature of the extractant recovery tower is 90-150° C., the bottom temperature is 120-200° C., and the pressure is 10-70 kPa.

[0099] The present invention can make the content of oxygen-containing compounds in the deoxygenated oil ≤200ppm through the above steps.

[0100] Individual fractions with different carbon numbers can be obtained by distillation cutting. In some embodiments, the distillation cutting includes a first distillation cutting, a second distillation cutting, a third distillation cutting and a fourth distillation cutting; S4 includes:

[0101] S41, feeding the deoxygenated oil into the C5 tower, and after the first distillation and cutting, obtaining a C5 fraction at the top of the C5 tower and a C6-C9 fraction section at the bottom of the tower;

[0102] S42, feeding the C6-C9 fraction segment into the C6 tower, and after the second distillation cutting, obtaining the C6 fraction at the top of the C6 tower and obtaining the C7-C9 fraction segment at the bottom of the tower;

[0103] S43, feeding the C7-C9 fraction segment into the C7 tower, and after the third distillation cutting, obtaining the C7 fraction at the top of the C7 tower and obtaining the C8-C9 fraction segment at the bottom of the tower;

[0104] S44, feed the C8-C9 fraction segment into the C8 tower, and after the fourth distillation cutting, obtain the C8 fraction at the top of the C8 tower and obtain the C9 fraction at the bottom of the tower.

[0105] Specifically, the deoxygenated oil is fed into the C5 tower, and after the first distillation cutting, the C5 fraction with a relatively low boiling point is separated at the top of the tower, and the C6-C9 fraction segment with a relatively high boiling point is separated at the bottom of the tower; the C6-C9 fraction segment is fed into the C6 tower, and after the second distillation cutting, the C6 fraction with a relatively low boiling point is separated at the top of the tower, and the C7-C9 fraction segment with a relatively high boiling point is separated at the bottom of the tower; the C7-C9 fraction segment is fed into the C7 tower, and after the third distillation cutting, the C7 fraction with a relatively low boiling point is separated at the top of the tower, and the C8-C9 fraction segment with a relatively high boiling point is separated at the bottom of the tower; the C8-C9 fraction segment is fed into the C8 tower, and after the fourth distillation cutting, the C8 fraction with a relatively low boiling point is separated at the top of the C8 tower, and the C9 fraction with a relatively high boiling point is separated at the bottom of the tower.

[0106] In order to achieve the first distillation cut, the second distillation cut, the third distillation cut and the fourth distillation cut, in some preferred embodiments, the number of plates of the C5 tower is 20-60, the reflux ratio is 3-15, the top pressure is 0.1-0.2 MPa, the top temperature is 55-70°C, and the bottom temperature is 105-130°C; the number of plates of the C6 tower is 20-60, the reflux ratio is 2-15, the top temperature is 50-70°C, and the bottom temperature is 110-130°C; the number of plates of the C7 tower is 20-50, the reflux ratio is 1-15, the top temperature is 90-100°C, and the bottom temperature is 120-140°C; the number of plates of the C8 tower is 20-50, the reflux ratio is 1-15, the top temperature is 110-120°C, and the bottom temperature is 185-210°C. The feed positions of C5 tower, C6 tower, C7 tower and C8 tower are all in the middle of the tower, that is to say, deoxygenated oil, C6-C9 fraction section, C7-C9 fraction section and C8-C9 fraction section are fed from the middle of C5 tower, C6 tower, C7 tower and C8 tower respectively.

[0107] The C5 fraction can be used to produce n-hexanol, as an additive for high-octane gasoline, and as a raw material for organic synthesis. During the distillation and cutting process, oxygen-containing compounds will be enriched in the individual fractions of each carbon number. For example, oxygen-containing compounds such as 1-butanol are enriched in the C6 fraction, oxygen-containing compounds such as 1-pentanol are enriched in the C7 fraction, and oxygen-containing compounds such as 1-hexanol are enriched in the C8 fraction, which will cause the content of oxygen-containing compounds to seriously exceed the standard.

[0108] The present invention has been studied and believes that by rationally formulating corresponding fine separation and purification steps according to different carbon number fractions, not only can the enriched oxygen-containing compounds be further removed to meet the index requirement of less than 5ppm of oxygen-containing compounds in each product, but also the rational and efficient utilization of each fraction can be achieved. Specifically, in some embodiments, S5 includes:

[0109] S51, feeding the C6 fraction into a first extractive distillation tower to contact with a first extractant in a reverse direction, and obtaining an alkane-rich component at the top of the first extractive distillation tower after the first extractive distillation, and obtaining a mixture containing the extractant and C6 olefin-rich components at the bottom of the tower;

[0110] S52, feeding a mixture containing an extractant and C6 olefin-rich components into a first extractant regeneration tower, and obtaining a first regenerated extractant at the top of the first extractant regeneration tower after regeneration treatment, and obtaining a C6 olefin-rich component at the bottom of the tower;

[0111] S53, returning the first regenerated extractant to the first extractive distillation tower, feeding the C6 olefin-rich component to the first precision distillation tower, and obtaining a crude 1-hexene product at the top of the first precision distillation tower after the first precision distillation;

[0112] S54, feed the crude 1-hexene product into the first adsorption deoxygenation tower, and obtain the 1-hexene product after the first adsorption deoxygenation.

[0113] For the C6 fraction, first, it is sent to the first extractive distillation tower, and is in reverse contact with the first extractant to achieve the separation of C6 rich olefins; then, the mixture containing the extractant and C6 rich olefins is sent to the first extractant regeneration tower for regeneration treatment to obtain the regenerated first extractant. The regenerated first extractant is returned to the first extractive distillation tower, and the C6 rich olefin component needs to be fed to the first precision distillation tower, and after further distillation, a 1-hexene crude product is obtained at the top of the tower; finally, the 1-hexene crude product needs to be treated by the first adsorption deoxygenation tower to remove residual oxides, so that a 1-hexene product with a purity of more than 99% can be obtained.

[0114] In order to achieve the fine separation of the above C6 fraction, in some embodiments, the number of plates of the first extractive distillation tower is 90-130, the reflux ratio is 5-20, the top temperature is 65-70°C, and the bottom temperature is 140-190°C; more preferably, the C6 fraction feed position of the first extractive distillation tower is at 80-120 plates, and the first extractant feed position is at 10-20 plates; the number of plates of the first extractant regeneration tower is 30-50, the reflux ratio is 3-10, the top temperature is 60-68°C, and the bottom temperature is 200-230°C; the number of plates of the first precise distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 60-65°C, and the bottom temperature is 65-85°C. The volume ratio of the first extractant to the C6 fraction is (5-20):1;

[0115] The feed position of the first extractant regeneration tower and the first precision distillation tower is the middle of the tower, that is, the mixture containing the extractant and C6-rich olefins and the C6-rich olefin component enter the first extractant regeneration tower and the first precision distillation tower respectively from the middle of the tower.

[0116] Similarly, the C7 fraction also needs to be finely separated similar to the C6 fraction to obtain the 1-heptene product. In some embodiments, S6 comprises:

[0117] S61, feeding the C7 fraction into a second extractive distillation tower to contact with a second extractant in a reverse direction, and obtaining an alkane-rich component at the top of the second extractive distillation tower after the second extractive distillation, and obtaining a mixture containing the extractant and C7 olefin-rich components at the bottom of the tower;

[0118] S62, feeding a mixture containing an extractant and C7 olefin-rich components into a second extractant regeneration tower, and obtaining a second regenerated extractant at the top of the second extractant regeneration tower after regeneration treatment, and obtaining a C7 olefin-rich component at the bottom of the tower;

[0119] S63, circulating the second regenerated extractant back to the second extractive distillation tower, feeding the C7 olefin-rich component to the second precision distillation tower, and obtaining a crude 1-heptene product at the top of the second precision distillation tower after the second precision distillation;

[0120] S64, feed the crude 1-heptene product into a second adsorption deoxygenation tower, and obtain a 1-heptene product after the second adsorption deoxygenation.

[0121] For the C7 fraction, first, it is sent to the second extraction distillation tower, and is in reverse contact with the second extractant to achieve the separation of C7 rich olefins; then, the mixture containing the extractant and C7 rich olefins is sent to the second extractant regeneration tower for regeneration treatment to obtain the regenerated second extractant. The regenerated second extractant is returned to the second extraction distillation tower, and the C7 rich olefin component needs to be fed to the second precision distillation tower. After further distillation, the 1-heptene crude product is obtained at the top of the tower; finally, the 1-hexene crude product needs to be treated by the second adsorption deoxygenation tower to remove the residual oxides, so that a 1-heptene product with a purity of more than 99% can be obtained.

[0122] In order to achieve the fine separation of the above-mentioned C7 fraction, in some embodiments, the number of plates of the second extractive distillation tower is 90-130, the reflux ratio is 5-20, the top temperature is 95-100°C, and the bottom temperature is 160-200°C; the C7 fraction feeding position of the second extractive distillation tower is at 80-120 plates, and the second extractant feeding position is at 10-20 plates; the number of plates of the second extractant regeneration tower is 30-50, the reflux ratio is 3-10, the top temperature is 90-98°C, and the bottom temperature is 210-240°C; the number of plates of the second precise distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 90-95°C, and the bottom temperature is 115-125°C; the volume ratio of the second extractant to the C7 fraction is (5-20):1.

[0123] The feed position of the second extractant regeneration tower and the second precision distillation tower is the middle of the tower; that is, the mixture containing the extractant and C7-rich olefins and the C7-rich olefin component enter the second extractant regeneration tower and the second precision distillation tower respectively from the middle.

[0124] The present invention has been studied and believed that the extraction effect is better when a composite extractant is selected for extractive distillation. In some embodiments, the first extractant and the second extractant both include a main extractant and a secondary extractant, wherein the main extractants of the first extractant and the second extractant are each independently at least one of dimethyl phthalate, morpholine, ethanolamine, N-formylmorpholine, butyl acetate or γ-butyrolactone, ε-caprolactone, and the secondary extractants of the first extractant and the second extractant are each independently at least one of water, DMF, and N-methylpyrrolidone; preferably, in the first extractant and the second extractant, the mass ratio of the main extractant to the secondary extractant is each independently (2 to 10):1.

[0125] In some embodiments, the secondary distillation cutting includes a first distillation cutting and a second distillation cutting; S7 includes:

[0126] S71, feeding the C8 fraction into a reactor to undergo an etherification reaction with a low-carbon alcohol to obtain an etherified product;

[0127] S72, feeding the etherification product into a dehydrogenation tower for a first distillation and cutting to remove light components, and then feeding the product into a de-heavy tower for a second distillation and cutting to remove heavy components, and obtaining a crude 1-octene product at the top of the de-heavy tower;

[0128] S73, feeding the crude 1-octene product into a third adsorption deoxygenation tower, and obtaining a 1-octene product after the third adsorption deoxygenation.

[0129] For the C8 fraction, the treatment process is different. First, the C8 fraction needs to undergo an etherification reaction with a low-carbon alcohol in a reactor. In essence, 2-methyl-1-heptene reacts with a low-carbon alcohol to generate an etherified product, and the low-carbon alcohol reacts with 2-methyl-1-heptene to generate a high-boiling-point 2-methoxy-2-methylheptane, while 1-octene does not react. At this time, the etherification product includes unreacted low-carbon alcohol, 2-methoxy-2-methylheptane and 1-octene; then, the etherification product is sent to a light removal tower for the first distillation cutting to remove light components (unreacted low-carbon alcohol), and then sent to a heavy removal tower for the second distillation cutting to remove heavy components (2-methoxy-2-methylheptane), and finally a 1-octene crude product is obtained at the top of the tower; finally, the 1-octene crude product needs to be treated by a third adsorption deoxygenation tower to remove residual oxygenated compounds to obtain a 1-octene product with a purity of not less than 98%.

[0130] In some embodiments, the low-carbon alcohol is one or more of methanol, ethanol, and propanol; the catalyst for the etherification reaction is an ion exchange resin; the number of plates of the light-removing tower is 110-140, the reflux ratio is 10-40, the top temperature is 116-119°C, and the bottom temperature is 120-130°C; the number of plates of the heavy-removing tower is 110-140, the reflux ratio is 10-40, the top temperature is 117-120°C, and the bottom temperature is 125-135°C; the feed positions of the light-removing tower and the heavy-removing tower are both in the middle of the tower, that is, the etherification product and the product of removing the light component enter the light-removing tower and the heavy-removing tower from the middle of the tower respectively.

[0131] According to the mass percentage, the C8 fraction includes 0.2-0.8% of 2-methyl-1-heptene; more preferably, the molar ratio of 2-methyl-1-heptene to low-carbon alcohol is 1:(1.5-8). By limiting the molar ratio of 2-methyl-1-heptene to low-carbon alcohol, 2-methyl-1-heptene can be removed to the maximum extent and the purity of 1-octene product can be improved.

[0132] In some embodiments, the first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower are all loaded with an adsorbent, and the adsorbent is a molecular sieve; preferably, the molecular sieve includes at least one of a 4A molecular sieve, a 5A molecular sieve, a ZSM-5 molecular sieve, a ZSM-11 molecular sieve, a ZSM-34 molecular sieve, a 13X molecular sieve, a Y-type molecular sieve, and an MCM-22 molecular sieve; more preferably, the molecular sieve is a 13X molecular sieve and / or a Y-type molecular sieve.

[0133] The first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower all include two parallel adsorption towers, one of which is used for adsorption deoxygenation, and the other is used for regenerating the adsorbent, and the two adsorption towers are used alternately to achieve continuous production. More preferably, the regeneration of the adsorbent includes: using high-temperature hot nitrogen to purge and regenerate the adsorbent, and the temperature of the high-temperature hot nitrogen is 250-300°C; preferably, the temperature of the first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower during the adsorption deoxygenation process is 20-60°C, and the pressure is 10kPa-50kPa.

[0134] The present invention not only improves the purity of α-olefins, but also effectively reduces energy consumption and production costs. In particular, by using a specific regeneration process, the recycling of the extractant is achieved, waste emissions are reduced, production efficiency is improved, and it is environmentally friendly. The method is suitable for large-scale industrial production and can provide high-quality raw materials for downstream chemical products such as polyolefins, lubricating oils, surfactants, etc., with significant economic and environmental benefits.

[0135] The second aspect of the present invention provides an α-olefin product, which is produced by the method provided by the first aspect, and the α-olefin product includes a 1-hexene product, a 1-heptene product and a 1-octene product.

[0136] By the method provided by the present invention, high-purity α-olefins, including 1-hexene, 1-heptene and 1-octene, can be effectively separated from Fischer-Tropsch synthesis naphtha. In some embodiments, the purity of the 1-hexene product is ≥99%, the purity of the 1-heptene product is ≥99%, and the purity of the 1-octene product is ≥98%.

[0137] The present application is further described in detail below in conjunction with specific embodiments, and these embodiments should not be construed as limiting the scope of protection claimed in the present application. Figure 1 As shown, the device used in the embodiment includes: a deacidification tank 1, a deacidification water washing tower 2, a C4 tower 3, a C9 tower 4, an extractive deoxygenation tower 5, an extractant recovery tower 6, a C5 tower 7, a C6 tower 8, a C7 tower 9, a C8 tower 10, a first extractive distillation tower 11, a first extractant regeneration tower 12, a first precision distillation tower 13, a first adsorption deoxygenation tower 14, a second extractive distillation tower 15, a second extractant regeneration tower 16, a second precision distillation tower 17, a second adsorption deoxygenation tower 18, a reactor 19, a light removal tower 20, a heavy removal tower 21, and a third adsorption deoxygenation tower 22;

[0138] The deacidification tank 1 includes a Fischer-Tropsch synthesis naphtha inlet 102, an alkali solution inlet 101, and a deacidified oil outlet; wherein the Fischer-Tropsch synthesis naphtha inlet 102 and the alkali solution inlet 101 are located in the middle of the deacidification tank 1, and the deacidified oil outlet is located at the top of the deacidification tank 1;

[0139] The deacidification water washing tower 2 comprises a deacidification oil inlet, a deacidification oil outlet and a wastewater outlet, and the deacidification oil outlet of the deacidification tank is connected to the deacidification oil inlet of the deacidification water washing tower; wherein the deacidification oil inlet is located in the middle of the deacidification water washing tower, the deacidification oil outlet is located at the top of the deacidification water washing tower, and the wastewater outlet is located at the bottom of the deacidification water washing tower;

[0140] C4 tower 3 includes a deacidified oil inlet, a C4 fraction outlet and a C4+ fraction section outlet; the deacidified oil inlet of C4 tower 3 is connected to the deacidified oil outlet of deacidified water washing tower 2; the deacidified oil inlet is located in the middle of C4 tower 3, the C4 fraction outlet is located at the top of C4 tower, and the C4+ fraction section outlet is located at the bottom of C4 tower; the number of plates of C4 tower 3 is 35-55, the reflux ratio is 2-10, the tower top temperature is 35-50°C, and the pressure is 0.3-0.5MPa;

[0141] C9 tower 4 includes a C4+ fraction section inlet, a C5-C9 fraction section outlet and a C9+ fraction section outlet; the C4+ fraction section inlet of the C9 tower is connected to the C4+ fraction section outlet of the C4 tower 3, the C4+ fraction section inlet is located in the middle of the C9 tower 4, the C5-C9 fraction section outlet is located at the top of the C9 tower 4, and the C9+ fraction section outlet is located at the bottom of the C9 tower 4; the number of plates of the C9 tower 4 is 30-60, the reflux ratio is 1-20, and the tower bottom temperature is 170-175°C;

[0142] The extractive deoxygenation tower 5 includes a C5-C9 fraction section inlet, a first extractive deoxidant inlet, a deoxygenated oil outlet and an oxygen-containing extractant outlet; the C5-C9 fraction section inlet of the extractive deoxygenation tower 5 is connected to the C5-C9 fraction section outlet of the C9 tower, the C5-C9 fraction section inlet is located at the bottom side of the extractive deoxygenation tower, the first extractive deoxidant inlet is located at the top side of the extractive deoxygenation tower, the deoxygenated oil outlet is located at the top of the extractive deoxygenation tower, and the oxygen-containing extractant outlet is located at the bottom of the extractive deoxygenation tower; the number of plates of the extractive deoxygenation tower is 20-100, the reflux ratio is 1-20, and the temperature of the extractive deoxygenation tower 5 is 30-50°C; the extractant recovery tower 6 includes an oxygen-containing extractant recovery tower 6; The extractant inlet of the extractant recovery tower 6 is connected to the oxygenated extractant outlet of the extractant recovery tower 5, and the extractant recovery outlet of the extractant recovery tower 6 is connected to the first extractant deoxidant inlet of the extractant recovery tower 5; the oxygenated extractant inlet is located in the middle of the extractant recovery tower 6, the extractant recovery outlet is located at the bottom of the extractant recovery tower 6, and the oxide outlet is located at the top of the extractant recovery tower 6; the top temperature of the extractant recovery tower 6 is 90-150°C, the pressure is 10-70kPa, the top temperature of the extractant recovery tower 6 is 80-150°C, and the bottom temperature is 150-220°C;

[0143] C5 tower 7 includes a deoxygenated oil inlet, a C5 fraction outlet and a C6-C9 fraction section outlet; the deoxygenated oil inlet of C5 tower 7 is connected to the deoxygenated oil outlet of the extractive deoxygenation tower; the deoxygenated oil inlet is located in the middle of C5 tower 7, the C5 fraction outlet is located at the top of C5 tower 7, and the C6-C9 fraction section outlet is located at the bottom of C5 tower 7; the number of plates of C5 tower 7 is 20-60, the reflux ratio is 3-15, the tower top pressure is 0.1-0.2MPa, the tower top temperature is 55-70°C, and the tower bottom temperature is 105-130°C;

[0144] The C6 tower 8 includes a C6-C9 fraction section inlet, a C6 fraction outlet and a C7-C9 fraction section outlet; the C6-C9 fraction section inlet of the C6 tower 8 is connected to the C6-C9 fraction section outlet of the C5 tower 7, the C6-C9 fraction section inlet is located in the middle of the C6 tower 8, the C6 fraction outlet is located at the top of the C6 tower 8, and the C7-C9 fraction section outlet is located at the bottom of the C6 tower 8; the number of plates of the C6 tower 8 is 20-60, the reflux ratio is 2-15, the tower top temperature is 50-70°C, and the tower bottom temperature is 110-130°C;

[0145] C7 tower 9 includes a C7-C9 fraction section inlet, a C7 fraction outlet and a C8-C9 fraction section outlet; the C7-C9 fraction section inlet of C7 tower 9 is connected to the C7-C9 fraction section outlet of C6 tower 8, the C7-C9 fraction section inlet is located in the middle of C7 tower 9, the C7 fraction outlet is located at the top of C7 tower 9, and the C8-C9 fraction section outlet is located at the bottom of C7 tower 9; the number of plates of C7 tower 9 is 20-50, the reflux ratio is 1-15, the tower top temperature is 90-100°C, and the tower bottom temperature is 120-140°C;

[0146] The C8 tower 10 includes a C8-C9 fraction section inlet, a C8 fraction outlet and a C9 fraction outlet; the C8-C9 fraction section inlet of the C8 tower 10 is connected to the C8-C9 fraction section outlet of the C7 tower 9, the C8-C9 fraction section inlet is located in the middle of the C8 tower 10, the C8 fraction outlet is located at the top of the C8 tower 10, and the C9 fraction outlet is located at the bottom of the C8 tower 10; the number of plates of the C8 tower 10 is 20-50, the reflux ratio is 1-15, the tower top temperature is 110-120° C., and the tower bottom temperature is 185-210° C.;

[0147] The first extractive distillation tower 11 includes a C6 fraction inlet, a first extractant inlet 103, an alkane-rich component outlet, and an outlet for a mixture containing an extractant and C6-rich olefins; the C6 fraction inlet is connected to the C6 fraction outlet of the C6 tower, the C6 fraction inlet is located at the bottom side, the first extractant inlet 103 is located at the tower top side, the alkane-rich component outlet is located at the tower top, and the outlet for a mixture containing an extractant and C6-rich olefins is located at the tower bottom; the first extractive distillation tower 11 has a plate number of 90 to 130, a reflux ratio of 5 to 20, a tower top temperature of 65 to 70° C., and a tower bottom temperature of 140 to 190° C.; the C6 fraction inlet of the first extractive distillation tower 11 is at 80 to 120 plates, and the first extractant inlet 103 is at 10 to 20 plates;

[0148] The first extractant regeneration tower 12 includes an extractant and C6 olefin-rich mixture inlet, a first regenerated extractant outlet and a C6 olefin-rich component outlet, and the first regenerated extractant outlet of the first extractant regeneration tower 12 is connected to the first extractant inlet 103 of the first extractive distillation tower; the extractant and C6 olefin-rich mixture inlet of the first extractant regeneration tower 12 is connected to the extractant and C6 olefin-rich mixture outlet of the first extractive distillation tower, the extractant and C6 olefin-rich mixture inlet is located in the middle of the tower, the first regenerated extractant outlet is located at the top of the tower, and the C6 olefin-rich component outlet is located at the bottom of the tower; the first extractant regeneration tower 12 has a plate number of 30 to 50, a reflux ratio of 3 to 10, a tower top temperature of 60 to 68° C., and a tower bottom temperature of 200 to 230° C.;

[0149] The first precision distillation tower 13 includes a C6 olefin-rich component inlet, a 1-hexene crude product outlet and an impurity outlet; the C6 olefin-rich component inlet is connected to the C6 olefin-rich component outlet, the C6 olefin-rich component inlet is located in the middle of the tower, the 1-hexene crude product outlet is located at the top of the tower, and the impurity outlet is located at the bottom of the tower; the first precision distillation tower 13 has a plate number of 110 to 140, a reflux ratio of 10 to 30, a tower top temperature of 60 to 65° C., and a tower bottom temperature of 65 to 85° C.;

[0150] The first adsorption deoxygenation tower 14 includes two adsorption towers connected in parallel, one of which is used for adsorption deoxygenation, and the other is used for regenerating the adsorbent, and the two adsorption towers are used alternately; the two adsorption towers are loaded with molecular sieves, and each has a 1-hexene crude product inlet and a 1-hexene product outlet 105; the 1-hexene crude product inlet is connected to the 1-hexene crude product outlet of the first precision distillation tower; the 1-hexene crude product inlet is located at the top of the tower, and the 1-hexene product outlet 105 is located at the bottom of the tower;

[0151] The second extractive distillation tower comprises a C7 fraction inlet, a second extractant inlet 104, an alkane-rich component outlet, and an outlet for a mixture containing an extractant and C7-rich olefins; the C7 fraction inlet is connected to the C7 fraction outlet of the C7 tower, the C7 fraction inlet is located at the bottom side of the tower, the second extractant inlet is located at the top side of the tower, the alkane-rich component outlet is located at the top of the tower, and the outlet for a mixture containing an extractant and C7-rich olefins is located at the bottom of the tower; the number of plates of the second extractive distillation tower is 90-130, the reflux ratio is 5-20, the tower top temperature is 95-100°C, and the tower bottom temperature is 160-200°C; the C7 fraction inlet of the second extractive distillation tower is at 80-120 plates, and the second extractant inlet is at 10-20 plates;

[0152] The second extractant regeneration tower 16 comprises an extractant and C7 olefin-rich mixture inlet, a second regenerated extractant outlet and a C7 olefin-rich component outlet, the second regenerated extractant outlet of the second extractant regeneration tower 16 is connected to the second extractant inlet of the second extractive distillation tower 15; the extractant and C7 olefin-rich mixture inlet of the second extractant regeneration tower 16 is connected to the extractant and C7 olefin-rich mixture outlet of the second extractive distillation tower 15, the extractant and C7 olefin-rich mixture inlet is located in the middle of the tower, the second regenerated extractant outlet is located at the top of the tower, and the C7 olefin-rich component outlet is located at the bottom of the tower; the second extractant regeneration tower 16 has a plate number of 30 to 50, a reflux ratio of 3 to 10, a tower top temperature of 90 to 98° C., and a tower bottom temperature of 210 to 240° C.;

[0153] The second precision distillation tower 17 includes a C7 olefin-rich component inlet, a 1-heptene crude product outlet and an impurity outlet; the C7 olefin-rich component inlet is connected to the C7 olefin-rich component outlet, the C7 olefin-rich component inlet is located in the middle of the tower, the 1-heptene crude product outlet is located at the top of the tower, and the impurity outlet is located at the bottom of the tower; the second precision distillation tower 17 has a plate number of 110 to 140, a reflux ratio of 10 to 30, a tower top temperature of 90 to 96° C., and a tower bottom temperature of 115 to 125° C.;

[0154] The second adsorption deoxygenation tower 18 includes two adsorption towers connected in parallel, one of which is used for adsorption deoxygenation, and the other is used for regenerating the adsorbent, and the two adsorption towers are used alternately; the two adsorption towers are loaded with molecular sieves, and each has a 1-heptene crude product inlet and a 1-heptene product outlet; the 1-heptene crude product inlet is connected to the 1-heptene crude product outlet of the second precision distillation tower; the 1-heptene crude product inlet is located at the top of the tower, and the 1-heptene product outlet 106 is located at the bottom of the tower;

[0155] The reactor 19 includes a C8 fraction inlet, an etherification product outlet, and a low-carbon alcohol inlet 108. The C8 fraction inlet of the reactor 19 is connected to the C8 fraction outlet of the C8 tower. The C8 fraction inlet is located at the top of the reactor 19, and the etherification product outlet is located at the bottom of the reactor.

[0156] The light removal tower 20 includes an etherification product inlet, a light component outlet and a light removal product outlet; the etherification product inlet of the light removal tower 20 is connected to the etherification product outlet of the reactor, the etherification product inlet is located in the middle of the tower, the light component outlet is located at the top of the tower, and the light removal product outlet is located at the bottom of the tower; the number of plates of the light removal tower 20 is 110-140, the reflux ratio is 10-40, the tower top temperature is 116-119° C., and the tower bottom temperature is 120-130° C.;

[0157] The de-weighting tower 21 includes a de-lightening product outlet, a heavy component outlet and a 1-octene crude product outlet; the de-lightening product outlet of the de-weighting tower 21 is connected to the de-lightening product outlet of the de-lighting tower 20, the de-lightening product outlet is located in the middle of the tower, the heavy component outlet is located at the bottom of the tower, and the 1-octene crude product outlet is located at the top of the tower; the number of plates of the de-weighting tower 21 is 110-140, the reflux ratio is 10-40, the tower top temperature is 117-120°C, and the tower bottom temperature is 125-135°C;

[0158] The third adsorption deoxygenation tower 22 includes two adsorption towers connected in parallel, one of which is used for adsorption deoxygenation, and the other is used for regenerating the adsorbent, and the two adsorption towers are used alternately; the two adsorption towers are loaded with molecular sieves, and each has a 1-octene crude product inlet and a 1-octene product outlet; the 1-octene crude product inlet is connected to the 1-octene crude product outlet of the deweighting tower; the 1-octene crude product inlet is located at the top of the tower, and the 1-octene product outlet 107 is located at the bottom of the tower;

[0159] The temperature of the first adsorption deoxygenation tower, the second adsorption deoxygenation tower and the third adsorption deoxygenation tower during the adsorption deoxygenation process is 20° C. to 60° C., and the pressure is 10 kPa to 50 kPa.

[0160] Example 1

[0161] S1, feeding Fischer-Tropsch synthesis naphtha and alkali solution into a deacidification tank for mixing to generate an acid-base neutralization reaction, and obtaining deacidified oil after deacidification; washing the deacidified oil in a deacidification water washing tower to obtain deacidified oil with an acid value of 0.01 mg KOH / g; wherein the alkali solution is a potassium hydroxide solution with a mass content of 2%, and the mass ratio of Fischer-Tropsch synthesis naphtha to the alkali solution is 1:3;

[0162] S2, feeding the deacidified oil from the middle of the tower into the C4 tower, obtaining a C4 fraction at the top of the C4 tower and a C4+ fraction section at the bottom of the tower; feeding the C4+ fraction section into the C9 tower, obtaining a C5-C9 fraction section at the top of the C9 tower and a C9+ fraction section at the bottom of the tower; wherein the C4 tower has 40 plates, a reflux ratio of 8, and a pressure of 0.4 MPa; the C9 tower has 40 plates, and a reflux ratio of 8;

[0163] S3, feeding the C5-C9 fraction into an extraction deoxygenation tower to contact the first extraction deoxygenator in reverse, and obtaining deoxygenated oil and oxygen-containing extractant after extraction deoxygenation; wherein the first extraction deoxygenator is 1,4-butanediol and cyclopentane sulfone (volume ratio 4:1); the mass ratio of the first extraction deoxygenator to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 180 ppm;

[0164] Feeding the oxygenated extractant to an extractant recovery tower for regeneration to obtain a recovered extractant; returning the recovered extractant to the extraction deoxygenation tower;

[0165] S4, distilling and cutting the deoxygenated oil, specifically including:

[0166] S41, feeding the deoxygenated oil to the C5 tower, and after the first distillation cutting, obtaining a C5 fraction section with a purity of 99.1% at the top of the tower, and obtaining a C6-C9 fraction section at the bottom of the tower; wherein the number of plates of the C5 tower is 30, the reflux ratio is 12, and the pressure is 0.1 MPa;

[0167] S42, feeding the C6-C9 fraction segment into the C6 tower, and after the second distillation cutting, obtaining a C6 fraction with a purity of 99% at the top of the tower, and obtaining a C7-C9 fraction segment at the bottom of the tower; wherein the number of plates of the C6 tower is 50, and the reflux ratio is 8;

[0168] S43, feed the C7-C9 fraction segment into the C7 tower, and after the third distillation cutting, obtain the C7 fraction at the top of the tower and the C8-C9 fraction segment at the bottom of the tower; wherein,

[0169] S44, feeding the C8-C9 fraction segment into the C8 tower, and after the fourth distillation cutting, obtaining the C8 fraction at the top of the tower and the C9 fraction at the bottom of the tower;

[0170] S5, sequentially performing a first extractive distillation, a first precise distillation and a first adsorptive deoxygenation on the C6 fraction, specifically comprising:

[0171] S51, feeding the C6 fraction into the first extractive distillation tower to contact with the first extractant in reverse, and after the first extractive distillation, obtaining an alkane-rich component at the top of the tower, and obtaining a mixture containing the extractant and C6-rich olefins at the bottom of the tower; wherein the first extractant is N-methylpyrrolidone (NMP) and γ-butyrolactone (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the olefin component accounts for 95.3% of the mixture containing the extractant and C6-rich olefins;

[0172] S52, feeding a mixture containing an extractant and C6 olefin-rich components into a first extractant regeneration tower, and obtaining a first regenerated extractant at the top of the first extractant regeneration tower after regeneration treatment, and obtaining a C6 olefin-rich component at the bottom of the tower;

[0173] S53, returning the first regenerated extractant to the first extractive distillation tower, feeding the C6 olefin-rich component to the first precision distillation tower, and obtaining a 1-hexene crude product with a purity of 99.1% at the top of the first precision distillation tower after the first precision distillation; the first extractive distillation tower has 120 plates and a reflux ratio of 25;

[0174] S54, feeding the crude 1-hexene product into a first adsorption deoxygenation tower, and obtaining a 1-hexene product after first adsorption deoxygenation; the adsorbent in the first adsorption deoxygenation tower is 13X molecular sieve;

[0175] S6, sequentially subjecting the C7 fraction to a second extractive distillation, a second precise distillation, and a second adsorptive deoxygenation, specifically comprising:

[0176] S61, feeding the C7 fraction into a second extractive distillation tower to contact it with a second extractant in reverse, and after the second extractive distillation, obtaining an alkane-rich component at the top of the second extractive distillation tower, and obtaining a mixture containing an extractant and C7 olefin-rich components at the bottom of the tower; wherein the second extractive distillation tower is NMP and γ-butyrolactone (mass ratio is 4:1), the number of plates of the second extractive distillation tower is 100, the reflux ratio is 15, the feeding position of the C7 fraction of the second extractive distillation tower is at 90 plates, and the feeding position of the second extractant is at 15 plates;

[0177] S62, feeding the mixture containing the extractant and the C7 olefin-rich component into the second extractant regeneration tower, and obtaining the second regenerated extractant at the top of the second extractant regeneration tower after regeneration treatment, and obtaining the C7 olefin-rich component at the bottom of the tower; the number of plates of the second extractant regeneration tower is 50, and the reflux ratio is 8;

[0178] S63, circulating the second regenerated extractant back to the second extractive distillation tower, feeding the C7 olefin-rich component to the second precision distillation tower, and obtaining a crude 1-heptene product at the top of the second precision distillation tower after the second precision distillation; the second precision distillation tower has a plate number of 120 and a reflux ratio of 20;

[0179] S64, feeding the crude 1-heptene product into a second adsorption deoxygenation tower, and obtaining a 1-heptene product after the second adsorption deoxygenation;

[0180] S7, sequentially subjecting the C8 fraction to etherification reaction, secondary distillation cutting, and third adsorption deoxygenation, specifically comprising:

[0181] S71, feeding the C8 fraction into a reactor and mixing it with methanol to cause an etherification reaction to obtain an etherification product; the reactor is loaded with a catalyst, which is a strongly acidic cation exchange resin; the mass content of 2-methyl-1-heptene in the C8 fraction is 0.45%, and the mass content of 2-methyl-1-heptene in the etherification product is 0.038%;

[0182] S72, feeding the etherification product to a light removal tower for a first distillation cut to remove light components (methanol and light components before 1-octene), and then feeding the product to a heavy removal tower for a second distillation cut to remove heavy components, and obtaining a 1-octene crude product with a purity of 98.4% at the top of the heavy removal tower; wherein the light removal tower has 120 plates and a reflux ratio of 26; the heavy removal tower has 130 plates and a reflux ratio of 20;

[0183] S73, feeding the crude 1-octene product into a third adsorption deoxygenation tower, and obtaining a 1-octene product after the third adsorption deoxygenation.

[0184] Example 2

[0185] The difference from Example 1 is that the preparation parameters of S4 are different, specifically:

[0186] S4, distilling and cutting the deoxygenated oil, specifically including:

[0187] S41, feeding the deoxygenated oil to the C5 tower, and after the first distillation, obtaining a C5 fraction section with a purity of 99.3% at the top of the tower, and obtaining a C6-C9 fraction section at the bottom of the tower; wherein the number of plates of the C5 tower is 50, the reflux ratio is 6, and the pressure is 0.15 MPa;

[0188] S42, feeding the C6-C9 fraction segment into the C6 tower, and after the second distillation cutting, obtaining a C6 fraction with a purity of 99.1% at the top of the tower, and obtaining a C7-C9 fraction segment at the bottom of the tower; wherein the number of plates of the C6 tower is 30, and the reflux ratio is 12;

[0189] S43, feeding the C7-C9 fraction segment into the C7 tower, and after the third distillation cutting, obtaining a C7 fraction with a purity of 98.9% at the top of the tower, and obtaining a C8-C9 fraction segment at the bottom of the tower; wherein the number of plates of the C7 tower is 45, and the reflux ratio is 3;

[0190] S44, feed the C8-C9 fraction segment into the C8 tower, and after the fourth distillation cutting, obtain a C8 fraction with a purity of 99.2% at the top of the tower, and obtain a C9 fraction at the bottom of the tower; wherein, the number of plates of the C8 tower is 25, and the reflux ratio is 12.

[0191] Example 3

[0192] The difference from Example 1 is that in S3, the first extraction deoxidant is 1,4-butanediol and propylene glycol (volume ratio 8:1), the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 120 ppm.

[0193] Example 4

[0194] The difference from Example 1 is that in S3, the first extraction deoxygenating agent is 1,4-butanediol and propylene glycol (volume ratio 2:1), the mass ratio of the first extraction deoxygenating agent to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 250 ppm.

[0195] Example 5

[0196] The difference from Example 1 is that in S3, the first extraction deoxidant is 1,4-butanediol, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 60 ppm.

[0197] Example 6

[0198] The difference from Example 1 is that in S3, the first extraction deoxidant is sulfolane, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 600 ppm.

[0199] Example 7

[0200] The difference from Example 1 is that in S3, the first extraction deoxidant is butyl acetate, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 300 ppm.

[0201] Example 8

[0202] The difference from Example 1 is that in S3, the first extraction deoxidant is acetonitrile, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 800 ppm.

[0203] Example 9

[0204] The difference from Example 1 is that in S3, the first extraction deoxidant is dimethyl sulfoxide, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 200 ppm.

[0205] Example 10

[0206] The difference from Example 1 is that in S3, the first extraction deoxidant is ethanolamine, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 180 ppm;

[0207] Embodiment 11

[0208] The difference from Example 1 is that in S3, the first extraction deoxidant is 1-methyl-2-pyrrolidone, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, the content of oxygen-containing compounds in the deoxygenated oil is 330 ppm, the regenerated extraction agent is not complete, and a small amount of oxides are present.

[0209] Example 12

[0210] The difference from Example 1 is that in S3, the first extraction deoxidant is glycerol, the mass ratio of the first extraction deoxidant to the C5-C9 fraction is 4:1, and the content of oxygen-containing compounds in the deoxygenated oil is 1500 ppm.

[0211] Example 13

[0212] The difference from Example 1 is that in S51, the first extractant is N-methylpyrrolidone (NMP) and dimethyl phthalate (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the proportion of olefin components in the mixture containing the extractant and C6 rich olefins is 93.8%.

[0213] Embodiment 14

[0214] The difference from Example 1 is that in S51, the first extractant is N-methylpyrrolidone (NMP) and ε-caprolactone (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the olefin component accounts for 93.1% of the mixture containing the extractant and C6 rich olefins.

[0215] Embodiment 15

[0216] The difference from Example 1 is that in S51, the first extractant is N-methylpyrrolidone (NMP) and N-formylmorpholine (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the proportion of olefin components in the mixture containing the extractant and C6 rich olefins is 96.7%.

[0217] Example 16

[0218] The difference from Example 1 is that in S51, the first extractant is N,N-dimethylformamide and γ-butyrolactone (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the olefin component accounts for 93.7% of the mixture containing the extractant and C6 rich olefins.

[0219] Embodiment 17

[0220] The difference from Example 1 is that in S51, the first extractant is N,N-dimethylformamide and morpholine (mass ratio is 4:1), the number of plates of the first extractive distillation tower is 120, the feeding position of the C6 fraction is the 90th plate, the feeding position of the first extractant is the 15th plate, the volume ratio of the first extractant to the C6 fraction is 10:1, and the reflux ratio is 6:1; the proportion of olefin components in the mixture containing the extractant and C6 rich olefins is 92.8%.

[0221] Table 1

[0222]

[0223]

[0224] It can be seen that by cooperating with each other through the steps of deacidification, pre-cutting, extraction deoxygenation, distillation cutting and adsorption deoxygenation, the isomers, organic acids and oxygen-containing compounds in the oil products can be removed to the maximum extent, and the content of oxygen-containing compounds in the oil products can be reduced to below 5ppm, meeting the requirements of polymerization grade indicators, and finally effectively separating high-purity 1-hexene products, 1-heptene products and 1-octene products, etc. In addition, the present invention reasonably prepares corresponding fine separation and purification steps according to different carbon number fractions, which can not only further remove oxygen-containing compounds, but also realize the reasonable and efficient utilization of each fraction, and effectively reduce energy consumption and production costs.

[0225] By comparing Example 1 and Examples 3-12, it can be seen that the selection of different first extraction deoxidizers has a great impact on the regeneration cycle of the adsorption tower during the adsorption deoxidation process. The lower the concentration of residual oxides in the early stage, the longer the regeneration cycle of the adsorption deoxidation tower, and the lower the energy consumption. At the same time, the boiling point difference between the extractant and the oil phase should be considered. There is an extractant with good extraction effect, and its boiling point is close to that of the oil phase, resulting in incomplete regeneration. The extraction effect of the circulating extractant is getting worse and worse. At this time, compound extraction is required to achieve better extraction effect and complete regeneration. In particular, in Examples 5 and 7, the extractant regenerated from the extractant regeneration tower contains a small amount of oxides. Under long-term operation, the purity of the extractant will become lower and lower, and the recovery effect will become worse and worse, and there is a problem of incomplete regeneration of the extractant.

[0226] The above description is only a preferred embodiment of the present invention and is 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 method for separating α-olefins from Fischer-Tropsch naphtha, characterized in that: The following steps are involved: S1, deacidifying Fischer-Tropsch synthesis naphtha to obtain deacidified oil; S2, pre-cutting the deacidified oil to obtain a C5-C9 fraction; S3, extracting and deoxygenating the C5-C9 fraction to obtain deoxygenated oil; S4, distilling and cutting the deoxygenated oil to obtain a C6 fraction, a C7 fraction and a C8 fraction respectively; S5, sequentially subjecting the C6 fraction to a first extractive distillation, a first precise distillation and a first adsorptive deoxygenation to obtain a 1-hexene product; S6, sequentially subjecting the C7 fraction to a second extractive distillation, a second precise distillation, and a second adsorptive deoxygenation to obtain a 1-heptene product; S7, sequentially subjecting the C8 fraction to etherification reaction, secondary distillation cutting and third adsorption deoxygenation to obtain a 1-octene product.

2. The method according to claim 1, characterized in that The S1 includes: The Fischer-Tropsch synthesis naphtha is mixed with alkali solution in a deacidification tank to obtain deacidified oil after deacidification; the deacidified oil is washed with water in a deacidification water washing tower to obtain deacidified oil; Preferably, the alkaline substance in the alkali solution includes at least one of potassium hydroxide, sodium hydroxide, sodium carbonate and potassium carbonate, and the mass concentration of the alkaline substance in the alkali solution is 2% to 8%; Preferably, the acid value of the deacidified oil is less than 0.05 mg KOH / g.

3. The method according to claim 1, characterized in that The pre-cutting includes a first pre-cutting and a second pre-cutting; The S2 includes: The deacidified oil is fed into a C4 tower, and after a first pre-cutting, a C4 fraction is obtained at the top of the C4 tower, and a C4+ fraction segment is obtained at the bottom of the tower; the C4+ fraction segment is fed into a C9 tower, and after a second pre-cutting, a C5-C9 fraction segment is obtained at the top of the C9 tower, and a C9+ fraction segment is obtained at the bottom of the tower; Preferably, the number of plates of the C4 tower is 35 to 55, the reflux ratio is 2 to 10, the top temperature is 35 to 50° C., and the pressure is 0.3 to 0.5 MPa; Preferably, the C9 tower has a plate number of 30 to 60, a reflux ratio of 1 to 20, and a tower bottom temperature of 170 to 175°C.

4. The method according to claim 1, characterized in that: The S3 includes: Feeding the C5-C9 fraction segment into an extracting deoxygenation tower to contact with the first extracting deoxygenating agent in reverse order, and obtaining deoxygenated oil and an oxygen-containing extracting agent after extracting and deoxygenating; Preferably, the first extractive deoxidant comprises at least one of 1,2-propylene glycol, cyclopentane sulfone, butyl acetate, acetonitrile, dimethyl sulfoxide, 1,4-butanediol, ethanolamine, 1-methyl-2-pyrrolidone, and glycerol; More preferably, the first extracting deoxidizing agent is a mixed system of 1,4-butanediol and glycerol or sulfolane, wherein the volume ratio of the 1,4-butanediol to the glycerol or the sulfolane is (1-8):1; Preferably, the number of plates of the extractive deoxygenation tower is 20 to 100, the reflux ratio is 1 to 20, and the temperature of the extractive deoxygenation tower is 30 to 50°C; Preferably, S3 further comprises: feeding the oxygenate-containing extractant to an extractant recovery tower for regeneration to obtain a recovered extractant; returning the recovered extractant to the extraction deoxygenation tower; Preferably, the top temperature of the extractant recovery tower is 90-150°C, the bottom temperature is 120-200°C, and the pressure is 10-70 kPa; Preferably, the mass ratio of the first extractive deoxidant to the C5-C9 fraction segment is (1-5):

1.

5. The method according to claim 4, characterized in that The distillation cutting includes the first distillation cutting, the second distillation cutting, the third distillation cutting and the fourth distillation cutting; the S4 includes: S41, feeding the deoxygenated oil into a C5 tower, and after the first distillation and cutting, obtaining a C5 fraction at the top of the C5 tower and a C6-C9 fraction section at the bottom of the tower; S42, feeding the C6-C9 fraction segment into a C6 tower, and after the second distillation cutting, obtaining a C6 fraction at the top of the C6 tower and a C7-C9 fraction segment at the bottom of the tower; S43, feeding the C7-C9 fraction segment into the C7 tower, and after the third distillation cutting, obtaining the C7 fraction at the top of the C7 tower and obtaining the C8-C9 fraction segment at the bottom of the tower; S44, feeding the C8-C9 fraction segment into a C8 tower, and after the fourth distillation cutting, obtaining a C8 fraction at the top of the C8 tower and a C9 fraction at the bottom of the tower; Preferably, the number of plates of the C5 tower is 20 to 60, the reflux ratio is 3 to 15, the top pressure is 0.1 to 0.2 MPa, the top temperature is 55 to 70° C., and the bottom temperature is 105 to 130° C.; Preferably, the C6 tower has a plate number of 20 to 60, a reflux ratio of 2 to 15, a top temperature of 50 to 70° C., and a bottom temperature of 110 to 130° C.; Preferably, the C7 tower has a plate number of 20 to 50, a reflux ratio of 1 to 15, a top temperature of 90 to 100° C., and a bottom temperature of 120 to 140° C.; Preferably, the C8 tower has a plate number of 20 to 50, a reflux ratio of 1 to 15, a top temperature of 110 to 120° C., and a bottom temperature of 185 to 210° C.

6. The method according to any one of claims 1 to 5, characterized in that The S5 includes: S51, feeding the C6 fraction into a first extractive distillation tower to contact with a first extractant in a reverse direction, and after the first extractive distillation, obtaining an alkane-rich component at the top of the first extractive distillation tower and obtaining a mixture containing the extractant and C6 olefin-rich components at the bottom of the tower; S52, feeding the mixture containing the extractant and the C6 olefin-rich component into a first extractant regeneration tower, and obtaining a first regenerated extractant at the top of the first extractant regeneration tower after regeneration treatment, and obtaining a C6 olefin-rich component at the bottom of the tower; S53, returning the first regenerated extractant to the first extractive distillation tower, feeding the C6 olefin-rich component to the first precision distillation tower, and obtaining a crude 1-hexene product at the top of the first precision distillation tower after the first precision distillation; S54, feeding the crude 1-hexene product into a first adsorption deoxygenation tower, and obtaining the 1-hexene product after first adsorption deoxygenation; Preferably, the first extractive distillation tower has a plate number of 90 to 130, a reflux ratio of 5 to 20, a top temperature of 65 to 70° C., and a bottom temperature of 140 to 190° C.; Preferably, the number of plates of the first extractant regeneration tower is 30-50, the reflux ratio is 3-10, the top temperature is 60-68°C, and the bottom temperature is 200-230°C; Preferably, the number of plates of the first precision distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 60-65°C, and the bottom temperature is 65-85°C; Preferably, the volume ratio of the first extractant to the C6 fraction is (5-20):

1.

7. The method according to claim 6, characterized in that The S6 includes: S61, feeding the C7 fraction into a second extractive distillation tower to contact with a second extractant in a reverse direction, and obtaining an alkane-rich component at the top of the second extractive distillation tower after the second extractive distillation, and obtaining a mixture containing the extractant and C7 olefin-rich components at the bottom of the tower; S62, feeding the mixture containing the extractant and the C7 olefin-rich component into a second extractant regeneration tower, and obtaining a second regenerated extractant at the top of the second extractant regeneration tower after regeneration treatment, and obtaining a C7 olefin-rich component at the bottom of the tower; S63, circulating the second regenerated extractant back to the second extractive distillation tower, feeding the C7 olefin-rich component to the second precision distillation tower, and obtaining a crude 1-heptene product at the top of the second precision distillation tower after the second precision distillation; S64, feeding the crude 1-heptene product into a second adsorption deoxygenation tower, and obtaining the 1-heptene product after the second adsorption deoxygenation; Preferably, the number of plates of the second extractive distillation tower is 90-130, the reflux ratio is 5-20, the top temperature is 95-100°C, and the bottom temperature is 160-200°C; Preferably, the number of plates of the second extractant regeneration tower is 30-50, the reflux ratio is 3-10, the top temperature is 90-98°C, and the bottom temperature is 210-240°C; Preferably, the number of plates of the second precision distillation tower is 110-140, the reflux ratio is 10-30, the top temperature is 90-96°C, and the bottom temperature is 100-115°C; Preferably, the first extractant and the second extractant both comprise a main extractant and a secondary extractant, wherein the main extractant of the first extractant and the second extractant is independently selected from at least one of dimethyl phthalate, morpholine, ethanolamine, N-formylmorpholine, butyl acetate, γ-butyrolactone, and ε-caprolactone, and the secondary extractant of the first extractant and the second extractant is independently selected from at least one of water, N,N-dimethylformamide, and N-methylpyrrolidone; Preferably, in the first extractant and the second extractant, the mass ratio of the main extractant to the secondary extractant is independently (2-10):1; Preferably, the volume ratio of the second extractant to the C7 fraction is (5-20):

1.

8. The method according to claim 7, characterized in that The secondary distillation cutting includes a first distillation cutting and a second distillation cutting; S7 includes: S71, feeding the C8 fraction into a reactor to undergo an etherification reaction with a low-carbon alcohol to obtain an etherified product; S72, feeding the etherification product to a light-removing tower for a first distillation and cutting to remove light components, and then feeding the etherification product to a heavy-removing tower for a second distillation and cutting to remove heavy components, and obtaining a crude 1-octene product at the top of the heavy-removing tower; S73, feeding the crude 1-octene product into a third adsorption deoxygenation tower, and obtaining the 1-octene product after the third adsorption deoxygenation; Preferably, the low-carbon alcohol is one or more of methanol, ethanol, and propanol, more preferably methanol; Preferably, the catalyst for the etherification reaction is an ion exchange resin; Preferably, the number of plates of the light-removal tower is 110-140, the reflux ratio is 10-40, the top temperature is 116-119° C., and the bottom temperature is 120-130° C.; Preferably, the number of plates of the deweighting tower is 110-140, the reflux ratio is 10-40, the top temperature is 117-120°C, and the bottom temperature is 125-135°C; Preferably, the C8 fraction comprises 0.2% to 0.8% of 2-methyl-1-heptene in terms of mass percentage; More preferably, the molar ratio of the 2-methyl-1-heptene to the lower carbon alcohol is 1:(1.5-8).

9. The method according to claim 8, characterized in that The first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower each include two adsorption towers connected in parallel, each of the adsorption towers is loaded with an adsorbent, one of the adsorption towers is used for adsorption deoxygenation, and the other adsorption tower is used for regenerating the adsorbent, and the two adsorption towers are used alternately; Preferably, the regeneration of the adsorbent comprises: using high-temperature hot nitrogen to purge and regenerate the adsorbent, the temperature of the high-temperature hot nitrogen being 250-300° C.; Preferably, the temperature of the first adsorption deoxygenation tower, the second adsorption deoxygenation tower, and the third adsorption deoxygenation tower during the adsorption deoxygenation process is 20°C to 60°C, and the pressure is 10kPa to 50kPa; Preferably, the adsorbent is a molecular sieve, and the molecular sieve includes at least one of 4A molecular sieve, 5A molecular sieve, ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-34 molecular sieve, 13X molecular sieve, Y-type molecular sieve, and MCM-22 molecular sieve.

10. An alpha-olefin product, characterized in that: The α-olefin product is produced by the method according to any one of claims 1 to 9, and the α-olefin product includes a 1-hexene product, a 1-heptene product and a 1-octene product; Preferably, the purity of the 1-hexene product is ≥99%, the purity of the 1-heptene product is ≥99%, and the purity of the 1-octene product is ≥98%.

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