A method and system for separating high-purity alpha-olefins from Fischer-Tropsch light oil

Abstract

The present invention provides a method for separating alpha-olefins from Fischer-Tropsch light oil and a system for implementing the method. The method comprises fraction cutting, light removal, enrichment in an enrichment tower, oxygen-containing organic matter removal and purification of the Fischer-Tropsch light oil, thereby obtaining a high-purity alpha-olefin product. The method of the present invention has the advantages of being simple and flexible, introducing few impurities, and being able to obtain alpha-olefins with higher purity at a high yield.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry of Fischer-Tropsch synthesis products, and in particular relates to a system and method for separating high-value-added alpha-olefins from light oil as an intermediate oil product of Fischer-Tropsch synthesis. Background Art

[0002] α-olefins are important raw materials for petrochemicals and can be used in many chemical fields such as comonomers, surfactant synthesis intermediates, plasticizers, synthetic lubricants and oil additives. At present, the main ways to produce α-olefins in the petrochemical field are ethylene polymerization and paraffin cracking, but these two production processes have certain disadvantages. For example, the ethylene polymerization process cannot produce high-carbon α-olefins, and the paraffin cracking process has complex products and the cost of separating α-olefins is high.

[0003] Fischer-Tropsch synthesis converts CO and H2 (also known as synthesis gas) into hydrocarbon compounds (mainly straight-chain alkanes and olefins) under certain reaction conditions through catalysis. Its product distribution characteristics are hydrocarbon compounds containing C1 to C100, which can usually be further converted to obtain clean liquid fuels (such as gasoline, diesel, etc.). At the same time, according to the carbon number distribution characteristics of the products, the hydrocarbon compounds obtained by Fischer-Tropsch synthesis can also be used to separate α-olefins.

[0004] Among the projects that have been started, the intermediate products of Fischer-Tropsch synthesis are mainly light oil, heavy oil, heavy wax and LPG. Among them, the light oil intermediate products are mainly composed of C4-C30 normal alkanes and normal olefins. The normal olefin content is about 55wt% and is mainly α-olefins. Impurity olefins such as isoolefins and diolefins are very few, which is very suitable for the production of α-olefins. Compared with the production process in the petrochemical field, the technical advantages of separating α-olefins from Fischer-Tropsch synthesis intermediate oil products are more obvious, and the separation cost is lower.

[0005] In addition to hydrocarbon compounds, the Fischer-Tropsch light oil also contains 2wt% to 5wt% of oxygenated organic matter, mainly alcohols, aldehydes, acids, ketones, esters, etc. The presence of these oxygenated compounds not only affects the purity of the product after α-olefin separation, but also affects the downstream production of α-olefin (such as polymerization, acylation reaction, etc.), and will cause side reactions and catalyst poisoning and deactivation. Therefore, they must be removed cleanly during the separation process.

[0006] Patent CN105777467B describes the separation of oxygenated compounds and 1-hexene in Fischer-Tropsch synthetic oil products, mainly by cutting the C6 fraction with a cutting tower, removing oxygenated compounds with an extraction tower, further converting tertiary carbon into ethers through methanol etherification, and further purifying through distillation, and finally removing C6 isoparaffins and cycloolefins to obtain 1-hexene products. Although the method obtains 1-hexene products with high purity, the separation process is too complicated and needs to be separated again through methanol etherification to improve the purity. The process applicability is poor, the product is relatively single, and it cannot solve the separation and purification problems of α-olefins of various carbon numbers in Fischer-Tropsch light oil.

[0007] Patent CN103360195B discloses a method for separating and purifying 1-octene, wherein 1-octene is obtained by azeotropic distillation to remove oxides, distillation to remove isomers, and refining of crude products. This process adds an azeotropic agent and an extractant during the distillation process, which has the risk of introducing impurities and also increases the operating cost of the distillation process.

[0008] Patent CN100575320C uses a mixture of methanol and water as a solvent to remove olefins in the range of C6-C16 through a liquid-liquid extraction tower, and at the same time recycles the top products of oil-containing methanol, olefins and alkanes from the recovery tower to the extraction tower, thereby improving the total recovery rate of olefins and alkanes. However, the extraction tower is affected by the mass transfer rate and efficiency during operation. In order to ensure the extraction efficiency, the required number of trays is relatively high, and its separation fraction section is relatively narrow, which cannot be fully used for the removal of oxygenated organic matter in Fischer-Tropsch light oil. Summary of the invention

[0009] The present invention uses Fischer-Tropsch synthetic light oil as raw material, provides a method for separating high value-added C6-C12 single-carbon alpha-olefins from Fischer-Tropsch synthetic light oil, and removes oxygen-containing organic matter therefrom, ultimately obtaining high-purity (purity ≥ 95%) single-carbon alpha-olefin products.

[0010] In one aspect, the present invention provides a method for separating α-olefins from Fischer-Tropsch light oil, comprising:

[0011] (1) fractionating the Fischer-Tropsch synthesis light oil to obtain narrow fraction oil and fraction-cut bottom oil;

[0012] (2) subjecting the narrow fraction oil to light component removal treatment to obtain a distillate oil from which light components have been removed and a light component after light component removal;

[0013] (3) enriching the distillate oil after light components are removed by using an enrichment tower to obtain a crude α-olefin product and a residual fraction after α-olefin removal, wherein the number of plates of the enrichment tower is not less than 60 and the tower top temperature is 62° C. to 215° C.;

[0014] (4) removing oxygen-containing organic matter from the crude α-olefin product to obtain an α-olefin product from which oxygen-containing organic matter has been removed;

[0015] (5) Purifying the α-olefin product after removing the oxygen-containing organic matter to obtain a light component at the top of the tower, a heavy component at the bottom of the tower, and an α-olefin product.

[0016] On the other hand, the present invention relates to a system for implementing the above method, comprising: a fraction cutting tower, a light removal tower, an enrichment tower, an oxygen-containing organic matter removal unit and a purification tower connected in sequence in a fluid-connected manner, wherein the number of plates of the enrichment tower is not less than 60.

[0017] The method of the present invention has the following beneficial effects:

[0018] 1. Fewer impurity components are introduced during the separation process and can be reused, thus achieving a green separation process.

[0019] 2. The production process is simple and flexible, and the target product can be flexibly adjusted according to actual conditions to increase product returns.

[0020] 3. The enrichment tower is used for enrichment, which can improve the yield and purity of α-olefins. The α-olefins separated by the method of the present invention are of high purity and can be directly used as production raw materials for further deep processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are a part of the specification and together with the detailed description, they provide further explanation of the present invention but are not intended to limit the present invention.

[0022] Figure 1 A schematic diagram of an exemplary α-olefin separation process of the present invention is shown in FIG.

[0023] Figure 2 A simplified flow diagram of the oxygenated organic removal step in an exemplary method of the present invention.

[0024] The reference numerals in the figures represent:

[0025] 1. Fraction cutting tower; 2. Light removal tower; 3. Enrichment tower; 4. Oxygen-containing organic matter removal unit; 5. Purification tower;

[0026] 6. Centrifugal extraction; 7. Water washing; 8. Adsorption separation; 9. Water washing; 10. Distillation;

[0027] 12, extractant; 13, crude α-olefin product after extraction; 14, α-olefin product after washing; 15, extractant after centrifuge separation; 16, extractant after washing; 17, waste water; 18, α-olefin product recovered from the extractant;

[0028] 101, Fischer-Tropsch synthesis light oil; 102, narrow fraction oil; 103, fraction cut tower bottom oil; 104, light components; 105, fraction oil after removing light components; 106, α-olefin crude product; 107, residual fraction after removing α-olefin; 108, α-olefin after removing oxygenated organic matter; 109, purified α-olefin product; 110, light components at the top of the purification tower; 111, heavy components in the bottom of the purification tower. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are described in detail below. The specific embodiments described here are only used to illustrate and explain the present invention, but are not used to limit the present invention.

[0030] In one embodiment, the present invention provides a method for separating α-olefins from Fischer-Tropsch light oil, comprising:

[0031] (1) fractionating the Fischer-Tropsch synthesis light oil to obtain narrow fraction oil and fraction-cut bottom oil;

[0032] (2) subjecting the narrow fraction oil to light component removal treatment to obtain a distillate oil from which light components have been removed and a light component after light component removal;

[0033] (3) enriching the distillate oil after light components are removed by using an enrichment tower to obtain a crude α-olefin product and a residual fraction after α-olefin removal, wherein the number of plates of the enrichment tower is not less than 60 and the tower top temperature is 62 to 215° C.;

[0034] (4) removing oxygen-containing organic matter from the crude α-olefin product to obtain an α-olefin product from which oxygen-containing organic matter has been removed;

[0035] (5) Purifying the α-olefin product after removing the oxygen-containing organic matter to obtain a light component at the top of the tower, a heavy component at the bottom of the tower, and an α-olefin product.

[0036] In this article, the Fischer-Tropsch synthesis light oil in step (1) is an oil phase intermediate product obtained after two flash distillations and oil-water separation of the gas phase product at the top of the Fischer-Tropsch synthesis reactor, and its distillation temperature is 0-500° C., preferably 20° C.-450° C., and more preferably 50° C.-300° C. In some preferred embodiments, the Fischer-Tropsch synthesis light oil mainly contains C4-C37 normal alkanes and normal olefins, preferably mainly contains C5-C30 normal alkanes and normal olefins, more preferably mainly contains C6-C17 normal alkanes and normal olefins, and also contains 4wt%-6wt% of isoalkanes and internal olefins, and 3wt%-5wt% of oxygen-containing organic matter.

[0037] In this article, the normal olefin refers to a linear monoolefin with a double bond at the terminal position, that is, an α-olefin. In some embodiments, the α-olefin is any one of C6 to C12 α-olefins.

[0038] As used herein, the internal olefins are alpha-olefin isomers, meaning olefins whose double bonds are not terminal.

[0039] In some preferred embodiments, the fraction cutting in step (1) is performed in a fraction cutting tower, wherein the Fischer-Tropsch synthesis light oil is fed into the fraction cutting tower, and the components containing the target carbon number hydrocarbon products are preliminarily separated, thereby obtaining a narrow fraction oil containing a higher content of the target carbon number alkane olefin products and a fraction cutting tower bottom oil.

[0040] In some further preferred embodiments, the fraction cutting tower is a continuous or intermittent distillation tower, and the number of plates may be not less than 20, preferably 20 to 60. Preferably, the Fischer-Tropsch synthesis light oil can be fed from the lower middle part and / or the bottom of the fraction cutting tower, and the narrow fraction oil can be obtained from the top and / or the side line.

[0041] In some preferred embodiments, the conditions for fraction cutting in step (1) are: tower top temperature of 63°C to 220°C, pressure of 10 kPa to 100 kPa, and reflux ratio of 10:1 to 1:10 (e.g., 5:1 to 1:5). Specifically, the tower top temperature can be determined according to the target product (i.e., the α-olefin product desired to be separated). When the target product is C6 olefin, the tower top temperature can be 63°C to 90°C; when the target product is C7 olefin, the tower top temperature can be 90°C to 120°C; when the target product is C8 olefin, the tower top temperature can be 120°C to 140°C; when the target product is C9 olefin, the tower top temperature can be 120°C to 160°C; when the target product is C10 olefin, the tower top temperature can be 160°C to 190°C; when the target product is C11 olefin, the tower top temperature can be 180°C to 200°C; when the target product is C12 olefin, the tower top temperature can be 190°C to 220°C. The inventors have noticed that if the top temperature of the fraction cutting tower is too high, the tower bottom heating temperature may be higher than 300°C, which may cause the material to be thermally cracked in the tower and cause the composition to change. In order to prevent the material from being thermally cracked in the tower and causing the composition to change, it is preferred to use a reduced pressure operation, and the operating pressure may be 10kPa to 100kPa. During the reduced pressure operation, due to the decrease in the boiling point of the fraction, the top temperature of the tower is preferably also reduced to 10°C to 40°C higher than the boiling point of the target fraction under the operating pressure.

[0042] In some preferred embodiments, the light component removal treatment in step (2) is carried out in a light component removal tower. Specifically, the light components with a boiling point lower than the single carbon number α-olefin to be separated (i.e., the light components after light component removal) are separated from the top of the light component removal tower, and a distillate oil containing a high content of α-olefins with the carbon number to be separated is obtained from the bottom of the light component removal tower. In some preferred embodiments, the light component removal tower is a continuous distillation tower, and the number of plates may be not less than 40, for example, 60 to 120, preferably 60 to 80. In the method described herein, the distillate oil from which the light components are removed contains the single carbon number α-olefin to be separated, specifically any one of the α-olefins of C6 to C12.

[0043] In some further preferred embodiments, the feed position of the narrow fraction oil in the light fraction removal treatment in step (2) is in the lower middle part of the light fraction removal tower.

[0044] In some preferred embodiments, the conditions of the light removal treatment in step (2) are: the tower top temperature is 40°C to 210°C, the pressure is 10 to 100 kPa, and the reflux ratio is 10:1 to 1:10 (e.g., 5:1 to 1:5, 3:1 to 1:1). In some preferred embodiments, the pressure is 100 kPa, and according to the carbon number difference of the separated α-olefins, the tower top temperature of the light removal tower can be 40°C to 60°C (C6 olefins), 60°C to 90°C (C7 olefins), 80°C to 120°C (C8 olefins), 120°C to 146°C (C9 olefins), 140°C to 169°C (C10 olefins), 160°C to 190°C (C11 olefins), and 180°C to 210°C (C12 olefins). When the pressure of the light-removal tower is reduced, the boiling point of the α-olefin to be separated can be calculated based on the actual operating pressure in the tower and with reference to the Antoine equation (the equation relating boiling point to vapor pressure), and the tower top temperature can preferably be set to be 0 to 20°C lower than the boiling point of the single-carbon α-olefin to be separated.

[0045] In some preferred embodiments, in step (3), the distillate oil containing the α-olefin to be separated and the light components are removed is enriched in an enrichment tower, and then the crude α-olefin product is separated from the top of the enrichment tower. The use of an enrichment tower for treatment is conducive to enriching the α-olefins of the target carbon number, so as to achieve the subsequent target α-olefin product with a higher yield and higher purity. The number of plates of the enrichment tower is preferably 60 to 120, more preferably 60 to 80. In some preferred embodiments, the feed position of the distillate oil from which the light components are removed is the lower middle part of the enrichment tower or the bottom of the tower.

[0046] In the distillate oil from which the light components are removed, the component with the lowest distillation temperature is the α-olefin to be separated. In some preferred embodiments, in step (3), in order to obtain α-olefins with relatively high purity, the top temperature of the enrichment tower can be controlled according to the α-olefin to be separated. For α-olefins to be separated with different carbon numbers, the top temperature of the enrichment tower can be controlled at: C6 olefin, 62°C to 65°C; C7 olefin 90°C to 95°C; C8 olefin 115°C to 122°C; C9 olefin 140°C to 147°C; C10 olefin 165°C to 171°C; C11 olefin 185°C to 193°C; C12 olefin 205°C to 215°C; thereby further improving the yield of the target α-olefin. In some preferred embodiments, the reflux ratio of the enrichment tower can be controlled to be 10:1 to 1:10 (e.g., 5:1 to 1:5, 5:1 to 1:1).

[0047] In some further preferred embodiments, the oxygen-containing organic matter is one or more of C2-C20 alcohol, aldehyde, acid, ester and ketone organic matter.

[0048] In some preferred embodiments, in step (4), the oxygen-containing organic matter can be removed mainly by extracting the crude α-olefin product, preferably by centrifugal extraction of the crude α-olefin product to remove the oxygen-containing organic matter, thereby removing the oxygen-containing organic matter in the crude α-olefin product.

[0049] In some further preferred embodiments, the above extraction can be carried out using a polar alcohol extractant. Preferably, the polar alcohol extractant can be at least one of methanol, ethanol, ethylene glycol, and isobutanol. More preferably, the polar alcohol extractant can further contain water to help reduce the solubility of the crude α-olefin product in the extractant, and the amount of water contained in the extractant can be, for example, 0 to 100 wt%, preferably 5 wt% to 50 wt%, and more preferably 5 wt% to 30 wt% (e.g. 10 wt% to 20 wt%).

[0050] In some further preferred embodiments, the mass ratio of the extractant to the crude α-olefin product is (0.2-5):1, preferably (0.5-2):1.

[0051] In some preferred embodiments, the centrifugal extraction is performed using a centrifuge, and the separation factor of the centrifuge (i.e., the ratio of centrifugal force to gravity) may be not less than 50 g, preferably not less than 100 g, and more preferably not less than 150 g. The higher the gravitational acceleration, the more conducive it is to improving the mass transfer rate and facilitating the separation of the extractant and the α-olefin crude product after mixing. In some embodiments, the centrifugal extraction uses at least one level of centrifugal extraction, preferably three levels of centrifugal extraction, to further improve the extraction effect.

[0052] In some further preferred embodiments, the centrifugal extraction is used to remove oxygenated organic matter, and the extractant and the crude α-olefin product can be fully mixed before entering the centrifuge. Preferably, a static mixer, a flow restriction orifice plate and / or an agitator (e.g., an agitator provided at the inlet of the centrifuge) can be used for the mixing, wherein the agitator provided at the inlet of the centrifuge can utilize the rotation of the centrifuge rotor to fully stir and mix the extractant and the crude α-olefin product before entering the centrifuge, which is beneficial for the oxygenated organic matter to enter the extractant phase.

[0053] In the method described herein, for the above centrifugal extraction, if the separation of the extractant and the α-olefin crude product at the light and heavy phase outlets of the centrifuge is poor, the feed rate can be appropriately reduced and / or the residence time can be increased according to the situation to improve the separation effect.

[0054] In some further preferred embodiments, after the above centrifugal extraction, the extractant obtained by centrifuge separation can be washed with water (for separating a small amount of α-olefins in the extractant), and the alcohol extractant can be further recovered by distillation. In this article, the number of distillation tower plates used for distillation is not less than 40, preferably 40-60, and the top temperature of the distillation tower can be determined according to the boiling point of the extractant, such as 62-65°C for methanol, 78-80°C for ethanol, 87-98°C for propanol, and the reflux ratio is 1:10 to 10:1 (e.g., 1:5 to 5:1), and the recovered alcohol extractant can be reused. Preferably, the α-olefin obtained by washing can be returned to the extractant inlet of the centrifuge for re-extraction.

[0055] In some preferred embodiments, after the oxygen-containing organic matter is removed in step (4), the remaining extractant and oxygen-containing organic matter (the content of which may be, for example, less than 1 wt%) contained in the obtained crude α-olefin product may be further separated to obtain an α-olefin product from which oxygen-containing organic matter has been removed. Preferably, an adsorbent may be used to further separate the crude α-olefin product by adsorption separation.

[0056] In some further preferred embodiments, the adsorbent used in the above-mentioned adsorption separation may be one or more of a resin, a molecular sieve or magnesium silicate, preferably a molecular sieve adsorbent, for example, 5A, 13A, 10X and / 13X molecular sieves. The temperature of the adsorption separation is 10°C to 60°C (for example, 40°C to 60°C). Optionally, before the adsorption separation, the extracted α-olefin crude product obtained by extracting the α-olefin crude product may be washed with water, thereby removing the dissolved extractant and oxygen-containing organic matter from the α-olefin crude product. Preferably, the water washing is to wash the α-olefin with desalted water, and more preferably, the mass of the desalted water is 0.2 to 5 times the mass of the α-olefin crude product.

[0057] In some preferred embodiments, the purification of the α-olefin product from which oxygen-containing organic matter is removed as described in step (5) is carried out in a purification tower, and the purity of the product can be further improved after purification to obtain an α-olefin product with a purity that meets the expectations. Wherein, the number of plates of the purification tower may be 20 to 100, preferably 40 to 80, the α-olefin product from which oxygen-containing organic matter is removed is fed from the middle and lower part of the purification tower, and the α-olefin product is extracted from the top of the tower or the side line of the top of the tower. The operating pressure of the purification tower may be normal pressure (i.e., 1 atmosphere). The top temperature of the purification tower may be 62° C. to 215° C. Further, the top temperature of the purification tower can be adjusted according to the boiling point of the α-olefin to be separated, and is controlled at: C6 olefin, 62°C to 65°C; C7 olefin 92°C to 95°C; C8 olefin 120°C to 122°C; C9 olefin 145°C to 147°C; C10 olefin 169°C to 171°C; C11 olefin 191°C to 193°C; C12 olefin 212°C to 215°C. In some embodiments, the reflux ratio of the purification tower is 10:1 to 1:10 (e.g., 5:1 to 1:5, 5:1 to 1:1).

[0058] In some preferred embodiments, in step (5), the light components at the top of the tower and the heavy components at the bottom of the tower obtained can be returned to step (2) for re-light removal treatment, thereby further improving the yield of the olefin product.

[0059] In one embodiment, the present invention relates to a system for implementing the above method, comprising: a fraction cutting tower, a light removal tower, an enrichment tower, an oxygen-containing organic matter removal unit and a purification tower connected in sequence in a fluid-connected manner, wherein the number of plates of the enrichment tower is not less than 60.

[0060] In some embodiments, the fraction cutting tower is a continuous or intermittent distillation tower, and the number of plates may be no less than 20, preferably 20 to 60.

[0061] In some embodiments, a feed port is provided at the middle and lower part of the fraction cutting tower and / or the bottom of the tower for feeding the Fischer-Tropsch synthesis light oil. In some embodiments, a discharge port is provided at the top and / or the side line of the fraction cutting tower, from which the narrow fraction oil flows out.

[0062] In some embodiments, the lightness removal tower is a continuous distillation tower, and the number of plates may be not less than 40, for example, 60 to 120, preferably 60 to 80. In some embodiments, the feed position of the lightness removal tower is set in the lower middle part of the lightness removal tower.

[0063] In some embodiments, the number of plates of the enrichment tower is preferably 60 to 120, more preferably 60 to 80. In some preferred embodiments, the feed position of the enrichment tower is the lower middle part of the enrichment tower or the bottom of the tower.

[0064] In some embodiments, the oxygenated organic removal unit may be an extraction device, such as a centrifuge.

[0065] In some embodiments, a static mixer, a flow restriction orifice plate and / or an agitator (eg, an agitator disposed at the inlet of the centrifuge) is disposed before the centrifuge.

[0066] In some embodiments, the number of plates of the purification tower may be 20 to 100, preferably 40 to 80. In some embodiments, a feed port is provided in the lower middle portion of the purification tower. In some embodiments, a discharge port is provided at the top of the purification tower or at the side line of the top of the tower, where an α-olefin product is obtained.

[0067] Next, some preferred embodiments of the present invention are exemplarily described through the following numbered paragraphs:

[0068] 1. A method for separating α-olefins from Fischer-Tropsch light oil, comprising:

[0069] (1) fractionating the Fischer-Tropsch synthesis light oil to obtain narrow fraction oil and fraction-cut bottom oil;

[0070] (2) subjecting the narrow fraction oil to light component removal treatment to obtain a distillate oil from which light components have been removed and a light component after light component removal;

[0071] (3) enriching the distillate oil after light components are removed by using an enrichment tower to obtain a crude α-olefin product and a residual fraction after α-olefin removal, wherein the number of plates of the enrichment tower is not less than 60 and the tower top temperature is 62 to 215° C.;

[0072] (4) removing oxygen-containing organic matter from the crude α-olefin product to obtain an α-olefin product from which oxygen-containing organic matter has been removed;

[0073] (5) Purifying the α-olefin product after removing the oxygen-containing organic matter to obtain a light component at the top of the tower, a heavy component at the bottom of the tower, and an α-olefin product.

[0074] 2. The method as described in paragraph 1, wherein the distillation range temperature of the Fischer-Tropsch synthetic light oil is 0 to 500°C.

[0075] 3. The method of paragraph 1 or 2, wherein the fraction cutting is performed in a fraction cutting tower.

[0076] 4. The method as described in paragraph 3, wherein the fraction cutting tower is a continuous or intermittent distillation tower with a number of plates of not less than 20.

[0077] 5. The method as described in paragraph 3 or 4, wherein the Fischer-Tropsch synthetic light oil is fed from the lower middle part and / or the bottom of the fraction cutting tower, and the narrow fraction oil is obtained from the top and / or the side line.

[0078] 6. The method as described in any of paragraphs 1 to 5, wherein the conditions for fraction cutting are: tower top temperature is 63° C. to 220° C., pressure is 10 kPa to 100 kPa, and reflux ratio is 10:1 to 1:10.

[0079] 7. The method as described in any one of paragraphs 1 to 6, wherein the light removal treatment is carried out in a light removal tower.

[0080] 8. The method as described in paragraph 7, wherein the lightness removal tower is a continuous distillation tower with no less than 40 plates.

[0081] 9. The method of paragraph 7 or 8, wherein the narrow fraction oil is fed into the lower middle portion of the light fraction removal tower.

[0082] 10. The method as described in any of paragraphs 1 to 9, wherein the conditions for the light removal treatment are: the tower top temperature is 40°C to 210°C, the pressure is 10 to 100 kPa, and the reflux ratio is 10:1 to 1:10.

[0083] 11. A method as described in any of paragraphs 1 to 10, wherein the pressure of the light olefin removal treatment is 100 kPa, and according to the carbon number of the α-olefin to be separated, the top temperature of the light olefin removal tower is: C6 olefin, 40°C to 60°C; C7 olefin, 60°C to 90°C; C8 olefin, 80°C to 120°C; C9 olefin, 120°C to 146°C; C10 olefin, 140°C to 169°C; C11 olefin, 160°C to 190°C; C12 olefin, 180°C to 210°C.

[0084] 12. The method as described in any one of paragraphs 1 to 11, wherein in step (3), the distillate oil from which light components have been removed is enriched in the enrichment tower and then separated from the top of the enrichment tower to obtain a crude α-olefin product.

[0085] 13. The method as described in any one of paragraphs 1 to 12, wherein the number of plates of the enrichment tower is 60 to 120, and the reflux ratio is 10:1 to 1:10.

[0086] 14. The method as described in any one of paragraphs 1 to 13, wherein the feed position of the distillate oil from which light components are removed is the lower middle part or the bottom of the enrichment tower.

[0087] 15. A method as described in any of paragraphs 1 to 14, wherein, according to the carbon number of the α-olefin to be separated, the top temperature of the enrichment tower is controlled at: C6 olefin, 62°C to 65°C; C7 olefin, 90°C to 95°C; C8 olefin, 115°C to 122°C; C9 olefin, 140°C to 147°C; C10 olefin, 165°C to 171°C; C11 olefin, 185°C to 193°C; C12 olefin, 205°C to 215°C.

[0088] 16. The method as described in any of paragraphs 1 to 15, wherein the oxygen-containing organic matter is one or more of C2 to C20 alcohols, aldehydes, acids, esters and ketones.

[0089] 17. The method as described in any of paragraphs 1 to 16, wherein in step (4), the oxygen-containing organic matter is removed by extracting the crude α-olefin product.

[0090] 18. The method of paragraph 17, wherein the crude α-olefin product is subjected to centrifugal extraction to remove oxygenated organic matter.

[0091] 19. The method of paragraph 17 or 18, wherein the extraction is performed using a polar alcohol extractant.

[0092] 20. The method of paragraph 19, wherein the polar alcohol extractant is at least one of methanol, ethanol, ethylene glycol, and isobutanol.

[0093] 21. The method of paragraph 19 or 20, wherein the polar alcohol extractant further contains water.

[0094] 22. The method according to paragraph 21, wherein the amount of water contained in the polar alcohol extractant is 0 to 100 wt%.

[0095] 23. The method as described in any of paragraphs 19 to 22, wherein the mass ratio of the polar alcohol extractant to the crude α-olefin product is (0.2 to 5):1.

[0096] 24. The method of any of paragraphs 18-23, wherein the centrifugal extraction is performed using a centrifuge having a separation factor of not less than 50 g.

[0097] 25. The method of any of paragraphs 18-24, wherein the centrifugal extraction uses at least one stage of centrifugal extraction.

[0098] 26. The method of paragraph 24 or 25, wherein after the centrifugal extraction, the extractant separated by the centrifuge is washed with water and further distilled to recover the polar alcohol extractant.

[0099] 27. The method as described in any one of paragraphs 1 to 26, wherein after the oxygen-containing organic matter is removed in step (4), the remaining extractant and oxygen-containing organic matter contained in the obtained crude α-olefin product are further separated.

[0100] 28. The method of paragraph 27, wherein the crude α-olefin product is further separated by adsorption separation using an adsorbent.

[0101] 29. The method of paragraph 28, wherein the adsorbent is one or more of a resin, a molecular sieve or magnesium silicate.

[0102] 30. The method of any of paragraphs 1 to 29, wherein the purification in step (5) is carried out in a purification tower.

[0103] 31. The method of paragraph 30, wherein the purification tower has 20 to 100 plates, a tower top temperature of 62° C. to 215° C., and a reflux ratio of 10:1 to 1:10.

[0104] 32. The method of paragraph 30 or 31, wherein the α-olefin product from which oxygen-containing organic matter is removed is fed from the lower part of the purification tower, and the α-olefin product is withdrawn from the top of the tower or from the side line of the top of the tower.

[0105] 33. The method as described in any one of paragraphs 1 to 32, wherein the light components at the top of the tower and the heavy components at the bottom of the tower obtained in step (5) can be returned to step (2) for re-light removal treatment.

[0106] 34. A system for implementing the method described in any one of paragraphs 1 to 33, comprising: a fraction cutting tower, a light removal tower, an enrichment tower, an oxygen-containing organic matter removal unit, and a purification tower connected in sequence in a fluid-connected manner, wherein the number of plates of the enrichment tower is not less than 60.

[0107] 35. The system of paragraph 34, wherein the fraction cutting tower is a continuous or intermittent distillation tower having no less than 20 plates.

[0108] 36. The system of paragraph 34 or 35, wherein a feed inlet is provided at a lower middle portion and / or a bottom portion of the fraction cutting tower, and a discharge inlet is provided at a top and / or a side line of the fraction cutting tower.

[0109] 37. The system of any of paragraphs 34-36, wherein the lightness removal tower is a continuous distillation tower having no less than 40 plates.

[0110] 38. The system of any one of paragraphs 34 to 37, wherein the feed position of the lightness removal tower is disposed in the lower middle portion of the lightness removal tower.

[0111] 39. The system of any of paragraphs 34-38, wherein the enrichment tower has 60 to 120 plates.

[0112] 40. The system of any of paragraphs 34 to 39, wherein the feed position of the enrichment tower is the lower middle portion or the bottom of the enrichment tower.

[0113] 41. The system of any of paragraphs 34-40, wherein the oxygenated organic removal unit is an extraction device.

[0114] 42. The system of any of paragraphs 34-41, wherein the oxygenated organic removal unit is a centrifuge.

[0115] 43. The system of paragraph 42, wherein a static mixer, a flow restriction orifice, and / or an agitator are provided before the centrifuge.

[0116] 44. The system of any of paragraphs 34-43, wherein the purification tower has 20 to 100 plates.

[0117] 45. The system of any of paragraphs 34 to 44, wherein a feed inlet is disposed at a lower portion of the purification tower, and a discharge outlet is disposed at the top or at a side line of the top of the purification tower.

[0118] The present invention is further described below by way of examples, but the present invention is not limited thereto.

[0119] Example

[0120] Unless otherwise specified, the reagents, materials and devices involved in the following examples are conventional in the art and are commercially available; the routine operations involved in the following examples are common operations in the art, such as those found in patents, patent applications and publications disclosed in the art.

[0121] Example 1 Separation of C6 α-olefins

[0122] The Fischer-Tropsch light oil 101 (distillation temperature of 0-430°C) from the upstream unit is fed into the fraction cutting tower 1 (continuous distillation tower), the tower top temperature is 63°C-90°C, the pressure is 100 kPa, the reflux ratio is 1:1, and a narrow fraction oil 102 containing α-olefin products with a high C6 content is obtained at the tower top, and the fraction cutting tower bottom oil 103 is obtained; the fraction cutting tower has 40 plates, and the feed position is the 30th plate from top to bottom;

[0123] 102 is fed into the light component removal tower 2 to obtain the distillate oil 105 after light component removal and the light component after light component removal; the top temperature of the light component removal tower is 40℃~60℃, the pressure is 100kPa, and the reflux ratio is 1:1; the light component removal tower has 80 plates, and the feed position is the middle of the tower section;

[0124] 105 is fed to the enrichment tower 3, and the α-olefin crude product 106 is obtained at the top of the tower, and the remaining fraction 107 after removing the α-olefin is obtained. The top temperature of the enrichment tower is 62°C to 65°C, and the reflux ratio is 3:1; the number of plates of the enrichment tower is 80, and the bottom of the tower is directly fed.

[0125] The α-olefin crude product 106 obtained from the top of the enrichment tower is supplied to the oxygen-containing organic matter removal unit 4, and centrifugal extraction 6 is used. The 106 and the methanol extractant 12 containing 10 wt% to 20 wt% of water are mixed by a stirrer provided at the inlet of the centrifuge, and then supplied to the centrifuge. The mass ratio of the extractant 12 to the α-olefin crude product 106 is (0.5 to 2):1;

[0126] In a centrifuge with a separation factor of 180g, a three-stage centrifugal extraction operation is performed; the extractant 15 separated by the centrifuge is washed with water 9 to separate a small amount of α-olefins entrained in the extractant, and an α-olefin product 18 recovered from the extractant is obtained; the washed extractant 16 is further recovered by distillation 10, wherein the number of distillation tower plates used in distillation 10 is not less than 40, the top temperature of the distillation tower is 62-65°C, the reflux ratio is 1:1, and the extractant is obtained at the top of the tower. The recovered extractant can be reused as an extractant; the small amount of α-olefin product 18 recovered from the extractant obtained by washing is mixed with 106 for re-extraction;

[0127] To the extracted α-olefin crude product 13, 0.2-5 times the mass of deionized water is added for water washing 7. After one or more mixing and separation in a centrifuge, a washed α-olefin product 14 is obtained. Subsequently, the α-olefin product is subjected to adsorption separation 8, wherein the adsorbent for the adsorption separation is 5A molecular sieve, and the adsorption separation operation is performed at room temperature to obtain α-olefin 108 from which oxygen-containing organic matter has been removed.

[0128] The α-olefin 108 after removing the oxygen-containing organic matter is supplied to the purification tower for further separation and purification. The top temperature of the tower is 62℃~65℃, normal pressure, and the reflux ratio is 5:1. The purified α-olefin product 109 can be obtained, and the light component 110 at the top of the purification tower and the heavy component 111 at the bottom of the purification tower are obtained. The two are returned for re-light removal treatment, thereby further improving the yield of the α-olefin product. The number of plates in the purification tower is 40 to 80. The feed is fed from the middle of the tower and extracted from the side line at the top of the tower. The relevant analysis results are as follows:

[0129] Table 1 Composition and content of main hydrocarbons in stream (%)

[0130] <C6 hydrocarbon C6 olefins Other C6 ≥C7 hydrocarbons 101 6.14 4.82 2.73 86.31 102 20.92 23.29 13.17 42.62 105 0.02 23.65 11.49 64.84 106 0.03 94.25 5.05 0.66 108 0.29 95.51 4.20 0 109 0.41 95.91 3.68 0

[0131] Example 2 Separation of C8 α-olefins

[0132] The Fischer-Tropsch synthetic light oil 101 (distillation temperature of 0-430°C) from the upstream unit is fed into the fraction cutting tower 1 (continuous distillation tower), the tower top temperature is 120-140°C, the pressure is 100 kPa, the reflux ratio is 1:3, and the narrow fraction oil 102 containing α-olefin products with a high C8 content is obtained at the tower top, and the fraction cutting tower bottom oil 103 is obtained; the fraction cutting tower has 40 plates, and the feed position is the 30th plate from top to bottom;

[0133] 102 is fed into the light component removal tower 2 to obtain the distillate oil 105 after light component removal and the light component after light component removal; the top temperature of the light component removal tower is 80℃~120℃, the pressure is 100kPa, and the reflux ratio is 2:1; the light component removal tower has 80 plates, and the feed position is the middle of the tower section;

[0134] 105 is fed to the enrichment tower 3, and the α-olefin crude product 106 is obtained at the top of the tower, and the remaining fraction 107 after removing the α-olefin is obtained. The top temperature of the enrichment tower is 115°C to 122°C, and the reflux ratio is 5:2; the number of plates of the enrichment tower is 80, and the bottom of the tower is fed;

[0135] The α-olefin crude product 106 obtained from the top of the enrichment tower is supplied to the oxygen-containing organic matter removal unit 4, and centrifugal extraction 6 is used. The 106 and the methanol extractant 12 containing 10 wt% to 20 wt% of water are mixed by a stirrer provided at the inlet of the centrifuge, and then supplied to the centrifuge. The mass ratio of the extractant 12 to the α-olefin crude product 106 is (0.5 to 2):1;

[0136] In a centrifuge with a separation factor of 180 g, a three-stage centrifugal extraction operation is performed; the extractant 15 separated by the centrifuge is washed with water 9 to separate a small amount of α-olefin entrained in the extractant, thereby obtaining an α-olefin product 18 recovered from the extractant; the washed extractant 16 is further recovered by distillation 10, wherein the number of distillation tower plates used in the distillation 10 is not less than 40, the top temperature of the distillation tower is 62-65° C., and the reflux ratio is 1:1, and the recovered extractant can be reused as an extractant; the small amount of α-olefin product 18 recovered from the extractant obtained by washing is mixed with 106 and extracted again;

[0137] To the extracted α-olefin crude product 13, 0.2-5 times the mass of deionized water is added for water washing 7. After one or more mixing and separation in a centrifuge, a washed α-olefin product 14 is obtained. Subsequently, the α-olefin product is subjected to adsorption separation 8, wherein the adsorbent for the adsorption separation is 5A molecular sieve, and the adsorption separation operation is performed at room temperature to obtain α-olefin 108 from which oxygen-containing organic matter has been removed.

[0138] The α-olefin 108 after removing oxygen-containing organic matter is supplied to the purification tower for further separation and purification. The tower top temperature is 120℃~122℃, normal pressure, and the reflux ratio is 5:1. The purified α-olefin product 109 can be obtained, and the light component 110 at the top of the purification tower and the heavy component 111 at the bottom of the purification tower are obtained. The two are returned for re-light removal treatment, thereby further improving the yield of the α-olefin product. The number of plates in the purification tower is 40 to 80. The feed is fed from the middle of the tower and extracted from the side line at the top of the tower. The relevant analysis results are as follows:

[0139] Table 2 Composition and content of main hydrocarbons in the stream

[0140] <C8 hydrocarbon C8 olefins Other C8 ≥C9 hydrocarbons 101 20.66 5.92 2.76 70.80 102 54.51 15.62 7.31 22.59 105 0 26.46 14.16 59.38 106 0.58 81.90 15.12 2.37 108 3.71 88.12 7.44 0.73 109 0.37 96.39 3.24 0

[0141] Table 3 Composition and content of oxygenated organic matter and main hydrocarbons in the stream

[0142] acid Alcohol (including methanol) Aldehyde Ketone Esters Alkane 13 0 0 0.0048 99.6961 14 0 0 0 100

[0143] Example 3 Separation of C9 α-olefins

[0144] The Fischer-Tropsch light oil 101 (distillation temperature of 0-430°C) from the upstream unit is fed into the fraction cutting tower 1 (continuous distillation tower), the tower top temperature is 120-160°C, the pressure is 100 kPa, the reflux ratio is 5:1, and the narrow fraction oil 102 containing α-olefin products with a high C9 content is obtained at the tower top, and the fraction cutting tower bottom oil 103 is obtained; the fraction cutting tower has 40 plates, and the feed position is the 30th plate from top to bottom;

[0145] 102 is fed into the light component removal tower 2 to obtain the distillate oil 105 after light component removal and the light component after light component removal; the top temperature of the light component removal tower is 120℃~146℃, the pressure is 100kPa, and the reflux ratio is 2:1; the light component removal tower has 80 plates, and the feed position is the middle of the tower section;

[0146] 105 is fed to the enrichment tower 3, and the α-olefin crude product 106 is obtained at the top of the tower, and the remaining fraction 107 after removing the α-olefin is obtained. The top temperature of the enrichment tower is 140°C to 147°C, and the reflux ratio is 5:1; the number of plates of the enrichment tower is 80, and the bottom of the tower is fed;

[0147] The α-olefin crude product 106 obtained from the top of the enrichment tower is supplied to the oxygen-containing organic matter removal unit 4, and centrifugal extraction 6 is used. The 106 and the methanol extractant 12 containing 5 wt% to 15 wt% of water are mixed by a stirrer arranged at the inlet of the centrifuge, and then supplied to the centrifuge. The mass ratio of the extractant 12 to the α-olefin crude product 106 is (0.5 to 2):1;

[0148] In a centrifuge with a separation factor of 180 g, a three-stage centrifugal extraction operation is performed; the extractant 15 separated by the centrifuge is washed with water 9 to separate a small amount of α-olefin entrained in the extractant, thereby obtaining an α-olefin product 18 recovered from the extractant; the washed extractant 16 is further recovered by distillation 10, wherein the number of distillation tower plates used in the distillation 10 is not less than 40, the top temperature of the distillation tower is 62-65° C., and the reflux ratio is 1:1, and the recovered extractant can be reused as an extractant; the small amount of α-olefin product 18 recovered from the extractant obtained by washing is mixed with 106 and extracted again;

[0149] To the extracted α-olefin crude product 13, 0.2-5 times the mass of desalted water is added for water washing 7. After one or more mixing and separation in a centrifuge, a washed α-olefin product 14 is obtained. Subsequently, the α-olefin product is subjected to adsorption separation 8, wherein the adsorbent for the adsorption separation is 13A molecular sieve, and the adsorption separation operation is performed at 40°C to obtain α-olefin 108 from which oxygen-containing organic matter has been removed.

[0150] The α-olefin 108 from which oxygen-containing organic matter has been removed is supplied to a purification tower for further separation and purification, with a tower top temperature of 145°C to 147°C, normal pressure, and a reflux ratio of 5:1, to obtain a purified α-olefin product 109, and a light component 110 at the top of the purification tower and a heavy component 111 at the bottom of the purification tower, which are returned for light removal treatment, thereby further improving the yield of the α-olefin product. The number of plates in the purification tower is 40 to 80, and the feed is fed from the middle of the tower and extracted from the side line at the top of the tower.

[0151] Table 4 Composition and content of main hydrocarbons in the stream

[0152] <C9 hydrocarbon C9 olefins Other C9 ≥C10 hydrocarbons 101 29.34 5.85 2.71 62.10 102 63.56 12.88 4.90 18.66 105 0 30.25 15.00 54.75 106 0.10 84.04 13.62 2.24 108 0.25 85.08 14.24 0.43 109 0.08 96.46 3.46 0

[0153] Example 4 Separation of C12 α-olefins

[0154] The Fischer-Tropsch synthetic light oil 101 (distillation temperature of 0-430°C) from the upstream unit is fed into the fraction cutting tower 1 (intermittent distillation tower), the tower top temperature is 190-220°C, the pressure is 100 kPa, the reflux ratio is 1:4, and the tower top is obtained with a narrow fraction oil 102 containing α-olefin products with a high C12 content, and the fraction cutting tower bottom oil 103 is obtained; the fraction cutting tower has 40 plates, and the feed position is the 30th plate from top to bottom;

[0155] 102 is fed into the light component removal tower 2 to obtain the distillate oil 105 after light component removal and the light component after light component removal; the top temperature of the light component removal tower is 180℃~210℃, the pressure is 100kPa, and the reflux ratio is 3:1; the light component removal tower has 80 plates, and the feed position is the middle of the tower section;

[0156] 105 is fed to the enrichment tower 3, and the α-olefin crude product 106 is obtained at the top of the tower, and the remaining fraction 107 after removing the α-olefin is obtained. The top temperature of the enrichment tower is 205℃~215℃, and the reflux ratio is 3:1; the number of plates of the enrichment tower is 80, and the feed is from the bottom of the tower;

[0157] The α-olefin crude product 106 obtained from the top of the enrichment tower is fed into the oxygen-containing organic matter removal unit 4, and centrifugal extraction 6 is used to mix 106 and an ethanol extractant 12 containing 5 wt% to 10 wt% of water using a stirrer provided at the inlet of the centrifuge, and then fed into the centrifuge, and the ratio of the extractant 12 to the α-olefin crude product 106 is (0.5 to 2):1;

[0158] In a centrifuge with a separation factor of 180 g, a three-stage centrifugal extraction operation is performed; the extractant 15 separated by the centrifuge is washed with water 9 to separate a small amount of α-olefin entrained in the extractant, thereby obtaining an α-olefin product 18 recovered from the extractant; the extractant 16 after washing with water is further recovered by distillation 10, wherein the number of plates of the distillation tower used in the distillation 10 is not less than 40, the top temperature of the distillation tower is 78-80° C., and the reflux ratio is 1:1, and the recovered extractant can be reused as an extractant; the small amount of α-olefin product 18 recovered from the extractant obtained by washing with water is mixed with 106 and extracted again;

[0159] To the extracted α-olefin crude product 13, 0.2 to 5 times the mass of desalted water is added for water washing 7. After one or more mixing and separation in a centrifuge, a washed α-olefin product 14 is obtained. Subsequently, the α-olefin product is subjected to adsorption separation 8, wherein the adsorbent for the adsorption separation is 13X molecular sieve, and the adsorption separation operation is performed at 40°C to 60°C to obtain α-olefin 108 from which oxygen-containing organic matter has been removed.

[0160] The α-olefin 108 from which oxygen-containing organic matter has been removed is supplied to a purification tower for further separation and purification. The tower top temperature is 212°C to 215°C, the pressure is normal, and the reflux ratio is 5:1. A purified α-olefin product 109 can be obtained, and a light component 110 at the top of the purification tower and a heavy component 111 in the bottom of the purification tower can be obtained. The two components are returned for light removal treatment again, thereby further improving the yield of the α-olefin product. The number of plates in the purification tower is 40 to 80. The feed is fed from the middle of the tower and extracted from the top of the tower.

[0161] Table 5 Composition and content of main hydrocarbons in the stream

[0162] <C12 hydrocarbon C12 Olefins Other C12 ≥C13 hydrocarbons 101 43.21 20.15 11.92 24.72 105 0.82 59.74 31.17 8.27 106 0.41 78.94 18.02 2.63 108 0.12 80.12 16.23 3.53 109 0.08 95.46 3.46 1.00

Claims

1. A method for separating α-olefins from Fischer-Tropsch light oil, comprising: (1) fractionating the Fischer-Tropsch synthesized light oil to obtain narrow fraction oil and fraction-cutting tower bottom oil, wherein the fraction cutting is performed in a fraction cutting tower, the fraction cutting tower is a continuous or intermittent distillation tower, the number of plates is not less than 20, the fraction cutting conditions are: the tower top temperature is 63° C. to 220° C., the pressure is 10 kPa to 100 kPa, the reflux ratio is 10:1 to 1:10, and the Fischer-Tropsch synthesized light oil mainly contains C4 to C37 normal alkanes and normal olefins; (2) subjecting the narrow fraction oil to light component removal treatment to obtain a distillate oil from which light components have been removed and a light component after light component removal, wherein the light component removal treatment is carried out in a light component removal tower, the light component after light component removal is separated from the top of the light component removal tower, and the distillate oil from which light components have been removed is obtained from the bottom of the light component removal tower, the light component removal tower is a continuous distillation tower with a number of plates of not less than 40, and the conditions for the light component removal treatment are: a tower top temperature of 40° C. to 210° C., a pressure of 10 to 100 kPa, and a reflux ratio of 10:1 to 1:10; (3) enriching the distillate oil after light components are removed by using an enrichment tower to obtain a crude α-olefin product and a residual fraction after α-olefin removal, wherein the crude α-olefin product is separated from the top of the enrichment tower, the number of plates of the enrichment tower is not less than 60, the reflux ratio is 5:1 to 1:1, and the top temperature of the enrichment tower is controlled at: C6 olefin, 62°C to 65°C; C7 olefin, 90°C to 95°C; C8 olefin, 115°C to 122°C; C9 olefin, 140°C to 147°C; C10 olefin, 165°C to 171°C; C11 olefin, 185°C to 193°C; C12 olefin, 205°C to 215°C according to the carbon number of the α-olefin to be separated; (4) subjecting the crude α-olefin product to centrifugal extraction to remove oxygen-containing organic matter, thereby obtaining an α-olefin product free of oxygen-containing organic matter, wherein the centrifugal extraction is performed using a centrifuge having a separation factor of not less than 50; (5) Purifying the α-olefin product after removing oxygen-containing organic matter in a purification tower to obtain a light component at the top of the tower, a heavy component at the bottom of the tower and an α-olefin product, wherein the number of plates of the purification tower is 20 to 100, the top temperature is 62° C. to 215° C., and the reflux ratio is 10:1 to 1:

10. The light component at the top of the tower and the heavy component at the bottom of the tower are returned to step (2) for re-light removal.

2. The method of claim 1, wherein: The distillation range temperature of the Fischer-Tropsch synthesis light oil is 0-500°C.

3. The method of claim 1, wherein: The Fischer-Tropsch synthetic light oil is fed from the lower middle part and / or the bottom of the fraction cutting tower, and the narrow fraction oil is obtained from the top and / or the side line.

4. The method of claim 1, wherein: The feeding position of the narrow fraction oil is in the lower middle part of the light fraction removal tower.

5. The method according to any one of claims 1 to 4, wherein: The pressure of the light-removal treatment is 100 kPa. According to the carbon number of the α-olefin to be separated, the top temperatures of the light-removal tower are: C6 olefin, 40°C to 60°C; C7 olefin, 60°C to 90°C; C8 olefin, 80°C to 120°C; C9 olefin, 120°C to 146°C; C10 olefin, 140°C to 169°C; C11 olefin, 160°C to 190°C; C12 olefin, 180°C to 210°C.

6. The method according to any one of claims 1 to 4, wherein: The number of plates of the enrichment tower is 60 to 120.

7. The method according to any one of claims 1 to 4, wherein: The feeding position of the distillate oil from which light components are removed is the lower middle part or the bottom of the enrichment tower.

8. The method according to any one of claims 1 to 4, wherein: The oxygen-containing organic matter is one or more of C2-C20 alcohol, aldehyde, acid, ester and ketone organic matter.

9. The method according to any one of claims 1 to 4, wherein: The centrifugal extraction is carried out using a polar alcohol extractant.

10. The method of claim 9, wherein: The polar alcohol extractant is at least one of methanol, ethanol, ethylene glycol and isobutanol.

11. The method of claim 9, wherein: The polar alcohol extractant further contains water.

12. The method of claim 11, wherein: The amount of water contained in the polar alcohol extractant is greater than 0 to less than 100 wt %.

13. The method of claim 9, wherein: The mass ratio of the polar alcohol extractant to the crude α-olefin product is (0.2-5):

1.

14. The method according to any one of claims 1 to 4, wherein: The centrifugal extraction uses more than one level of centrifugal extraction.

15. The method of claim 9, wherein: After the centrifugal extraction, the extractant obtained by centrifugal separation is washed with water and further distilled to recover the polar alcohol extractant.

16. The method according to any one of claims 1 to 4, wherein: After the oxygen-containing organic matter is removed in step (4), the remaining extractant and oxygen-containing organic matter contained in the obtained crude α-olefin product are further separated.

17. The method of claim 16, wherein: The α-olefin crude product is further separated by using an adsorbent through adsorption separation.

18. The method of claim 17, wherein: The adsorbent is one or more of resin, molecular sieve or magnesium silicate.

19. The method according to any one of claims 1 to 4, wherein: The α-olefin product from which oxygen-containing organic matter has been removed is fed from the lower part of the purification tower.

20. A system for implementing the method of any one of claims 1 to 19, comprising: A fraction cutting tower, a light removal tower, an enrichment tower, an oxygen-containing organic matter removal unit and a purification tower are sequentially connected in a fluid-connected manner, wherein the fraction cutting tower is a continuous or intermittent distillation tower with no less than 20 plates and a reflux ratio of 5:1 to 1:1, the light removal tower is a continuous distillation tower with no less than 40 plates, the oxygen-containing organic matter removal unit is a centrifuge, and the purification tower has 20 to 100 plates.

21. The system of claim 20, wherein: A feed inlet is arranged at the middle and lower part of the fraction cutting tower and / or the bottom of the tower, and a discharge outlet is arranged at the top of the tower and / or the side line of the fraction cutting tower.

22. The system of claim 20 or 21, wherein: The feed position of the lightness removal tower is arranged in the lower middle part of the lightness removal tower.

23. The system of claim 20 or 21, wherein: The number of plates of the enrichment tower is 60 to 120.

24. The system of claim 20 or 21, wherein: The feed position of the enrichment tower is the lower middle part or the bottom of the enrichment tower.

25. The system of claim 20 or 21, wherein: A static mixer, a flow restriction orifice plate and / or a stirrer are arranged before the centrifuge.

26. The system of claim 20 or 21, wherein: A feed inlet is arranged at the lower middle part of the purification tower, and a discharge outlet is arranged at the top of the purification tower or at the side line of the top of the tower.

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