A method for separating a mixture containing oxygenates, alkanes and olefins

Abstract

The present invention provides a method for separating a mixture, the method comprising: (1) performing deoxygenation extraction on the mixture to reduce the content of oxygen-containing compounds in the mixture to below 10 ppm; then performing alkane and olefin separation comprising: a) performing multi-stage countercurrent extraction on the raw material to be separated, an olefin extractant, and an alkane separator to obtain an olefin fraction product comprising olefin, most of the olefin extractant, and an alkane separator, and an alkane fraction product comprising alkane and a small part of the olefin extractant; b) performing a separation operation on the olefin fraction product to obtain an extractant and an olefin product; and / or performing a separation operation on the alkane fraction product to obtain an alkane product and an extractant; the present invention can achieve the separation of alkane-olefin mixtures in a wide fraction to obtain olefins. The method of the present invention is simple, efficient and energy-saving.

Description

Technical Field

[0001] The present invention relates to a process for separating a mixture containing oxygenates, alkanes and olefins. Background Art

[0002] Coal-based Fischer-Tropsch synthetic light oil mainly contains a large amount of C5-C12 normal olefins and normal alkanes, a small amount of isoalkanes and olefins, and a small amount of oxygen-containing compounds, among which the α-olefin content is 50%-75%, and the oxygen-containing compound content is 2wt%-6wt%. The types of oxygen-containing compounds are complex, including alcohols, aldehydes, acids, and esters with different carbon numbers. Since the boiling points of olefins and alkanes are very different, it is difficult to separate alkanes and olefins with the same carbon number by distillation or extraction. In addition, due to the mixture of a wide variety of oxides, azeotropy may also occur, making separation more difficult.

[0003] α-olefins are key raw materials for the production of other fine chemical products and have a significant impact on downstream industries. However, due to the difficulty in separating α-olefins and alkanes, coal-based Fischer-Tropsch synthetic oil is mainly used as a primary chemical raw material or fuel oil, with low economic benefits and weak market competitiveness. If the α-olefins can be separated, it will not only increase the added value of coal-based Fischer-Tropsch synthetic oil and thus greatly improve the economic benefits, but also enhance the ability of coal-based Fischer-Tropsch synthetic oil to resist market risks and promote the sustainable and healthy development of my country's coal chemical industry.

[0004] At present, the main method for removing oxygen-containing compounds in industry is hydrogenation. In the process of hydrogenating and removing oxides, the hydrogenation method is also accompanied by olefin hydrogenation saturation, which causes olefin loss on the one hand and affects the subsequent application of olefins, especially α-olefins on the other hand. Other methods for separating and extracting fatty alcohols and removing oxygen-containing compounds include adsorption and extraction, but there are some problems with separation and they are not efficient.

[0005] US3485879 discloses a method for separating alcohols from olefins and alkanes, which uses aluminum oxide for selective adsorption to achieve the purpose of separation. However, this method has the problem of being difficult to scale up industrially.

[0006] US2610977 discloses separation of alcohols from hydrocarbons, specifically a method of extracting with an aqueous solution of a low-carbon alcohol, wherein the low-carbon alcohol is a methanol aqueous solution, but the ratio of the extraction phase to the oil is 8-9:1, the amount of extractant used is large, and the solvent is recovered by extraction with low-carbon hydrocarbons.

[0007] GB716131 discloses extraction with an aqueous solution of a low-carbon alcohol. However, since the distillation range of the crude oil is very wide, the same extractant is used for small-molecule oxygen-containing compounds and large-molecule oxygen-containing compounds, resulting in a high content of hydrocarbons in the extract.

[0008] In terms of alkane-olefin separation, the methods for separating olefins from Fischer-Tropsch synthetic oil products at home and abroad are mainly based on traditional extraction, distillation or extractive distillation processes. In 1994, South Africa's SASOL company developed a combined process route of "alkali washing-etherification-distillation-extraction" to achieve the preparation of polymerization-grade 1-hexene and 1-octene. However, the process route is relatively complicated and the operation energy consumption is high, resulting in very high investment and operating costs. In addition, this technology can only separate C6 and C8 components, and cannot achieve complete separation of components with other carbon numbers.

[0009] CN106966852 A (Tianjin University) and CN109627137A (Inner Mongolia Yitai) both use continuous extraction and distillation to separate high-carbon normal alkanes and normal olefins, and both use phthalic acid diesters to separate high-carbon normal alkanes and normal olefins. A method for continuous extraction and distillation separation of high-carbon normal alkanes and normal olefins is disclosed, which generally comprises the following steps: (1) adding a mixture of high-carbon normal alkanes and normal olefins from the middle of an extraction distillation tower and performing a decompression operation; (2) adding an extractant phthalate compound from the upper part of the extraction distillation tower, and extracting high-carbon normal alkanes from the top of the extraction distillation tower; (3) feeding a mixture of high-carbon normal olefins and the extractant extracted from the bottom of the extraction distillation tower from the middle of a solvent recovery tower, performing a decompression operation, extracting high-carbon normal olefins from the top of the solvent recovery tower, and extracting the extractant from the bottom of the solvent recovery tower, and reusing the extractant. The invention can obtain two high-purity products, high-carbon normal alkanes and normal olefins. The patents all use reduced pressure operation to separate olefins, and only obtain normal alkanes and olefins with one carbon number. The equipment cost is high and the efficiency is low.

[0010] CN109652111A introduces a device and method for separating olefins from Fischer-Tropsch synthetic oil, and introduces a device combining a bulkhead tower and an extractive distillation technology, wherein a partition plate is arranged in the bulkhead tower, and the bulkhead tower is divided into an extractive distillation section, a distillation section and a common distillation section, wherein the extractive distillation section is used to produce alkanes; the side distillation section is used to produce olefins, and the common distillation section is used to produce a mixture of oxygenated compounds and an extractant, thereby achieving the purpose of simultaneously separating alkanes, olefins and oxygenated compounds from the cut Fischer-Tropsch synthetic oil in one bulkhead tower. However, it only involves the separation of alkanes and olefins with one carbon number, and cannot achieve the separation of olefins with multiple carbon numbers, and the process route is long and the energy consumption is high.

[0011] CN103232313A introduces an alkane / olefin extraction separation method, in which a mixture containing normal alkanes and high-carbon alpha-olefins to be separated is fully contacted and mixed with an extractant, and then allowed to stand for stratification and separation, wherein the extractant is N-methylpyrrolidone (NMP), N-formylmorpholine (NFM), 1-methylimidazole (1-MI) or γ-butyrolactone (γ-BL). Although the method is simple, it cannot achieve a thorough separation of alkanes and olefins with a variety of different carbon numbers. Summary of the invention

[0012] In view of the defects of olefin separation such as high energy consumption and complex process, it is urgently necessary to develop an effective and low-energy separation method to make the separation of alkanes and olefins more economical and efficient, and to provide an efficient and energy-saving separation method that can simultaneously remove oxygen-containing compounds and separate wide-fraction alkanes and olefins at one time.

[0013] Prior art: CN 103232313 A introduces a simple extraction method for separating alkanes and alkenes. It mentions that an extractant can be used to separate alkanes and alkenes with the same carbon number, but only some basic experiments were done in principle to confirm that polar extractants have a certain effect on alkane-alkene separation, and only a simple step of alkane-alkene separation was performed. The raffinate phase still contains alkanes, and the alkene is not completely separated. According to this technology, high-purity olefins cannot be obtained. In addition, this technology only involves the separation of alkanes and alkenes with the same carbon number, and does not mention the simultaneous separation of alkanes and alkenes in a wide fraction with different carbon numbers.

[0014] CN 106966852 A (Tianjin University) and CN 109627137 A (Inner Mongolia Yitai) both use continuous extraction distillation to separate high-carbon normal alkanes and normal olefins, and both use phthalic acid diesters to separate high-carbon normal alkanes and normal olefins. A major problem with this method is that the process route is long, because both are for the separation of alkanes and olefins with the same carbon number, so it is necessary to cut the fractions first, and then perform the separation operation, which is complicated, time-consuming and energy-consuming. In addition, the olefin separation process needs to be carried out under reduced pressure conditions, which is harsh and requires high equipment investment.

[0015] Some of the above technologies do not involve the removal of oxygenates, and the separation process has high energy consumption and complex process, and cannot achieve the separation of various α-olefins with different carbon numbers. Therefore, it is urgent to find a simple process to simultaneously achieve the removal of oxygenates and the separation of alkanes and olefins in Fischer-Tropsch naphtha to obtain high-purity and high-yield α-olefins.

[0016] The main purpose of the present invention is to provide a complete separation technology that can be used for separating α-olefins from Fischer-Tropsch naphtha, and to obtain high-purity olefin products.

[0017] The present invention provides a method for separating a mixture containing oxygen-containing compounds, alkanes and olefins, the method comprising:

[0018] (1) subjecting a mixture containing oxygen-containing compounds, alkanes and olefins to deoxygenation extraction to reduce the content of oxygen-containing compounds in the mixture to below 10 ppm, thereby obtaining a raw material to be separated from which oxygen-containing compounds have been removed;

[0019] (2) The method of separating the alkanes and olefins from the raw material to be separated is carried out by the following method I or method II:

[0020] Method I:

[0021] a) subjecting the raw material to be separated, the olefin extractant and the alkane separating agent to multi-stage countercurrent extraction to obtain an olefin fraction product comprising olefin, most of the olefin extractant and the alkane separating agent, and an alkane fraction product comprising alkane and a small part of the olefin extractant;

[0022] b) subjecting the olefin-based product to a separation operation to obtain an extractant and an olefin product; and / or subjecting the alkane-based product to a separation operation to obtain an alkane product and an extractant;

[0023] Method II:

[0024] A) first mixing the raw material to be separated with an olefin extractant and then extracting to obtain an extract phase A containing the olefin extractant, olefins and a small portion of alkanes, and a raffinate phase a containing most of the alkanes and a small portion of the olefins;

[0025] B) subjecting the extract phase A to a second mixing contact with the alkane separating agent and then separating the layers to obtain a lower mixed liquid B containing olefins, the olefin extractant and the alkane separating agent, and an upper mixed liquid b containing most of the alkane and a small amount of the alkene;

[0026] C) separating the lower mixed liquid B to obtain olefin products; and / or separating the raffinate phase a containing most alkanes and a small amount of olefins and / or the upper mixed liquid b containing most alkanes and a small amount of olefins.

[0027] Preferably, in method I, the operating temperature of the multi-stage countercurrent extraction is room temperature and the operating pressure is normal pressure.

[0028] Preferably, in method I, the multi-stage countercurrent extraction is carried out in a sieve plate extraction tower or a packed extraction tower.

[0029] Preferably, in mode I, when both the olefin and the alkane separating agent include at least two or more olefins with different carbon numbers, the step b) of separating the first olefin product comprises: firstly subjecting the first olefin product to a first distillation to separate the olefin extractant from the first olefin product to obtain a mixture containing olefins and the alkane separating agent; returning the separated olefin extractant to step a) for recycling, and dividing the mixture containing olefins and the alkane separating agent obtained after separation into part a and part b, wherein the part a is returned to step a) to be mixed with the alkane separating agent, and the part b is subjected to a distillation operation.

[0030] Preferably, when the olefin to be separated is a single olefin and the alkane separating agent is the same as the olefin to be separated, the step b) of performing a separation operation on the olefin product comprises:

[0031] First, the first olefin fraction product is subjected to a first distillation to separate the olefin extractant from the first olefin fraction product to obtain a mixture containing olefins and alkane separating agents; then the separated olefin extractant is returned to step a) for recycling, and part a of the mixture containing olefins and alkane separating agents obtained after separation is returned to step a) for mixing with the alkane separating agent for recycling, and part b is produced as an olefin product.

[0032] Preferably, in mode I, the olefin extractant is an organic substance with a certain polarity, a conventional polar organic solvent such as γ-butyrolactone, N-methylpyrrolidone (NMP), N,N,-methylformamide, N,N,-methylacetamide, N-formylmorpholine, morpholine, dimethyl sulfoxide, acetonitrile, imidazole compounds such as 1-methylimidazole, etc., phthalic acid diesters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, etc., alcohol compounds such as ethylene glycol, ethanol, etc., and can also be a mixed solvent.

[0033] Preferably, the olefin extractant is a polar organic solvent; preferably, the olefin extractant is selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-formylmorpholine, morpholine, dimethyl sulfoxide, acetonitrile, 1-methylimidazole, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, ethylene glycol, and ethanol; more preferably, the olefin extractant is selected from at least one of γ-butyrolactone, N-formylmorpholine, dimethyl sulfoxide, 1-methylimidazole, N-methylpyrrolidone, and N,N-dimethylformamide.

[0034] Preferably, in method I, the mass ratio of the olefin extractant to the material to be separated is 1-5:1, preferably 1.5-3:1.

[0035] Preferably, in method I, the mass ratio of the alkane separating agent to the material to be separated is 0.4-3:1, preferably 0.6-2:1.

[0036] Preferably, in method I, the number of extraction stages is 3 or more, preferably 6-8 stages.

[0037] Preferably, in mode I, the raw material to be separated is fed from the 6th to 8th tower plates, the olefin extractant is fed from the top of the tower, and the alkane separating agent is fed from the bottom of the tower.

[0038] Preferably, in Mode II, the olefin extractant is a weak polar solvent or a compound extractant, wherein the compound extractant comprises the weak polar solvent and a strong polar solvent.

[0039] Preferably, in method II, the weakly polar solvent is selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N-formylmorpholine, morpholine, dimethyl sulfoxide and acetonitrile.

[0040] Preferably, in method II, the weakly polar solvent is selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N-formylmorpholine and dimethyl sulfoxide.

[0041] Preferably, in method II, the highly polar solvent is selected from alcohol and / or water, preferably water;

[0042] Preferably, in Mode II, in the composite extractant of the weak polar solvent and the strong polar solvent, the mass ratio of the weak polar solvent to the strong polar solvent is 10-1000:1, preferably 50-100:1, and more preferably 8-30:1.

[0043] Preferably, in mode II, in step A), the mass ratio of the olefin extractant to the material to be separated is 0.1-10:1, preferably 0.5-5:1.

[0044] Preferably, in mode II, in step A), the conditions of the extraction operation include: the number of plates is 2-30, preferably 5-10; the extraction temperature is 0-50° C., preferably 10-30° C.; and the extraction process is reverse contact.

[0045] Preferably, in mode II, in step B), the mass ratio of the alkane separating agent to the extraction phase A is 0.01-15:1, preferably 0.06-0.15:1.

[0046] Preferably, in mode II, in step B), the operating conditions of the layering include: being carried out in an extraction tower, the number of plates of the extraction tower is 2-20, more preferably 3-6; the temperature is 0-80°C, more preferably 10-30°C; and the extraction process is reverse contact.

[0047] Preferably, in method II, step B) further comprises repeating the stratification operation on the obtained lower mixed liquid B until the mass content of alkanes in the obtained lower mixed liquid B is less than or equal to 0.15%, preferably less than or equal to 0.07%.

[0048] Preferably, in method II, in step C), the distillation is atmospheric pressure distillation.

[0049] Preferably, in Mode II, the mass ratio of the alkane separating agent to the extraction phase A is 0.1-10.0, preferably 0.2-2.0.

[0050] Preferably, in mode II, in the extraction phase A, the content of the extractant is 81-93wt%, preferably 83-89wt%; the content of olefins is 6-14wt%, preferably 9-12.5wt%; the content of alkanes is 1-5wt%, preferably 2-4.5wt%.

[0051] Preferably, in Mode I and Mode II, the alkane separating agent is each one olefin or a mixture of multiple olefins, preferably the same as the olefin in the feedstock to be separated.

[0052] Preferably, the alkane separating agent can be an organic solvent with a certain polarity, or can be a certain olefin or olefin mixture, preferably a low-priced α-olefin, and more preferably the same as the olefin in the feedstock.

[0053] Preferably, in the distillation process, the distillation process parameters can be adjusted according to the requirements for the product to obtain various high-purity olefins at one time.

[0054] Preferably, the olefin extractants and alkane separating agents involved can be separated through distillation and rectification processes, and reused repeatedly through methods such as recycling.

[0055] Preferably, the operating conditions of the deoxygenation extraction in step (1) include: the extractant is a polar solvent and optionally water, the polar solvent is one or a mixture of γ-butyrolactone, diethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, N-formylmorpholine, N-methylpyrrolidone, dimethyl sulfoxide, and the water content in the extractant is 0-60% by weight, preferably 10-25% by weight.

[0056] Preferably, the amount of the deoxygenation extractant used in the deoxygenation extraction of step (1) is 0.5 to 4 times, preferably 1 to 2 times, the weight of the mixture containing oxygen-containing compounds, alkanes and olefins.

[0057] Preferably, the deoxygenation extraction temperature in step (1) is 10-50°C, preferably 20-40°C.

[0058] Preferably, the deoxygenation extraction in step (1) can be a multi-stage countercurrent extraction method.

[0059] Preferably, the theoretical number of stages of the multi-stage countercurrent extraction in the deoxygenation extraction of step (1) is 5 to 15, preferably 8 to 12.

[0060] Preferably, the mixture containing oxygen-containing compounds, alkanes and olefins in step (1) contains 2-6% by weight of oxygenated compounds, 19-48% by weight of alkanes and 46-79% by weight of olefins.

[0061] Preferably, the alkane in step (1) is a C5-C12 alkane, the olefin is a C5-C12 olefin, the oxygenate is selected from one or more of alcohols, aldehydes, acids and ketones, and preferably the number of carbon atoms of the oxygenate is C1-C9;

[0062] Preferably, the mixture containing oxygen-containing compounds, alkanes and olefins in step (1) is Fischer-Tropsch naphtha, and preferably the distillation range of the Fischer-Tropsch naphtha is 30-200°C.

[0063] The naphtha in step (1) has a wide distillation range, which can be 30-200°C, or any fraction below 200°C, such as 30-180°C, 40-120°C, etc. The raw material can be unheated or preheated before entering the extraction tower for separation.

[0064] The present invention can separate the alkane-olefin mixture in the wide fraction to obtain olefins. After deoxygenation treatment and multi-stage extraction treatment in an extraction tower, the alkanes and olefins in the wide fraction section can be separated at one time to obtain two types of substances, alkanes and olefins. The olefin extractant and the olefin product are then separated by distillation. The olefin product enters a distillation tower for distillation to obtain olefin products with different carbon numbers, without having to process alkanes and olefins of each carbon number separately. The method of the present invention is simple, efficient and energy-saving.

[0065] The method of the present invention is not only applicable to the separation of alkanes and alkenes in naphtha, or alkanes and alkenes with the same carbon number, such as 1-hexene / n-hexane separation, 1-heptene / n-heptane separation, etc. The present invention can realize the one-step separation of all alkenes and alkanes in a complex alkene mixture such as naphtha, and obtain olefin products with various carbon numbers, such as pentene, hexene, heptene, octene, nonene, decene, etc., and can also obtain olefin combinations according to the requirements of downstream polymerization on raw materials, such as pentene+hexene, etc.

[0066] The present invention adopts the method of deoxygenation, solvent extraction separation and distillation to separate oxygen-containing compounds, alkanes and olefins. First, the raw materials to be separated containing oxygen-containing compounds, alkanes and olefins are firstly contacted with an extractant for deoxygenation treatment, and then fully mixed with an olefin extractant and an alkane separation agent to perform separation operation in an extraction tower. The obtained products are further subjected to a step of distillation to obtain a series of high-purity α-olefin products with different carbon numbers.

[0067] The method of the invention has simple operating conditions and high separation efficiency, can fully separate oxygen-containing compounds, alkanes and olefins, greatly saves energy consumption, and has good industrial application prospects.

[0068] In summary, compared with the related prior art, the present invention has the following advantages:

[0069] (1) The present invention is a complete method for completely separating oxygenates, alkanes and olefins, thereby obtaining high-purity olefins. The present invention is a complete extraction method for preparing olefins from Fischer-Tropsch naphtha by extractive deoxygenation and liquid-liquid extraction, and then obtaining high-purity olefin products through simple distillation and rectification.

[0070] (2) The method of the present invention is efficient, energy-saving and simple in process. It effectively realizes the one-time separation of alkanes and olefins in a wide fraction and the one-time separation of alkanes and olefins with various carbon numbers, thereby obtaining a mixture of olefins with various carbon numbers at one time, and then obtaining olefins with different carbon numbers and high purity through simple distillation and rectification of the olefin mixture.

[0071] (3) According to the method of the present invention, the deoxygenation extractant, olefin extractant and alkane separation agent can be recovered and reused repeatedly, which is economical and environmentally friendly. DETAILED DESCRIPTION

[0072] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0073] The present invention provides a method for separating a mixture containing oxygen-containing compounds, alkanes and olefins, the method comprising:

[0074] (1) subjecting a mixture containing oxygen-containing compounds, alkanes and olefins to deoxygenation extraction to reduce the content of oxygen-containing compounds in the mixture to below 10 ppm, thereby obtaining a raw material to be separated from which oxygen-containing compounds have been removed;

[0075] (2) The method of separating the alkanes and olefins from the raw material to be separated is carried out by the following method I or method II:

[0076] Method I:

[0077] a) subjecting the raw material to be separated, the olefin extractant and the alkane separating agent to multi-stage countercurrent extraction to obtain an olefin fraction product comprising olefin, most of the olefin extractant and the alkane separating agent, and an alkane fraction product comprising alkane and a small part of the olefin extractant;

[0078] b) subjecting the olefin-based product to a separation operation to obtain an extractant and an olefin product; and / or subjecting the alkane-based product to a separation operation to obtain an alkane product and an extractant;

[0079] Method II:

[0080] A) first mixing the raw material to be separated with an olefin extractant and then extracting to obtain an extract phase A containing the olefin extractant, olefins and a small portion of alkanes, and a raffinate phase a containing most of the alkanes and a small portion of the olefins;

[0081] B) subjecting the extract phase A to a second mixing contact with the alkane separating agent and then separating the layers to obtain a lower mixed liquid B containing olefins, the olefin extractant and the alkane separating agent, and an upper mixed liquid b containing most of the alkane and a small amount of the alkene;

[0082] C) separating the lower mixed liquid B to obtain olefin products; and / or separating the raffinate phase a containing most alkanes and a small amount of olefins and / or the upper mixed liquid b containing most alkanes and a small amount of olefins.

[0083] According to a preferred embodiment of the present invention, in method I, in step a),

[0084] In a preferred embodiment, in the multi-stage countercurrent extraction, the olefin extractant is fed from the top, the alkane separating agent is fed from the bottom, and the raw material to be separated is fed from the middle. In the present invention, the raw material to be separated is fed from the middle, which means that it is fed from any position between the olefin extractant feeding position and the alkane separating agent feeding position, preferably from the middle between the olefin extractant feeding position and the alkane separating agent feeding position. For example, in a vertical extraction tower, the olefin extractant is fed from the top of the extraction tower, the alkane separating agent is fed from the bottom of the extraction tower, and the raw material to be separated is fed from any plate in the extraction tower, preferably from a plate close to the middle of the extraction tower.

[0085] In the vertical extraction tower, after the raw material to be separated is fed, it moves downward. Below the feed of the raw material to be separated, the olefin extractant contacts the raw material to be separated, extracts olefins from the mixture, and moves downward with the extracted olefins; the alkane separating agent contacts the mixture extracted with the olefin extractant in reverse order, separates alkanes from it, and the alkane separating agent moves upward with the separated alkanes. Above the feed of the mixture, the alkane separating agent moving upward with the separated alkanes contacts in reverse order with the olefin extractant. The olefin extractant extracts the alkane separating agent therein, and moves downward with the extracted alkane separating agent, so that the alkane separating agent is separated from the alkanes. The separated alkanes move upward due to their light weight, and mix with a part of the extractant to form a first-part alkane product. The olefin extractant moving downward with the extracted olefins and the olefin extractant moving downward with the extracted alkane separating agent mix to form a first-part alkene product.

[0086] In a preferred embodiment, the mixture containing oxygen-containing compounds, alkanes and olefins contains at least one alkane and olefin having the same carbon number.

[0087] The carbon number of alkanes and olefins is not particularly limited in the present invention, and may be C5-C12, preferably C5-C10. The structure of alkanes is not particularly limited in the present invention, and may be straight-chain alkanes, branched-chain alkanes or cycloalkanes, preferably straight-chain alkanes. The structure of olefins is not particularly limited in the present invention, and may be α-olefins or internal olefins, preferably α-olefins.

[0088] In the present invention, the raw material to be separated can be a mixture containing multiple alkanes and olefins with the same carbon number, or a mixture containing only one alkane and olefin with the same carbon number. Among them, the present invention can separate multiple alkanes and olefins with the same carbon number at one time to obtain a high-purity mixed olefin product. For example, a complex alkane-olefin mixture naphtha is separated to obtain a high-purity mixed olefin, and then the high-purity mixed olefin obtained is further separated to obtain olefin products with various carbon numbers, such as pentene, hexene, heptene, octene, nonene, decene and other products, or it can be obtained according to actual production needs. Olefin combinations, such as pentene + hexene, etc. can also be obtained. A mixture containing only one alkane and olefin with the same carbon number can also be separated to obtain high-purity olefins, for example, 1-hexene / n-hexane can be separated to obtain high-purity 1-hexene; 1-heptene / n-heptane can be separated to obtain high-purity 1-heptene.

[0089] Among them, the mixture comprising an alkane and an olefin with the same carbon number is preferably a mixture comprising a normal alkane and an α-olefin with the same carbon number, further preferably a mixture of a normal alkane and an α-olefin with the same carbon number between 5 and 12, such as 5 and 10, and more preferably a mixture of 1-hexene and normal hexane.

[0090] The present invention does not impose any particular limitation on the source of the mixture containing oxygen-containing compounds, alkanes and olefins.

[0091] In a preferred embodiment, the olefin extractant is a polar organic solvent, preferably selected from at least one of γ-butyrolactone, N-methylpyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, N-formylmorpholine, morpholine, dimethyl sulfoxide, acetonitrile, 1-methylimidazole, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, ethylene glycol, and ethanol; preferably selected from at least one of γ-butyrolactone, N-formylmorpholine, dimethyl sulfoxide, 1-methylimidazole, N-methylpyrrolidone, and N,N-dimethylformamide, and further preferably at least one of γ-butyrolactone, N-formylmorpholine, and dimethyl sulfoxide.

[0092] In a preferred embodiment, the alkane separating agent is an olefin or a mixture of multiple olefins, preferably the same as the olefin to be separated. The olefin to be separated refers to the olefin in the mixture containing oxygen-containing compounds, alkanes and olefins.

[0093] In order to reduce the subsequent separation operation difficulty and simplify the separation process, the alkane separating agent is preferably the same as the alkene to be separated. When the alkene to be separated comprises multiple alkene, the alkane separating agent is at least one of the multiple alkene to be separated, and can be a single alkene or multiple alkene. Wherein, the present invention does not make special requirements to the specific mixing ratio of the multiple alkene in the alkane separating agent. For example, when separating the mixture of 1-heptene, 1-hexene, normal heptane and normal hexane, the alkane separating agent can be a mixture of 1-hexene, 1-heptene or 1-hexene and 1-heptene in any proportion.

[0094] In a preferred embodiment, the mass ratio of the extractant to the raw material to be separated is 1-5:1, preferably 1.5-3:1; the mass ratio of the alkane separating agent to the raw material to be separated is 0.4-3:1, preferably 0.6-2:1.

[0095] In a preferred embodiment, the number of extraction stages is 3 or more, preferably 6-8 stages.

[0096] In a preferred embodiment, the raw materials to be separated are fed from the 6th to 8th tower plates, the olefin extractant is fed from the top of the tower, and the alkane separating agent is fed from the bottom of the tower.

[0097] In a preferred embodiment, the olefins-1 product further contains a very small amount of alkanes, wherein in the olefins-1 product, the alkanes account for less than 0.1% of the total mass of alkanes in the raw material to be separated. In the alkanes-1 product, the content of alkanes accounts for more than 99.9% of the total mass of alkanes in the raw material to be separated.

[0098] In the present invention, since the amount of alkane entering the olefin-1 product is very small, accounting for less than 0.1% of the total mass of alkanes in the mixture, it can be almost ignored, so the present invention can achieve efficient separation of olefins and alkanes.

[0099] In a preferred embodiment, the alkane-fraction product further comprises a small amount of olefins and an alkane separating agent, wherein in the alkane-fraction product, olefins and the alkane separating agent account for less than 2% of the total mass of the mixture and the alkane separating agent, and in the olefin-fraction product, olefins and the alkane separating agent account for more than 98% of the total mass of the raw material to be separated and the alkane separating agent.

[0100] In the present invention, since most of the olefin and alkane separation agents enter into the olefin-one product, and only a small amount of the olefin and alkane separation agents enter into the alkane-one product, the loss of olefin in the present invention is relatively small, and most of the olefin can be separated from the mixture containing alkanes and olefins, thereby improving the separation yield of olefin.

[0101] In a preferred embodiment, the multi-stage countercurrent extraction is operated at room temperature and at atmospheric pressure; the room temperature is not particularly limited in the present invention and may be 10-40° C., preferably 20-35° C. The atmospheric pressure is not particularly limited in the present invention and may be 0.1 MPa.

[0102] Compared with extractive distillation, the present invention utilizes an extractant and an alkane separating agent to perform a multi-stage countercurrent operation on a mixture of alkanes and olefins. No heating is required. The efficient separation of alkanes and olefins can be achieved through liquid-liquid extraction at room temperature. Not only is the process simple but also the energy consumption is low, and it is suitable for industrial promotion.

[0103] In a preferred embodiment, the multi-stage countercurrent extraction is carried out in a sieve plate extraction tower or a packed extraction tower, and is further preferably carried out in a sieve plate extraction tower. Wherein, when the multi-stage countercurrent extraction is carried out in a sieve plate extraction tower, the theoretical number of plates of the sieve plate extraction tower is 5-20, preferably 8-16, the olefin extractant is fed from the top of the sieve plate extraction tower, the alkane separation agent is fed from the bottom of the sieve plate extraction tower, and the raw material to be separated is fed from the sieve plate extraction tower from the 2nd to 13th plates, preferably the 6th to 8th plates. When the multi-stage countercurrent extraction is carried out in a packed extraction tower, the theoretical number of plates of the packed extraction tower is 5-20, preferably 8-16, the olefin extractant is fed from the top of the packed extraction tower, the alkane separation agent is fed from the bottom of the packed extraction tower, and the raw material to be separated is fed from the packed extraction tower from the 2nd to 13th plates, preferably the 6th to 8th plates.

[0104] According to the present invention, in mode I, in step b), when the olefin and the alkane separating agent both include at least two or more olefins with different carbon numbers,

[0105] In a preferred embodiment, the step b) comprises first subjecting the first olefin fraction product to a first distillation to separate the extractant from the first olefin fraction product to obtain a mixture containing olefins and alkane separating agents; then returning the olefin extractant separated from the first olefin fraction product to step a) for recycling, and dividing the mixture containing olefins and alkane separating agents obtained after separation into part a and part b, wherein the part a is returned to step a) for mixing with the alkane separating agent for recycling, and the part b is subjected to a distillation operation to obtain an olefin product.

[0106] Part a accounts for 15-30 wt % of the total mass of the mixture containing olefins and alkane separating agents obtained after separation, and preferably accounts for 20-25 wt %.

[0107] In the present invention, since the alkane separation agent is also an olefin, the olefin product in the present invention includes the olefin separation agent and the olefin in the feedstock. According to demand, a single carbon number olefin product or a combination product containing olefins of different carbon numbers can be produced.

[0108] In a preferred embodiment, the step b) comprises first distilling the olefin fraction product, separating the olefin extractant from the olefin fraction product, and obtaining a mixture containing olefins and alkane separating agents; then returning the olefin extractant separated from the olefin fraction product to step a) for recycling, and subjecting the mixture containing olefins and alkane separating agents obtained after separation to rectification operation to obtain olefin products and alkane separating agents. The separated alkane separating agent is returned to step a) and mixed with the alkane separating agent for recycling.

[0109] When the olefin is a single olefin and the alkane separating agent is the same as the olefin to be separated,

[0110] In a preferred embodiment, the step b) comprises first subjecting the first olefin fraction product to a first distillation to separate an olefin extractant from the first olefin fraction product to obtain a mixture containing olefins and alkane separating agents; then returning the olefin extractant separated from the first olefin fraction product to step a) for recycling, returning part a of the mixture containing olefins and alkane separating agents obtained after separation to step a) for mixing with the alkane separating agent for recycling, and producing part b as an olefin product.

[0111] Among them, since the alkane separating agent is the same as the olefin to be separated, the obtained olefin product includes both the olefin separated from the mixture containing alkane and olefin and the added alkane separating agent. And because the alkane separating agent and the olefin to be separated are the same olefin, the olefin product can be obtained after the extractant is separated by the first distillation, and no further distillation operation is required.

[0112] In a preferred embodiment, the present invention does not make special provisions for the distillation and rectification operations, which can be performed according to common means in the art, and the present invention will not elaborate on them.

[0113] In a preferred embodiment, the purity of the olefin in the olefin product is above 98%, preferably above 99%.

[0114] According to the present invention, in the method I, in step b), in a preferred embodiment, the alkane product is distilled. The present invention does not specifically limit the distillation conditions, and can be specifically selected according to the difference of the alkane product. By distillation, the alkane and the extractant having a large difference in boiling point can be basically completely separated to obtain the alkane product and the extractant.

[0115] The alkane product in the present invention refers to the product remaining after the olefin extractant is separated from the alkane product.

[0116] In a preferred embodiment, in order to save production costs, the olefin extractant obtained in b) is returned to step a).

[0117] Mode II of the present invention is introduced below. In a preferred embodiment, the mixture comprising alkanes and alkenes is a mixture comprising a plurality of alkanes and alkenes having the same carbon number or a mixture comprising a single alkane and alkene having the same carbon number.

[0118] The carbon number of alkanes and olefins is not particularly limited in the present invention, and may be C5-C12, preferably C5-C10. The structure of alkanes is not particularly limited in the present invention, and may be straight-chain alkanes, branched-chain alkanes or cycloalkanes, preferably straight-chain alkanes. The structure of olefins is not particularly limited in the present invention, and may be α-olefins or internal olefins, preferably α-olefins.

[0119] The present invention can separate multiple alkanes and olefins with the same carbon number in a wide fraction section at one time to obtain a high-purity mixed olefin product. For example, complex alkane-olefin mixture naphtha can be separated to obtain high-purity mixed olefins, and then the high-purity mixed olefins obtained can be further separated to obtain olefin products with various carbon numbers, such as pentene, hexene, heptene, octene, nonene, decene and the like. It can also be based on actual production needs to obtain olefin combinations, such as pentene + hexene, etc. A mixture containing an alkane and olefin with the same carbon number can also be separated to obtain high-purity olefins, for example, 1-hexene / normal hexane can be separated to obtain high-purity 1-hexene; 1-heptene / normal heptane can be separated to obtain high-purity 1-heptene.

[0120] In a preferred embodiment, the mixture comprising alkanes and olefins is a mixture comprising an alkane and an olefin with the same carbon number, preferably a mixture comprising an alkane and an α-olefin with the same carbon number, further preferably a mixture of an alkane and an α-olefin with the same carbon number between 5 and 12, such as 5 and 10, more preferably a mixture of 1-hexene and n-hexane.

[0121] In a preferred embodiment, the present invention does not specifically limit the source of the mixture, for example, it is Fischer-Tropsch naphtha in coal chemical production as mentioned above.

[0122] In a preferred embodiment, the olefin extractant is a weak polar solvent or a compound extractant, wherein the compound extractant comprises the weak polar solvent and a strong polar solvent;

[0123] In a preferred embodiment, the weak polar solvent is selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N-formylmorpholine, morpholine, dimethyl sulfoxide, and acetonitrile; preferably selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N-formylmorpholine and dimethyl sulfoxide; the strong polar solvent is selected from alcohol and / or water, preferably water.

[0124] In a preferred embodiment, the alcohol can be selected from monohydric alcohol or polyhydric alcohol, preferably monohydric alcohol, more preferably C1-C4 monohydric alcohol, preferably C2-C3 monohydric alcohol, such as ethanol.

[0125] In order to further improve the extraction and separation efficiency of alkanes and olefins, in a preferred embodiment, the olefin extractant is preferably a composite extractant of the weak polar solvent and the strong polar solvent; wherein the mass ratio of the weak polar solvent to the strong polar solvent is 10-1000:1, preferably 5-100:1, and more preferably 8-30:1.

[0126] In a further preferred embodiment, the composite extractant is selected from at least one of γ-butyrolactone+water, N-methylpyrrolidone+water, N,N-dimethylformamide+water, N-formylmorpholine+water, and dimethyl sulfoxide+water.

[0127] In a preferred embodiment, at 25°C, the separation coefficient of olefin in the olefin extractant is β>1.3, preferably β>1.5, more preferably β>1.9.

[0128] Wherein, separation coefficient β=(olefin content in the extract phase / alkane content in the extract phase) / (olefin content in the raffinate phase / alkane content in the raffinate phase).

[0129] In a preferred embodiment, the mass ratio of the olefin extractant to the mixture comprising alkanes and olefins is 0.1-15:1, preferably 0.5-5:1, and more preferably 1-2.5:1.

[0130] In a preferred embodiment, the present invention does not specifically limit the first mixing method of the olefin extractant and the mixture containing alkanes and alkenes. At room temperature, the mixture can be mixed by relying on the difference in gravitational buoyancy, or by mechanical assistance such as shaking, stirring, and shaking. The present invention does not specifically limit the mixing time of the extraction, and the specific mixing time can be adjusted according to the mixing method and the size of the processing volume.

[0131] In a preferred embodiment, in step A), the extraction is carried out at room temperature, and the extraction temperature may be 5-40° C., preferably 10-30° C. The present invention does not specifically limit the extraction time, and the specific extraction time may be adjusted according to the processing volume.

[0132] In a preferred embodiment, after the extraction is completed, an extraction phase A containing an extractant, olefins and a small portion of alkanes, and a raffinate phase a containing most of the alkanes are obtained. Wherein, based on 100% of the total amount of the extraction phase A, the content of the extractant in the extraction phase A is 81-93wt%, preferably 83-89wt%; the content of the olefins is 6-14wt%, preferably 9-12.5wt%; and the content of the alkanes is 1-5wt%, preferably 2-4.5wt%.

[0133] In step B):

[0134] In a preferred embodiment, the alkane separating agent is one olefin or a mixture of multiple olefins, preferably the same as the olefin to be separated.

[0135] In the present invention, the olefin to be separated refers to the olefin in the mixture containing alkanes and alkenes. The inventor creatively discovered through research that the extraction phase A is a homogeneous mixture of extractant-olefin-alkane. Since the polarity of the olefin extractant and the olefin is large, and the polarity of the alkane is small, after adding the alkane separation agent with large polarity to the extraction phase A, the original polarity balance in the extraction phase A can be broken, so that the newly added alkane separation agent gradually replaces the alkane and enters the extraction phase A, forming a homogeneous solution of the extractant-olefin-alkane separation agent, while the alkane with smaller polarity is separated from the homogeneous mixture of the olefin extractant-olefin-alkane and enters the upper layer of the homogeneous solution of the olefin extractant-alkane-alkane separation agent, so that the mixed solution is phase-separated, thereby separating the alkane from the extraction phase A.

[0136] In order to reduce the separation operation difficulty of subsequent olefin extraction agent-olefin-alkane separating agent, simplify separation process, described alkane separating agent is preferably identical with alkene to be separated.When the alkene in described raw material to be separated comprises multiple alkene, described alkane separating agent is at least one of multiple alkene to be separated, can be single alkene, also can be the mixture of multiple alkene.When described alkane separating agent is the mixture of multiple alkene, the present invention does not make special requirements to the specific mixing ratio of multiple alkene in the mixture.For example, when separating the mixture of 1-heptene, 1-hexene / normal heptane, normal hexane, alkane separating agent can be the mixture of 1-hexene, 1-heptene or 1-hexene and 1-heptene in any proportion.

[0137] In a preferred embodiment, the mass ratio of the alkane separating agent to the extraction phase A is 0.01-15:1, preferably 0.02-5:1, more preferably 0.05-0.5:1, and more preferably 0.06-0.15:1.

[0138] In a preferred embodiment, the present invention does not specifically limit the second mixing method of the alkane separating agent and the extraction phase A, and the mixing can be performed by relying on the difference in gravitational buoyancy, or by mechanical assistance such as vibration, stirring, shaking, etc. The present invention does not specifically limit the mixing time of the alkane separating agent and the extraction phase A, and the specific mixing time can be adjusted according to the mixing method and the size of the processing volume.

[0139] In a preferred embodiment, the stratification is performed at room temperature, wherein the present invention does not specifically limit the room temperature, which may be 5-40°C, preferably 10-30°C.

[0140] In a preferred embodiment, the stratification includes standing and liquid separation. The present invention does not specifically limit the standing time, and the specific standing time can be adjusted according to the processing volume.

[0141] In a preferred embodiment, after the standing is completed, a liquid separation operation is performed to obtain a lower mixed liquid B containing olefins, an extractant and an alkane separating agent, and an upper mixed liquid b containing alkanes;

[0142] In a preferred embodiment, step (2) further comprises repeating the stratification operation on the obtained lower mixed liquid B until the mass content of alkanes in the obtained lower mixed liquid B is less than or equal to 0.15%, preferably less than or equal to 0.07%.

[0143] Among them, after repeated operations for many times, the alkanes in the extraction phase A can be basically completely removed, and the lower mixed liquid B containing almost no alkanes is obtained.

[0144] In step C):

[0145] The present invention does not specifically limit the distillation operation conditions in step C), and the operation can be carried out according to the prior art, and atmospheric distillation can be preferred. The atmospheric pressure in the present invention refers to 0.1 MPa.

[0146] Since the alkane separating agent is also an alkene, in the present invention, the alkene product separated in step C) not only includes the alkene to be separated from the mixture containing alkanes and alkene, but also includes the added alkane separating agent. When the alkane separating agent is preferably the same as the alkene in the raw material, the lower mixed liquid B is subjected to a rectification operation to obtain high-purity alkene and an extractant. Wherein, the high-purity alkene product obtained by rectification at this time includes both the alkene to be separated and the added alkane separating agent. The obtained extractant can be recycled, can save production costs, and is suitable for industrial promotion. When the alkane separating agent is an alkene different from the alkene to be separated, the lower mixed liquid B is subjected to a rectification operation, and the obtained alkene product can be the alkene product to be separated and a separate alkane separating agent. Wherein, the obtained extractant and alkane separating agent can both be recycled.

[0147] In a preferred embodiment, the purity of the separated olefins is above 99 wt %, preferably above 99.7 wt %.

[0148] In a preferred embodiment, the purity of the separated olefin extractant is 99 wt%, preferably above 99.5 wt%.

[0149] In a preferred embodiment, in order to further increase the amount of olefins separated from the raw material to be separated, the operations of step A) and step B) may be repeated multiple times.

[0150] Example 1

[0151] The raw material to be separated is non-deoxygenated Fischer-Tropsch synthesis naphtha (the composition is shown in Table 1, and the rest is the same). A γ-butyrolactone aqueous solution (containing 15% by weight of water) is used as a deoxygenation extractant. Multi-stage countercurrent extraction is carried out in a deoxygenation extraction tower. The number of extraction stages is 9, the extraction temperature is 25°C, and the volume ratio of the extractant to the naphtha is 1.0:1.

[0152] After deoxygenation treatment, the deoxygenated raffinate phase enters the extraction tower and is fed from the 6th tower plate to separate alkanes and olefins. During alkane-olefin separation, γ-butyrolactone is used as an olefin extractant, fed from the top of the tower, and n-hexene is used as an alkane separating agent to feed from the bottom of the tower. Alkane-olefin separation is carried out according to mode I, and the raw material is sampled at room temperature. The olefin extractant / stock oil in the extraction process is 2.0, the alkane separating agent / stock oil is 1.0, and the countercurrent extraction stage is 6. Through distillation, olefins are separated from γ-butyrolactone, and γ-butyrolactone is circulated and continues to enter the extraction tower as an extractant, and olefins enter the subsequent distillation tower for distillation separation to obtain various olefin products. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0153] Example 2

[0154] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha. A diethylene glycol aqueous solution (containing 20 weight percent water) is used as a deoxygenation extractant. Multi-stage countercurrent extraction is carried out in an extraction tower. The extraction temperature is 20°C. After deoxygenation treatment in the deoxygenation extraction tower, the extraction stage is 7, the extraction temperature is 25°C, and the volume ratio of the extractant to naphtha is 0.8:1.

[0155] The raffinate phase after deoxidation is fed from the 6th plate and enters the extraction tower to separate alkanes and olefins. N-formylmorpholine is used as an olefin extraction agent during alkane-olefin separation, and is fed from the top of the tower. N-octene is fed from the bottom of the tower as an alkane separation agent. Alkane-olefin separation is carried out according to mode I, and the raw material room temperature is sampled. The extraction process olefin extraction agent / stock oil is 1.8, and the alkane separation agent / stock oil is 0.8, and the countercurrent extraction stage is 6. Through distillation, olefins are separated from gamma-butyrolactone, and gamma-butyrolactone is circulated and continues to enter the extraction tower as an extraction agent, and olefins enter the subsequent distillation tower for rectification and separation to obtain various olefin products. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0156] Example 3

[0157] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha, and N,N-dimethylformamide aqueous solution (containing 15 weight % water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 10, the extraction temperature is 20°C, and the volume ratio of the deoxygenating extractant to naphtha is 2.0:1.

[0158] After deoxygenation treatment, the raffinate phase after deoxygenation is fed from the 8th plate and enters the extraction tower for separation of alkanes and olefins. During alkane-olefin separation, dimethyl sulfoxide is used as an olefin extraction agent to feed from the top of the tower, and n-octene is used as an alkane separation agent to feed from the bottom of the tower. Alkane-olefin separation is carried out according to mode I, and the raw material is sampled at room temperature. The olefin extraction agent / stock oil in the extraction process is 2.0, and the stripping agent / stock oil in the stripping process is 0.8, and the countercurrent extraction stage is 8. Through distillation, olefins are separated from dimethyl sulfoxide, and dimethyl sulfoxide is circulated and continues to enter the extraction tower as an extraction agent, and olefins enter the subsequent distillation tower for distillation separation to obtain various olefin products. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0159] Example 4

[0160] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha, and N,N-dimethylacetamide aqueous solution (containing 20 weight % water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 8, the extraction temperature is 25°C, and the volume ratio of the deoxygenating extractant to naphtha is 1.0:1.

[0161] After deoxygenation treatment, the raffinate phase after deoxygenation is fed from the 7th plate and enters the extraction tower to separate alkanes and olefins. N-methyl pyrrolidone is used as an extraction agent during alkane-olefin separation, and is fed from the top of the tower. N-octene is fed from the bottom of the tower as an alkane separating agent. Alkane-olefin separation is carried out according to mode I, and the raw material is sampled at room temperature. The extraction process olefin extractant / stock oil is 3.0, the alkane separating agent / stock oil is 1.5, and the countercurrent extraction stage is 7. Through distillation, olefins are separated from N-methyl pyrrolidone, and N-methyl pyrrolidone is separated and circulated and continues to enter the extraction tower as an extraction agent, and olefins enter the subsequent distillation tower for distillation separation to obtain various olefin products. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0162] Example 5

[0163] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha. An aqueous solution of N-methylpyrrolidone (containing 25 weight percent water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 8. The extraction temperature is 25°C. The volume ratio of the deoxygenating extractant to naphtha is 1.2:1.

[0164] After deoxygenation treatment, the raffinate phase after deoxygenation is fed from the 6th plate and enters the extraction tower to separate alkanes and olefins. 1-methylimidazole is used as an extraction agent during alkane-olefin separation, and is fed from the top of the tower. N-octene is fed from the bottom of the tower as an alkane separating agent. Alkane-olefin separation is carried out according to mode I, and the raw material room temperature is sampled. The extraction process olefin extraction agent / stock oil is 2.5, and the alkane separating agent / stock oil is 1.2, and the countercurrent extraction stage is 6. Through distillation, olefins are separated from 1-methylimidazole, and 1-methylimidazole is circulated and continues to enter the extraction tower as an extraction agent, and olefins enter the subsequent distillation tower for rectification and separation to obtain various olefin products. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0165] Example 6

[0166] The raw material to be separated is non-deoxygenated Fischer-Tropsch synthesis naphtha (the composition is shown in Table 1, and the rest is the same). A diethylene glycol aqueous solution (containing 15% by weight of water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 8, the extraction temperature is 25°C, and the volume ratio of the deoxygenating extractant to the naphtha is 1.0:1.

[0167] After deoxygenation, an aqueous solution of γ-butyrolactone (γ-butyrolactone content of 85% by weight) is added to the deoxygenated raffinate phase as an extractant, fully mixed and contacted, and then extracted and separated. The olefin extractant / raw oil in the extraction process is 2. The specific operation is as follows: at 20°C, shake for 1min, then stand for 15min, and then separate the liquid to obtain a new extraction phase; add 1-hexene to the extraction phase as an alkane separation agent, and the alkane separation agent / raw oil is 1.0. The specific operation is: shake for 2min, then stand for 10min, and then separate the liquid to obtain a lower layer mixed liquid; repeat the layering operation three times for the obtained lower layer mixed liquid. The lower layer mixed liquid is distilled to separate olefins from γ-butyrolactone, and the olefin enters the subsequent distillation tower for distillation and separation to obtain various olefin products. γ-Butyrolactone can continue to be used as an extractant. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0168] Example 7

[0169] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha, and a γ-butyrolactone aqueous solution (containing 15 weight % water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 6, the extraction temperature is 25°C, and the volume ratio of the deoxygenating extractant to naphtha is 1.5:1.

[0170] After deoxygenation, an aqueous solution of N,N-dimethylformamide (N,N-dimethylformamide content of 90% by weight) is added to the deoxygenated raffinate phase as an olefin extractant, fully mixed and contacted, and then extracted and separated. The olefin extractant / raw oil in the extraction process is 2.5. The specific operation is as follows: at 20°C, shake for 1 minute, then stand for 15 minutes, and then separate the liquid to obtain a new extraction phase; add 1-hexene to the extraction phase as an alkane separation agent, and the alkane separation agent / raw oil is 0.8. The specific operation is: shake for 2 minutes, then stand for 10 minutes, and then separate the liquid to obtain a lower layer mixed liquid; repeat the layering operation three times for the obtained lower layer mixed liquid. The lower layer mixed liquid is separated from olefins and N,N-dimethylformamide by distillation, and the olefins enter the subsequent distillation tower for distillation and separation to obtain various olefin products. N,N-dimethylformamide can continue to be used as an extractant. The purity of various olefins and olefin recovery rates are shown in Table 2.

[0171] Example 8

[0172] The raw material to be separated is non-deoxygenated Fischer-Tropsch naphtha. An aqueous solution of N-methylpyrrolidone (containing 10 weight % water) is used as a deoxygenating extractant. Multi-stage countercurrent extraction is carried out in a deoxygenating extraction tower. The number of extraction stages is 6. The extraction temperature is 25°C. The volume ratio of the deoxygenating extractant to naphtha is 1.2:1.

[0173] After deoxygenation, the aqueous solution (85% by weight of N-methylpyrrolidone) added to the deoxygenated raffinate phase is used as an extractant, fully mixed and contacted, and then extracted and separated. The olefin extractant / raw oil in the extraction process is 2. The specific operation is as follows: at 20°C, shake for 1min, then stand for 15min, and then separate the liquid to obtain a new extraction phase; add 1-hexene to the extraction phase as an alkane separation agent, and the alkane separation agent / raw oil is 1.0. The specific operation is: shake for 2min, then stand for 10min, and then separate the liquid to obtain a lower layer mixed liquid; repeat the layering operation three times on the obtained lower layer mixed liquid. The lower layer mixed liquid is separated from the olefin and N-methylpyrrolidone by distillation, and the olefin enters the subsequent distillation tower for distillation and separation to obtain various olefin products. N-methylpyrrolidone can continue to be used as an extractant. The purity of various olefins and the olefin recovery rate are shown in Table 2.

[0174] Table 1 Fischer-Tropsch naphtha raw material composition

[0175]

[0176] Table 2 Comparison of liquid-liquid extraction separation effects

[0177]

[0178] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the method of the present invention is also applicable to the separation of other alkane-olefin mixtures and the separation of alkanes and alkenes according to this process under other process parameters. In addition, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for separating a mixture containing oxygenates, alkanes and olefins, characterized in that: The method includes: (1) subjecting a mixture containing oxygen-containing compounds, alkanes and olefins to deoxygenation extraction so that the content of oxygen-containing compounds in the mixture is reduced to below 10 ppm, thereby obtaining a raw material to be separated from which oxygen-containing compounds have been removed; the content of oxygenates in the mixture containing oxygen-containing compounds, alkanes and olefins is 2-6% by weight, the content of alkanes is 19-48% by weight, and the content of olefins is 46-79% by weight; the alkanes are C5-C12 alkanes, the olefins are C5-C12 alkenes, and the oxygenates are selected from one or more of alcohols, aldehydes, acids and ketones; and the mixture containing oxygenates, alkanes and olefins is Fischer-Tropsch naphtha; (2) The method of separating alkanes and olefins from the raw material to be separated is carried out by the following method I or method II: Method I: a) subjecting the raw material to be separated, an olefin extractant and an alkane separating agent to multi-stage countercurrent extraction to obtain an olefin fraction product comprising olefin, a major part of the olefin extractant and an alkane separating agent, and an alkane fraction product comprising alkane and a minor part of the olefin extractant; the olefin extractant is at least one selected from the group consisting of γ-butyrolactone, N-formylmorpholine, dimethyl sulfoxide, 1-methylimidazole, N-methylpyrrolidone and N,N-dimethylformamide; and the alkane separating agent is one olefin or a mixture of multiple olefins; b) subjecting the first olefin product to a separation operation to obtain an extractant and an olefin product; and / or subjecting the first alkane product to a separation operation to obtain an alkane product and an extractant; The operating temperature of the multi-stage countercurrent extraction is room temperature, and the operating pressure is normal pressure; Method II: A) first mixing the raw material to be separated with an olefin extractant and then extracting to obtain an extract phase A containing the olefin extractant, olefins and a small portion of alkanes, and a raffinate phase a containing most of alkanes and a small portion of olefins; the olefin extractant is a weak polar solvent or a composite extractant, wherein the composite extractant comprises the weak polar solvent and a strong polar solvent; the weak polar solvent is selected from at least one of γ-butyrolactone, N-methylpyrrolidone, N,N-dimethylformamide, N-formylmorpholine and dimethyl sulfoxide; the strong polar solvent is selected from alcohol and / or water; B) subjecting the extract phase A to a second mixing contact with an alkane separating agent and then separating the layers to obtain a lower mixed liquid B containing olefins, an olefin extractant and an alkane separating agent, and an upper mixed liquid b containing a majority of alkanes and a small amount of olefins; the alkane separating agent is one olefin or a mixture of multiple olefins; C) separating the lower mixed liquid B to obtain olefin products; and / or separating the raffinate phase a containing most alkanes and a small amount of olefins and / or the upper mixed liquid b containing most alkanes and a small amount of olefins.

2. The method according to claim 1, wherein: In method I, The multi-stage countercurrent extraction is carried out in a sieve plate extraction tower or a packed extraction tower; and / or When the olefin and alkane separating agents both include at least two or more olefins with different carbon numbers, The step b) of separating the olefin-1 product comprises: First, the first olefin fraction product is subjected to a first distillation to separate the olefin extractant from the first olefin fraction product to obtain a mixture containing olefins and alkane separating agents; the separated olefin extractant is returned to step a) for recycling, and the mixture containing olefins and alkane separating agents obtained after separation is divided into part a and part b, wherein the part a is returned to step a) to be mixed with the alkane separating agent, and the part b is subjected to a rectification operation.

3. The method according to claim 1 or 2, wherein: In method I, When the olefin to be separated is a single olefin and the alkane separation agent is the same as the olefin to be separated, the step b) of separating the olefin product comprises: First, the olefin fraction product is subjected to a first distillation to separate the olefin extractant from the olefin fraction product to obtain a mixture containing olefins and alkane separating agents; then the separated olefin extractant is returned to step a) for recycling, and part a of the mixture containing olefins and alkane separating agents obtained after separation is returned to step a) for mixing with the alkane separating agent for recycling, and part b is produced as an olefin product.

4. The method according to claim 1 or 2, wherein: In method I, The mass ratio of the olefin extractant to the material to be separated is 1-5:1; and / or The mass ratio of the alkane separating agent to the material to be separated is 0.4-3:

1.

5. The method according to claim 4, wherein: In method I, The mass ratio of the olefin extractant to the material to be separated is 1.5-3:1; and / or The mass ratio of the alkane separating agent to the material to be separated is 0.6-2:

1.

6. The method according to claim 1, wherein: In method II, The highly polar solvent is water.

7. The method according to claim 1, wherein: In the composite extractant of the weak polar solvent and the strong polar solvent, the mass ratio of the weak polar solvent to the strong polar solvent is 10-1000:

1.

8. The method according to claim 7, wherein: In the composite extractant of the weak polar solvent and the strong polar solvent, the mass ratio of the weak polar solvent to the strong polar solvent is 50-100:

1.

9. The method according to claim 8, wherein: In the composite extractant of the weak polar solvent and the strong polar solvent, the mass ratio of the weak polar solvent to the strong polar solvent is 8-30:

1.

10. The method according to claim 1, wherein: In method II, in step A), The mass ratio of the olefin extractant to the material to be separated is 0.1-10:1; and / or The conditions of the extraction operation include: extraction temperature of 0-50°C; and / or The extraction level is 3 or above; and / or The raw materials to be separated are fed from the 6th to 8th tower plates, the olefin extractant is fed from the top of the tower, and the alkane separating agent is fed from the bottom of the tower.

11. The method according to claim 10, wherein: In method II, in step A), The mass ratio of the olefin extractant to the material to be separated is 0.5-5:1; and / or The conditions of the extraction operation include: extraction temperature is 10-30°C; and / or The extraction stages are 6-8.

12. The method according to claim 1, wherein: In method II, step B), The mass ratio of the alkane separating agent to the extraction phase A is 0.01-15:

1.

13. The method according to claim 12, wherein: In method II, step B), The mass ratio of the alkane separating agent to the extraction phase A is 0.5-5:

1.

14. The method according to claim 13, wherein: In method II, step B), The operating conditions of the layering include: a temperature of 0-80°C.

15. The method according to claim 14, wherein: The operating conditions of the layering include: a temperature of 10-30°C.

16. The method according to claim 1 or 2, wherein: In Mode I and Mode II, the alkane separating agent is each selected from one or more olefins in the raw material to be separated.

17. The method according to claim 1 or 2, wherein: The operating conditions of the deoxygenation extraction in step (1) include: The extractant is a polar solvent and optionally water, wherein the polar solvent is one or a mixture of γ-butyrolactone, diethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, N-formylmorpholine, N-methylpyrrolidone, and dimethyl sulfoxide, and the water content in the extractant is 0-60% by weight; The amount of the extractant used is 0.5 to 4 times the weight of the mixture containing oxygen-containing compounds, alkanes and olefins; The extraction temperature is 10-50°C; The extraction method is a multi-stage countercurrent extraction method.

18. The method according to claim 17, wherein: The operating conditions of the deoxygenation extraction in step (1) include: The water content of the extractant is 10-25% by weight; and / or The amount of the extractant used is 1 to 2 times the weight of the mixture containing oxygen-containing compounds, alkanes and olefins; and / or The extraction temperature is 20-40°C; and / or The theoretical number of stages of the multi-stage countercurrent extraction is 5 to 15 stages.

19. The method according to claim 18, wherein: The operating conditions of the deoxygenation extraction in step (1) include: the theoretical number of stages of the multi-stage countercurrent extraction is 8 to 12 stages.

20. The method according to claim 1 or 2, wherein: The carbon number of the oxide is C1-C9; and / or The distillation range of the Fischer-Tropsch naphtha is 30-200°C.

Images