Process for separating 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream

Abstract

The present invention relates to the field of separating and purifying high-value-added chemicals from hydrocarbon-containing logistics, and discloses a method for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing logistics, comprising: (I) fractionating the hydrocarbon-containing logistics to obtain a C6<supgt;‑< / supgt; fraction logistics, a C6-C8 fraction logistics, a C9 and C9<supgt;+< / supgt> fraction logistics; (II) subjecting the C6-C8 fraction logistics to an oxygenated compound removal treatment to obtain a deoxygenated C6-C8 fraction logistics; (III) successively subjecting the deoxygenated C6-C8 fraction logistics to a rectification separation treatment, an extractive rectification treatment, a solvent removal treatment and a fine fractionation and heavy component removal treatment to obtain 1-hexene, 1-heptene and 1-octene. It can effectively remove the oxygenated compounds in the Fischer-Tropsch synthesis oil during the separation process, reduce the content of oxygenated compounds in the deoxygenated Fischer-Tropsch synthesis oil to less than 10 ppm (by mass), and the retention rate of α-olefins can reach more than 99%; the separation effect between alkanes and olefins is good, and the energy consumption of the separation process is low; the product yield is greater than 95%, and the purity is greater than 98.5%.

Description

Technical Field

[0001] The invention relates to the field of separation and purification of high value-added chemicals from hydrocarbon-containing logistics, and in particular to a method for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing logistics. Background Art

[0002] Fischer-Tropsch synthetic oil products contain a large amount of olefins and alkanes, among which olefins are mainly linear α-olefins. Among the above-mentioned α-olefins, 1-butene, 1-hexene and 1-octene have high added value and can be used as important organic raw materials with a wide range of applications. At present, foreign countries mainly use the ethylene polymerization method to produce α-olefins, and the α-olefins produced by this method are of high quality. The South African Sasol company separates and purifies linear α-olefins such as 1-hexene and 1-octene from high-temperature Fischer-Tropsch synthetic oil products using an extraction method, which has significantly lower costs than the polymerization method.

[0003] CN103819299B discloses a method for separating and purifying 1-hexene from a hydrocarbon mixture, which includes the steps of: the hydrocarbon mixture raw material flow passes through a raw material pre-cutting unit, an etherification reactor, a reaction distillation tower, a light component removal tower, a heavy component removal tower, an extractive distillation tower, a 1-hexene separation tower, a water washing tower, a methanol absorption tower, etc., to obtain a polymerization-grade 1-hexene product. In this method, a separation tower is used for the separation of alkanes and olefins, and the number of plates is very high, the reflux ratio is large, the theoretical number of plates is 80-250, and the reflux ratio is 10-40.

[0004] CN102452888A discloses a method for purifying 1-hexene from Fischer-Tropsch synthetic oil products. Fischer-Tropsch synthetic light distillate oil is first cut into fractions to obtain a C6 fraction segment; then the organic oxygen-containing compounds in the C6 fraction are removed by extractive distillation; then the C6 fraction segment is separated from alkanes and olefins by extractive distillation; the C6 olefins obtained by extractive distillation are subjected to reactive distillation, and under the action of a catalyst, the tertiary carbon olefins in the C6 olefins react with low-carbon alcohols to generate high-boiling-point ethers, thereby removing the tertiary carbon olefins; then the ethanol remaining in the C6 olefins is removed by liquid-liquid extraction; finally, the 1-hexene product that meets the polymerization grade requirements is purified from the C6 olefins by a precision distillation method. The extractant used for the extractive distillation of C6 alkanes and olefins is a polar solvent such as ACN, NMP or DMF. In order to improve the selectivity of the solvent, the preferred extractant is a binary mixed solvent composed of ACN or NMP and water. In this method, a solvent recovery tower and a dehydration tower need to be used in the solvent recovery process, making the process lengthy. In addition, the polarity of water is too different from that of the solvent, which makes the entire process complicated and affects the stability of the entire operation.

[0005] CN105777467B discloses a method for separating oxygen-containing compounds and 1-hexene from Fischer-Tropsch synthetic oil products, comprising: (1) using the Fischer-Tropsch synthetic oil product as a raw material, cutting it in a pre-cutting tower to obtain C6 - Distillate stream, C6 distillate stream and C6 + (2) in an extraction tower, using two extractant feeds consisting of a first extractant and a second extractant to remove oxygen-containing compounds from the C6 fraction stream for the first time, thereby obtaining a mixed stream of extractant and oxygen-containing compounds and a crude C6 hydrocarbon stream; (3) in an oxygen-containing compound separation tower, separating the mixed stream of extractant and oxygen-containing compounds to obtain a regenerated extractant stream and an oxygen-rich stream; (4) in an extractive distillation and oxygen-containing compound removal tower, using a third extractant to remove oxygen-containing compounds from the crude C6 hydrocarbon stream for a second time, thereby obtaining a mixed stream of a third extractant and oxygen-containing compounds and an oxygen-free C6 hydrocarbon fraction; (5) in an etherification reaction distillation tower, using methanol to convert tertiary carbon olefins in the oxygen-free C6 hydrocarbon fraction into corresponding ethers under the action of an etherification catalyst, and at the same time separating The refined C6 hydrocarbon stream is separated; (6) in the refinement and light component removal tower, the refined C6 hydrocarbon stream is separated to obtain a mixed stream containing 1-hexene and a hydrocarbon fraction with a higher boiling point than 1-hexene and a mixed stream of methanol and a hydrocarbon fraction with a lower boiling point than 1-hexene; (7) in the refinement and heavy component removal tower, the stream containing 1-hexene and a hydrocarbon fraction with a higher boiling point than 1-hexene is separated to obtain a 1-hexene-rich stream; (8) in the extractive distillation and isoparaffin removal tower, the C6 isoparaffin component in the 1-hexene-rich stream is removed with a fourth extractant to obtain a mixed stream of the fourth extractant and 1-hexene-rich stream; (9) in the 1-hexene separation tower, the cycloolefin component in the mixed stream of the fourth extractant and 1-hexene-rich stream is removed with a fifth extractant to obtain a mixed stream of the extractant and cycloolefin and a 1-hexene product stream. In this method, deoxygenation is carried out by extraction and extractive distillation, two extractants are used for extraction, and the raffinate phase needs to be further extracted and distilled to remove oxygenated compounds. The separation of normal alkanes and 1-hexene uses a refinement tower with a high plate number and a large reflux ratio, resulting in a low recovery rate of 1-hexene.

[0006] In view of the above problems, it is of great significance to provide a new method for separating α-olefins from a hydrocarbon-containing stream, especially a method for separating 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of unsatisfactory deoxygenation effect, low product purity, low recovery rate, complex process flow and high energy consumption in the existing method for separating and purifying α-olefins from hydrocarbon streams, and to provide a method for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing streams.

[0008] In order to achieve the above object, the present invention provides a method for separating 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream, comprising:

[0009] (I) Cutting the hydrocarbon-containing stream into fractions to obtain C6 - Distillate stream, C6-C8 distillate stream, C9 and C9 + fraction logistics;

[0010] (II) removing oxygen-containing compounds from the C6-C8 fraction stream to obtain a deoxygenated C6-C8 fraction stream;

[0011] (III) subjecting the deoxygenated C6-C8 fraction stream to a distillation separation treatment, an extractive distillation treatment, a solvent removal treatment, and a fine separation and deweighting treatment to obtain 1-hexene, 1-heptene, and 1-octene;

[0012] Wherein, the oxygen-containing compound removal treatment comprises:

[0013] (A) subjecting the C6-C8 fraction stream to countercurrent extraction with a composite extraction solvent to obtain a first extraction phase and a first raffinate phase;

[0014] (B) washing the first raffinate phase with water to obtain the deoxygenated C6-C8 fraction stream; recovering the first solvent and the second solvent from the mixture obtained at the same time, and / or returning the composite extraction solvent in step (A);

[0015] (C) The first extraction phase is subjected to first solvent recovery and second solvent recovery, the obtained first circulating solvent and second circulating solvent are cyclically added into the composite extraction solvent in step (A), the aqueous organic matter obtained by the second solvent recovery is subjected to static stratification, the bottom material obtained by stratification is separated, and the separated aqueous phase is circulated back to step (B).

[0016] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0017] (1) The oxygen-containing compounds are removed by extraction, and the use of a specific composite extraction solvent can solve the problem of the difficulty in balancing the deoxygenation effect and the hydrocarbon recovery rate. The oxygen-containing compounds such as alcohols, ketones, aldehydes, acids and esters in the Fischer-Tropsch synthetic oil can be effectively removed. The content of oxygen-containing compounds in the deoxygenated Fischer-Tropsch synthetic oil is reduced to less than 10 ppm (mass), the recovery rate of olefins and paraffins is greater than 98%, and the retention rate of α-olefins can reach more than 99%;

[0018] (2) The method of combining separation and deweighting with extractive distillation is adopted, and an extractant with good selectivity is used in the extractive distillation stage, so that the olefins separated are of high purity and the energy consumption of the separation process is low;

[0019] (3) The product yield is greater than 95% and the purity is greater than 98.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process provided by the present invention.

[0021] Description of Reference Numerals

[0022] A. First distillation tower B. Second distillation tower C. Extraction tower

[0023] D, water washing tower E, first solvent recovery tower F, second solvent recovery tower

[0024] G decantation tower H, stripping tower I, third distillation tower

[0025] J, first extraction distillation tower K, third solvent recovery tower L, first separation and deweighting tower

[0026] M, the fourth distillation tower N, the second extractive distillation tower O, the fourth solvent recovery tower

[0027] P, the second deweighting tower Q, the third extractive distillation tower R, the fifth solvent recovery tower

[0028] S, third fine separation and deweighting tower 1, Fischer-Tropsch synthetic oil 2, C9 - Distillate logistics

[0029] 3. C9 and C9 + Distillate stream 4, C6-C8 distillate stream 5, C6 - Distillate logistics

[0030] 6. First raffinate phase 7. First extraction phase 8. A-share material at the bottom of the water washing tower

[0031] 9. Wash the B-stock material at the bottom of the tower with water 10. The bottom product of the first solvent recovery tower

[0032] 11. First cycle solvent 12. Recycled materials 13. Second cycle solvent

[0033] 14. Decantation tower bottom product 15. Decantation tower top product 16. Circulating water

[0034] 17. Oxygenated compounds 18. Deoxygenated C6-C8 fraction logistics

[0035] 19, C6 fraction logistics 20, C7-C8 fraction logistics 21, first mixed logistics

[0036] 22. n-hexane and isohexane 23. crude 1-hexene 24. third circulation solvent

[0037] 25. 1-hexene 26. Bottom product of the first de-heavy fractionation tower

[0038] 27. C7 fraction logistics 28. C8 fraction logistics 29. n-heptane and isoheptane

[0039] 30. Second mixed stream 31. Crude 1-heptene 32. Fourth circulating solvent

[0040] 33. 1-heptene 34. Second fine separation and deheaving tower bottom product 35. n-octane and isooctane

[0041] 36. third mixed stream 37. crude 1-octene 38. fifth circulating solvent

[0042] 39. 1-octene 40. Bottom product of the third deweighting tower DETAILED DESCRIPTION

[0043] 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.

[0044] The present invention provides a method for separating 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream, comprising:

[0045] (I) Cutting the hydrocarbon-containing stream into fractions to obtain C6 - Distillate stream, C6-C8 distillate stream, C9 and C9 + fraction logistics;

[0046] (II) removing oxygen-containing compounds from the C6-C8 fraction stream to obtain a deoxygenated C6-C8 fraction stream;

[0047] (III) subjecting the deoxygenated C6-C8 fraction stream to a distillation separation treatment, an extractive distillation treatment, a solvent removal treatment, and a fine separation and deweighting treatment to obtain 1-hexene, 1-heptene, and 1-octene;

[0048] Wherein, the oxygen-containing compound removal treatment comprises:

[0049] (A) subjecting the C6-C8 fraction stream to countercurrent extraction with a composite extraction solvent to obtain a first extraction phase and a first raffinate phase;

[0050] (B) washing the first raffinate phase with water to obtain the deoxygenated C6-C8 fraction stream; recovering the first solvent and the second solvent from the mixture obtained at the same time, and / or returning the composite extraction solvent in step (A);

[0051] (C) The first extraction phase is subjected to first solvent recovery and second solvent recovery, the obtained first circulating solvent and second circulating solvent are cyclically added into the composite extraction solvent in step (A), the aqueous organic matter obtained by the second solvent recovery is subjected to static stratification, the bottom material obtained by stratification is separated, and the separated aqueous phase is circulated back to step (B).

[0052] In some embodiments of the present invention, the hydrocarbon-containing stream comprises alkanes, olefins and oxygenates. More specifically, the hydrocarbon-containing stream that can meet the requirement can be a naphtha fraction, typically preferably a condensate product of a Fischer-Tropsch synthesis reaction, and can be a condensate product of a low-temperature or high-temperature Fischer-Tropsch reaction. More preferably, the hydrocarbon-containing stream is a Fischer-Tropsch synthetic oil, wherein the content of α-olefins is 40-70wt%, preferably 50-70wt%.

[0053] In some embodiments of the present invention, the oxygen-containing compound in the hydrocarbon-containing stream comprises at least one of alcohol, ketone, aldehyde, carboxylic acid and ester. Further, based on the total amount of the hydrocarbon-containing stream, the total content of the oxygen-containing compound in the hydrocarbon-containing stream is 0.1-10wt%. Further, among the oxygen-containing compounds, the main oxygen-containing compound is alcohol, and the content of alcohol is 0.04-9.9wt%; the total content of ketone and aldehyde can be determined by carbonyl oxygen content, which can be 0.05-1wt%, the content of ester can be 0.01-0.2wt%, and the content of carboxylic acid can be determined by acidity, which can be 30-100mg / 100mL KOH. The alkanes in the hydrocarbon-containing stream are mainly normal alkanes, and there are also a small amount of isoalkanes.

[0054] In some embodiments of the present invention, in step (I), the fraction cutting comprises:

[0055] (i) cutting the hydrocarbon-containing stream into a first fraction to obtain C9 - Fraction and C9 fraction logistics and C9 + fraction logistics;

[0056] (ii) the C9 - The fraction stream is subjected to a second fraction cut to obtain C6 - Fraction and C6-C8 fraction logistics.

[0057] Preferably, the conditions for cutting the first fraction include: a reflux ratio of 2-5; a bottom temperature of 155-170° C.; and a top pressure of normal pressure.

[0058] Preferably, the hydrocarbon-containing stream can be subjected to the first fraction cutting in the first distillation tower to obtain C9 and C9 at the bottom of the first distillation tower. + The fraction stream is C9 obtained at the top of the first distillation tower. -The fraction logistics, wherein the number of theoretical plates of the first distillation tower is 30-50, the feed position of the hydrocarbon-containing logistics is the 15th-25th theoretical plate from the bottom to the top, and the conditions for cutting the first fraction include: the reflux ratio is 2-5; the bottom temperature is 155-170°C; and the top pressure is normal pressure.

[0059] Preferably, the conditions for cutting the second fraction include: a reflux ratio of 2-5; a bottom temperature of 80-90° C.; and a top pressure of normal pressure.

[0060] Preferably, the C9 - The fraction stream is subjected to the second fraction cutting in the second distillation tower, and a C6-C8 fraction stream is obtained at the bottom of the second distillation tower, and a C6-C8 fraction stream is obtained at the top of the second distillation tower. - The fraction flow, wherein the number of theoretical plates of the second distillation tower is 30-50, the C9 - The feed position of the distillate flow is the 15th to 25th theoretical plates from bottom to top, and the conditions for cutting the second distillate include: the reflux ratio is 2-5; the bottom temperature is 80-90° C.; and the top pressure is normal pressure.

[0061] In some embodiments of the present invention, in step (II), the oxygen-containing compound removal treatment is performed by extraction. In the oxygen-containing compound removal step (A), the composite extraction solvent can be used to remove the oxygen-containing compounds from the entire fraction of the hydrocarbon-containing stream by extraction, and can well balance the deoxygenation effect and the recovery rate of hydrocarbons after deoxygenation treatment. Preferably, the composite extraction solvent comprises a heavy polar solvent, methanol and water; wherein the heavy polar solvent is selected from at least one of ester compounds, glycol compounds, amide compounds, pyrrolidone compounds, diol compounds and alcohol amine compounds; the ester compound is selected from at least one of benzoate compounds, carbonate compounds and lactone compounds, preferably at least one of dimethyl phthalate, ethylene glycol carbonate and γ-butyrolactone; the glycol compound is selected from diethylene glycol and / or triethylene glycol; the amide compound is selected from N,N-dimethylformamide and / or N,N-dimethylacetamide; the pyrrolidone compound is N-methylpyrrolidone; the diol compound is propylene glycol; the alcohol amine compound is ethanolamine.

[0062] In the present invention, based on the total amount of the composite extraction solvent, the water content in the composite extraction solvent is 3-20 wt %, and the methanol content is 5-10 wt %.

[0063] In some embodiments of the present invention, in the conditions for implementing the countercurrent extraction in step (A), preferably, the weight ratio of the composite extraction solvent to the C6-C8 fraction flow is 0.5-4:1, preferably 0.8-2:1.

[0064] In some embodiments of the present invention, in step (A), preferably, the temperature of the countercurrent extraction is 10-50°C, preferably 20-50°C. The operation process of the countercurrent extraction can be a multi-stage countercurrent extraction method. Preferably, the theoretical number of stages of the multi-stage countercurrent extraction can be 5-15 stages, preferably 8-12 stages. The countercurrent extraction can be carried out in an extraction tower, and a first raffinate phase is obtained at the top of the tower, and a first extraction phase is obtained at the bottom of the tower. The first extraction phase is rich in oxygen-containing compounds; the first raffinate phase is rich in hydrocarbon compounds and has a low content of oxygen-containing compounds.

[0065] According to the above method provided by the present invention, the first raffinate phase obtained in step (A) contains a small amount of the composite extraction solvent, and the composite extraction solvent can be washed away by water washing in step (B) to obtain a deoxygenated hydrocarbon phase, that is, the deoxygenated C6-C8 fraction flow. The water washing can be carried out by introducing the first raffinate phase into a water washing tower, and the hydrocarbon phase is drawn out as the top product of the tower. A mixture of water and a small amount of composite extraction solvent can be obtained at the bottom of the tower, which can be directly returned to the composite extraction solvent in step (A) for recycling, or it can be sequentially introduced into the first solvent recovery tower and the second solvent recovery tower to perform the first solvent recovery treatment and the second solvent recovery treatment. Preferably, the conditions of the water washing include: the water washing temperature is 10-80°C, and the weight ratio of water to the first raffinate phase is 0.4-1:1.

[0066] In some embodiments of the present invention, in step (C), the first extraction phase is subjected to first solvent recovery and second solvent recovery, which can be achieved by distillation to obtain oxygenated compounds and circulating solvents, which can be carried out in the first solvent recovery tower and the second solvent recovery tower in sequence. The first solvent recovery treatment is carried out in the first solvent recovery tower, and the first circulating solvent (mainly methanol and azeotropic hydrocarbons) is obtained at the top of the tower, which can be returned to the composite extraction solvent in step (A) for recycling, and the bottom product (mainly heavy polar solvent, oxygenated compounds and water) is introduced into the second solvent recovery tower for the second solvent recovery treatment. The second circulating solvent (mainly heavy polar solvent) is obtained at the bottom of the second solvent recovery tower, which can also be returned to the composite extraction solvent in step (A) for recycling. In the present invention, the material obtained at the bottom of the water washing tower can also be returned to step (A) together with the first circulating solvent obtained at the top of the first solvent recovery tower and the second circulating solvent obtained at the bottom of the second solvent recovery tower, and added to the composite extraction solvent for recycling, which can adjust the water content in the obtained composite circulating solvent, and then adjust the effect of extraction and deoxygenation. In the present invention, the material obtained at the bottom of the water washing tower can also be sequentially introduced into the first solvent recovery tower and the second solvent recovery tower together with the first extraction phase. In the present invention, the recovered material obtained at the top of the second solvent recovery tower may contain oxygen-containing compounds and water. Furthermore, the recovered material is also subjected to static stratification after being drawn out, and can be introduced into a decanting tower for carrying out, and an organic phase insoluble in water is obtained at the top of the decanting tower, which is mainly oxygen-containing compounds, and water and water-soluble oxygen-containing compounds are obtained at the bottom of the decanting tower. Preferably, the conditions for the recovery of the first solvent include: a temperature of 80-100°C, a pressure of normal pressure, and a reflux ratio of 1-2; the conditions for the recovery of the second solvent include: a temperature of 150-250°C, a pressure of -0.01 to 0.08MPa, and a reflux ratio of 0.5-1; the reflux ratio refers to the weight ratio of the flow rate of the reflux liquid returned to the recovery tower to the flow rate of the recovered material at the top of the recovery tower. The temperature may refer to the temperature at the bottom of the recovery tower.

[0067] In some embodiments of the present invention, in step (C), the material obtained at the bottom of the decantation tower after static separation can be further separated to separate the organic phase and water. Preferably, the separation is distillation or stripping. Specifically, the material obtained from the bottom of the decantation tower can be introduced into a distillation tower or a stripping tower, and the organic phase of oxygen-containing compounds is mainly obtained at the top of the distillation tower or the stripping tower, and water is mainly obtained at the bottom of the tower; further, the obtained water is circulated to the water washing tower. In some embodiments of the present invention, preferably, the conditions of the stripping include: temperature of 100-120°C, pressure of normal pressure, and reflux ratio of 1-2; the conditions of the distillation include: temperature of 100-120°C, pressure of normal pressure, and reflux ratio of 1-2.

[0068] By removing oxygenated compounds in step (II) of the present invention, the recovery rate of olefins and paraffins in the deoxygenated C6-C8 fraction stream is preferably greater than 98%, while at least substantially maintaining the ratio of olefins / paraffins. Not only is the content of α-olefins in the Fischer-Tropsch synthetic oil maintained, but alcohols, ketones, aldehydes, acids and esters in the Fischer-Tropsch synthetic oil can also be effectively removed, and the content of oxygenated compounds in the deoxygenated C6-C8 fraction stream is reduced to less than 10 ppm (mass).

[0069] In some embodiments of the present invention, in step (III), the distillation separation treatment can achieve cutting of the deoxygenated C6-C8 fraction stream to obtain a C6 fraction stream, a C7 fraction stream and a C8 fraction stream. The distillation separation treatment comprises: subjecting the deoxygenated C6-C8 fraction stream to a first distillation separation treatment to obtain a C6 fraction stream and a C7-C8 fraction stream; and then subjecting the C7-C8 fraction stream to a second distillation separation treatment to obtain a C7 fraction stream and a C8 fraction stream.

[0070] Preferably, the conditions of the first distillation separation treatment include: a reflux ratio of 2-5; a bottom temperature of 105-115° C.; and a top pressure of normal pressure.

[0071] Preferably, the deoxygenated C6-C8 fraction logistics can be subjected to the first distillation separation treatment in a third distillation tower to obtain a C7-C8 fraction logistics at the bottom of the third distillation tower, and a C6 fraction logistics is obtained at the top of the third distillation tower, wherein the third distillation tower has 30-50 theoretical plates, and the feed position of the deoxygenated C6-C8 fraction logistics is at the 15th to 25th theoretical plate from bottom to top, and the conditions for the first distillation separation treatment include: a reflux ratio of 2-5; a bottom temperature of 105-115°C; and a top pressure of normal pressure.

[0072] Preferably, the conditions of the second distillation separation treatment include: a reflux ratio of 2-5; a bottom temperature of 120-130° C.; and a top pressure of normal pressure.

[0073] Preferably, the C7-C8 fraction logistics can be subjected to the second distillation separation treatment in a fourth distillation tower to obtain a C8 fraction logistics at the bottom of the fourth distillation tower, and a C7 fraction logistics at the top of the fourth distillation tower, wherein the fourth distillation tower has 30-50 theoretical plates, and the feed position of the C7-C8 fraction logistics is the 15th to 25th theoretical plate from the bottom up, and the conditions for the second distillation separation treatment include: a reflux ratio of 2-5; a bottom temperature of 120-130°C; and a top pressure of normal pressure.

[0074] In some embodiments of the present invention, in step (III), the extractive distillation treatment is intended to remove the alkane stream in the C6 fraction stream, the C7 fraction stream and the C8 fraction stream. The composite extractant used in the extractive distillation treatment is a mixture of extractant a and extractant b; the extractant a is selected from N-methylpyrrolidone and / or N,N-dimethylacetamide, and the extractant b is selected from γ-butyrolactone and / or N-formylmorpholine. The use of the composite extractant can take into account both the selectivity of the solvent and the solubility of the solvent.

[0075] Preferably, based on the weight of the composite extractant, the content of the extractant a is 70-30wt%, preferably 40-65wt%; the content of the extractant b is 30-70wt%, preferably 35-60wt%.

[0076] In the present invention, the extractive distillation treatment is carried out in an extractive distillation tower. Preferably, the conditions of the extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 120-190°C; a top pressure of normal pressure; and a theoretical number of plates of 50-100.

[0077] In some embodiments of the present invention, the extractive distillation treatment includes: subjecting the C6 fraction logistics and the compound extractant to a first extractive distillation treatment to obtain a first mixed stream rich in hexene and the compound extractant, as well as n-hexane and isohexane; subjecting the C7 fraction logistics and the compound extractant to a second extractive distillation treatment to obtain a second mixed stream rich in heptene and the compound extractant, as well as n-heptane and isoheptane; subjecting the C8 fraction logistics and the compound extractant to a third extractive distillation treatment to obtain a third mixed stream rich in octene and the compound extractant, as well as n-octane and isooctane.

[0078] Preferably, the conditions of the first extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 120-160° C.; a top pressure of normal pressure; and a theoretical number of plates of 50-80.

[0079] Preferably, the C6 fraction stream can be subjected to the first extractive distillation treatment in a first extractive distillation tower, the C6 fraction stream enters from the lower part of the first extractive distillation tower, and the compound extractant enters from the upper part of the tower. The volume ratio of the compound extractant to the C6 fraction stream is 4-12:1, preferably 5-8:1. The content of the extractant b in the compound extractant is 30-60wt%, preferably 35-50wt%. A first mixed stream rich in hexene and the compound extractant is obtained at the bottom of the tower, and n-hexane and isohexane are obtained at the top of the tower. Among them, the number of theoretical plates of the first extractive distillation tower is 50-80, the feeding position of the C6 fraction logistics is the 15th to 35th theoretical plates from the bottom to the top, the feeding position of the composite extractant is the 3rd to 6th theoretical plates from the top to the bottom, and the conditions of the first extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 120-160°C; a top pressure of normal pressure; and a theoretical number of 50-80 plates.

[0080] Preferably, the conditions of the second extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 150-170° C.; a top pressure of normal pressure; and a theoretical number of plates of 60-90.

[0081] Preferably, the C7 fraction stream can be subjected to the second extractive distillation treatment in a second extractive distillation tower, the C7 fraction stream enters from the lower part of the second extractive distillation tower, and the compound extractant enters from the upper part of the tower. The volume ratio of the compound extractant to the C7 fraction stream is 4-12:1, preferably 5-8:1. The content of the extractant b in the compound extractant is 35-65wt%, preferably 45-55wt%. A second mixed stream rich in heptene and the compound extractant is obtained at the bottom of the tower, and n-heptane and isoheptane are obtained at the top of the tower. Among them, the number of theoretical plates of the second extractive distillation tower is 60-90, the feeding position of the C7 fraction logistics is the 15th to 40th theoretical plates from the bottom to the top, the feeding position of the composite extractant is the 3rd to 6th theoretical plates from the top to the bottom, and the conditions of the second extractive distillation treatment include: the reflux ratio is 1-4; the bottom temperature is 150-170°C; the top pressure is normal pressure; the number of theoretical plates is 60-90.

[0082] Preferably, the conditions of the third extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 170-190° C.; a top pressure of normal pressure; and a theoretical number of plates of 60-100.

[0083] Preferably, the C8 fraction stream can be subjected to the third extractive distillation treatment in a third extractive distillation tower, the C8 fraction stream enters from the lower part of the third extractive distillation tower, and the compound extractant enters from the upper part of the tower. The volume ratio of the compound extractant to the C8 fraction stream is 4-12:1, preferably 5-8:1. The content of the extractant b in the compound extractant is 40-70wt%, preferably 50-60wt%. A third mixed stream rich in octene and the compound extractant is obtained at the bottom of the tower, and n-octane and isooctane are obtained at the top of the tower. Among them, the theoretical number of plates of the third extractive distillation tower is 60-100, the feeding position of the C8 fraction logistics is the 15th to 45th theoretical plates from the bottom to the top, the feeding position of the composite extractant is the 3rd to 6th theoretical plates from the top to the bottom, and the conditions of the third extractive distillation treatment include: a reflux ratio of 1-4; a bottom temperature of 170-190°C; a top pressure of normal pressure; and a theoretical number of plates of 60-100.

[0084] In some embodiments of the present invention, after the extractive distillation treatment, the obtained mixed stream is subjected to a desolventizing treatment, including: subjecting the first mixed stream to a first desolventizing treatment to obtain crude 1-hexene; subjecting the second mixed stream to a second desolventizing treatment to obtain crude 1-heptene; subjecting the third mixed stream to a third desolventizing treatment to obtain crude 1-octene. The desolventizing treatment separates and removes the composite extractant in the first mixed stream, the second mixed stream, and the third mixed stream to obtain crude 1-hexene, crude 1-heptene, and crude 1-octene, and the obtained circulating extractant (i.e., the regenerated composite extractant) is returned to the extractive distillation treatment step for recycling.

[0085] In some embodiments of the present invention, the desolventizing treatment is carried out in a solvent recovery tower. For example, the first mixed stream, the second mixed stream and the third mixed stream can be subjected to the first desolventizing treatment, the second desolventizing treatment and the third desolventizing treatment in the third solvent recovery tower, the fourth solvent recovery tower and the fifth solvent recovery tower, respectively. The solvent recovery tower is preferably a distillation tower having 15-30 theoretical plates, the feed position being the 10th to 15th theoretical plates from bottom to top, and the conditions of the desolventizing treatment include: a reflux ratio of 0.5-1, a bottom temperature of 150-250°C, and a top pressure of -0.01 to 0.08MPa.

[0086] In some embodiments of the present invention, in step (III), the precise separation and de-weighting treatment can remove the corresponding 2-olefins in the crude 1-hexene, crude 1-heptene and crude 1-octene. The precise separation and de-weighting treatment can be carried out in the form of distillation. Preferably, the precise separation and de-weighting treatment conditions include: a reflux ratio of 5-8; a bottom temperature of 69-135°C; a top pressure of normal pressure; and a theoretical number of 60-100 plates.

[0087] In the present invention, the fine separation and de-weighting treatment includes: subjecting the crude 1-hexene to a first fine separation and de-weighting treatment to obtain 1-hexene, 2-hexene and a C6 component with a higher boiling point; subjecting the crude 1-heptene to a second fine separation and de-weighting treatment to obtain 1-heptene, 2-heptene and a C7 component with a higher boiling point; subjecting the crude 1-octene to a third fine separation and de-weighting treatment to obtain 1-octene, 2-octene and a C8 component with a higher boiling point.

[0088] Preferably, the conditions of the first fine separation and deweighting treatment include: a reflux ratio of 5-8; a bottom temperature of 69-75°C; a top pressure of normal pressure; and a theoretical number of plates of 60-100.

[0089] Preferably, the crude 1-hexene can be subjected to the first fine separation and deweighting treatment in a first fine separation and deweighting tower, the crude 1-hexene enters from the lower part of the first fine separation and deweighting tower, 2-hexene and C6 components with higher boiling points are obtained at the bottom of the tower, and 1-hexene is obtained at the top of the tower, wherein the theoretical number of plates of the first fine separation and deweighting tower is 60-100, the feeding position of the C6 fraction logistics is the 30th to 50th theoretical plate from the bottom to the top, and the conditions of the first fine separation and deweighting treatment include: a reflux ratio of 5-8; a bottom temperature of 69-75°C; a top pressure of normal pressure; and a theoretical number of 60-100 plates.

[0090] Preferably, the conditions of the second fine separation and deweighting treatment include: a reflux ratio of 5-8; a bottom temperature of 99-105° C.; a top pressure of normal pressure; and a theoretical number of plates of 60-100.

[0091] Preferably, the crude 1-heptene can be subjected to the second fine separation and deweighting treatment in a second fine separation and deweighting tower, the crude 1-heptene enters from the lower part of the second fine separation and deweighting tower, 2-heptene and C7 components with higher boiling points are obtained at the bottom of the tower, and 1-heptene is obtained at the top of the tower, wherein the theoretical number of plates of the second fine separation and deweighting tower is 60-100, the feed position of the crude 1-heptene is the 30th to 50th theoretical plate from the bottom to the top, and the conditions of the second fine separation and deweighting treatment include: a reflux ratio of 5-8; a bottom temperature of 99-105°C; a top pressure of normal pressure; and a theoretical number of 60-100 plates.

[0092] Preferably, the conditions of the third fine separation and degravity treatment include: a reflux ratio of 5-8; a bottom temperature of 128-135° C.; a top pressure of normal pressure; and a theoretical number of plates of 60-100.

[0093] Preferably, the crude 1-octene can be subjected to the third fine separation and deweighting treatment in a third fine separation and deweighting tower, the crude 1-octene enters from the lower part of the third fine separation and deweighting tower, 2-octene and C8 components with a higher boiling point are obtained at the bottom of the tower, and 1-octene is obtained at the top of the tower, wherein the theoretical number of plates of the third fine separation and deweighting tower is 60-100, the feed position of the crude 1-octene is the 30th to 50th theoretical plate from the bottom to the top, and the conditions of the third fine separation and deweighting treatment include: a reflux ratio of 5-8; a bottom temperature of 128-135° C.; a top pressure of normal pressure; and a theoretical number of 60-100 plates.

[0094] According to a specific embodiment of the present invention, Figure 1As shown, a method for separating 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream. The method can be carried out in the following separation system, which includes: a first distillation tower, a second distillation tower, an extraction tower, a water washing tower, a first solvent recovery tower, a second solvent recovery tower, a decantation tower, a stripping tower, a third distillation tower, a first extractive distillation tower, a third solvent recovery tower, a first clean deweighting tower, a fourth distillation tower, a second extractive distillation tower, a fourth solvent recovery tower, a second clean deweighting tower, a third extractive distillation tower, a fifth solvent recovery tower, and a third clean deweighting tower; wherein the first distillation tower is sequentially connected to the second distillation tower, and the lower discharge port of the second distillation tower is connected to the extraction tower; the top of the extraction tower is connected to the water washing tower, The bottom of the tower is connected to the first solvent recovery tower. The extraction tower is provided with a lower feed port for feeding the C6-C8 fraction logistics, and an upper feed port is provided for feeding the composite extraction solvent; the water washing tower is provided with a lower feed port for feeding the first raffinate phase, and an upper feed port is provided for feeding water. The water washing tower is also provided with a top outlet to discharge the obtained deoxygenated C6-C8 fraction logistics to the lower feed port of the third distillation tower, and a bottom outlet is provided to discharge the bottom material and is connected to the upper feed port of the extraction tower; the first solvent recovery tower is provided with a recovery feed port connected to the bottom of the extraction tower and the bottom outlet of the water washing tower, and an upper outlet of the tower is also provided to discharge the first circulating solvent to The extraction tower, and the lower discharge port is connected to the feed port of the second solvent recovery tower; the second solvent recovery tower is also provided with a top recovery discharge port, and a bottom outlet and connected to the upper feed port of the extraction tower; the decantation tower is provided with a decantation feed port connected to the recovery discharge port of the second solvent recovery tower, a top organic phase outlet and a bottom discharge port; the stripping tower is provided with a separation feed port connected to the bottom discharge port of the decantation tower, a bottom outlet connected to the upper feed port of the water washing tower, and an organic phase outlet at the top of the stripping tower; the third distillation tower, the first extractive distillation tower, the third solvent recovery tower and the first fine separation and deweighting tower are connected in sequence, and the tower of the third solvent recovery tower The bottom discharge port is connected to the upper extractant feed port of the first extractive distillation tower; the fourth distillation tower, the second extractive distillation tower, the fourth solvent recovery tower and the second fractionation and de-weighting tower are connected in sequence, and the feed port of the fourth distillation tower is connected to the bottom discharge port of the third distillation tower, and the bottom discharge port of the fourth solvent recovery tower is connected to the upper extractant feed port of the second extractive distillation tower; the third extractive distillation tower, the fifth solvent recovery tower and the third fractionation and de-weighting tower are connected in sequence, and the feed port of the third extractive distillation tower is connected to the bottom discharge port of the fourth distillation tower, and the bottom discharge port of the fifth solvent recovery tower is connected to the upper extractant feed port of the third extractive distillation tower. The method provided by the present invention can be implemented in the above system, comprising the following steps:

[0095] The Fischer-Tropsch naphtha fraction is cut into fractions by passing through the first distillation tower and the second distillation tower to obtain C6 - Distillate stream, C6-C8 distillate stream, C9 and C9 + Distillate stream.

[0096] The C6-C8 fraction flow and the composite extraction solvent are introduced into the extraction tower through the lower feed port and the upper feed port respectively, and multi-stage countercurrent extraction is performed to obtain a first extraction phase and a first raffinate phase.

[0097] The first raffinate phase is introduced into a water washing tower to wash away a small amount of composite extraction solvent contained therein by water washing, and a deoxygenated C6-C8 fraction flow is drawn out from the top of the water washing tower, which contains more than 96wt% of olefins and alkanes, and less than 10ppm (mass) of oxygen-containing compounds; the mixture of water and a small amount of composite extraction solvent obtained at the bottom of the water washing tower can be divided into A-share material at the bottom of the water washing tower and B-share material at the bottom of the water washing tower, A-share returns to the extraction tower to add the composite extraction solvent, and B-share is mixed with the first extraction phase and enters the first solvent recovery tower; the first solvent recovery tower is distilled and recovered, and a first circulating solvent is obtained from the top of the tower, which can be returned to add the composite extraction solvent for recycling, and the bottom product (mainly heavy polar solvent, oxygen-containing compounds and water) is drawn out. Enter the second solvent recovery tower for further distillation and recovery; obtain a recovered material from the top of the second solvent recovery tower, including oxygen-containing compounds and water, and obtain a second circulating solvent (mainly a heavy polar solvent) from the bottom of the tower, which can be returned to the composite extraction solvent for recycling; in the present invention, the amount and composition of the A-share material at the bottom of the water washing tower and the first and second circulating solvents returned when adding the composite extraction solvent are used to adjust the composition of the composite extraction solvent to meet the extraction process. For example, the A-share material at the bottom of the water washing tower and the first circulating solvent and the second circulating solvent can be mixed to prepare a suitable composition and added to the extraction solvent. If the water content is excessive, the mixture can be distributed to more B-share material at the bottom of the water washing tower, and even all the mixture obtained at the bottom of the water washing tower enters the first solvent recovery tower.

[0098] The recovered material obtained from the top of the second solvent recovery tower is introduced into a decantation tower for static separation, and the decantation tower top product, which is mainly oxygen-containing compounds, is obtained at the upper part of the decantation tower, and the decantation tower bottom product obtained at the bottom of the decantation tower can be recovered water and a small amount of water-soluble oxygen-containing compounds; further, the decantation tower bottom product of the decantation tower is introduced into a stripping tower to separate water and oxygen-containing compounds, and oxygen-containing compounds are obtained at the top of the tower, and circulating water is obtained at the bottom of the tower, which is circulated back to the water washing tower.

[0099] The deoxygenated C6-C8 fraction logistics enters the third distillation tower and the fourth distillation tower successively for distillation and separation treatment to obtain a C6 fraction logistics, a C7 fraction logistics and a C8 fraction logistics. The C6 fraction logistics enters the first extractive distillation tower, the third solvent recovery tower and the first precise de-weighting tower in sequence, and performs the first extractive distillation treatment (using the composite extractant), the first desolventizing treatment and the first precise de-weighting treatment in sequence to obtain 1-hexene, and the obtained third circulating solvent is returned to the first extractive distillation tower for recycling; the C7 fraction logistics enters the second extractive distillation tower, the fourth solvent recovery tower and the second precise de-weighting tower in sequence, and performs the second extractive distillation treatment (using the composite extractant), the second desolventizing treatment and the second precise de-weighting treatment in sequence to obtain 1-heptene, and the obtained fourth circulating solvent is returned to the second extractive distillation tower for recycling; the C8 fraction logistics enters the third extractive distillation tower, the fifth solvent recovery tower and the third precise de-weighting tower in sequence, and performs the third extractive distillation treatment (using the composite extractant), the third desolventizing treatment and the third precise de-weighting treatment in sequence to obtain 1-octene, and the obtained fifth circulating solvent is returned to the third extractive distillation tower for recycling.

[0100] The present invention will be described in detail below through examples.

[0101] Recovery rate of deoxygenated C6-C8 fraction stream % = mass of deoxygenated naphtha obtained from the top of the water scrubber / [feed amount of C6-C8 fraction stream in the extraction tower × (1-content of oxygen-containing compounds %)] × 100%

[0102] Yield of product (1-hexene, 1-heptene or 1-octene) % = mass of product (1-hexene, 1-heptene or 1-octene) / (feed amount of Fischer-Tropsch oil × percentage content of 1-hexene, 1-heptene or 1-octene) × 100%

[0103] The content of each component in Fischer-Tropsch naphtha was measured by chromatography, among which the content of alcohol and ester in oxygen-containing compounds was determined by chromatography, the content of carbonyl oxygen was determined according to GB / T 6324.5-2008, and the acidity was determined according to GB / T264;

[0104] The content of each component in the product (1-hexene, 1-heptene or 1-octene) is measured by chromatography, wherein the content of oxygen-containing compounds is determined by chromatography;

[0105] The composition and content of raw material Fischer-Tropsch synthesis naphtha are shown in Table 1.

[0106] Table 1

[0107] Raw material composition Content (wt%) α-Olefins 51.2 Normal alkanes 31.5 2-Olefin 10.1 Isoalkanes 3.0 Isoolefins 2.4 alcohol 1.6 Carbonyl oxygen 0.2

[0108] Example 1

[0109] (I) Fischer-Tropsch naphtha (composition shown in Table 1) is subjected to first fraction cutting in the first distillation tower to obtain C9 - Fractions and C9 and C9 + The fraction stream is then - The fraction stream is cut into the second fraction in the second distillation tower to obtain C6 - The specific operating conditions of the fractions and C6-C8 fraction logistics are shown in Table 2;

[0110] (II) subjecting the C6-C8 fraction stream and a composite extraction solvent (82 wt % of γ-butyrolactone, 8 wt % of methanol, and 10 wt % of water) to multi-stage countercurrent extraction in an extraction tower to obtain a first extraction phase and a first raffinate phase; wherein the countercurrent extraction temperature is 25° C., the feed rate of the C6-C8 fraction stream is 15 g / min, the feed rate of the composite extraction solvent is 18 g / min (the weight ratio of the composite extraction solvent to the C6-C8 fraction stream is 1.2:1), and the theoretical number of extraction stages is 10;

[0111] The first raffinate phase at the top of the extraction tower is introduced into a water washing tower, and the composite extraction solvent is washed away by water washing. The water washing temperature is 50°C, and the weight ratio of water to the first raffinate phase is 0.5:1. A deoxygenated C6-C8 fraction flow is obtained at the top of the water washing tower and drawn out; the mixture (γ-butyrolactone, methanol and water) obtained at the bottom of the water washing tower is divided into a stock A at the bottom of the water washing tower and a stock B at the bottom of the water washing tower. The stock A at the bottom of the water washing tower can be directly returned to the extraction tower for recycling. The stock B at the bottom of the water washing tower and the first extraction phase are introduced into the first solvent recovery tower and the second solvent recovery tower for sequential first solvent recovery treatment and second solvent recovery treatment; the first solvent recovery conditions: temperature 88-92°C, pressure is normal pressure, and reflux ratio is 2; the second solvent recovery The recovery conditions include: temperature of 175-180°C, pressure of -0.05MPa, and reflux ratio of 1; the first circulating solvent obtained at the top of the first solvent recovery tower is returned to the extraction tower and added to the composite extraction solvent for recycling, and the bottom product is introduced into the second solvent recovery tower; the second circulating solvent obtained at the bottom of the second solvent recovery tower is returned to the extraction tower and added to the composite extraction solvent for recycling, the recovered material obtained at the top is introduced into the decanting tower for static separation, and the top product of the decanting tower obtained at the top is mainly oxygen-containing compounds; the bottom product of the decanting tower obtained at the bottom is introduced into the stripping tower to separate water and water-soluble oxygen-containing compounds, and the stripping conditions include: temperature of 100-105°C, pressure of normal pressure, reflux ratio of 2, and the circulating water obtained is reused in the water washing tower;

[0112] 100 min was taken for material balance, and 1443.5 g of deoxygenated C6-C8 fraction logistics was obtained, and the recovery rate of the deoxygenated C6-C8 fraction logistics was 98.0%;

[0113] By gas chromatography, the content of α-olefins in the deoxygenated C6-C8 fraction stream was 52.1 wt%, and the content of oxygen-containing compounds was 6 ppm; the alcohol content in the oxygen-containing compounds was 0 ppm (weight), the content of carbonyl oxygen was 3 ppm (weight), and the acidity was 0.37 mg / 100 mL KOH;

[0114] (III) subjecting the deoxygenated C6-C8 fraction stream to a first distillation separation treatment in a third distillation tower to obtain a C7-C8 fraction stream at the bottom of the tower and a C6 fraction stream at the top of the tower; subjecting the C7-C8 fraction stream to a second distillation separation treatment in a fourth distillation tower to obtain a C8 fraction stream at the bottom of the tower and a C7 fraction stream at the top of the tower; the specific operating conditions are shown in Table 2;

[0115] The C6 fraction logistics is introduced into a first extractive distillation tower and a composite extractant (the content of N-methylpyrrolidone is 55wt%, the content of γ-butyrolactone is 45wt%) for a first extractive distillation treatment (wherein the volume ratio of the composite extractant to the C6 fraction logistics is 7:1), and the C7 fraction logistics is introduced into a second extractive distillation tower and a composite extractant (the content of N-methylpyrrolidone is 50wt%, the content of γ-butyrolactone is 50wt%) for a second extractive distillation treatment (wherein the composite extractant is 50wt%). The C8 fraction stream is introduced into a third extractive distillation tower and subjected to a third extractive distillation treatment with a composite extractant (the content of N-methylpyrrolidone is 50wt%, the content of γ-butyrolactone is 50wt%) (wherein the volume ratio of the composite extractant to the C8 fraction stream is 7:1), and a first mixed stream, a second mixed stream and a third mixed stream are obtained at the bottom of the tower respectively; and corresponding normal alkanes and isoalkanes are obtained at the top of the tower respectively; the specific operating conditions are shown in Table 2;

[0116] The first mixed stream is introduced into a third solvent recovery tower for a first desolventizing treatment, the second mixed stream is introduced into a fourth solvent recovery tower for a second desolventizing treatment, and the third mixed stream is introduced into a fifth solvent recovery tower for a third desolventizing treatment, and crude 1-hexene, crude 1-heptene and crude 1-octene are obtained at the top of the tower, respectively, and the third circulating extractant, the fourth circulating extractant and the fifth circulating extractant obtained at the bottom of the tower are respectively returned to the first extractive distillation tower, the second extractive distillation tower and the third extractive distillation tower for recycling. The specific operating conditions are shown in Table 2;

[0117] The crude 1-hexene is introduced into the first fine separation and deweighting tower for the first fine separation and deweighting treatment, the crude 1-heptene is introduced into the second fine separation and deweighting tower for the second fine separation and deweighting treatment, and the crude 1-octene is introduced into the third fine separation and deweighting tower for the third fine separation and deweighting treatment, and 1-hexene product (denoted as S1), 1-heptene product (denoted as P1) and 1-octene product (denoted as X1) are obtained at the top of the tower respectively; the corresponding 2-olefins and higher boiling point components are obtained at the bottom of the tower respectively; the specific operating conditions are shown in Table 2.

[0118] Table 2

[0119]

[0120]

[0121] After testing, the purity of 1-hexene in product S1 is 99.1wt%, the content of oxygen-containing compounds is 4ppm, and the yield of 1-hexene is 96%; the purity of 1-heptene in product P1 is 98.9wt%, the content of oxygen-containing compounds is 5ppm, and the yield of 1-heptene is 96.5%; in product X1, the purity of 1-octene is 98.6wt%, the content of oxygen-containing compounds is 6ppm, and the yield of 1-octene is 96.5%.

[0122] In summary, by adopting the method of the present invention, the content of α-olefins can be maintained during the process of removing oxygen-containing compounds, so that the content of oxygen-containing compounds in the Fischer-Tropsch synthetic oil after deoxygenation and refining is reduced to below 10 ppm, and the yield of the separated products 1-hexene, 1-heptene, and 1-octene is greater than 95%, and the purity is greater than 98.5%.

[0123] 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 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 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream, comprising: (I) Cutting the hydrocarbon-containing stream into fractions to obtain C6 - Distillate stream, C6-C8 distillate stream, C9 and C9 + fraction logistics; (II) removing oxygen-containing compounds from the C6-C8 fraction stream to obtain a deoxygenated C6-C8 fraction stream; (III) subjecting the deoxygenated C6-C8 fraction stream to a distillation separation treatment, an extractive distillation treatment, a solvent removal treatment, and a fine separation and deweighting treatment to obtain 1-hexene, 1-heptene, and 1-octene; Wherein, the oxygen-containing compound removal treatment comprises: (A) subjecting the C6-C8 fraction stream to countercurrent extraction with a composite extraction solvent to obtain a first extraction phase and a first raffinate phase; (B) washing the first raffinate phase with water to obtain the deoxygenated C6-C8 fraction stream; recovering the first solvent and the second solvent from the mixture obtained at the same time, and / or returning the composite extraction solvent in step (A); (C) recovering the first solvent and the second solvent from the first extraction phase, cyclically adding the obtained first circulating solvent and the second circulating solvent into the composite extraction solvent in step (A), stratifying the aqueous organic matter obtained by the second solvent recovery, separating the bottom material obtained by stratification, and recycling the separated aqueous phase to step (B); The composite extraction solvent comprises a heavy polar solvent, methanol and water; wherein the heavy polar solvent is an ester compound; the ester compound is selected from at least one of benzoate compounds, carbonate compounds and lactone compounds; The composite extractant used in the extractive distillation treatment is a mixture of extractant a and extractant b; the extractant a is selected from N-methylpyrrolidone and / or N,N-dimethylacetamide, and the extractant b is selected from γ-butyrolactone and / or N-formylmorpholine.

2. The method according to claim 1, wherein: The hydrocarbon-containing stream comprises alkanes, olefins and oxygen-containing compounds; and / or, the hydrocarbon-containing stream is a naphtha fraction; and / or, the oxygen-containing compound comprises at least one of an alcohol, a ketone, an aldehyde, a carboxylic acid, and an ester; And / or, based on the total amount of the hydrocarbon-containing stream, the content of the oxygen-containing compound in the hydrocarbon-containing stream is 0.1-10 wt %.

3. The method according to claim 2, wherein: The hydrocarbon-containing stream is a condensate product of the Fischer-Tropsch synthesis reaction.

4. The method according to any one of claims 1 to 3, wherein: The ester compound is at least one of dimethyl phthalate, ethylene glycol carbonate and gamma-butyrolactone.

5. The method according to claim 4, wherein: Based on the total amount of the composite extraction solvent, the water content in the composite extraction solvent is 3-20 wt %, and the methanol content is 5-10 wt %.

6. The method according to any one of claims 1 to 3, wherein: The weight ratio of the composite extraction solvent to the C6-C8 fraction flow is 0.5-4:

1.

7. The method according to claim 6, wherein: The weight ratio of the composite extraction solvent to the C6-C8 fraction flow is 0.8-2:

1.

8. The method according to any one of claims 1 to 3, wherein: The temperature of the countercurrent extraction is 10-50°C.

9. The method according to claim 8, wherein: The temperature of the countercurrent extraction is 20-50°C.

10. The method according to any one of claims 1 to 3, wherein: The conditions for recovering the first solvent include: temperature 80-100°C, pressure normal pressure, and reflux ratio 1-2; the conditions for recovering the second solvent include: temperature 150-250°C, pressure -0.01 to 0.08 MPa, and reflux ratio 0.5-1; And / or, the separation is distillation or stripping; And / or, the stripping conditions include: temperature of 100-120° C., pressure of normal pressure, and reflux ratio of 1-2; the distillation conditions include: temperature of 100-120° C., pressure of normal pressure, and reflux ratio of 1-2.

11. The method according to any one of claims 1 to 3, wherein: Based on the weight of the composite extractant, the content of the extractant a is 70-30wt%; the content of the extractant b is 30-70wt%.

12. The method according to claim 11, wherein: Based on the weight of the compound extractant, the content of the extractant a is 40-65wt%; the content of the extractant b is 35-60wt%.

13. The method according to any one of claims 1 to 3, wherein: The conditions of the extractive distillation treatment include: a reflux ratio of 1-4; a tower bottom temperature of 120-190° C.; a tower top pressure of normal pressure, and a theoretical tower plate number of 50-100.

14. The method according to any one of claims 1 to 3, wherein: The conditions of the fine separation and deweighting treatment include: a reflux ratio of 5-8; a tower bottom temperature of 69-135° C.; a tower top pressure of normal pressure; and a theoretical tower plate number of 60-100.

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