Method and apparatus for separating 1-hexene from a hydrocarbon stream containing C6 olefins

Abstract

The present invention relates to the technical field of separation and purification of high value-added chemicals from hydrocarbon streams, and in particular to a method and device for separating 1-hexene from hydrocarbon streams containing C6 olefins. The method comprises: (1) subjecting a hydrocarbon stream containing C6 olefins to distillation and cutting to obtain a C6 fraction stream; (2) washing the C6 fraction stream with water to obtain a crude C6 hydrocarbon stream; (3) subjecting the crude C6 hydrocarbon stream to extractive distillation with a composite extractant to obtain a mixed stream rich in 1-hexene and the composite extractant; (4) separating the mixed stream to obtain a 1-hexene stream and a regenerated composite extractant stream; (5) adsorbing the 1-hexene stream to obtain a 1-hexene product. Compared with the prior art, the method provided by the present invention effectively improves the purity and recovery rate of 1-hexene; and at the same time, simplifies the process device.

Description

Technical Field

[0001] The present invention relates to the technical field of separation and purification of high value-added chemicals in hydrocarbon logistics, and in particular to a method and device for separating 1-hexene from hydrocarbon logistics containing C6 olefins. Background Art

[0002] α-Olefins are an important organic raw material and intermediate product with a wide range of uses. 1-Butene, 1-hexene and 1-octene can be used as comonomers of polyethylene (PE) resin to improve the performance of PE. At present, the production of α-olefins in industry is mainly obtained by ethylene polymerization. Fischer-Tropsch synthetic oil products contain olefins and alkanes. Olefins are mainly linear α-olefins, and the content of α-olefins in Fischer-Tropsch light oil can reach more than 50%. The α-olefins produced by ethylene polymerization are of high quality. This method is mainly used in the production of α-olefins abroad. The domestic polymerization technology has developed relatively late. Only in recent years has an industrial device for the production of 1-hexene by ethylene polymerization been built. The extraction method was developed by Sasol Company of South Africa from the separation of Fischer-Tropsch synthetic oil products. It separates and purifies linear α-olefins such as 1-hexene and 1-octene from high-temperature Fischer-Tropsch synthetic oil products. Compared with the polymerization method, this method has obvious cost advantages.

[0003] EP1835011 proposed a distillation treatment method for the crude product of Fischer-Tropsch synthesis and the obtained intermediate distillate oil, the main process is to cut the crude FTS product into naphtha and intermediate distillate oil. 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.

[0004] CN103819299A discloses a method for separating and purifying 1-hexene from a hydrocarbon mixture. The hydrocarbon mixture raw material flow is subjected to processing steps such as 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, and a methanol absorption tower to obtain a polymerization-grade 1-hexene product. The separation of alkanes and olefins adopts a separation tower with a high number of plates and a large reflux ratio, wherein the theoretical number of plates is 80-250 and the reflux ratio is 10-40.

[0005] CN102452888A discloses a method for purifying 1-hexene from Fischer-Tropsch synthetic oil products, the method comprising: first cutting the Fischer-Tropsch synthetic light distillate oil into a C6 fraction; then removing the organic oxygen-containing compounds in the C6 fraction by extractive distillation; then separating the alkanes and olefins in the C6 fraction by extractive distillation; subjecting the C6 olefins obtained by extractive distillation to reactive distillation, and in the presence of a catalyst, allowing the tertiary carbon olefins in the C6 olefins to react with low-carbon alcohols to generate high-boiling-point ethers, thereby removing the tertiary carbon olefins; then removing the ethanol remaining in the C6 olefins by liquid-liquid extraction; and finally purifying the C6 olefins by precision distillation to obtain 1-hexene products that meet polymerization grade requirements. The extractant used for extractive distillation of C6 alkanes and olefins is a polar solvent such as acetonitrile (ACN), N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF). To improve the selectivity of the solvent, the extractant is preferably a binary mixed solvent consisting of ACN or NMP and water. Therefore, in the entire flow chart, it can be seen that a solvent recovery tower and a dehydration tower are required in the solvent recovery process, which increases the complexity of the process. In addition, the polarity of water is too different from that of the solvent, and the entire process is complicated to operate, affecting the stability of the entire operation. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of low 1-hexene purity, low recovery rate, high energy consumption and complicated process flow in the prior art method for fractionating and purifying 1-hexene from hydrocarbon streams, and to provide a method and device for separating 1-hexene from a hydrocarbon stream containing C6 olefins. The method effectively improves the purity and recovery rate of 1-hexene in the 1-hexene product; at the same time, simplifies the process recovery device.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for separating 1-hexene from a hydrocarbon stream containing C6 olefins, the method comprising the following steps:

[0008] (1) distilling and cutting a hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream;

[0009] (2) washing the C6 fraction stream with water to obtain a crude C6 hydrocarbon stream;

[0010] (3) contacting the crude C6 hydrocarbon stream with a composite extractant to perform extractive distillation to obtain a mixed stream rich in 1-hexene and the composite extractant;

[0011] (4) separating the mixed stream to obtain a 1-hexene stream and a regenerated composite extractant stream;

[0012] (5) Adsorbing the 1-hexene stream to obtain a 1-hexene product.

[0013] The second aspect of the present invention provides a device for separating 1-hexene from a hydrocarbon stream containing C6 olefins, the device comprising: a distillation cutting unit, a water washing tower, an extractive distillation tower, a solvent recovery tower and a molecular sieve bed connected in sequence;

[0014] The distillation and cutting unit is used to distill and cut the hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream;

[0015] The water washing tower is used to wash the C6 fraction stream with water to obtain a crude C6 fraction stream;

[0016] The extractive distillation tower is used to extract and distill the crude C6 fraction stream to obtain a mixed stream rich in 1-hexene and a composite extractant;

[0017] The solvent recovery tower is used to separate the mixed flow to obtain a 1-hexene flow and a regenerated composite extractant flow;

[0018] The molecular sieve bed is used to adsorb the 1-hexene flow to obtain a 1-hexene product.

[0019] Through the above technical scheme, in the method provided by the present invention, oxygen-containing compounds in the C6 fraction flow are removed by water washing, and in particular, the flow rich in oxygen-containing compounds is returned, which not only reduces the content of oxygenated compounds in the 1-hexene product, but also simplifies the process and omits the recovery device; at the same time, the present invention uses a composite extractant to separate alkanes in the crude C6 hydrocarbon flow to obtain a mixed flow rich in 1-hexene and the composite extractant, and separates it to obtain a 1-hexene flow, which can reduce energy consumption, thereby improving the purity and recovery rate of 1-hexene in the 1-hexene product.

[0020] Compared with the prior art, in the 1-hexene product prepared by the method provided by the present invention, the purity of 1-hexene is ≥95wt%, the content of oxygen-containing compounds is <10ppm, and the recovery rate of 1-hexene is ≥95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a device for separating 1-hexene from hydrocarbons provided by the present invention.

[0022] Description of Reference Numerals

[0023] A. First distillation tower B. Second distillation tower C. Water washing tower

[0024] D. Extraction distillation tower E. Solvent recovery tower F. Molecular sieve bed

[0025] 1. Hydrocarbon streams containing C6 olefins 2. C6 - Distillate and C6 distillate logistics 3, C6 + Distillate logistics

[0026] 4. C6 fraction logistics 5. C6 - Distillate Stream 6, Water

[0027] 7. Oxygen-containing compound-rich stream 8. Crude C6 hydrocarbon stream 9. Composite extractant

[0028] 10. C6 alkane flow 11. Mixed flow 12. 1-hexene flow

[0029] 13. Regeneration of composite extractant logistics 14. 1-hexene product DETAILED DESCRIPTION

[0030] 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.

[0031] In the present invention, unless otherwise specified, the top of the container refers to the position of 0-10% from top to bottom of the container; the upper part of the container refers to the position of 10-30% from top to bottom of the container; the lower part of the container refers to the position of 60-90% from top to bottom of the container; and the bottom of the container refers to the position of 90-100% from top to bottom of the container.

[0032] A first aspect of the present invention provides a method for separating 1-hexene from a hydrocarbon stream containing C6 olefins, the method comprising the following steps:

[0033] (1) distilling and cutting a hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream;

[0034] (2) washing the C6 fraction stream with water to obtain a crude C6 hydrocarbon stream;

[0035] (3) contacting the crude C6 hydrocarbon stream with a composite extractant to perform extractive distillation to obtain a mixed stream rich in 1-hexene and the composite extractant;

[0036] (4) separating the mixed stream to obtain a 1-hexene stream and a regenerated composite extractant stream;

[0037] (5) Adsorbing the 1-hexene stream to obtain a 1-hexene product.

[0038] According to the present invention, preferably, the hydrocarbon stream containing C6 olefins is Fischer-Tropsch light oil.

[0039] In the present invention, unless otherwise specified, the Fischer-Tropsch synthesis light oil is a light fraction in the Fischer-Tropsch synthesis reaction process. Preferably, the Fischer-Tropsch synthesis light oil is selected from Fischer-Tropsch synthesis naphtha.

[0040] In some embodiments of the present invention, preferably, the Fischer-Tropsch synthetic light oil contains olefins, oxygen-containing compounds and alkanes, wherein the olefins are mainly α-olefins; the oxygen-containing compounds are mainly alcohols, and there are also small amounts of ketones, aldehydes and acids; the alkanes are mainly normal alkanes, and there are also small amounts of isoalkanes.

[0041] According to the present invention, preferably, based on the total weight of the Fischer-Tropsch synthetic light oil, the content of olefins is 60-80wt%, preferably 70-80wt%; the content of oxygen-containing compounds is 0.1-10wt%, preferably 0.5-5wt%; the content of alkanes is 15-35wt%, preferably 15-25wt%.

[0042] According to the present invention, preferably, in step (1), the distillation cutting comprises:

[0043] 1) subjecting the hydrocarbon stream containing C6 olefins to a first distillation cut to obtain C6 - Fraction and C6 fraction logistics and C6 + fraction logistics;

[0044] 2) The C6 - The fraction and C6 fraction flow are subjected to the second distillation cutting to obtain C6 - fraction stream and C6 fraction stream.

[0045] Preferably, the conditions for the first distillation cut include: a reflux ratio of 1-10, preferably 2-5; a bottom temperature of 105-125°C, preferably 110-120°C; and a top pressure of 1-1.1 bar, preferably 1-1.05 bar.

[0046] Preferably, the first distillation cutting is performed in a first distillation tower, wherein the number of theoretical plates of the first distillation tower is 30-50.

[0047] In a preferred embodiment of the present invention, the hydrocarbon stream containing C6 olefins enters a first distillation tower for first distillation cutting, and the bottom of the first distillation tower obtains C6 olefins. + The top of the first distillation tower obtains C6 - The feed position of the hydrocarbon logistics containing C6 olefins is the 15th to 25th theoretical plates from the bottom to the top of the first distillation tower, and the conditions of the first distillation cutting include: the reflux ratio is 1-10, the bottom temperature is 105-125°C, and the top pressure is 1-1.1 bar.

[0048] Preferably, the conditions of the second distillation cutting include: a reflux ratio of 1-10, preferably 2-5; a bottom temperature of 60-70°C, preferably 64-67°C; and a top pressure of 1-1.1 bar, preferably 1-1.05 bar. Preferably, the second distillation cutting is performed in a second distillation tower, wherein the number of theoretical plates of the second distillation tower is 30-50.

[0049] In a preferred embodiment of the present invention, the C6 - The fraction and C6 fraction flow enter the second distillation tower for second distillation cutting. The C6 fraction flow is obtained at the bottom of the second distillation tower, and the C6 fraction flow is obtained at the top of the second distillation tower. - Distillate stream, wherein the C6 - The feed position of the fraction and C6 fraction logistics is the 15th to 25th theoretical plates from the bottom to the top of the second distillation tower. The conditions of the second distillation cutting include: reflux ratio of 1-10, bottom temperature of 60-70°C, and top pressure of 1-1.1 bar.

[0050] According to the present invention, in step (2), the water washing is mainly used to remove water-soluble oxygen-containing compounds and part of oil-soluble oxygen-containing compounds in the C6 fraction stream. Preferably, the water washing comprises contacting the C6 fraction stream with water in countercurrent.

[0051] Further preferably, the volume ratio of the C6 fraction logistics to water is 1:0.1-2, for example, 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.5, 1:2, and a range consisting of any two values, preferably 1:0.2-1.

[0052] Preferably, the water washing is carried out in a water washing tower. In the present invention, there is a wide range of choices for the type of the water washing tower.

[0053] According to a preferred embodiment of the present invention, the C6 fraction flow enters from the lower part of the water washing tower, and the water enters from the upper part of the water washing tower, thereby achieving countercurrent contact between the C6 fraction flow and water, which is beneficial to reducing the content of oxygen-containing compounds in the C6 fraction flow.

[0054] According to the present invention, preferably, the water washing also obtains a stream rich in oxygen-containing compounds, and the stream rich in oxygen-containing compounds is returned and mixed into the water to maintain the content of oxygen-containing compounds in the water at 15-25 wt%.

[0055] In the present invention, the oxygen-containing compound-rich stream is directly returned to the top of the water washing tower for utilization, and the oxygen-containing compound-rich stream at the bottom of the water washing tower is recycled. As the oxygen-containing compounds in the water accumulate, the deoxygenation effect is enhanced due to the solubility of the oxygen-containing compounds for the water-insoluble oxygen-containing compounds. When the content of oxygen-containing compounds in the water is greater than 25wt%, the content of oxygen-containing compounds in the water can be maintained at 15-25% by removing a part of it or adding fresh water.

[0056] In the present invention, in step (3), the extractive distillation is intended to remove the C6 alkane stream from the crude C6 hydrocarbon stream. Preferably, the volume ratio of the crude C6 hydrocarbon stream to the composite extractant is 1:1-15, such as 1:1, 1:3, 1:5, 1:6, 1:8, 1:10, 1:13, 1:15, and a range consisting of any two values, preferably 1:5-10. The preferred conditions are more conducive to reducing the C6 alkane content in the 1-hexene and regenerated composite extractant streams.

[0057] In the present invention, the composite extractant has a wide selection range. Preferably, the composite extractant is extractant A and extractant B, wherein 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 a composite catalyst can take into account both the selectivity of the solvent and the solubility of the solvent.

[0058] Further preferably, based on the weight of the composite extractant, the content of the extractant A is 40-65wt%, preferably 50-60wt%; the content of the extractant B is 35-60wt%, preferably 40-50wt%.

[0059] In the present invention, the extractive distillation is carried out in an extractive distillation tower, wherein the number of theoretical plates of the extractive distillation tower is 50-80.

[0060] In a preferred embodiment of the present invention, the crude C6 hydrocarbon flow and the composite catalyst are subjected to extractive distillation in an extractive distillation tower, wherein the feed position of the crude C6 hydrocarbon flow is the 15th to 35th theoretical plates of the extractive distillation tower from bottom to top, and the feed position of the composite extractant is the 5th to 10th theoretical plates of the extractive distillation tower from top to bottom; the conditions of the extractive distillation include: a reflux ratio of 0.5-2, preferably 0.5-1.5; a bottom temperature of 120-160°C, preferably 130-150°C; and a top pressure of 1-1.1 bar, preferably 1-1.05 bar.

[0061] According to the present invention, in step (4), the separation refers to separating the mixed flow rich in 1-hexene and the composite extractant to obtain a 1-hexene flow and a regenerated composite extractant flow.

[0062] In the present invention, the separation method has a wide range of options, as long as the purpose of separation is achieved. Preferably, the separation is carried out in a solvent recovery tower, wherein the number of theoretical plates of the solvent recovery tower is 15-30, the reflux ratio is 1-3, the bottom temperature is 200-220°C, and the top pressure is 1-1.1 bar.

[0063] According to a preferred embodiment of the present invention, the mixed flow rich in 1-hexene and the composite extractant enters a solvent recovery tower for separation, and a 1-hexene flow is obtained at the top of the solvent recovery tower, and a regenerated composite extractant flow is obtained at the bottom of the solvent recovery tower; wherein, the feed position of the mixed flow rich in 1-hexene and the composite extractant is the 10th to 20th theoretical plates from the bottom to the top of the solvent recovery tower.

[0064] According to the present invention, preferably, in step (4), the content of oxygen-containing compounds in the 1-hexene flow is 50-200 ppm, preferably 50-150 ppm.

[0065] Preferably, the regenerated composite extractant stream is returned to the composite extractant in step (3), so as to achieve the reuse of the regenerated composite extractant, reduce costs and achieve the reuse of resources.

[0066] According to the present invention, in step (5), the adsorption is intended to remove the remaining oxygenates in the 1-hexene stream. Preferably, the adsorption comprises contacting the 1-hexene stream with a molecular sieve.

[0067] In the present invention, the type of the molecular sieve has a wide selection range, preferably, at least one of 4A molecular sieve, 5A molecular sieve and 13X molecular sieve and / or at least one of metal-modified 4A molecular sieve, 5A molecular sieve and 13X molecular sieve. The use of the preferred conditions is more conducive to reducing the content of oxygen-containing compounds in the 1-hexene product and improving the purity of 1-hexene.

[0068] Preferably, the adsorption is carried out in a molecular sieve bed, wherein the thickness of the molecular sieve bed depends on the content of oxygen-containing compounds in the 1-hexene stream.

[0069] The method provided by the present invention can effectively improve the purity and recovery rate of 1-hexene. Preferably, in the 1-hexene product, the purity of 1-hexene is ≥95wt%, preferably 96-98wt%; the content of oxygen-containing compounds is <10ppm, preferably ≤8ppm; and the recovery rate of 1-hexene is ≥95%.

[0070] The second aspect of the present invention provides a device for separating 1-hexene from a hydrocarbon stream containing C6 olefins, the device comprising: a distillation cutting unit, a water washing tower, an extractive distillation tower, a solvent recovery tower and a molecular sieve bed connected in sequence;

[0071] The distillation and cutting unit is used to distill and cut the hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream;

[0072] The water washing tower is used to wash the C6 fraction stream with water to obtain a crude C6 fraction stream;

[0073] The extractive distillation tower is used to extract and distill the crude C6 fraction stream to obtain a mixed stream rich in 1-hexene and a composite extractant;

[0074] The solvent recovery tower is used to separate the mixed flow to obtain a 1-hexene flow and a regenerated composite extractant flow;

[0075] The molecular sieve bed is used to adsorb the 1-hexene flow to obtain a 1-hexene product.

[0076] According to the device provided by the present invention, preferably, the distillation cutting unit comprises a first distillation tower and a second distillation tower connected in series.

[0077] Further preferably, the first distillation tower is used to perform a first distillation cut on the hydrocarbon stream to obtain C6 - Fraction and C6 fraction logistics and C6 + Distillate stream.

[0078] Further preferably, the second distillation tower is used to separate the C6 - The fraction and C6 fraction flow are subjected to the second distillation cutting to obtain C6 - fraction stream and C6 fraction stream.

[0079] According to the present invention, preferably, the top of the first distillation tower is connected to the lower part of the second distillation tower.

[0080] According to the present invention, preferably, the bottom of the water washing tower is connected to the upper part of the water washing tower, so as to return the oxygen-containing compound-rich stream obtained by the water washing to the absorption tower, and maintain the oxygen-containing compound content in the water at 15-25wt%.

[0081] According to the present invention, preferably, the bottom of the solvent recovery tower is connected to the upper part of the extractive distillation tower for returning the regenerated extract flow to the extractive distillation tower.

[0082] The present invention provides a schematic diagram of a device for separating 1-hexene from a hydrocarbon stream containing C6 olefins, such as Figure 1As shown, the device includes a first distillation tower A, a second distillation tower B, a water washing tower C, an extractive distillation tower D, a solvent recovery tower E and a molecular sieve bed F which are connected in sequence;

[0083] The first distillation tower A is used to perform a first distillation cut on the hydrocarbon stream 1 containing C6 olefins to obtain C6 - Fraction and C6 fraction stream 2 and C6 + Fraction stream 3; the second distillation tower B is used to distill C6 - The fraction and C6 fraction stream 2 are subjected to a second distillation cut to obtain C6 - The water washing tower C is used to wash the C6 fraction stream 4 with water 6 to obtain a crude C6 fraction stream 8 and a stream 7 rich in oxygen-containing compounds; the extractive distillation tower D is used to extract and distill the crude C6 fraction stream 8 with a composite extractant 9 to obtain a mixed stream 11 rich in 1-hexene and the composite extractant and a C6 alkane stream 10; the solvent recovery tower E is used to separate the mixed stream 11 to obtain a 1-hexene stream 12 and a regenerated composite extractant stream 13; the molecular sieve bed F is used to adsorb the 1-hexene stream 12 to obtain a 1-hexene product 14;

[0084] The bottom of the water washing tower C is connected to the upper part of the water absorption tower C, and is used to return the oxygen-containing compound-rich stream 7 obtained by the water washing to the absorption tower, and maintain the content of oxygen-containing compounds in the water at 15-25wt%;

[0085] The bottom of the solvent recovery tower E is connected to the upper part of the extractive distillation tower D, so as to return the regenerated extract flow 13 to the extractive distillation tower D.

[0086] The present invention will be described in detail below through examples.

[0087] The content of each component in Fischer-Tropsch naphtha was measured by chromatography, where the determination of aldehyde and ketone content was in accordance with GB / T 6324.5-2008;

[0088] The content of 1-hexene and the content of 2-hexene are each independently measured by chromatography;

[0089] Calculation formula:

[0090] Example 1

[0091] (1) Fischer-Tropsch naphtha (composition, see Table 1) is subjected to the first distillation in the first distillation tower to obtain C6 - Fraction and C6 fraction logistics and C6 +The fraction logistics, wherein the number of theoretical plates of the first distillation tower is 40, the feed position of the Fischer-Tropsch synthesis naphtha is the 20th theoretical plate from the bottom to the top of the first distillation tower, the reflux ratio is 3, the bottom temperature is 115°C, and the top pressure is 1 bar;

[0092] (2) C6 - The fraction and the C6 fraction flow are subjected to the second distillation in the second distillation tower to obtain C6 - The second distillation tower has 40 theoretical plates, and the C6 fraction stream is - The feed position of the distillate and C6 fraction streams is the 20th theoretical plate from the bottom to the top of the second distillation tower, the reflux ratio is 3, the bottom temperature is 65°C, and the top pressure is 1 bar;

[0093] (3) contacting the C6 fraction stream with water in a water scrubber in countercurrent to obtain a crude C6 hydrocarbon stream, and recycling the obtained oxygen-containing compound-rich stream back to the top of the tower to enter the tower, so that the content of oxygen-containing compounds in the water is 20 wt %, wherein the volume ratio of the C6 fraction stream to water is 1:0.2;

[0094] (4) extracting and distilling the crude C6 hydrocarbon stream and the composite extractant in an extractive distillation tower to obtain a mixture rich in 1-hexene and the composite extractant and a C6 alkane stream, wherein the extractive distillation tower has 60 theoretical plates, the feed position of the crude C6 hydrocarbon stream is the 30th theoretical plate from the bottom of the extractive distillation tower, the feed position of the composite extractant is the 5th theoretical plate from the top of the extractive distillation tower, the reflux ratio is 1, the bottom temperature is 147° C., the top pressure is 1.01 bar, and the volume ratio of the crude C6 hydrocarbon stream to the composite extractant is 1:7;

[0095] The composite extractant is N-methylpyrrolidone and γ-butyrolactone, wherein the content of N-methylpyrrolidone is 55wt% and the content of γ-butyrolactone is 45wt%;

[0096] (5) separating the mixture rich in 1-hexene and the composite extractant in a solvent recovery tower to obtain a 1-hexene stream P1 and a regenerated composite extractant stream, wherein the number of theoretical plates of the solvent recovery tower is 20, the feeding position of the mixture rich in 1-hexene and the composite extractant is the 12th theoretical plate from the bottom to the top of the solvent recovery tower, the reflux ratio is 1, the bottom temperature is 206° C., and the top pressure is 1.01 bar;

[0097] (6) separating the 1-hexene stream in a 4A molecular sieve bed to obtain a 1-hexene product S1;

[0098] Wherein, the content of oxygen-containing compounds in the 1-hexene stream P1 is 80 ppm;

[0099] Among them, in the 1-hexene product S1, the purity of 1-hexene is 97.2wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 5ppm, and the recovery rate of 1-hexene is 95.6%.

[0100] Table 1

[0101] composition Content (wt%) α-Olefins 70 Normal alkanes 23.8 2-Olefin 1.3 Isoalkanes 2.1 Isoolefins 0.3 alcohol 2.2 Carbonyl oxygen content 0.3

[0102] Example 2

[0103] The method of Example 1 is followed, except that the composition of the hydrocarbon stream containing C6 olefins is listed in Table 2.

[0104] According to the complete process flow provided in Example 1, 1-hexene stream P2 and 1-hexene product S2 are obtained;

[0105] Wherein, the content of oxygen-containing compounds in the 1-hexene stream P2 is 120 ppm;

[0106] Among them, in the 1-hexene product S2, the purity of 1-hexene is 97.6wt%, the content of 2-hexene is 1.4wt%, the content of oxygen-containing compounds is 7ppm, and the recovery rate of 1-hexene is 95.4%.

[0107] Table 2

[0108] composition Content (wt%) α-Olefins 80 Normal alkanes 12 2-Olefin 1.4 Isoalkanes 2 Isoolefins 0.2 alcohol 4 Carbonyl oxygen content 0.4

[0109] Example 3

[0110] According to the method of Example 1, except that the content of N-methylpyrrolidone in the composite extractant is replaced with 75wt%, and the content of γ-butyrolactone is replaced with 25wt%, to obtain 1-hexene stream P3 and 1-hexene product S3;

[0111] Wherein, the content of oxygen-containing compounds in the 1-hexene stream P3 is 80 ppm;

[0112] Among them, in the 1-hexene product S3, the purity of 1-hexene is 92wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 5ppm, and the recovery rate of 1-hexene is 93.2%.

[0113] Example 4

[0114] The method of Example 1 is used, except that the oxygen-containing compound-rich stream is not recycled to the top of the tower, that is, the oxygen-containing compound content in water is 0 wt % in step (3), to obtain a 1-hexene stream P4 and a 1-hexene product S4;

[0115] Wherein, the content of oxygen-containing compounds in the 1-hexene stream P4 is 280 ppm;

[0116] Among them, in the 1-hexene product S4, the purity of 1-hexene is 97.2wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 40ppm, and the recovery rate of 1-hexene is 95.6%.

[0117] Example 5

[0118] According to the method of Example 1, except that in step (3), the content of oxygen-containing compounds in water is 30wt%, to obtain 1-hexene stream P5 and 1-hexene product S5;

[0119] Wherein, the content of oxygen-containing compounds in the 1-hexene stream P5 is 250 ppm;

[0120] Among them, in the 1-hexene product S5, the content of 1-hexene is 97.2wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 35ppm, and the recovery rate of 1-hexene is 95.6%.

[0121] Comparative Example 1

[0122] The method of Example 1 is different from that of washing with water, that is, the C6 fraction stream obtained in step (2) is directly subjected to extractive distillation, separation, and adsorption to obtain a 1-hexene stream DP1 and a 1-hexene product DS1;

[0123] Wherein, the content of oxygen-containing compounds in the 1-hexene stream DP1 is 25000 ppm;

[0124] Among them, in the 1-hexene product DS1, the content of 1-hexene is 97.2wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 400ppm, and the recovery rate of 1-hexene is 95.6%.

[0125] Comparative Example 2

[0126] According to the method of Example 1, the difference is that the Fischer-Tropsch synthesis naphtha is first washed with water, and then subjected to the first distillation cutting and the second distillation cutting, and the remaining steps are the same, to obtain a 1-hexene stream DP2 and a 1-hexene product DS2;

[0127] Wherein, the content of oxygen-containing compounds in the 1-hexene stream DP2 is 220 ppm;

[0128] Among them, in the 1-hexene product DS2, the content of 1-hexene is 97.2wt%, the content of 2-hexene is 1.2wt%, the content of oxygen-containing compounds is 30ppm, and the recovery rate of 1-hexene is 95.6%.

[0129] Comparative Example 3

[0130] According to the method of Example 1, the difference is that the composite extractant is replaced by extractant A, i.e., N-methylpyrrolidone, to obtain 1-hexene stream DP3 and 1-hexene product DS3;

[0131] Wherein, the content of oxygen-containing compounds in the 1-hexene stream DP3 is 80 ppm;

[0132] Among them, in the 1-hexene product DS3, the purity of 1-hexene is 90.2wt%, the content of 2-hexene is 1.3wt%, the content of oxygen-containing compounds is 5ppm, and the recovery rate of 1-hexene is 92.8%.

[0133] Comparative Example 4

[0134] According to the method of Example 1, the difference is that the composite extractant is replaced by extractant B, i.e., γ-butyrolactone, to obtain 1-hexene stream DP4 and 1-hexene product DS4;

[0135] Wherein, the content of oxygen-containing compounds in the 1-hexene stream DP4 is 80 ppm;

[0136] Among them, in the 1-hexene product DS4, the purity of 1-hexene is 88.2wt%, the content of 2-hexene is 1.3wt%, the content of oxygen-containing compounds is 5ppm, and the recovery rate of 1-hexene is 91.8%.

[0137] According to the above results, the method for separating 1-hexene from a hydrocarbon stream provided by the present invention effectively improves the purity and recovery rate of 1-hexene, simplifies the process and reduces energy consumption; in particular, the stream rich in oxygenates is returned to the water washing tower, and the deoxygenation effect of the hydrocarbon stream is improved by limiting the content of oxygen-containing compounds in the water; at the same time, the selection of the composite extractant effectively improves the purity and recovery rate of 1-hexene.

[0138] 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 from a hydrocarbon stream containing C6 olefins, It is characterized in that The method comprises the following steps: (1) distilling and cutting a hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream; (2) washing the C6 fraction stream with water to obtain a crude C6 hydrocarbon stream; (3) extracting and distilling the crude C6 hydrocarbon stream and the composite extractant to obtain a mixed stream rich in 1-hexene and the composite extractant; (4) separating the mixed stream to obtain a 1-hexene stream and a regenerated composite extractant stream; (5) adsorbing the 1-hexene stream to obtain a 1-hexene product; The composite extractant is extractant A and extractant B, wherein 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; Based on the weight of the composite extractant, the content of the extractant A is 40-65wt%; the content of the extractant B is 35-60wt%.

2. The method according to claim 1, in, The hydrocarbon stream is Fischer-Tropsch light oil.

3. The method according to claim 2, in, The Fischer-Tropsch synthetic light oil is Fischer-Tropsch synthetic naphtha.

4. The method according to claim 2, in, The Fischer-Tropsch synthetic light oil contains olefins, oxygen-containing compounds and alkanes.

5. The method according to claim 4, in, Based on the total weight of the Fischer-Tropsch synthetic light oil, the content of the olefin is 60-80wt%; The content of the compound is 0.1-10wt%; the content of the alkane is 15-35wt%.

6. The method according to claim 5, in, Based on the total weight of the Fischer-Tropsch synthetic light oil, the content of the olefins is 70-80wt%; the content of the oxygen-containing compounds is 0.5-5wt%; and the content of the alkanes is 15-25wt%.

7. The method according to claim 1 or 2, in, In step (1), the distillation cutting comprises: 1) subjecting the hydrocarbon stream containing C6 olefins to a first distillation cut to obtain C6 - Fraction and C6 fraction logistics and C6 + fraction logistics; 2) The C6 - The fraction and C6 fraction flow are subjected to the second distillation cutting to obtain C6 - fraction stream and C6 fraction stream.

8. The method according to claim 7, in, The conditions of the first distillation cutting include: reflux ratio of 1-10; tower bottom temperature of 105-125° C.; tower top pressure of 1-1.1 bar; And / or, the conditions for the second distillation cutting include: a reflux ratio of 1-10; a bottom temperature of 60-70° C.; and a top pressure of 1-1.1 bar.

9. The method according to claim 8, in, The conditions of the first distillation cutting include: reflux ratio of 2-5; tower bottom temperature of 110-120°C; tower top pressure of 1-1.05 bar; And / or, the conditions for the second distillation cutting include: a reflux ratio of 2-5; a bottom temperature of 64-67° C.; and a top pressure of 1-1.05 bar.

10. The method according to claim 1 or 2, in, In step (2), the water washing comprises contacting the C6 fraction stream with water in countercurrent.

11. The method according to claim 10, in, The volume ratio of the C6 fraction flow to water is 1:0.1-2.

12. The method according to claim 11, in, The volume ratio of the C6 fraction flow to water is 1:0.2-1.

13. The method according to claim 10, in, The water washing also obtains a stream rich in oxygen-containing compounds, and the stream rich in oxygen-containing compounds is returned and mixed into water to maintain the oxygen-containing compound content in the water at 15-25 wt%.

14. The method according to claim 1, in, In step (3), the volume ratio of the crude C6 hydrocarbon stream to the composite extractant is 1:1-15; And / or, based on the weight of the composite extractant, the content of the extractant A is 50-60wt%; the content of the extractant B is 40-50wt%.

15. The method according to claim 14, in, In step (3), the volume ratio of the crude C6 hydrocarbon flow to the composite extractant is 1:5-10.

16. The method according to claim 1 or 14, in, The conditions of the extractive distillation include: a reflux ratio of 0.5-2; a bottom temperature of 120-160° C.; and a top pressure of 1-1.1 bar.

17. The method according to claim 16, in, The conditions of the extractive distillation include: a reflux ratio of 0.5-1.5; a bottom temperature of 130-150° C.; and a top pressure of 1-1.05 bar.

18. The method according to claim 1, in, In step (4), the content of oxygen-containing compounds in the 1-hexene stream is 50-200 ppm; and / or, returning the regenerated composite extractant stream and mixing it into the composite extractant in step (3); And / or, in step (4), the separation is carried out in a solvent recovery tower.

19. The method according to claim 18, in, In step (4), the content of oxygen-containing compounds in the 1-hexene flow is 50-150 ppm.

20. The method according to claim 1, in, In step (5), the adsorption includes contacting the 1-hexene flow with a molecular sieve.

21. The method according to claim 20, in, The molecular sieve is selected from at least one of 4A molecular sieve, 5A molecular sieve and 13X molecular sieve and / or at least one of metal-modified 4A molecular sieve, 5A molecular sieve and 13X molecular sieve; And / or, in the 1-hexene product, the purity of 1-hexene is ≥95wt%; the content of oxygen-containing compounds is <10ppm; and the recovery rate of 1-hexene is ≥95%.

22. A device for separating 1-hexene from a hydrocarbon stream containing C6 olefins, It is characterized in that The device comprises: a distillation cutting unit, a water washing tower, an extraction distillation tower, a solvent recovery tower and a molecular sieve bed layer which are connected in sequence; The distillation and cutting unit is used to distill and cut the hydrocarbon stream containing C6 olefins to obtain a C6 fraction stream; The water washing tower is used to wash the C6 fraction stream with water to obtain a crude C6 fraction stream; The extractive distillation tower is used to extract and distill the crude C6 fraction stream to obtain a mixed stream rich in 1-hexene and a composite extractant; The solvent recovery tower is used to separate the mixed flow to obtain a 1-hexene flow and a regenerated composite extractant flow; The molecular sieve bed is used to adsorb the 1-hexene flow to obtain a 1-hexene product.

23. The device according to claim 22, in, The distillation cutting unit comprises a first distillation tower and a second distillation tower connected in series; The first distillation tower is used to perform a first distillation on the hydrocarbon stream containing C6 olefins to obtain C6 - Fraction and C6 fraction logistics and C6 + fraction logistics; The second distillation tower is used to distill the C6 - The fraction and C6 fraction flow are subjected to the second distillation cutting to obtain C6 - fraction stream and C6 fraction stream.

24. The device according to claim 23, wherein the top of the first distillation tower is connected to the bottom of the second distillation tower.

25. The device according to claim 22 or 23, in, The bottom of the water washing tower is connected to the upper part of the water washing tower, and is used to return the oxygen-containing compound-rich stream obtained by the water washing to the water washing tower, so as to maintain the oxygen-containing compound content in the water at 15-25wt%; And / or, the bottom of the solvent recovery tower is connected to the upper part of the extractive distillation tower for returning the regenerated composite extractant stream to the extractive distillation tower.

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