CN115806463A - Process for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing stream - Google Patents

Abstract

The invention relates to the field of separating and purifying high value-added chemicals from a hydrocarbon-containing stream, and discloses a method for separating 1-hexene, 1-heptene and 1-octene from the hydrocarbon-containing stream, which comprises the following steps: (I) subjecting the hydrocarbon-containing stream to a fractional cut to obtain C6 ^‑ A distillate stream, a C6-C8 distillate stream, C9 and C9 ⁺ A distillate stream; (II) removing oxygen-containing compounds from the C6-C8 fraction material flow to obtain deoxidized C6-C8 fraction material flow; (III) subjecting said deoxy C6-And (3) sequentially carrying out rectification separation treatment, extractive rectification treatment, solvent removal treatment and rectification heavy weight removal treatment on the C8 fraction material flow to obtain 1-hexene, 1-heptene and 1-octene. The method can effectively remove the oxygen-containing compounds in the Fischer-Tropsch synthetic oil in the separation process, the content of the oxygen-containing compounds in the deoxidized Fischer-Tropsch synthetic oil is reduced to be below 10ppm (by mass), and the alpha-olefin retention rate can reach more than 99%; the separation effect of alkane and alkene is good, and the energy consumption in the separation process is low; the product yield is more than 95 percent, and the purity is more than 98.5 percent.

Description

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

Technical Field

The invention relates to the field of separating and purifying high value-added chemicals from hydrocarbon-containing streams, in particular to a method for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing streams.

Background

The fischer-tropsch oil product contains a significant amount of olefins and paraffins, with the olefins being predominantly linear alpha-olefins. Among the above alpha-olefins, 1-butene, 1-hexene and 1-octene have high added values, and can be used as important organic raw materials and widely applied. At present, the ethylene oligomerization method is mainly adopted to produce alpha olefin abroad, and the alpha-olefin produced by the method has higher quality. And linear alpha-olefin such as 1-hexene, 1-octene and the like is separated and purified from high-temperature Fischer-Tropsch synthesis oil products by Sasol company in south Africa, and an extraction method is adopted, so that the cost is obviously lower compared with an oligomerization method.

CN103819299B discloses a method for separating and purifying 1-hexene from a hydrocarbon mixture, which comprises the steps of subjecting a hydrocarbon mixture raw material flow to a raw material pre-cutting unit, an etherification reactor, a reaction rectifying tower, a rectification light component removing tower, a rectification heavy component removing tower, an extraction rectifying tower, a 1-hexene separation tower, a water washing tower, a methanol absorption tower and the like to obtain a polymer grade 1-hexene product. In the method, a fine separation tower is adopted for separating alkane and alkene, the number of tower plates is very high, the reflux ratio is large, the number of theoretical tower plates is 80-250, and the reflux ratio is 10-40.

CN102452888A discloses a method for purifying 1-hexene from Fischer-Tropsch synthesis oil. The Fischer-Tropsch synthesis light distillate oil is subjected to fraction cutting to obtain a C6 fraction section; then removing organic oxygen-containing compounds in the C6 fraction by extractive distillation; then the C6 fraction paraffin and olefin are separated by an extractive distillation method; c6 olefin obtained by extraction rectification is subjected to reactive rectification, and tertiary carbon olefin in the C6 olefin reacts with low carbon alcohol to generate high boiling point ether under the action of a catalyst, so that the tertiary carbon olefin is removed; removing ethanol remained in the C6 olefin by a liquid-liquid extraction method; and finally, purifying the C6 olefin by a precision rectification method to obtain a 1-hexene product meeting the polymerization grade requirement. The extractant used for the C6 alkane and alkene extractive distillation is polar solvent such as ACN, NMP or DMF, and the preferential extractant for improving the selectivity of the solvent is binary mixed solvent consisting of ACN or NMP and water. In addition, the difference between the polarity of water and the polarity of a solvent is too large, the whole process is complex to operate, and the stability of the whole operation is influenced.

CN105777467B discloses a method for separating oxygen-containing compounds and 1-hexene from Fischer-Tropsch synthesis oil products, which comprises the following steps: (1) Cutting Fischer-Tropsch synthetic oil serving as a raw material in a pre-cutting tower to obtain C6 ^- A distillate stream, a C6 distillate stream and C6 ⁺ A distillate stream; (2) In an extraction tower, carrying out first removal on oxygen-containing compounds in a C6 fraction stream by using two extraction agent feeding operations consisting of a first extraction agent and a second extraction agent to obtain a mixed stream of the extraction agent and the oxygen-containing compounds and a crude C6 hydrocarbon stream; (3) Separating the mixture stream of the extractant and the oxygenate in an oxygenate separation column to obtain a regenerated extractant stream and an oxygen compound-rich stream; (4) In an extraction rectification oxygen-containing compound removing tower, a third extracting agent is used for carrying out secondary removal on oxygen-containing compounds in the crude C6 hydrocarbon material flow to obtain a mixed material flow of the third extracting agent and the oxygen-containing compounds and oxygen-free C6 hydrocarbon fraction; (5) In an etherification reaction rectifying tower, under the action of an etherification catalyst, converting tertiary carbon olefin in the oxygen-free C6 hydrocarbon fraction into corresponding ether by using methanol, and simultaneously separating a refined C6 hydrocarbon material flow; (6) In the fine light component removing tower, the fine C6 hydrocarbon material flow is dividedSeparating to obtain a hydrocarbon fraction mixed material flow containing 1-hexene and having a boiling point higher than that of 1-hexene and a hydrocarbon fraction mixed material flow containing methanol and having a boiling point lower than that of 1-hexene; (7) In a fine component heavy component removal tower, separating a hydrocarbon fraction stream containing 1-hexene and having a boiling point higher than that of the 1-hexene to obtain a 1-hexene-rich stream; (8) In an extraction, rectification and isoparaffin removal tower, removing C6 isoparaffin components in the 1-hexene-rich material stream by using a fourth extractant to obtain a mixed material stream of the fourth extractant and the 1-hexene-rich material stream; (9) In the 1-hexene separation tower, a fifth extracting agent is used for removing the cycloolefin component in the mixed material flow of the fourth extracting agent and the 1-hexene-rich material flow to obtain the mixed material flow of the extracting agent and the cycloolefin and the 1-hexene product material flow. In the method, the deoxidation adopts an extraction and extractive distillation mode, the extraction adopts two extracting agents, and the raffinate phase also needs to be further subjected to extractive distillation to remove oxygen-containing compounds. The separation of normal alkane and 1-hexene adopts a fine separation tower, the number of tower plates is high, the reflux ratio is large, and the recovery rate of 1-hexene is low.

In view of the above problems, it would be of great interest to provide a new process for separating α -olefins from hydrocarbon-containing streams, in particular 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing streams.

Disclosure of Invention

The invention aims to overcome the problems of unsatisfactory deoxidation effect, low product purity, low recovery rate, complex process flow, high energy consumption and the like in the method for separating and purifying alpha-olefin from hydrocarbon material flow in the prior art, and provides a method for separating 1-hexene, 1-heptene and 1-octene from hydrocarbon material flow.

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

subjecting the hydrocarbon-containing stream to a cut to obtain C6 ^- A distillate stream, a C6-C8 distillate stream, C9 and C9 ⁺ A distillate stream;

(II) removing oxygen-containing compounds from the C6-C8 fraction material flow to obtain deoxidized C6-C8 fraction material flow;

(III) sequentially carrying out rectification separation treatment, extractive rectification treatment, desolvation treatment and rectification de-heavy treatment on the deoxidized C6-C8 fraction material flow to obtain 1-hexene, 1-heptene and 1-octene;

wherein the oxygenate removal treatment comprises:

(A) Carrying out countercurrent extraction on the C6-C8 fraction material flow and 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; carrying out first solvent recovery and second solvent recovery on the mixture obtained simultaneously, and/or returning and adding the composite extraction solvent in the step (A);

(C) And (3) carrying out first solvent recovery and second solvent recovery on the first extraction phase, circularly adding the obtained first circulating solvent and second circulating solvent into the composite extraction solvent in the step (A), standing and layering the water-containing organic matter obtained by recovering the second solvent, separating the bottom material obtained by layering, and recycling the water phase obtained by separation to the step (B).

Through the technical scheme, the invention can obtain the following beneficial effects:

(1) The method has the advantages that the method adopts an extraction mode to remove oxygen-containing compounds, combines the use of a specific composite extraction solvent, can solve the problem that the deoxidation effect and the recovery rate of hydrocarbon are difficult to be considered at the same time, can effectively remove the oxygen-containing compounds such as alcohol, ketone, aldehyde, acid, ester and the like in the Fischer-Tropsch synthetic oil, reduces the content of the oxygen-containing compounds in the deoxidized Fischer-Tropsch synthetic oil to be less than 10ppm (mass), ensures that the recovery rate of olefin and paraffin is more than 98 percent, and ensures that the retention rate of alpha-olefin is more than 99 percent;

(2) The method adopts a mode of matching the separation and the removal of heavy hydrocarbon with the extractive distillation, and an extractant with better selectivity is used in the extractive distillation stage, so that the purity of the separated olefin is high, and the energy consumption in the separation process is low;

(3) The product yield is more than 95 percent, and the purity is more than 98.5 percent.

Drawings

FIG. 1 is a schematic flow diagram of a method provided by the present invention.

Description of the reference numerals

A. A first rectifying tower B, a second rectifying tower C and an extraction tower

D. A water washing tower E, a first solvent recovery tower F and a second solvent recovery tower

G a decantation tower H, a stripping tower I and a third rectifying tower

J. A first extractive distillation column K, a third solvent recovery column L and a first fine separation de-heavy tower

M, a fourth rectifying tower N, a second extractive rectifying tower O and a fourth solvent recovery tower

P, a second fine separation and de-heavy tower Q, a third extraction and rectification tower R and a fifth solvent recovery tower

S, a third fine separation heavy component removal tower 1, fischer-Tropsch synthetic oil 2, C9 ^- Distillate stream

3. C9 and C9 ⁺ Fraction stream 4, C6-C8 fraction stream 5, C6 ^- Distillate stream

6. A first raffinate phase 7, a first extract phase 8 and a material A at the bottom of a water washing tower

9. Washing the tower bottom B strand material 10, the first solvent recovery tower bottom product

11. A first circulating solvent 12, a recovered material 13 and a second circulating solvent

14. Decant bottom product 15, decant overhead product 16, recycle water

17. Oxygenate 18, deoxygenated C6-C8 cut stream

19. A C6 fraction stream 20, a C7-C8 fraction stream 21, a first mixture stream

22. N-hexane and isohexane 23, crude 1-hexene 24, and third circulating solvent

25. 1-hexene 26, first fine separation heavy component removal tower bottom product

27. C7 cut stream 28, C8 cut stream 29, n-heptane and iso-heptane

30. A second mixture stream 31, crude 1-heptene 32, a fourth recycle solvent

33. 1-heptene 34, a second refined heavy component removal tower bottom product 35, n-octane and isooctane

36. Third mixture stream 37, crude-1 octene 38, fifth recycle solvent

39. 1-octene 40, third fine fraction de-heavy tower bottom product

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

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

subjecting the hydrocarbon-containing stream to a cut to obtain C6 ^- A distillate stream, a C6-C8 distillate stream, C9 and C9 ⁺ A distillate stream;

(II) removing oxygen-containing compounds from the C6-C8 fraction material flow to obtain deoxidized C6-C8 fraction material flow;

(III) sequentially carrying out rectification separation treatment, extractive rectification treatment, desolvation treatment and rectification de-heavy treatment on the deoxidized C6-C8 fraction material flow to obtain 1-hexene, 1-heptene and 1-octene;

wherein the oxygenate removal treatment comprises:

(A) Carrying out countercurrent extraction on the C6-C8 fraction material flow and 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; carrying out first solvent recovery and second solvent recovery on the mixture obtained simultaneously, and/or returning and adding the composite extraction solvent in the step (A);

(C) And (3) carrying out first solvent recovery and second solvent recovery on the first extraction phase, circularly adding the obtained first circulating solvent and second circulating solvent into the composite extraction solvent in the step (A), standing and layering the water-containing organic matter obtained by recovering the second solvent, separating the bottom material obtained by layering, and recycling the water phase obtained by separation to the step (B).

In some embodiments of the invention, the hydrocarbon-containing stream comprises alkanes, alkenes, and oxygenates. More particularly, the hydrocarbon-containing stream which can be satisfied can be a naphtha fraction, typically preferably a condensation product of the fischer-tropsch synthesis reaction, which can be a condensation product of the low-temperature or high-temperature fischer-tropsch reaction. More preferably, the hydrocarbonaceous stream is a Fischer-Tropsch synthesis oil having an alpha-olefin content of from 40 to 70wt%, preferably from 50 to 70wt%.

In some embodiments of the invention, the oxygenate in the hydrocarbon-containing stream comprises at least one of an alcohol, a ketone, an aldehyde, a carboxylic acid, and an ester. Further, the total content of said oxygenates in said hydrocarbon-containing stream is from 0.1 to 10wt% based on the total amount of said hydrocarbon-containing stream. Further, the main oxygen-containing compound in the oxygen-containing compounds is alcohol, and the content of the alcohol is 0.04-9.9wt%; the total ketone and aldehyde content may be determined as the carbonyl oxygen content and may be from 0.05 to 1 wt.%, the ester content may be from 0.01 to 0.2 wt.%, the carboxylic acid content may be determined by the acidity, which may be from 30 to 100mg/100mL KOH. The alkanes in the hydrocarbon-containing stream are predominantly normal alkanes, with a minor amount of isoparaffins.

In some embodiments of the invention, in step (i), the cut comprises:

(i) Subjecting the hydrocarbon-containing stream to a first cut to obtain C9 ^- Fraction and C9 fraction stream and C9 ⁺ A distillate stream;

(ii) Mixing the C9 ^- Subjecting the distillate stream to a second distillate cut to obtain C6 ^- Fractions and C6-C8 fraction streams.

Preferably, the conditions for the first cut include: the reflux ratio is 2-5; the temperature of the tower kettle is 155-170 ℃; the pressure at the top of the column was atmospheric.

Preferably, the hydrocarbon-containing stream may be subjected to said first cut in a first rectification column, obtaining C9 and C9 at the bottom of the first rectification column ⁺ Fraction flow, obtaining C9 at the top of the first rectifying tower ^- A distillate stream, wherein the number of theoretical plates of the first distillation column is 30 to 50, the hydrocarbon-containing stream is fed at a position from the bottom up to the 15 th to 25 th theoretical plates, and the first distillation columnThe conditions for the cleavage include: the reflux ratio is 2-5; the temperature of the tower kettle is 155-170 ℃; the pressure at the top of the column was atmospheric.

Preferably, the conditions for the second cut include: the reflux ratio is 2-5; the temperature of the tower kettle is 80-90 ℃; the pressure at the top of the column was atmospheric.

Preferably, said C9 may be ^- The distillate stream is subjected to second fraction cutting in a second rectifying tower, a C6-C8 distillate stream is obtained at the bottom of the second rectifying tower, and C6 is obtained at the top of the second rectifying tower ^- A distillate stream, wherein the theoretical plate number of the second rectifying column is 30 to 50, and the C9 ^- The feeding position of the fraction stream is from 15 th to 25 th theoretical plates from bottom to top, and the conditions for cutting the second fraction comprise: the reflux ratio is 2-5; the temperature of the tower kettle is 80-90 ℃; the pressure at the top of the column was atmospheric.

In some embodiments of the invention, in step (ii), the oxygenate removal treatment is carried out by means of extraction. In the step (a) of removing the oxygen-containing compounds, the removal of the oxygen-containing compounds from the whole fraction of the hydrocarbon-containing material flow can be realized by extracting with the composite extraction solvent, and the deoxidation effect and the recovery rate of the deoxidized hydrocarbons can be well considered. Preferably, the complex extraction solvent comprises a heavy polar solvent, methanol and water; wherein the heavy polar solvent is at least one selected from ester compounds, glycol compounds, amide compounds, pyrrolidone compounds, dihydric alcohol compounds and alcohol amine compounds; the ester compound is selected from at least one of a benzene acid ester compound, a carbonic ester compound and a lactone compound, and is preferably at least one of dimethyl phthalate, ethylene glycol carbonate and gamma-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-methyl pyrrolidone; the dihydric alcohol compound is propylene glycol; the alcohol amine compound is ethanolamine.

In the present invention, the composite extraction solvent has a water content of 3 to 20wt% and a methanol content of 5 to 10wt%, based on the total amount of the composite extraction solvent.

In some embodiments of the invention, in the conditions under which step (a) effects the countercurrent extraction, preferably the weight ratio of the composite extraction solvent to the C6-C8 fraction stream is from 0.5 to 4:1, preferably 0.8 to 2:1.

in some embodiments of the present invention, in step (a), preferably, the temperature of the countercurrent extraction is in the range of 10 to 50 ℃, preferably 20 to 50 ℃. The operation process of the countercurrent extraction can be a multistage countercurrent extraction method. Preferably, the theoretical number of stages of the multistage countercurrent extraction can be 5 to 15 stages, preferably 8 to 12 stages. The countercurrent extraction can be carried out in an extraction column, a first raffinate phase is obtained at the top of the column, and a first extract phase is obtained at the bottom of the column. The first extract phase is enriched in oxygenates; the first raffinate phase is rich in hydrocarbon compounds and low in oxygen-containing compounds.

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 in step (B) by a water washing method to obtain a deoxygenated hydrocarbon phase, i.e. the deoxygenated C6-C8 fraction stream. The water washing can be carried out by introducing the first raffinate phase into a water washing tower, leading out a hydrocarbon phase as a tower top product, obtaining a mixture of water and a small amount of composite extraction solvent at the tower bottom, directly returning and adding the mixture into the step (A) to recycle the composite extraction solvent, or sequentially entering a first solvent recovery tower and a second solvent recovery tower to carry out first solvent recovery treatment and second solvent recovery treatment. Preferably, the conditions of the water washing include: the washing temperature is 10-80 ℃, the weight ratio of water to the first raffinate phase is 0.4-1:1.

in some embodiments of the present invention, in step (C), the first extraction phase is subjected to a first solvent recovery and a second solvent recovery, the solvent recovery may be achieved by rectification, the oxygenate and the recycled solvent may be obtained, and the recovery may be performed in a first solvent recovery column and a second solvent recovery column in sequence. And (3) carrying out the first solvent recovery treatment in the first solvent recovery tower, obtaining a first circulating solvent (mainly methanol and azeotropic hydrocarbons) at the tower top, returning the first circulating solvent to the composite extraction solvent in the step (A) for recycling, and introducing a tower bottom product (mainly heavy polar solvent, oxygen-containing compounds and water) into the second solvent recovery tower for carrying out the second solvent recovery treatment. And (3) obtaining a second circulating solvent (mainly a heavy polar solvent) at the bottom of the second solvent recovery tower, and also returning the second circulating solvent to the composite extraction solvent in the step (A) for recycling. In the invention, the material obtained from the bottom of the water washing tower, the first circulating solvent obtained from the top of the first solvent recovery tower and the second circulating solvent obtained from the bottom of the second solvent recovery tower can be returned to the step (A) together, and the material is added into the composite extraction solvent for recycling, so that the content of water in the obtained composite circulating solvent can be adjusted, and the effect of extraction and deoxidation can be adjusted. In the invention, the material obtained from the bottom of the water washing tower and the first extraction phase can also enter the first solvent recovery tower and the second solvent recovery tower in sequence. In the present invention, the recovered material obtained at the top of the second solvent recovery column may contain an oxygen-containing compound and water. Further, the recovered material is discharged and then is subjected to still standing layering, and the settling layering can be carried out by introducing into a decantation tower, wherein a water-insoluble organic phase, mainly containing oxygen compounds, is obtained at the top of the decantation tower, and mainly containing water and water-soluble oxygen compounds are obtained at the bottom of the decantation tower. Preferably, the conditions for the recovery of the first solvent comprise: the temperature is 80-100 ℃, the pressure is normal pressure, and the reflux ratio is 1-2; the conditions for recovering the second solvent include: the temperature is 150-250 ℃, the pressure is-0.01-0.08 MPa, and the reflux ratio is 0.5-1; the reflux ratio is the weight ratio of the flow of reflux liquid returned into the recovery tower to the flow of materials recovered at the top of the recovery tower. The temperature may refer to the temperature of the bottom of the recovery column.

In some embodiments of the present invention, in step (C), the material obtained at the bottom of the decantation tower through still standing separation may be further separated to separate an organic phase and water. Preferably, the separation is rectification or stripping. Specifically, the material obtained from the bottom of the decantation tower may be introduced into a rectification tower or a stripping tower, where the organic phase containing oxygen compounds is mainly obtained at the top of the rectification tower or the stripping tower and water is mainly obtained at the bottom of the rectification tower or the stripping tower; further, the obtained water was circulated to the water washing column. In some embodiments of the present invention, preferably, the stripping conditions comprise: the temperature is 100-120 ℃, the pressure is normal pressure, and the reflux ratio is 1-2; the rectification conditions comprise: the temperature is 100-120 ℃, the pressure is normal pressure, and the reflux ratio is 1-2.

The recovery of olefins and paraffins in said deoxygenated C6-C8 cut stream obtained by means of said deoxygenation treatment according to step (II) of the present invention is preferably greater than 98% while at least substantially maintaining the olefin/paraffin ratio. Not only the content of alpha-olefin in the Fischer-Tropsch synthetic oil is maintained, but also the alcohol, ketone, aldehyde, acid and ester in the Fischer-Tropsch synthetic oil can be effectively removed, and the content of the oxygen-containing compound in the deoxidized C6-C8 fraction material flow is reduced to be below 10ppm (quality).

In some embodiments of the invention, in step (III), the fractionation process may effect the cutting of the deoxygenated C6-C8 fraction stream and yield a C6 fraction stream, a C7 fraction stream, and a C8 fraction stream. The rectification separation treatment comprises the following steps: performing first rectification separation treatment on the deoxidized C6-C8 fraction material flow to obtain a C6 fraction material flow and a C7-C8 fraction material flow; and then carrying out second rectification separation treatment on the C7-C8 fraction material flow to obtain a C7 fraction material flow and a C8 fraction material flow.

Preferably, the conditions of the first rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower kettle is 105-115 ℃; the pressure at the top of the column was atmospheric.

Preferably, the deoxygenated C6-C8 fraction stream may be subjected to the first rectification separation treatment in a third rectification column, to obtain a C7-C8 fraction stream at the bottom of the third rectification column, and to obtain a C6 fraction stream at the top of the third rectification column, wherein the theoretical plate number of the third rectification column is 30 to 50, the feeding position of the deoxygenated C6-C8 fraction stream is from the bottom to the top at the 15 th to 25 th theoretical plates, and the conditions of the first rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower kettle is 105-115 ℃; the pressure at the top of the column was atmospheric.

Preferably, the conditions of the second rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower kettle is 120-130 ℃; the pressure at the top of the column was atmospheric.

Preferably, the C7-C8 fraction stream may be subjected to the second rectification separation treatment in a fourth rectification column, the C8 fraction stream is obtained at the bottom of the fourth rectification column, the C7 fraction stream is obtained at the top of the fourth rectification column, wherein the theoretical plate number of the fourth rectification column is 30-50, the C7-C8 fraction stream is fed at a position from bottom to top at a theoretical plate 15-25 plate, and the conditions of the second rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower kettle is 120-130 ℃; the pressure at the top of the column was atmospheric.

In some embodiments of the invention, in step (III), the extractive distillation treatment is intended to remove alkane streams from the C6 fraction stream, the C7 fraction stream and the C8 fraction stream. The compound extractant used in the extraction rectification treatment is a mixture of an extractant a and an extractant b; the extractant a is selected from N-methyl pyrrolidone and/or N, N dimethyl acetamide, and the extractant b is selected from gamma-butyrolactone and/or N-formyl morpholine. The compound extractant can not only give consideration to the selectivity of the solvent, but also give consideration to the solubility of the solvent.

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

In the invention, the extractive distillation treatment is carried out in an extractive distillation tower, and preferably, the conditions of the extractive distillation treatment comprise: the reflux ratio is 1-4; the temperature of the tower kettle is 120-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 50-100 blocks.

In some embodiments of the invention, the extractive distillation process comprises: carrying out first extractive distillation treatment on the C6 fraction material flow and the compound extracting agent to obtain a first mixed material flow rich in hexene and the compound extracting agent, and normal hexane and isohexane; carrying out second extractive distillation treatment on the C7 fraction material flow and the compound extracting agent to obtain a second mixed material flow rich in heptene and the compound extracting agent, and n-heptane and iso-heptane; and carrying out third extractive distillation treatment on the C8 fraction material flow and the compound extracting agent to obtain a third mixed material flow rich in the octenes and the compound extracting agent, and n-octane and isooctane.

Preferably, the conditions of the first extractive distillation process include: the reflux ratio is 1-4; the temperature of the tower kettle is 120-160 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 50-80 blocks.

Preferably, the C6 fraction stream can be subjected to the first extractive distillation treatment in a first extractive distillation column, the C6 fraction stream enters from the lower part of the first extractive distillation column, and the built extractant enters from the upper part of the column. The volume ratio of the compound extractant to the C6 fraction stream is 4-12, preferably 5-8. The content of the extractant b in the compound extractant is 30-60wt%, and preferably 35-50wt%. Obtaining a first mixed material flow rich in hexene and the compound extracting agent at the bottom of the tower, and obtaining normal hexane and isohexane at the top of the tower. Wherein the number of theoretical plates of the first extractive distillation column is 50-80, the feeding position of the C6 fraction material flow is the 15 th-35 th theoretical plate from bottom to top, the feeding position of the compound extracting agent is the 3 rd-6 th theoretical plate from top to bottom, and the conditions of the first extractive distillation treatment comprise: the reflux ratio is 1-4; the temperature of the tower kettle is 120-160 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 50-80 blocks.

Preferably, the conditions of the second extractive distillation process include: the reflux ratio is 1-4; the temperature of the tower kettle is 150-170 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-90 blocks.

Preferably, the C7 fraction stream may be subjected to the second extractive distillation treatment in a second extractive distillation column, the C7 fraction stream entering from the lower part of the second extractive distillation column, and the built extractant entering from the upper part of the second extractive distillation column. The volume ratio of the compound extractant to the C7 fraction stream is 4-12, preferably 5-8. The content of the extractant b in the compound extractant is 35 to 65 weight percent, and preferably 45 to 55 weight percent. And obtaining a second mixed material flow rich in heptene and the compound extracting agent at the bottom of the tower, and obtaining n-heptane and isoheptane at the top of the tower. Wherein the number of theoretical plates of the second extractive distillation column is 60-90, the feeding position of the C7 fraction material flow is the 15 th-40 th theoretical plate from bottom to top, the feeding position of the compound extracting agent is the 3 rd-6 th theoretical plate from top to bottom, and the conditions of the second extractive distillation treatment comprise: the reflux ratio is 1-4; the temperature of the tower kettle is 150-170 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-90 blocks.

Preferably, the conditions of the third extractive distillation process include: the reflux ratio is 1-4; the temperature of the tower kettle is 170-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100.

Preferably, the C8 fraction stream may be subjected to the third extractive distillation treatment in a third extractive distillation column, the C8 fraction stream enters from the lower part of the third extractive distillation column, and the built extractant enters from the upper part of the column. The volume ratio of the compound extracting agent to the C8 fraction material flow is 4-12, preferably 5-8. The content of the extractant b in the compound extractant is 40-70wt%, preferably 50-60wt%. And obtaining a third mixed material flow rich in the octenes and the compound extractant at the bottom of the tower, and obtaining n-octane and isooctane at the top of the tower. Wherein the number of theoretical plates of the third extractive distillation column is 60-100, the feeding position of the C8 fraction stream is the 15 th-45 th theoretical plate from bottom to top, the feeding position of the compound extractant is the 3 rd-6 th theoretical plate from top to bottom, and the conditions of the third extractive distillation treatment comprise: the reflux ratio is 1-4; the temperature of the tower kettle is 170-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

In some embodiments of the invention, after the extractive distillation treatment, the resulting mixed stream is subjected to a desolventizing treatment comprising: carrying out first solvent removal treatment on the first mixed material flow to obtain crude 1-hexene; subjecting the second mixture stream to a second desolventizing treatment to obtain crude 1-heptene; and carrying out third solvent removal treatment on the third mixed material flow to obtain crude 1-octene. And the solvent removal treatment is used for separating and removing the compound extracting agent in the first mixed material flow, the second mixed material flow and the third mixed material flow to obtain crude 1-hexene, crude 1-heptene and crude 1-octene, and returning the obtained circulating extracting agent (namely the regenerated compound extracting agent) to the extraction rectification treatment step for recycling.

In some embodiments of the present invention, the desolvation treatment is performed in a solvent recovery column, for example, the first mixed stream, the second mixed stream, and the third mixed stream may be subjected to a first desolvation treatment, a second desolvation treatment, and a third desolvation treatment in a third solvent recovery column, a fourth solvent recovery column, and a fifth solvent recovery column, respectively. The solvent recovery tower is preferably a rectifying tower, the theoretical plate number of the rectifying tower is 15-30, the feeding position is the 10 th-15 th theoretical plate from bottom to top, and the conditions of the solvent removal treatment comprise: the reflux ratio is 0.5-1, the temperature of the tower bottom is 150-250 ℃, and the pressure of the tower top is-0.01-0.08 MPa.

In some embodiments of the invention, in step (III), the polishing de-heaving treatment is capable of removing the corresponding 2-olefins from the crude 1-hexene, crude 1-heptene and crude 1-octene. The fine separation and de-weight treatment can adopt a rectification mode, and preferably, the conditions of the fine separation and de-weight treatment comprise: the reflux ratio is 5-8; the temperature of the tower kettle is 69-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

In the invention, the fine separation and de-weighting treatment comprises the following steps: carrying out first fine separation and de-weight treatment on the crude 1-hexene to obtain 1-hexene, 2-hexene and a C6 component with a higher boiling point; carrying out second fine separation and heavy removal treatment on the crude 1-heptene to obtain 1-heptene, 2-heptene and a C7 component with a higher boiling point; and carrying out third fine de-weight treatment on the crude 1-octene to obtain 1-octene, 2-octene and C8 component with higher boiling point.

Preferably, the conditions of the first fine separation and de-weighting treatment include: the reflux ratio is 5-8; the temperature of the tower kettle is 69-75 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

Preferably, the crude 1-hexene may be subjected to the first fine de-weighting treatment in a first fine de-weighting column, wherein the crude 1-hexene enters from the middle lower part of the first fine de-weighting column, 2-hexene and C6 components with higher boiling points are obtained at the bottom of the first fine de-weighting column, and 1-hexene is obtained at the top of the first fine de-weighting column, the theoretical plates of the first fine de-weighting column are 60-100 blocks, the C6 fraction stream is fed at the 30 th-50 th theoretical plate from bottom to top, and the conditions of the first fine de-weighting treatment include: the reflux ratio is 5-8; the temperature of the tower kettle is 69-75 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100.

Preferably, the conditions of the second fine separation and de-weighting treatment include: the reflux ratio is 5-8; the temperature of the tower kettle is 99-105 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

Preferably, the crude 1-heptene is subjected to the second fine de-weighting treatment in a second fine de-weighting tower, the crude 1-heptene enters from the middle lower part of the second fine de-weighting tower, 2-heptene and C7 components with higher boiling points are obtained at the tower bottom, and 1-heptene is obtained at the tower top, wherein the theoretical plate number of the second fine de-weighting tower is 60-100, the feeding position of the crude 1-heptene is 30-50 theoretical plates from bottom to top, and the conditions of the second fine de-weighting treatment comprise: the reflux ratio is 5-8; the temperature of the tower kettle is 99-105 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

Preferably, the conditions of the third fine fractionation and de-heavy treatment include: the reflux ratio is 5-8; the temperature of the tower kettle is 128-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

Preferably, the crude 1-octene may be subjected to the third fine de-weighting treatment in a third fine de-weighting column, the crude 1-octene enters from the middle lower part of the third fine de-weighting column, 2-octene and C8 components with higher boiling points are obtained at the bottom of the third fine de-weighting column, 1-octene is obtained at the top of the column, wherein the theoretical plate number of the third fine de-weighting column is 60-100, the feeding position of the crude 1-octene is 30-50 theoretical plates from bottom to top, and the conditions of the third fine de-weighting treatment include: the reflux ratio is 5-8; the temperature of the tower kettle is 128-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

In accordance with one embodiment of the present invention, a process for separating 1-hexene, 1-heptene, and 1-octene from a hydrocarbon-containing stream is shown in FIG. 1. The method may be carried out in a separation system comprising: the device comprises a first rectifying tower, a second rectifying tower, an extracting tower, a water washing tower, a first solvent recovery tower, a second solvent recovery tower, a decanting tower, a stripping tower, a third rectifying tower, a first extractive rectifying tower, a third solvent recovery tower, a first fractional de-heavy tower, a fourth rectifying tower, a second extractive rectifying tower, a fourth solvent recovery tower, a second fractional de-heavy tower, a third extractive rectifying tower, a fifth solvent recovery tower and a third fractional de-heavy tower; the first rectifying tower is communicated with the second rectifying tower in sequence, and a discharge hole at the lower part of the second rectifying tower is communicated with the extraction tower; the top of the extraction tower is communicated with a water washing tower, the bottom of the extraction tower is communicated with a first solvent recovery tower, the extraction tower is provided with a lower feed port for feeding C6-C8 fraction material flow, and an upper feed port for feeding a composite extraction solvent; the washing tower is provided with a lower feed inlet for feeding a first raffinate phase, an upper feed inlet for feeding water, a tower top outlet for discharging the obtained deoxidized C6-C8 fraction material flow to a lower feed inlet of a third rectifying tower, and a bottom outlet for discharging tower bottom material and communicating the upper feed inlet of the extraction tower; the first solvent recovery tower is provided with a recovery feed inlet communicated with the tower bottom of the extraction tower and the bottom outlet of the water washing tower, an upper outlet of the first solvent recovery tower is also provided for discharging a first circulating solvent to the extraction tower, and a lower discharge outlet is communicated with a feed inlet of the second solvent recovery tower; the second solvent recovery tower is also provided with a tower top recovery discharge hole and a tower bottom outlet which is communicated with an upper feed inlet of the extraction tower; the decantation tower is provided with a decantation feed inlet communicated with a recovery discharge hole of the second solvent recovery tower, an organic phase outlet at the top of the tower and a discharge hole at the bottom of the tower; the stripping tower is provided with a separation feed inlet communicated with a discharge outlet at the bottom of the decanting tower, a bottom outlet communicated with a feed inlet at the upper part of the water washing tower and an organic phase outlet at the top of the stripping tower; the third rectifying tower, the first extractive rectifying tower, the third solvent recovery tower and the first fine component de-heavy tower are communicated in sequence, and a tower bottom discharge port of the third solvent recovery tower is communicated with an upper extractant feed port of the first extractive rectifying tower; the fourth rectifying tower, the second extractive rectifying tower, the fourth solvent recovery tower and the second fractional de-heavy tower are sequentially communicated, a feed inlet of the fourth rectifying tower is communicated with a tower bottom discharge port of the third rectifying tower, and a tower bottom discharge port of the fourth solvent recovery tower is communicated with an upper extractant feed inlet of the second extractive rectifying tower; the third extractive distillation column, the fifth solvent recovery column and the third fine separation and de-heavy column are communicated in sequence, a feed inlet of the third extractive distillation column is communicated with a discharge outlet at the bottom of the fourth distillation column, and a discharge outlet at the bottom of the fifth solvent recovery column is communicated with an upper extractant feed inlet of the third extractive distillation column. The method provided by the invention can be implemented in the system, and comprises the following steps:

subjecting the whole fraction of Fischer-Tropsch synthesis naphtha to fraction cutting in a first rectifying tower and a second rectifying tower to obtain C6 ^- A distillate stream, a C6-C8 distillate stream, C9 and C9 ⁺ A distillate stream.

And respectively introducing the C6-C8 fraction material flow and the composite extraction solvent through a lower feed inlet and an upper feed inlet of the extraction tower, and performing multistage countercurrent extraction to obtain a first extract phase and a first raffinate phase.

Introducing the first raffinate phase into a water washing tower, washing off a small amount of composite extraction solvent contained in the first raffinate phase by a water washing method, and leading a deoxidized C6-C8 fraction material flow out of the tower top of the water washing tower, wherein the deoxidized C6-C8 fraction material flow contains more than 96wt% of olefin and alkane and less than 10ppm (mass) of oxygen-containing compounds; the mixture of water and a small amount of compound extraction solvent obtained at the bottom of the water washing tower can be divided into a material A at the bottom of the water washing tower and a material B at the bottom of the water washing tower, wherein the material A returns to the extraction tower and is added with the compound extraction solvent, and the material B and the first extraction phase are mixed and enter a first solvent recovery tower; the first solvent recovery tower is used for rectification recovery, a first circulating solvent is obtained from the tower top and can be returned and added into the composite extraction solvent for recycling, and tower bottom products (mainly heavy polar solvent, oxygen-containing compound and water) are introduced into a second solvent recovery tower for further rectification recovery; obtaining a recovered material from the tower top of the second solvent recovery tower, wherein the recovered material contains oxygen-containing compounds and water, obtaining a second circulating solvent (mainly a heavy polar solvent) from the tower bottom, and returning and adding the second circulating solvent into the composite extraction solvent for recycling; in the invention, the amount and composition of the material A at the bottom of the washing tower and the first and second circulating solvents returned when the first and second circulating solvents are added back to the composite extraction solvent are used for adjusting the composition of the composite extraction solvent to meet the extraction process, for example, the material A at the bottom of the washing tower, the first circulating solvent and the second circulating solvent can be mixed to prepare a proper composition to be added into the extraction solvent, if the content of water is excessive, the mixture can be distributed to more material B at the bottom of the washing tower, even the whole mixture obtained at the bottom of the washing tower enters the first solvent recovery tower.

Introducing the recovered material obtained from the top of the second solvent recovery tower into a decantation tower for standing separation, wherein the top product of the decantation tower is obtained from the upper part of the decantation tower and mainly contains oxygen compounds, and the bottom product of the decantation tower obtained from the bottom of the decantation tower can be recovered water and a small amount of water-soluble oxygen compounds; and further, introducing the decantation tower bottom product of the decantation tower into a stripping tower, separating water and oxygen-containing compounds, obtaining the oxygen-containing compounds at the tower top, obtaining circulating water at the tower bottom, and circulating the circulating water back to the washing tower.

And sequentially feeding the deoxidized C6-C8 fraction material flow into a third rectifying tower and a fourth rectifying tower for rectifying and separating to obtain a C6 fraction material flow, a C7 fraction material flow and a C8 fraction material flow. C6 fraction material flow sequentially enters a first extraction rectifying tower, a third solvent recovery tower and a first fine separation and de-weight tower, first extraction rectifying treatment (using the compound extracting agent), first solvent removing treatment and first fine separation and de-weight treatment are sequentially carried out to obtain 1-hexene, and an obtained third circulating solvent is returned to the first extraction rectifying tower for recycling; sequentially feeding the C7 fraction material flow into a second extraction and rectification tower, a fourth solvent recovery tower and a second fine separation and de-weighting tower, sequentially carrying out second extraction and rectification treatment (using the compound extractant), second solvent removal treatment and second fine separation and de-weighting treatment to obtain 1-heptene, and returning the obtained fourth circulating solvent to the second extraction and rectification tower for recycling; and (3) sequentially feeding the C8 fraction stream into a third extractive distillation tower, a fifth solvent recovery tower and a third fine separation de-heavy tower, sequentially performing third extractive distillation treatment (using the compound extractant), third desolvation treatment and third fine separation de-heavy treatment to obtain 1-octene, and returning the obtained fifth circulating solvent into the third extractive distillation tower for recycling.

The present invention will be described in detail below by way of examples.

Recovery of the deoxygenated C6-C8 fraction stream% = deoxygenated naphtha quality obtained at the top of the water-washing column/[ feed amount of the C6-C8 fraction stream in the extraction column × (1-content of oxygen-containing compound%) ]. Times.100%

The yield of the product (1-hexene, 1-heptene or 1-octene) = the mass of the product (1-hexene, 1-heptene or 1-octene) (% of the feed of the Fischer-Tropsch synthetic oil x 1-hexene, 1-heptene or 1-octene) × 100%

The content of each component in the Fischer-Tropsch synthesis naphtha is measured by a chromatographic method, wherein the content of alcohol and ester in the oxygen-containing compound is measured by chromatography, the content of carbonyl oxygen is measured by reference to GB/T6324.5-2008, and the acidity is measured by reference to GB/T264;

the content of the individual components in the product (1-hexene, 1-heptene or 1-octene) is determined by means of a chromatographic method, the content of oxygenates being determined by means of chromatography;

the composition and content of the feed fischer-tropsch naphtha is shown in table 1.

TABLE 1

Composition of raw materials	Content (wt%)
		Alpha-olefins	51.2
N-alkanes	31.5
		2-olefins	10.1
Isoalkanes	3.0
		Isomeric olefins	2.4
Alcohol(s)	1.6
		Carbonyl oxygen	0.2

Example 1

Performing first fraction cutting on Fischer-Tropsch synthesis naphtha (the composition is shown in a table 1) in a first rectifying tower to obtain C9 ^- Fraction and C9 ⁺ Fraction flow, after which said C9 is ^- The fraction material flow is subjected to second fraction cutting in a second rectifying tower to obtain C6 ^- Fractions and C6-C8 fraction streams, the specific operating conditions are shown in Table 2;

(II) carrying out multi-stage countercurrent extraction on the C6-C8 distillate flow and a composite extraction solvent (gamma-butyrolactone 82wt%, methanol 8wt% and water 10 wt%) in an extraction tower to obtain a first extract phase and a first raffinate phase; wherein the temperature of the countercurrent extraction is 25 ℃, the feeding speed of the C6-C8 fraction material flow is 15g/min, the feeding speed of the composite extraction solvent is 18g/min (the weight ratio of the composite extraction solvent to the C6-C8 fraction material flow is 1.2), and the extraction theoretical stage number is 10;

introducing the first raffinate phase at the top of the extraction tower into a water washing tower, washing away the composite extraction solvent by a water washing method, wherein the water washing temperature is 50 ℃, and the weight ratio of water to the first raffinate phase is 0.5:1, obtaining a deoxidized C6-C8 fraction material flow at the top of a water washing tower and leading out the deoxidized C6-C8 fraction material flow; the mixture (gamma-butyrolactone, methanol and water) obtained at the bottom of the washing tower is divided into a material A at the bottom of the washing tower and a material B at the bottom of the washing tower, the material A at the bottom of the washing tower can be directly returned to the extraction tower for recycling, and the material B at the bottom of the washing tower and the first extraction phase are introduced into a first solvent recovery tower and a second solvent recovery tower to carry out first solvent recovery treatment and second solvent recovery treatment in sequence; first solvent recovery conditions: the temperature is 88-92 ℃, the pressure is normal pressure, and the reflux ratio is 2; the conditions for recovering the second solvent include: the temperature is 175-180 ℃, the pressure is-0.05 MPa, and the reflux ratio is 1; returning the first circulating solvent obtained from the tower top of the first solvent recovery tower to the extraction tower, adding the composite extraction solvent for recycling, and introducing the tower bottom product into a second solvent recovery tower; returning a second circulating solvent obtained at the bottom of the second solvent recovery tower to the extraction tower, adding the second circulating solvent into the composite extraction solvent for recycling, introducing a recovered material obtained at the top of the tower into a decantation tower for standing separation, wherein a product at the top of the decantation tower obtained at the top is mainly an oxygen-containing compound; the bottom decant bottoms are introduced into a stripper to separate water and water soluble oxygenates under stripping conditions comprising: the temperature is 100-105 ℃, the pressure is normal pressure, the reflux ratio is 2, and the obtained circulating water is recycled to the washing tower;

taking 100min for material balance to obtain 1443.5g of deoxidized C6-C8 fraction material flow, wherein the recovery rate of the deoxidized C6-C8 fraction material flow is 98.0%;

the content of alpha-olefins in the deoxygenated C6-C8 cut stream was 52.1wt% and the content of oxygenates was 6ppm, as determined by gas chromatography; the alcohol content in the oxygen-containing compound was 0ppm by weight, the carbonyl oxygen content was 3ppm by weight, and the acidity was 0.37mg/100mL KOH;

(III) subjecting the deoxygenated C6-C8 fraction stream to a first rectification separation treatment in a third rectification column to obtain a C7-C8 fraction stream at the bottom of the column and a C6 fraction stream at the top of the column; performing the second rectification separation treatment on the C7-C8 fraction material flow in a fourth rectification tower to obtain a C8 fraction material flow at the bottom of the tower and a C7 fraction material flow at the top of the tower; the specific operating conditions are shown in Table 2;

introducing the C6 distillate stream into a first extractive distillation tower, carrying out first extractive distillation treatment on the C6 distillate stream with a compound extracting agent (the content of N-methylpyrrolidone is 55wt%, and the content of gamma-butyrolactone is 45 wt%), introducing the C7 distillate stream into a second extractive distillation tower, carrying out second extractive distillation treatment on the C7 distillate stream with a compound extracting agent (the content of N-methylpyrrolidone is 50wt%, and the content of gamma-butyrolactone is 50 wt%), wherein the volume ratio of the compound extracting agent to the C7 distillate stream is 7; corresponding normal alkane and isoparaffin are respectively obtained at the top of the tower; the specific operating conditions are shown in Table 2;

introducing the first mixed material flow into a third solvent recovery tower to carry out first desolventizing treatment, introducing the second mixed material flow into a fourth solvent recovery tower to carry out second desolventizing treatment, introducing the third mixed material flow into a fifth solvent recovery tower to carry out third desolventizing treatment, respectively obtaining crude 1-hexene, crude 1-heptene and crude 1-octene at the tower top, and respectively returning a third circulating extraction agent, a fourth circulating extraction agent and a fifth circulating extraction agent obtained at the tower bottom to the first extractive distillation tower, the second extractive distillation tower and the third extractive distillation tower for recycling, wherein the specific operation conditions are shown in Table 2;

introducing the crude 1-hexene into a first fine de-weighting tower to carry out first fine de-weighting treatment, introducing the crude 1-heptene into a second fine de-weighting tower to carry out second fine de-weighting treatment, introducing the crude 1-octene into a third fine de-weighting tower to carry out third fine de-weighting treatment, and respectively obtaining a 1-hexene product (marked as S1), a 1-heptene product (marked as P1) and a 1-octene product (marked as X1) at the tower top; respectively obtaining corresponding 2-olefin and a component with a higher boiling point at the bottom of the tower; specific operating conditions are shown in table 2.

TABLE 2

Tests show that the purity of 1-hexene in the product S1 is 99.1wt%, the content of the oxygen-containing compound is 4ppm, and the yield of 1-hexene is 96%; the purity of 1-heptene in the product P1 is 98.9wt%, the content of oxygen-containing compounds is 5ppm, and the yield of 1-heptene is 96.5%; in the product X1, the purity of 1-octene was 98.6% by weight, the content of oxygen-containing compound was 6ppm, and the yield of 1-octene was 96.5%.

In conclusion, the method can keep the content of the alpha-olefin in the process of removing the oxygen-containing compound, so that the content of the oxygen-containing compound in the deoxidized and refined Fischer-Tropsch synthetic oil is reduced to be below 10ppm, the yield of the separated products of 1-hexene, 1-heptene and 1-octene is more than 95%, and the purity is more than 98.5%.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A process for separating 1-hexene, 1-heptene, and 1-octene from a hydrocarbon-containing stream, comprising:

(I) subjecting the hydrocarbon-containing stream to a fractional cut to obtain C6 ^- A distillate stream, a C6-C8 distillate stream, C9 and C9 ⁺ A distillate stream;

(II) removing oxygen-containing compounds from the C6-C8 fraction material flow to obtain deoxidized C6-C8 fraction material flow;

(III) sequentially carrying out rectification separation treatment, extractive rectification treatment, solvent removal treatment and fine separation and weight removal treatment on the deoxidized C6-C8 fraction material flow to obtain 1-hexene, 1-heptene and 1-octene;

wherein the oxygenate removal treatment comprises:

(A) Carrying out countercurrent extraction on the C6-C8 fraction material flow and 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; carrying out first solvent recovery and second solvent recovery on the mixture obtained simultaneously, and/or returning and adding the composite extraction solvent in the step (A);

(C) And (B) carrying out first solvent recovery and second solvent recovery on the first extraction phase, circularly adding the obtained first circulating solvent and second circulating solvent into the composite extraction solvent in the step (A), standing and layering the water-containing organic matter obtained by recovering the second solvent, separating the bottom material obtained by layering, and recycling the water phase obtained by separation to the step (B).

2. The method of claim 1, wherein the hydrocarbon-containing stream comprises alkanes, alkenes, and oxygenates;

and/or the hydrocarbon-containing stream is naphtha fraction, preferably Fischer-Tropsch synthesis reaction condensation product;

and/or, the oxygenate comprises at least one of an alcohol, a ketone, an aldehyde, a carboxylic acid, and an ester;

and/or the oxygenate content of the hydrocarbon-containing stream is from 0.1 to 10 wt. -%, based on the total amount of the hydrocarbon-containing stream.

3. The process of claim 1 or 2, wherein the complex extraction solvent comprises a heavy polar solvent, methanol, and water; wherein, the first and the second end of the pipe are connected with each other,

the heavy polar solvent is at least one selected from ester compounds, glycol compounds, amide compounds, pyrrolidone compounds, dihydric alcohol compounds and alcohol amine compounds;

preferably, the ester compound is selected from at least one of benzoate compounds, carbonate compounds and lactone compounds, and is further preferably at least one of dimethyl phthalate, ethylene glycol carbonate and gamma-butyrolactone;

preferably, the glycols are selected from diethylene glycol and/or triethylene glycol;

preferably, the amide compound is selected from N, N-dimethylformamide and/or N, N-dimethylacetamide;

preferably, the pyrrolidone compound is N-methyl pyrrolidone;

preferably, the dihydric alcohol compound is propylene glycol;

preferably, the alcamines are ethanolamine.

4. The process of claim 3, wherein the composite extraction solvent has a water content of 3 to 20wt% and a methanol content of 5 to 10wt%, based on the total amount of the composite extraction solvent.

5. The process of any one of claims 1 to 4, wherein the weight ratio of the complex extraction solvent to the C6-C8 fraction stream is from 0.5 to 4:1, preferably 0.8 to 2:1.

6. the process according to any one of claims 1 to 5, wherein the temperature of the counter-current extraction is 10 to 50 ℃, preferably 20 to 50 ℃.

7. The method of any one of claims 1-6, wherein the conditions for recovery of the first solvent comprise: the temperature is 80-100 ℃, the pressure is normal pressure, and the reflux ratio is 1-2; the conditions for recovering the second solvent include: the temperature is 150-250 ℃, the pressure is-0.01-0.08 MPa, and the reflux ratio is 0.5-1;

and/or, the separation is rectification or stripping;

and/or the stripping conditions include: the temperature is 100-120 ℃, the pressure is normal pressure, and the reflux ratio is 1-2; the rectification conditions include: the temperature is 100-120 ℃, the pressure is normal pressure, and the reflux ratio is 1-2.

8. The method according to any one of claims 1 to 7, wherein the built extractant used in the extractive distillation treatment is a mixture of an extractant a and an extractant b; the extractant a is selected from N-methyl pyrrolidone and/or N, N dimethyl acetamide, and the extractant b is selected from gamma-butyrolactone and/or N-formyl morpholine;

and/or, based on the weight of the compound extractant, the content of the extractant a is 70-30wt%, preferably 40-65wt%; the content of the extractant b is 30 to 70wt%, preferably 35 to 60wt%.

9. The method of any one of claims 1 to 8, wherein the conditions of the extractive distillation process comprise: the reflux ratio is 1-4; the temperature of the tower kettle is 120-190 ℃; the pressure at the top of the tower is normal pressure, and the theoretical plate number is 50-100.

10. The method of any one of claims 1-9, wherein the conditions of the polishing de-emphasis process comprise: the reflux ratio is 5-8; the temperature of the tower kettle is 69-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 60-100 blocks.

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