CN116836035A

CN116836035A - Method and system for separating and purifying 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing stream

Info

Publication number: CN116836035A
Application number: CN202210297758.0A
Authority: CN
Inventors: 黄鑫; 李丽; 朱豫飞; 郑志刚
Original assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2022-03-24
Filing date: 2022-03-24
Publication date: 2023-10-03

Abstract

The invention relates to the field of separation and purification of hydrocarbon-containing streams, and discloses a method and a system for separating and purifying 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing streams, wherein the method comprises the following steps: subjecting the hydrocarbon-containing stream to fractional cutting to obtain C ₅ ^‑ Fraction stream, C ₆ ‑C ₈ Fraction stream, C ₉ ⁺ A distillate stream; c is C ₆ ‑C ₈ The distillate material flow, the composite extractant and the water phase are contacted for extraction and separation to obtain an extraction phase and a raffinate phase; rectifying and separating the raffinate phase, carrying out separation and weight removal treatment on the extract and extraction and rectification treatment to obtain 1-hexene, 1-heptene and 1-octene; wherein, after the extraction phase is recovered by solvent, the obtained recovered extractant is circularly added into the composite extractant; the composite extractant comprises an extractant a and an extractant b, wherein the extractant a is selected from N-methylpyrrolidone and/or N, N-dimethylacetamide, and the extractant b is selected from gamma-butyrolactone and/or N-formylmorpholine; and the compound extractant is used for extractive distillation treatment. The extractant is single, and the content of the oxygen-containing compound in the final Fischer-Tropsch synthesis oil is less than 10ppm (mass).

Description

Method and system for separating and purifying 1-hexene, 1-heptene and 1-octene from hydrocarbon-containing stream

Technical Field

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

Background

Alpha-olefins are an important organic feedstock and intermediate product and are extremely widely used, and the use of 1-butene, 1-hexene and 1-octene as comonomers in Polyethylene (PE) resins can improve PE properties. Currently, the production of alpha-olefins in industry is mainly achieved by an ethylene oligomerization method. The Fischer-Tropsch synthesis oil product contains olefin and alkane. The olefin is mainly linear alpha-olefin, and the content of the alpha-olefin in the Fischer-Tropsch light oil can reach more than 50 percent. The alpha-olefin produced by the ethylene oligomerization method has higher quality, and the method is mainly used for foreign alpha-olefin production.

EP1835011 discloses a method for distillative processing of a fischer-tropsch synthesis raw product and the resulting middle distillates, the main process being cutting the FTS raw product into naphtha and middle distillates. The south Africa SASOL company developed a combined process route of alkali washing-etherification-rectification-extraction in 1994 to prepare the polymer grade 1-hexene and 1-octene, but the method involves chemical reaction, and the process route is complex and has relatively high cost.

WO2020177235A1 proposes to use a simulated moving bed process to separate alkanes from alkenes, and to use molecular sieves to separate alkanes from alkenes with different adsorption capacities, so that a purity of the alkene component of over 99.5% can be achieved. The process has high requirement on the content of the oxygen-containing compound in the raw material, and irreversible adsorption of the oxygen-containing compound by the adsorbent is avoided.

CN102452888A discloses a method for purifying 1-hexene from fischer-tropsch synthesis oils. The Fischer-Tropsch synthesis light distillate oil is firstly cut into C6 fraction sections; then removing organic oxygen-containing compounds in the C6 fraction through extractive distillation; then separating alkane and alkene in C6 fraction section by extraction and rectification method; the C6 olefin obtained by extraction rectification is subjected to reactive rectification, tertiary carbon olefin in the C6 olefin reacts with low-carbon alcohol under the action of a catalyst to generate high-boiling-point ether, so that the tertiary carbon olefin is removed; removing ethanol remained in the C6 olefin by a liquid-liquid extraction method; and finally, purifying C6 olefin by a precise rectification method to obtain a 1-hexene product meeting the requirements of a polymerization grade. The extractant used for extracting and rectifying the C6 alkane and the alkene is a polar solvent such as ACN, NMP or DMF, and the extractant which is preferential for improving the selectivity of the solvent is in a binary mixed solvent composed of ACN or NMP and water, so that a solvent recovery tower and a dehydration tower are needed in the solvent recovery process in the whole flow, and the complexity of the process is increased. In addition, the polarity of water and the phase difference of the solvent are too large, the whole process is complex to operate, and the stability of the whole operation is affected.

Accordingly, there is a need to provide a new process for separating alpha-olefins from hydrocarbon-containing streams.

Disclosure of Invention

The invention aims to solve the problems of low purification efficiency and product purity, low solvent recovery rate, complex process flow, high energy consumption and the like of the prior art that a plurality of extractants are used for respectively deoxidizing and separating alkane from a plurality of alpha-olefins in a method for separating and purifying a plurality of alpha-olefins from hydrocarbon streams, and provides a method for separating and purifying 1-hexene, 1-heptene and 1-octene from hydrocarbon streams.

To achieve the above object, a first aspect of the present invention provides a process for separating and purifying 1-hexene, 1-heptene and 1-octene from a hydrocarbon-containing stream, comprising:

(I) Subjecting the hydrocarbon-containing stream to fractional cutting to obtain C ₅ ^- Fraction stream, C ₆ -C ₈ Fraction stream, C ₉ ⁺ A distillate stream;

(II) subjecting the C ₆ -C ₈ The distillate material flow, the compound extractant and the water phase are contacted for extraction and separation to obtain an extract phase and deoxidized C ₆ -C ₈ A raffinate phase of the fraction;

(III) subjecting the raffinate phase to rectification separation treatment, rectification separation and heavy removal treatment and extraction rectification treatment in sequence to obtain 1-hexene, 1-heptene and 1-octene;

wherein, the extraction phase is recycled by solvent, and the obtained recycled extractant is circularly added into the composite extractant;

The composite extractant comprises an extractant a and an extractant b, wherein the extractant a is selected from N-methylpyrrolidone and/or N, N-dimethylacetamide, and the extractant b is selected from gamma-butyrolactone and/or N-formylmorpholine;

and the compound extractant is also used for the extractive distillation treatment.

In a second aspect the present invention provides a system for the separation and purification of 1-hexene, 1-heptene and 1-octene from a hydrocarbon containing stream, comprising:

the device comprises a fraction cutting unit, an extraction unit, a separation and purification unit and a composite extractant storage tank; wherein, the liquid crystal display device comprises a liquid crystal display device,

the fraction cutting unit is used for carrying out fraction cutting on hydrocarbon-containing stream to obtain C ₅ ^- Fraction stream, C ₆ -C ₈ Fraction stream, C ₉ ⁺ A distillate stream;

the extraction unit is communicated with the fraction cutting unit, the separation and purification unit and the composite extractant storage tank and is used for separating C ₆ -C ₈ Extracting and separating the fraction material flow, water and composite extractant from a composite extractant storage tank to obtain a composite extractant containing deoxidized C ₆ -C ₈ A raffinate phase of the fraction;

the separation and purification unit is communicated with the composite extractant storage tank and is used for sequentially carrying out rectification separation treatment, rectification separation weight removal treatment and extraction rectification treatment in the presence of the composite extractant to obtain 1-hexene, 1-heptene and 1-octene, and recovering the composite extractant and returning the composite extractant to the composite extractant storage tank.

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

(1) An extractant is used to simultaneously remove the oxygen-containing compound and separate the alkane alkene. The extractant has good deoxidizing effect, the oxygen content in the raffinate phase can be reduced to below 10 mass ppm, and the recovery rate of alkene and alkane after oxygen-containing removal is preferably more than 95%; meanwhile, the extractant has good separation selectivity of the alkane and the alkene, and improves the relative volatility of the alkane and the alkene solubility, so that the energy consumption of the alkane and the alkene separation unit is low. Realizes that an extractant can be simultaneously used for extracting and separating oxygen-containing compounds in hydrocarbon-containing streams and separating C by extractive distillation treatment ₆ -C ₈ Olefins and alkanes.

(2) According to the invention, the removal of the isoolefin and the separation of the alkane and the alkene are realized by a combination mode of separation, weight removal and extractive distillation. 2-alkene and a small amount of alkane are removed in the separation and heavy removal, and n-alkane and isoparaffin are removed by extraction and rectification, so that the target products of n-alkene (1-hexene, 1-heptene and 1-octene) are obtained by separation and purification from hydrocarbon-containing material flow, and the combination can achieve the separation purity and reduce the energy consumption of the whole process.

(3) The separation method of the alpha-olefin can ensure that the content of the oxygen-containing compound in the target product is less than 10 mass ppm, and the independent yield of various alpha-olefins in hydrocarbon-containing material flows is more than or equal to 83 percent. Under preferred conditions, the individual purities of the various alpha-olefins are all greater than 98.5%.

Drawings

FIG. 1 is a schematic flow chart of the method and process provided by the present invention.

Description of the reference numerals

A. First rectifying column B, second rectifying column C and extraction column

D. Fourth solvent recovery tower E, composite extractant storage tank F and third rectifying tower

G. First rectifying column H, fourth rectifying column I and second rectifying column H

J. Third separation heavy-removal tower K, first extraction rectifying tower L and first solvent recovery tower

M, a second extraction rectifying tower N, a second solvent recovery tower O and a third extraction rectifying tower

P, third solvent recovery tower

1. Hydrocarbon-containing stream 2, C ₈ ^- Mixed fractions 3, C ₉ ⁺ Fraction stream

4、C ₅ ^- Fraction stream 5、C ₆ -C ₈ Fraction stream6. Raffinate phase

7. Extract phase 8, oxygenate and water stream 9, first recovery line

10. A second recovery line 11, a second extractant line 12, a first extractant line

13、C ₆ Fraction stream 14, C ₇ -C ₈ Fraction stream 15, crude C ₆ Hydrocarbon stream

16. The first refined heavy ends bottoms stream 17, n-hexane and isohexane 18, enriched in 1-hexene and complex

Mixture of synthetic extractants

19. 1-hexene 20, C ₇ Fraction stream 21, crude C ₇ Hydrocarbon stream

22. A second refined split heavy bottoms stream 23, n-heptane and iso-heptane 24, enriched in 1-heptenes and built

Mixture of synthetic extractants

25. 1-heptene 26, C ₈ Fraction stream 27, crude C ₈ Hydrocarbon stream 27

28. A third refined heavy ends bottoms stream 29, n-octane and isooctane 30, enriched in 1-octene and complex

Mixture of synthetic extractants

31. 1-octene 32, water

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

In the present invention, "C", unless otherwise specified ₅ ^- "means that the carbon number is 5 or less (including C ₅ 、C ₄ 、C ₃ 、C ₂ 、C ₁ )，“C ₈ ^- "means that the carbon number is 8 or less (including C ₈ )，“C ₉ ⁺ "means that the carbon number is 9 or more (including C ₉ )。“C ₆ -C ₈ "includes carbon numbers of 6, 7, 8; "C ₇ -C ₈ "includes carbon numbers 7 and 8.

In a first aspect the present invention provides a process for the separation and purification of 1-hexene, 1-heptene and 1-octene from a hydrocarbon containing stream comprising:

The method is used for separating and purifying target products 1-hexene, 1-heptene and 1-octene from the mixture, and can complete removal of oxygen-containing compounds and separation of alkane and alkene by using a single extractant system under the condition of ensuring the purity and recovery rate of the products. In some embodiments of the invention, the hydrocarbon-containing stream is a mixture comprising alkanes, alkenes, and oxygenates. The hydrocarbon-containing stream may contain various alkanes, alkenes, oxygenates, etc., having a carbon number of 4 or more. More specifically, the hydrocarbon-containing stream that can be satisfied may be a naphtha fraction, typically preferably a Fischer-Tropsch reaction condensate, which may be a condensate of a low temperature or high temperature Fischer-Tropsch reaction. More preferably, the hydrocarbonaceous stream is a Fischer-Tropsch oil, wherein the total content of alpha olefins is from 50 to 80wt%.

In some embodiments of the invention, the oxygenate comprises at least one of an alcohol, a ketone, an aldehyde, a carboxylic acid, and an ester in the hydrocarbon-containing stream. Further, the total content of the oxygenates in the hydrocarbon-containing stream is from 0.1 to 10wt%, based on the total amount of the hydrocarbon-containing stream. Further, in the oxygen-containing compound, the main oxygen-containing compound 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, may be from 0.05 to 1wt%, the carboxylic acid content may be determined by acidity, and the acidity may be from 30 to 100mg/100mL KOH. In the hydrocarbon-containing stream, the alkane is predominantly normal, with a minor amount of isoparaffin.

In the invention, the method can combine fractional distillation, extraction, extractive distillation and other processes to realize that the alpha-olefin with specific carbon number in the hydrocarbon-containing material flow composition, in particular to 1-hexene, 1-heptene and 1-octene can be separated and purified. Can include cutting the hydrocarbon-containing stream into fractions, separating the fractions by carbon number, and extracting to obtain C ₆ -C ₈ A distillate stream containing organic compounds which may include alkanes, alkenes, oxygenates, and the like; then extracting and separating, and removing C in an extraction mode ₆ -C ₈ Part of the oxygenates in the distillate stream, the raffinate phase obtained is predominantly C-rich ₆ -C ₈ Hydrocarbon compounds of the fraction (wherein "deoxygenated C-containing" is present ₆ -C ₈ Fraction "means C contained in the composition of the raffinate phase ₆ -C ₈ The fraction has been freed of part of the oxygenates); and further separating and purifying by a combination of rectification separation treatment, rectification separation and heavy removal treatment and extraction rectification treatment to obtain 1-hexene, 1-heptene and 1-octene from the raffinate phase. Wherein the rectification separation treatment realizes the separation of the raffinate phase into C ₆ Fraction stream, C ₇ Fraction stream and C ₈ Fraction stream, then refined separation heavy removal treatment can make C ₆ Fraction stream, C ₇ Fraction stream and C ₈ The distillate flow is respectively removed with high boiling point compounds, and the obtained residues are further subjected to extractive distillation treatment to separate and purify 1-hexene, 1-heptene and 1-octene.

In some embodiments of the invention, step (I) is used to separate C from the hydrocarbon-containing stream by carbon number ₆ -C ₈ A distillate stream, in step (I), the process of cutting the distillate comprising:

(I-1) subjecting the hydrocarbon-containing stream to a first cut to obtain C ₉ ⁺ Fraction stream, C ₈ ^- Mixing the fractions;

(I-2) subjecting the C ₈ ^- Cutting the mixed fraction into a second fraction to obtain C ₅ ^- Fraction stream and C ₆ -C ₈ A distillate stream.

Preferably, the conditions for cutting the first fraction include: the reflux ratio is 2-5; the temperature of the tower kettle is 155-170 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

Preferably, the hydrocarbon-containing stream may be subjected to the first cut in a first rectification column, yielding C at the bottom of the first rectification column ₉ ⁺ Fractional stream, at the firstC is obtained at the top of a rectifying tower ₈ ^- And a fraction stream, wherein the theoretical plate number of the first rectifying tower is 30-50, and the feeding position of the hydrocarbon-containing stream is 15-25 theoretical plates from bottom to top.

Preferably, the conditions for cutting the second fraction include: the reflux ratio is 2-5; the temperature of the tower kettle is 80-90 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

Preferably, the C may be ₈ ^- The fraction stream is subjected to said second fraction cutting in a second rectifying column, obtaining C at the bottom of the second rectifying column ₆ -C ₈ Fraction stream, obtaining C at the top of the second rectifying column ₅ ^- A distillate stream, wherein the theoretical plate number of the second rectifying column is 30-50, the C ₈ ^- The feeding position of the fraction stream is 15 th to 25 th theoretical plates from bottom to top.

In some embodiments of the invention, step (II) is used to effect the extraction from C by means of extraction ₆ -C ₈ The distillate stream removes oxygenates. Preferably, the C is extracted by an extraction solvent consisting of the compound extractant and water ₆ -C ₈ The distillate stream is subjected to oxygenate removal. Preferably, the weight ratio of the composite extractant to water is 1:0.1-1, preferably 1:0.2-0.5. So as to realize better removal effect.

In some embodiments of the present invention, preferably, the content of the extractant a in the composite extractant is 50 to 80wt%, preferably 60 to 80wt%. Correspondingly, the extractant b is present in an amount of 20 to 50 wt.%, preferably 20 to 40 wt.%.

In some embodiments of the present invention, preferably, in step (II), the total amount of the complex extractant and water is equal to the C ₆ -C ₈ The weight ratio of the fraction stream is 0.5-4:1, preferably 0.8-3:1.

in some embodiments of the invention, preferably, the temperature of the extraction separation is 10-50 ℃, preferably 20-50 ℃.

In some embodiments of the invention, preferably, theThe extraction and separation mode is multistage countercurrent extraction. Preferably, the theoretical stage number of the multistage countercurrent extraction may be 5 to 15 stages, preferably 8 to 12 stages. The extraction separation can be carried out in an extraction tower, the extraction solvent formed by mixing the composite extractant and water is introduced into the extraction tower at the top of the tower or near the top of the tower, and the C ₆ -C ₈ The distillate stream is introduced into the extraction column at or near the bottom of the column, and then said C ₆ -C ₈ Carrying out multistage countercurrent extraction on the fraction flow and the extraction solvent in an extraction tower; the raffinate phase is obtained at the top of the tower, and the extract phase is obtained at the bottom of the tower. The extract phase comprises a composite extractant, water, an oxygen-containing compound and a small amount of alkene and alkane, so that the solvent recovery is carried out by introducing a fourth solvent recovery tower, wherein the fourth solvent recovery tower can be a rectifying tower, the theoretical plate number is 10-30, preferably 15-25, and the condition of solvent recovery is that the reflux ratio is 0.5-2; the temperature of the tower bottom is 164-237 ℃; the tower top pressure is normal pressure, preferably 1-1.02bar, the oxygen-containing compound obtained at the tower top of the fourth solvent recovery tower is discharged with water, and the composite extractant obtained at the tower bottom of the fourth solvent recovery tower is recycled; the raffinate phase is enriched in C ₆ -C ₈ The fraction has low content of hydrocarbon compounds and oxygen-containing compounds. Preferably, the conditions of the extraction separation described above enable obtaining a raffinate phase with an oxygenate content of less than 10 mass ppm and a total mass fraction of olefins and paraffins higher than 99%.

In some embodiments of the invention, step (III) is used to separate and purify 1-hexene, 1-heptene and 1-octene from the raffinate phase. Preferably, the rectification separation treatment can realize cutting the raffinate phase and obtaining C ₆ Fraction stream, C ₇ Fraction stream and C ₈ A distillate stream. Preferably, the conditions of the rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower bottom is 105-130 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

In some embodiments of the present invention, preferably, the process of the rectification separation treatment includes:

(III-1-1) subjecting the raffinate phase to a first rectification to give C ₆ Fraction stream, C ₇ -C ₈ A distillate stream;

(III-1-2) subjecting the C ₇ -C ₈ Performing second rectification on the fraction material flow to obtain C ₇ Fraction stream and C ₈ A distillate stream.

Preferably, the conditions of the first rectification include: the reflux ratio is 2-5; the temperature of the tower bottom is 105-115 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

Preferably, the raffinate phase may be subjected to the first rectification in a third rectification column, obtaining C at the bottom of the third rectification column ₇ -C ₈ Fraction stream, obtaining C at the top of the third rectifying column ₆ And a distillate stream, wherein the theoretical plate number of the third rectifying tower is 30-50, and the feeding position of the raffinate phase is 15-25 theoretical plates from bottom to top.

Preferably, the conditions of the second rectification include: the reflux ratio is 2-5; the temperature of the tower kettle is 120-130 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

Preferably, the C may be ₇ -C ₈ The distillate flow is subjected to the second rectification in a fourth rectification tower, and C is obtained at the bottom of the fourth rectification tower ₈ Fraction stream, obtaining C at the top of the fourth rectifying column ₇ A distillate stream, wherein the theoretical plate number of the fourth rectifying column is 30-50, the C ₇ -C ₈ The feeding position of the fraction stream is 15 th to 25 th theoretical plates from bottom to top.

In some embodiments of the present invention, preferably, the fine separation and weight removal treatment is capable of further separating the C ₆ Fraction stream, C ₇ Fraction stream and C ₈ The 2-olefin in the fraction flow is removed, and in the process of removing the 2-olefin, normal alkane in the fraction flow can be partially separated and removed due to the higher boiling point, so that the energy consumption of the subsequent extractive distillation treatment step can be reduced.

In some embodiments of the present invention, the separation and duplication removal treatment may adopt a rectification mode, and preferably, the conditions of the separation and duplication removal treatment include: the reflux ratio is 7-15; the temperature of the tower bottom is 69-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 80-150.

In some embodiments of the present invention, preferably, the process of the fine separation and duplication removal treatment includes:

(III-2-1) subjecting the C ₆ Carrying out first separation and weight removal on the fraction stream to obtain a first separation and weight removal tower top stream and a first separation and weight removal tower bottom stream;

(III-2-2) subjecting the C ₇ Carrying out second separation and heavy removal on the fraction stream to obtain a second separation and heavy removal overhead stream and a second separation and heavy removal bottom stream;

(III-2-3) subjecting the C ₈ And carrying out third separation and heavy removal on the fraction stream to obtain a third separation and heavy removal overhead stream and a third separation and heavy removal bottom stream.

Preferably, the conditions of the first separation and duplication removal treatment include: the reflux ratio is 7-15; 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 80-150.

Preferably, the C may be ₆ Subjecting the distillate stream to said first finishing heavy removal in a first finishing heavy removal column, said C ₆ The distillate stream enters from the middle lower part of the first refined heavy ends removing tower, and the first refined heavy ends removing tower bottom stream obtained at the tower bottom comprises 2-hexene and C with higher boiling point ₆ The components, and a part of n-hexane is distilled along with the tower top stream in the heavy removal process, and the first refined heavy removal tower top stream obtained at the tower top is crude C ₆ A hydrocarbon stream, which may be a mixture comprising 1-hexene and a complex extractant; wherein the theoretical plate number of the first refined separation heavy removal tower is 80-150, and the C ₆ The feeding position of the fraction stream is 20-60 trays of the theoretical trays from bottom to top in the first refined separation heavy removal tower.

Preferably, the conditions of the second separation and duplication removal treatment include: the reflux ratio is 7-15; the temperature of the tower bottom is 99-105 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 80-150.

Preferably, the C may be ₇ Subjecting the distillate stream to said second finishing heavy removal treatment in a second finishing heavy removal column, said C ₇ From the first fraction streamThe second refined heavy component removing tower stream obtained at the bottom of the tower comprises 2-heptene and C with higher boiling point ₇ The components, and a part of n-heptane in the process of removing the heavy component is distilled out along with the bottom stream, and the second refined heavy component obtained at the top of the tower is crude C ₇ A hydrocarbon stream, which may be a mixture comprising 1-heptene and a complex extractant; wherein the theoretical plate number of the second fine separation heavy removal tower is 80-150, and the C ₇ The feeding position of the fraction stream is 20-60 trays of the theoretical trays from bottom to top in the second fine separation heavy removal tower.

Preferably, the conditions of the third separation and duplication removal treatment include: the reflux ratio is 7-15; the temperature of the tower bottom is 128-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 80-150.

Preferably, the C may be ₈ The fraction stream is subjected to the third separation and heavy removal treatment in a third separation and heavy removal tower, the C8 fraction stream enters from the middle lower part of the third separation and heavy removal tower, and the third separation and heavy removal tower bottom stream obtained at the tower bottom contains 2-octene and C with higher boiling point ₈ The components, and a part of n-octane is distilled out along with the bottom stream in the heavy removal process, and the third refined heavy removal overhead stream obtained at the top of the tower is crude C ₈ A hydrocarbon stream, which may be a mixture comprising 1-ene and a complex extractant; wherein the theoretical plate number of the third fine separation heavy removal tower is 80-150, and the C ₈ The feeding position of the fraction stream is 20-60 trays of the theoretical trays from bottom to top in the third separation and weight removal tower.

In some embodiments of the invention, the first finishing heavy ends bottoms stream, the second finishing heavy ends bottoms stream, and the third finishing heavy ends bottoms stream are all vented.

In some embodiments of the invention, the extractive distillation process is capable of separately removing the crude C ₆ Hydrocarbon stream, crude C ₇ Hydrocarbon stream and crude C ₈ Alkane in the hydrocarbon material flow realizes alkane-alkene separation, and olefin products are obtained. The composite extractant is also used for the extractive distillation treatment, so that the selectivity and the solubility can be both considered. In the extraction separation and the extraction rectificationThe same compound extractant is used in the treatment process, so that a good deoxidizing effect can be provided when the hydrocarbon-containing material flow is separated and purified, and the recovery rate of the obtained 1-hexene, 1-heptene and 1-octene is high; meanwhile, the process is simplified, and the energy consumption of a system for running the method is reduced.

In the present invention, the extractive distillation treatment is performed in an extractive distillation column, and preferably, the conditions of the extractive distillation treatment include: the reflux ratio is 1-4; the temperature of the tower bottom is 120-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 40-80.

In some embodiments of the invention, the extractive distillation process comprises:

(III-3-1) subjecting the first separated heavy ends removal overhead stream and the complex extractant to a first extractive distillation, and subjecting the resulting mixture of 1-hexene and complex extractant to a first solvent recovery to yield 1-hexene;

(III-3-2) subjecting the second separated heavy ends removal overhead stream and the complex extractant to a second extractive distillation, and subjecting the resulting mixture of 1-heptene and complex extractant to a second solvent recovery to yield 1-heptene;

(III-3-3) subjecting the third separated heavy ends removal overhead stream and the complex extractant to a third extractive distillation, and subjecting the resulting mixture of 1-octene and complex extractant to a third solvent recovery to yield 1-octene.

Simultaneously, the first extractive distillation also obtains normal hexane and isohexane; the second extractive distillation also obtains n-heptane and iso-heptane; the third extractive distillation also yields n-octane and isooctane.

Preferably, the conditions of the first extractive distillation include: the reflux ratio is 1-4; the temperature of the tower bottom is 120-140 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 40-70.

Preferably, the first extractive distillation overhead stream may be subjected to the first extractive distillation in a first extractive distillation column, the first extractive distillation overhead stream entering from the lower portion of the first extractive distillation column and the complex extractant entering from the upper portion of the column. The volume ratio of the composite extractant to the first refined heavy ends removal overhead stream is 4-12:1, preferably 5-8:1. Obtaining a mixture rich in 1-hexene and the composite extractant at the bottom of the tower, and obtaining normal hexane and isohexane at the top of the tower. The theoretical plate number of the first extraction rectifying tower is 40-70, the feeding position of the first refined heavy removal tower top material flow is 15-35 theoretical plates from bottom to top, and the feeding position of the composite extractant is 3-6 theoretical plates from top to bottom.

Preferably, the conditions of the second extractive distillation include: the reflux ratio is 1-4; the temperature of the tower bottom is 150-170 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 40-70.

Preferably, the second refined heavy-removal tower top stream can be subjected to the second extractive distillation in a second extractive distillation tower, the second refined heavy-removal tower top stream enters from the lower part of the second extractive distillation tower, and the composite extractant enters from the upper part of the second extractive distillation tower; the volume ratio of the composite extractant to the second refined heavy ends removal overhead stream is 4-12:1, preferably 5-8:1. A mixture rich in 1-heptene and composite extractant is obtained at the bottom of the tower, and n-heptane and isoheptane are obtained at the top of the tower. The theoretical plate number of the second extraction rectifying tower is 40-70, the feeding position of the second refined separation heavy-removal tower top material flow is 15-35 theoretical plates from bottom to top, and the feeding position of the composite extractant is 3-6 theoretical plates from top to bottom.

Preferably, the conditions of the third extractive distillation include: the reflux ratio is 1-4; the temperature of the tower bottom is 170-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 40-70.

Preferably, the third extractive distillation column top stream may be subjected to the third extractive distillation in a third extractive distillation column, the third extractive distillation column top stream entering from the lower portion of the third extractive distillation column and the complex extractant entering from the upper portion of the column. The volume ratio of the composite extractant to the third refined heavy ends removal overhead stream is 4-12:1, preferably 5-8:1. And obtaining a mixture rich in 1-octene and the composite extractant at the bottom of the tower, and obtaining n-octane and isooctane at the top of the tower. The theoretical plate number of the third extraction rectifying tower is 40-70, the feeding position of the third refined heavy-removal tower top material flow is 15-35 theoretical plates from bottom to top, and the feeding position of the composite extractant is 3-6 theoretical plates from top to bottom.

In some embodiments of the invention, the extractive distillation process may take the form of a multistage countercurrent flow. For example, in a first extractive distillation column, the complex extractant is countercurrently contacted with the first split heavy overhead stream, in a second extractive distillation column, the complex extractant is countercurrently contacted with the second split heavy overhead stream, and in a third extractive distillation column, the complex extractant is countercurrently contacted with the third split heavy overhead stream.

Preferably, the first solvent recovery, the second solvent recovery and the third solvent recovery respectively realize recovery of the composite extractant, so as to obtain a final target product: 1-hexene, 1-heptene and 1-octene. And simultaneously, respectively recycling the obtained recycling extractant-I, recycling extractant-II and recycling extractant-III, and adding the recycling extractant-II and the recycling extractant-III back into the composite extractant for recycling.

In some embodiments of the present invention, the first solvent recovery, the second solvent recovery, and the third solvent recovery may be performed in a first solvent recovery column, a second solvent recovery column, and a third solvent recovery column, respectively. The first solvent recovery tower, the second solvent recovery tower and the third solvent recovery tower can be respectively preferably rectifying towers, the theoretical plate number is 15-30, the feeding position is 10-15 trays of the theoretical plate from bottom to top, and the solvent recovery conditions comprise: the reflux ratio is 0.5-1, the bottom temperature is 150-250 ℃, and the top pressure is-0.01-0.08 MPa.

According to a particularly preferred embodiment of the present invention, a process for the separation and purification of 1-hexene, 1-heptene and 1-octene from a hydrocarbon containing stream comprises:

(II) subjecting the C ₆ -C ₈ The distillate flow, the compound extractant and the water phase are contacted for extraction and separation to obtain an extract phase and deoxidized matterC ₆ -C ₈ A raffinate phase of the fraction;

and the compound extractant is also used for the extraction rectification treatment;

wherein the hydrocarbon-containing stream comprises alkanes, alkenes, and oxygenates; the hydrocarbon-containing stream is a naphtha fraction, preferably a Fischer-Tropsch synthesis reaction condensate; the oxygenate comprises at least one of an alcohol, a ketone, an aldehyde, a carboxylic acid, and an ester; the oxygenate content in the hydrocarbon-containing stream is from 0.1 to 10wt% and the alpha-olefin content is from 50 to 80wt%, based on the total amount of the hydrocarbon-containing stream;

In the step (II), the weight ratio of the composite extractant to the water is 1-10:1, preferably 2-5:1, a step of;

wherein, the content of the extractant a in the composite extractant is 50-80wt%, preferably 60-80wt%; the content of the extractant b is 20-50wt%, preferably 20-40wt%;

wherein in step (II), the total amount of the compound extractant and water is equal to the total amount of the C ₆ -C ₈ The weight ratio of the fraction stream is 0.5-4:1, preferably 0.8-3:1, a step of;

in the process of the extraction and rectification treatment, the volume ratio of the composite extractant to the first refined heavy-removal tower top stream, the second refined heavy-removal tower top stream and the third refined heavy-removal tower top stream is 4-12:1, preferably 5-8:1;

other conditions are as previously described.

In a second aspect the present invention provides a system for the separation and purification of 1-hexene, 1-heptene and 1-octene from a hydrocarbon containing stream using the method according to the present invention as shown in figure 1 comprising:

the device comprises a fraction cutting unit, an extraction unit, a separation and purification unit and a composite extractant storage tank E; wherein, the liquid crystal display device comprises a liquid crystal display device,

the fraction cutting unit is used for carrying out fraction cutting on the hydrocarbon-containing stream 1 to obtain C ₅ ^- Fraction stream 4, C ₆ -C ₈ Fraction stream 5, C ₉ ⁺ Fraction stream 3; wherein the fraction cutting unit comprises a first rectifying tower A and a second rectifying tower B which are sequentially communicated, a raw material inlet for introducing a hydrocarbon-containing material flow 1 is arranged at the lower part of the first rectifying tower A, and a middle material outlet is arranged at the upper part (at the side different from the raw material inlet) of the first rectifying tower A to obtain C ₈ ^- Fraction material flow 2, the bottom of the first rectifying tower A is provided with a discharge port to obtain C ₉ ⁺ Fraction stream 3; the lower part of the second rectifying tower B is provided with a feed inlet for introducing C ₈ ^- The mixed fraction 2, the upper part of the second rectifying column B (different from the feed inlet) is provided with C ₅ ^- The lower part (different from the feed inlet) of the second rectifying tower B is provided with a discharge port of the fraction material flow 4 to obtain C ₆ -C ₈ A discharge port for distillate stream 5;

the extraction unit is communicated with the fraction cutting unit, the separation and purification unit and the composite extractant storage tank E and is used for separating C ₆ -C ₈ The fraction material flow 5 is extracted and separated with water and composite extractant from a composite extractant storage tank E to obtain deoxidized C containing ₆ -C ₈ A raffinate phase 6 of the fraction; wherein the extraction unit comprises an extraction tower C and a fourth solvent recovery tower D, the extraction tower C is communicated with a second rectifying tower B, a composite extractant storage tank E (the extraction tower C and the composite extractant storage tank E are communicated through a first extractant pipeline 12 and are used for conveying the composite extractant), and a separation and purification unit, and the extraction tower C is communicated with a separation and purification unit ₆ -C ₈ The fraction material flow 5, the water 32 and the composite extractant contact to carry out the extraction separation to obtain a raffinate phase 6 and an extract phase 7; the fourth solvent recovery tower D is communicated with the extraction tower C and the composite extractant storage tank E and is used for carrying out solvent recovery on the extraction phase 7, the obtained stream 8 containing oxygen compounds and water is discharged, and the obtained recovered extractant passes through a first return The collecting pipeline 9 is led into a composite extractant storage tank E;

the separation and purification unit is communicated with a composite extractant storage tank E and is used for sequentially carrying out rectification separation treatment, rectification separation weight removal treatment and extraction rectification treatment in the presence of a composite extractant on the raffinate phase 6 to obtain 1-hexene, 1-heptene and 1-octene, and recovering the composite extractant and returning the composite extractant to the composite extractant storage tank E; wherein, separation and purification unit includes: a rectification separation treatment group, a rectification separation and weight removal treatment group and an extraction rectification treatment group; wherein the rectification separation treatment group comprises: a third rectifying tower F and a fourth rectifying tower H, wherein the third rectifying tower F is used for carrying out first rectification on the raffinate phase 6, and C is obtained from the top of the third rectifying tower F ₆ Fraction stream 13, C is obtained from the bottom of the third rectification column F ₇ -C ₈ Fraction stream 14, fourth rectifying column H is used to convert C ₇ -C ₈ The fraction stream 14 is subjected to a second rectification, from the top of which a C is obtained ₇ Fraction stream 20, C is obtained from the bottom of the fourth rectification column H ₈ Fraction stream 26;

wherein, the essence divides the heavy processing group of falling off includes: a first fine separation heavy-removal tower G, a second fine separation heavy-removal tower I and a third fine separation heavy-removal tower J which are mutually connected in parallel, wherein the first fine separation heavy-removal tower G is used for feeding C from the middle lower part of the first fine separation heavy-removal tower ₆ The fraction stream 13 is subjected to first separation and weight removal, a first separation and weight removal bottom stream 16 is obtained from the bottom of the first separation and weight removal tower G, and a crude C is obtained from the top of the first separation and weight removal tower G ₆ Hydrocarbon stream 15 (i.e., the first refined heavy ends overhead stream); the second separation heavy-removal column I is used for feeding C from the middle lower part of the second separation heavy-removal column ₇ The fraction stream 20 is subjected to a second separation and weight removal, a second separation and weight removal bottom stream 22 is obtained from the bottom of the second separation and weight removal tower I, and a crude C is obtained from the top of the second separation and weight removal tower I ₇ Hydrocarbon stream 21 (i.e., the second refined heavy ends overhead stream); the third separation heavy ends removal column J is used for feeding C from the middle lower part of the third separation heavy ends removal column ₈ The fraction stream 26 is subjected to third separation and weight removal, a third separation and weight removal bottom stream 28 is obtained from the bottom of the third separation and weight removal column J, and a crude C is obtained from the top of the third separation and weight removal column J ₈ Hydrocarbon stream 27 #I.e., a third refined heavy ends overhead stream);

wherein, the extractive distillation treatment group comprises: the first extraction and rectification subgroup comprises a first extraction and rectification tower K and a first solvent recovery tower L which are sequentially communicated, the second extraction and rectification subgroup comprises a second extraction and rectification tower M and a second solvent recovery tower N which are sequentially communicated, and the third extraction and rectification subgroup comprises a third extraction and rectification tower O and a third solvent recovery tower P which are sequentially communicated; the first extraction rectifying tower K, the second extraction rectifying tower M and the third extraction rectifying tower O are all communicated with the composite extractant storage tank E through a second extractant pipeline 11, and the second extractant pipeline 11 is used for conveying the composite extractant from the composite extractant storage tank E;

The lower part of the first extraction rectifying tower K is provided with a feed inlet communicated with the top of the first separation heavy removal tower G for introducing crude C ₆ A hydrocarbon material flow 15, and a liquid inlet communicated with a composite extractant storage tank E is arranged at the upper part of the first extraction rectifying tower K for introducing composite extractant, wherein crude C is in the first extraction rectifying tower K ₆ Carrying out first extraction rectification on the hydrocarbon material flow 15 and the composite extractant, obtaining a material flow 17 containing normal hexane and isohexane at a discharge port arranged at the upper part of a first extraction rectifying tower K, continuously feeding a mixture 18 rich in 1-hexene and the composite extractant obtained at a discharge port arranged at the lower part of the first extraction rectifying tower K into the lower part of a first solvent recovery tower L, carrying out first solvent recovery, obtaining 1-hexene 19 at a discharge port arranged at the upper part of the first solvent recovery tower L, and obtaining a recovered extractant I at a discharge port arranged at the lower part of the first solvent recovery tower L;

the lower part of the second extraction rectifying tower M is provided with a feed inlet communicated with the top of the second separation heavy removal tower I for introducing crude C ₇ A hydrocarbon stream 21, and a liquid inlet communicated with a composite extractant storage tank E is arranged at the upper part of the second extraction rectifying tower M for introducing composite extractant, wherein coarse C is arranged in the second extraction rectifying tower M ₇ The hydrocarbon material flow 20 and the composite extractant are subjected to second extraction rectification, a material flow 23 containing n-heptane and iso-heptane is obtained at a discharge port arranged at the upper part of the second extraction rectification column M, and the mixture is subjected to second extraction rectification column M The mixture 24 rich in 1-heptene and composite extractant obtained by the discharging hole arranged at the lower part continuously enters the lower part of the second solvent recovery tower N for second solvent recovery, the 1-heptene 25 is obtained at the discharging hole arranged at the upper part of the second solvent recovery tower L, and meanwhile, the recovered extractant-II is also obtained at the discharging hole arranged at the lower part of the second solvent recovery tower M;

the lower part of the third extraction rectifying tower O is provided with a feed inlet communicated with the top of the third separation heavy removal tower J for introducing crude C ₈ A hydrocarbon stream 27, and a liquid inlet communicated with a composite extractant storage tank E is arranged at the upper part of the third extraction rectifying tower O for introducing composite extractant, wherein crude C in the third extraction rectifying tower O ₈ The hydrocarbon material flow 27 and the compound extractant are subjected to third extraction rectification, a material flow 29 containing n-octane and isooctane is obtained at a discharge hole arranged at the upper part of the third extraction rectification tower O, a mixture 30 rich in 1-octene and compound extractant, which is obtained at a discharge hole arranged at the lower part of the third extraction rectification tower O, continuously enters the lower part of a third solvent recovery tower P, third solvent recovery is carried out, 1-octene 31 is obtained at a discharge hole arranged at the upper part of the third solvent recovery tower P, and meanwhile, the recovered extractant-III is also obtained at a discharge hole arranged at the lower part of the third solvent recovery tower P.

The first solvent recovery tower, the second solvent recovery tower N and the third solvent recovery tower P are respectively communicated with a composite extractant storage tank E, and the recovered extractant-I, the recovered extractant-II and the recovered extractant-III are converged and returned to the composite extractant storage tank E through a second recovery pipeline 10.

The method provided by the invention can be implemented in the system.

The present invention will be described in detail by examples.

Yield of product (1-hexene, 1-heptene or 1-octene)/(mass of product (1-hexene, 1-heptene or 1-octene)/(feed of Fischer-Tropsch oil ×percentage of 1-hexene, 1-heptene or 1-octene) ×100%

The content of each component in Fischer-Tropsch synthetic naphtha is measured by a chromatographic method, wherein the content of alcohol in oxygen-containing compounds is measured by chromatography, the measurement of the content of carbonyl oxygen (aldehyde and ketone) is referred to GB/T6324.5-2008, and the measurement of the content of hydrocarbon compounds is referred to SH/T1797-2015; acidity determination is referred to GB/T264;

the content of each component in the product (1-hexene, 1-heptene or 1-octene) is determined by chromatographic methods, wherein the content of the oxygenate is determined by chromatography;

the composition and content of the raw Fischer-Tropsch naphtha are shown in Table 1.

TABLE 1

Composition of raw materials	Content (wt%)
		Alpha-olefins	70
N-alkanes	23.8
		2-olefins	1.3
Isoparaffin(s)	2.1
		Isomerised olefins	0.3
Alcohols	2.2
		Carbonyl oxygen	0.3

Example 1

Cutting a first fraction of Fischer-Tropsch naphtha (composition shown in Table 1) in a first fractionator A to give C ₈ ^- Mixed fraction and C ₉ ⁺ Fraction stream, after which C ₈ ^- Cutting the mixed fraction in a second rectifying tower B to obtain C ₅ ^- Fraction stream and C ₆ -C ₈ The distillate streams, specific operating conditions are shown in Table 2;

(II) C ₆ -C ₈ Carrying out multistage countercurrent extraction on the fraction material flow, the composite extractant and water in an extraction tower C to obtain an extraction phase and a raffinate phase; wherein the compound extractant is N-methyl pyrrolidone and gamma-butyrolactone (the respective content is 70wt%/30 wt%): the weight ratio of water is 4:1, the temperature of countercurrent extraction is 25 ℃, and C ₆ -C ₈ The feed rate of the distillate stream was 15g/min and the feed rate of the complex extractant was 18g/min ((complex extractant+water): C) ₆ -C ₈ The weight ratio of the fraction material flows is 1.2:1), and the extraction theoretical stage number is 12; the extract phase and the raffinate phase are obtained. Leading an extraction phase at the bottom of the extraction tower C into a fourth solvent recovery tower D, leading out regenerated composite extractant from the bottom of the extraction tower after rectification, and returning the regenerated composite extractant to a composite extractant storage tank E;

introducing raffinate phase at the top of the extraction tower C into a third rectifying tower F for first rectifying, and obtaining C at the top of the extraction tower ₆ The fraction flow enters a first refined heavy-removal tower G for first refined heavy removal, and a first refined heavy-removal tower top flow (coarse C) is obtained from the tower top ₆ Hydrocarbon stream) into a first extractive distillation column K with a complex extractant from a complex extractant tank E (first split heavy overhead stream: the volume ratio of the composite extractant=1:7), the mixture of the 1-hexene and the composite extractant obtained at the bottom of the tower enters a first solvent recovery tower L for first solvent recovery to obtain 1-hexene, and the recovered extractant-I is returned to a composite extractant storage tank E; wherein the purity of 1-hexene was 99.1% by weight, the content of the oxygen-containing compound was 4ppm, and the yield of 1-hexene was 87.1%.

C obtained from the bottom of the third rectifying column F ₇ -C ₈ The fraction stream is introduced into a fourth rectifying columnH is subjected to second rectification, and C is obtained at the top of the tower ₇ Fraction material flow, C is obtained at the bottom of the tower ₈ A distillate stream;

C ₇ introducing the fraction stream into a second separation and heavy-removal column I for second separation and heavy removal, and obtaining a second separation and heavy-removal column top stream (crude C ₇ Hydrocarbon stream) into a second extractive distillation column M with a complex extractant from a complex extractant tank E (second split heavy ends overhead stream: the volume ratio of the compound extractant=1:7), the mixture of the 1-heptene and the compound extractant obtained at the bottom of the tower enters a second solvent recovery tower N for second solvent recovery to obtain the 1-heptene, and the recovered extractant-II is returned to a compound extractant storage tank E; wherein the purity of 1-heptene was 98.9wt%, the content of oxygen-containing compound was 4ppm, and the yield of 1-heptene was 88.2%.

C ₈ The fraction stream is introduced into a third separation heavy-removal column J for third separation heavy removal, and a third separation heavy-removal column top stream (crude C) is obtained from the column top ₈ Hydrocarbon stream) into a third extractive distillation column O with a complex extractant from a complex extractant tank E (third split heavy ends overhead stream: the volume ratio of the composite extractant=1:7), carrying out third extraction rectification, enabling the mixture of the 1-octene and the composite extractant obtained at the bottom of the tower to enter a third solvent recovery tower P for third solvent recovery, obtaining the 1-octene, and simultaneously returning the recovered extractant-III to a composite extractant storage tank E; wherein the purity of 1-octene was 98.8wt%, the content of oxygen-containing compound was 5ppm, and the yield of 1-octene was 88.3%.

Taking 100min running results of the device and the method to perform material balance calculation to obtain 1390.7g deoxidized C ₆ -C ₈ Distillate stream, deoxygenation C ₆ -C ₈ The recovery of the distillate stream was 88.1%;

deoxygenation C by gas chromatography detection ₆ -C ₈ The fraction stream had an alpha-olefin content of 71.3wt% and an oxygenate content of 5ppm; the content of alcohol in the oxygen-containing compound was 0ppm by weight, the content of carbonyl oxygen was 4ppm by weight, and the acidity was 0.37mg/100mL KOH.

TABLE 2

Examples 2 to 5

The procedure of example 1 was followed, except that the composition and the amount of the complex extractant used were as shown in Table 3.

Purifying and separating to obtain 1-hexene, 1-heptene and 1-octene respectively; the effect is shown in Table 3.

Taking 100min running results of the device and the method to perform material balance calculation to obtain deoxidized C ₆ -C ₈ Recovery of distillate stream and detection of deoxygenated C by gas chromatography ₆ -C ₈ The results of the alpha-olefin content, the oxygenate alcohol content, the carbonyl oxygen content, and the acidity in the distillate stream are shown in Table 3.

TABLE 3 Table 3

Table 3 (subsequent)

Comparative examples 1 to 2

The procedure of example 1 was followed, except that the composition and the amount of the complex extractant used were as shown in Table 4.

Purifying and separating to obtain 1-hexene, 1-heptene and 1-octene respectively; the effect is shown in Table 4.

Taking 100min running results of the device and the method to perform material balance calculation to obtain deoxidized C ₆ -C ₈ Recovery of distillate stream and detection of deoxygenated C by gas chromatography ₆ -C ₈ The fraction stream contains alpha-olefin, oxygen-containing compound, alcohol in oxygen-containing compound, carbonyl oxygen,The acidity results are shown in Table 4.

TABLE 4 Table 4

As can be seen from the data of examples, comparative examples and tables 2-4, the separation and purification of a variety of α -olefins, i.e., 1-hexene, 1-heptene and 1-octene, from hydrocarbon streams can be accomplished using the process of the present invention using only one complex extractant under controlled conditions for deoxygenation (extractive separation) and separation of the paraffins (extractive distillation). The method simplifies the process flow, can maintain the content of alpha-olefin in the process of removing the oxygen-containing compound, reduces the content of the oxygen-containing compound in the Fischer-Tropsch synthetic oil after deoxidization refining to below 10ppm, and the yield of the separated products of 1-hexene, 1-heptene and 1-octene is more than 83 percent, and the purity is more than 98.5 percent.

The composition of the complex extractant in comparative example 1 is not within the preferred range of the present application, and the composition of the complex extractant+water in the deoxidation process in comparative example 2 is not within the preferred range of the present application ₆ -C ₈ Fraction stream) is not within the preferred range of the present application, the volume ratio of the complex extractant to the refined heavy-ends-removed overhead stream in the separation (extractive distillation) of the alkylen in comparative example 3 is not within the preferred range of the present application, and as a result, the oxygenate content in the Fischer-Tropsch synthesis oil after the deoxygenation refining, the yield and purity of the obtained product 1-hexene, 1-heptene, 1-octene cannot simultaneously achieve the effects obtained by the present application.

The preferred embodiments of the present application have been described in detail above, but the present application is not limited thereto. Within the scope of the technical idea of the application, a number of simple variants of the technical solution of the application are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the application, all falling within the scope of protection of the application.

Claims

1. A process for the separation and purification of 1-hexene, 1-heptene and 1-octene from a hydrocarbon containing stream comprising:

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

preferably, the hydrocarbon-containing stream is a naphtha fraction, preferably a Fischer-Tropsch synthesis reaction condensate;

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

preferably, the oxygenate is present in the hydrocarbonaceous stream in an amount of from 0.1 to 10wt% and the alpha-olefin is present in an amount of from 50 to 80wt% based on the total amount of the hydrocarbonaceous stream.

3. A method according to claim 1 or 2, wherein in step (I), the process of cutting the fraction comprises: (I-1) subjecting the hydrocarbon-containing stream to a first cut to obtain C ₉ ⁺ Fraction stream, C ₈ ^- Mixing the fractions; (I-2) subjecting the C ₈ ^- The mixed fraction is subjected to a second distillationCutting to obtain C ₅ ^- Fraction stream and C ₆ -C ₈ A distillate stream.

4. A process according to any one of claims 1 to 3, wherein in step (II) the weight ratio of the complex extractant to water is from 1 to 10:1, preferably 2-5:1.

5. the process according to any one of claims 1 to 4, wherein the content of extractant a in the complex extractant is 50 to 80wt%, preferably 60 to 80wt%;

preferably, in step (II), the total amount of the complex extractant and water is equal to the C ₆ -C ₈ The weight ratio of the fraction stream is 0.5-4:1, preferably 0.8-3:1.

6. the process according to any one of claims 1-5, wherein the temperature of the extractive separation is 10-50 ℃, preferably 20-50 ℃;

preferably, the extraction separation mode is multistage countercurrent extraction, and the theoretical stage number of the multistage countercurrent extraction is 5-15 stages, preferably 8-12 stages.

7. The method of any one of claims 1-6, wherein the rectifying separation process comprises: (III-1-1) subjecting the raffinate phase to a first rectification to give C ₆ Fraction stream, C ₇ -C ₈ A distillate stream;

(III-1-2) subjecting the C ₇ -C ₈ Performing second rectification on the fraction material flow to obtain C ₇ Fraction stream and C ₈ A distillate stream;

preferably, the conditions of the rectification separation treatment include: the reflux ratio is 2-5; the temperature of the tower bottom is 105-130 ℃; the pressure at the top of the column is atmospheric pressure, preferably 1-1.02bar.

8. The method of claim 7, wherein the process of fine separation de-duplication processing comprises:

(III-2-1) the reaction mixtureThe C is ₆ Carrying out first separation and weight removal on the fraction stream to obtain a first separation and weight removal tower top stream and a first separation and weight removal tower bottom stream;

(III-2-3) subjecting the C ₈ Carrying out third separation and heavy removal on the fraction stream to obtain a third separation and heavy removal overhead stream and a third separation and heavy removal bottom stream;

preferably, the conditions of the fine separation heavy removal treatment include: the reflux ratio is 7-15; the temperature of the tower bottom is 69-135 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 80-150.

9. The method of claim 8, wherein the extractive distillation process comprises:

(III-3-3) subjecting the third separated heavy ends removal overhead stream and the complex extractant to a third extractive distillation, and subjecting the resulting mixture of 1-octene and complex extractant to a third solvent recovery to yield 1-octene;

preferably, the conditions of the extractive distillation treatment include: the reflux ratio is 1-4; the temperature of the tower bottom is 120-190 ℃; the pressure at the top of the tower is normal pressure; the theoretical plate number is 40-80;

preferably, the volume ratio of the composite extractant to the first, second and third split heavy overhead streams is 4-12:1, preferably 5-8:1, respectively.

10. The method of claim 9, wherein the first, second, and third extractive distillation further comprise obtaining n-hexane, n-heptane, and n-octane, respectively;

preferably, the first, second and third solvent recovery further comprises adding the recovered extractant-I, recovered extractant-II and recovered extractant-III, respectively, back into the complex extractant.

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