CN116178096B

CN116178096B - Method and device for separating 1-hexene from Fischer-Tropsch oil

Info

Publication number: CN116178096B
Application number: CN202211550240.XA
Authority: CN
Inventors: 董国如; 陈久洲; 石好亮; 石永杰; 杨顺; 黄浩; 金梦; 杨自玲; 袁华
Original assignee: National Energy Group Ningxia Coal Industry Co Ltd
Current assignee: National Energy Group Ningxia Coal Industry Co Ltd
Priority date: 2022-12-05
Filing date: 2022-12-05
Publication date: 2024-09-10
Anticipated expiration: 2042-12-05
Also published as: CN116178096A

Abstract

The present invention provides a method and apparatus for separating 1-hexene from Fischer-Tropsch oil. The method comprises the following steps: s1, rectifying and cutting Fischer-Tropsch synthetic oil to obtain a C ₆ fraction; alkali washing, neutralizing, and separating out an oil phase to obtain deacidified C ₆ fraction; washing with water, and drying to obtain dried C ₆ fraction; the mixture enters an extraction tower, and oxides in the mixture are removed by countercurrent with an extractant to obtain deoxidized C ₆ fraction; feeding the mixture into a selective hydrogenation reactor to convert diolefins in the deoxidized C ₆ fraction into monoolefins to obtain a C ₆ fraction after selective hydrogenation; inputting the mixture into an etherification rectifying tower, carrying out etherification reaction on tertiary carbon olefins in the C ₆ fraction after selective hydrogenation and low-carbon alcohol under the action of a catalyst, and separating an etherification product to obtain a C ₆ fraction with tertiary carbon olefins removed; removing internal olefins through rectification separation to obtain 1-hexene crude fraction; alkane-alkene separation is carried out through a simulated moving bed, and 1-hexene is obtained. The method has the advantages of high product purity, high yield, low energy consumption and the like.

Description

Method and device for separating 1-hexene from Fischer-Tropsch oil

Technical Field

The invention relates to the technical field of Fischer-Tropsch oil separation, in particular to a method and a device for separating 1-hexene from Fischer-Tropsch oil.

Background

As known in the art, the coal-fired boiler has an energy structure rich in coal, less in oil and deficient in gas, and the coal-fired boiler liquefies synthetic oil (direct liquefaction and indirect liquefaction) as one of important ways for relieving contradiction between supply and demand of oil and gas resource shortage. The coal liquefaction technology, in particular the indirect coal liquefaction technology, is mature, the core reaction is Fischer-Tropsch reaction, the reaction product is widely distributed (C ₁-C₁₀₀), the ASF (Anderson-Schulz-Flory) law is basically followed, but the product components are complex, and mainly comprise alpha-olefin, normal alkane, alcohol, ketone, aldehyde, ester, acid and other oxygen-containing compounds, the alpha-olefin content is 40-50%, and the oxide content is 2-5%.

1-Hexene is a very important comonomer of linear polypropylene (polyethylene) resin, the performance of the resin taking 1-hexene as the comonomer is far superior to that of the resin taking 1-butene as the comonomer, and the resin is produced by taking 1-hexene as the comonomer to drive the traditional polypropylene (polyethylene) material to be upgraded, so that the high-end and high-performance material is produced, the market demand of 1-hexene is rapidly increased, most 1-hexene in China depends on foreign import, the main method for producing 1-hexene at present comprises paraffin cracking, oligomerization and extractive distillation, the paraffin cracking method is mature in technology, but the product quality is lower; the oligomerization method has higher production quality, but domestic oligomerization technology production devices are demonstration, and the extractive distillation has higher energy consumption and operation cost.

The Fischer-Tropsch product of 400 ten thousand tons/year coal-to-liquid oil project is mainly used for primary chemical raw materials or semi-finished oil, and the economic benefit is low and the market competitiveness is not strong because the oil price is low for a long time, so that the alpha-olefin is separated from the Fischer-Tropsch oil product, the alpha-olefin product with high added value is obtained, and the economic benefit of coal-to-liquid oil enterprises and the capability of resisting market risks can be improved.

The patent application with publication number CN10245288A provides a method for purifying 1-hexene from Fischer-Tropsch synthetic oil, the Fischer-Tropsch oil is cut to obtain C ₆ fraction, the oxygenated compounds in the C ₆ fraction are removed by extractive distillation, the separation of C ₆ alkane and C ₆ alkene is carried out by extractive distillation, The obtained C ₆ olefin is subjected to etherification reaction in a rectifying tower to remove tertiary carbon olefin, and is further purified by a precise rectifying tower to obtain a 1-hexene product with the purity of 99%. the patent application with publication number CN105777467A provides a method for separating oxygen-containing compound and 1-hexene from Fischer-Tropsch synthetic oil, the Fischer-Tropsch synthetic oil is subjected to a bulkhead rectifying tower to obtain C ₆ fraction, the oxygen-containing compound in the C ₆ fraction is removed through extractive distillation, the separation of C ₆ alkane and C ₆ alkene is carried out through extractive distillation, The obtained C ₆ olefin is removed from tertiary carbon olefin in an etherification reaction rectifying tower, C ₆ isoparaffin and cycloolefin components are removed through extractive distillation, and further purification is carried out through superfractionation, so that a 1-hexene product with the purity of 98.41% is finally obtained. The patent with publication number CN111100683A discloses a separation method of long-chain alkane-alkene in Fischer-Tropsch synthetic oil, which comprises the steps of carrying out adsorption deoxidation on the Fischer-Tropsch synthetic oil, reducing the mass fraction of an oxidized substance to 0.1%, feeding the deoxidized material into a simulated moving bed adsorption separation system filled with alkane-alkene separation adsorbent for carrying out alkane-alkene adsorption separation to obtain alpha-alkene rich in alpha-alkene and alkane rich in alpha-alkene with purity of more than 98% and feeding the alpha-alkene into a rectification unit. The patent application with publication number CN109503307A provides a method for separating linear olefins from a material flow containing the olefins, which takes coal-based Fischer-Tropsch synthetic oil as a raw material, wherein the carbon number of the olefins is 4-18, and the raw material is deacidified, cut into fractions, de-oxygenated compounds, separated the olefins, separated isomers, adsorbed and dried to obtain the linear olefin product with the purity of 99.7 percent. The technology for separating 1-hexene from Fischer-Tropsch oil disclosed in the patent has the problems of complex flow, large equipment investment, high operation energy consumption, low purity, high operation cost, low yield and the like.

Disclosure of Invention

The invention mainly aims to provide a method and a device for separating 1-hexene from Fischer-Tropsch oil, which are used for solving the problems of low purity, low yield and high running cost of separating 1-hexene from Fischer-Tropsch oil in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided a process for separating 1-hexene from fischer-tropsch oil, the process comprising: s1, rectifying and cutting Fischer-Tropsch synthetic oil to obtain a C ₆ fraction; step S2, carrying out alkali washing on the C ₆ fraction, neutralizing, and separating out an oil phase to obtain a deacidified C ₆ fraction; step S3, washing the deacidified C ₆ fraction with water and drying to obtain a dried C ₆ fraction; s4, feeding the dried C ₆ fraction into an extraction tower, and removing oxides in the dried C ₆ fraction and an extracting agent in a countercurrent way to obtain a deoxidized C ₆ fraction; s5, introducing the deoxidized C ₆ fraction into a selective hydrogenation reactor, and converting the diolefins in the deoxidized C ₆ fraction into monoolefins to obtain a hydrogenated C ₆ fraction; s6, inputting the hydrogenated C ₆ fraction into an etherification rectifying tower, enabling tertiary carbon olefins in the hydrogenated C ₆ fraction to carry out etherification reaction with low carbon alcohols under the action of a catalyst, and separating an etherification product to obtain a C ₆ fraction with tertiary carbon olefins removed; s7, removing internal olefins from the C ₆ fraction from which tertiary carbon olefins are removed through rectification separation to obtain a 1-hexene crude fraction; and S8, carrying out alkane-alkene separation on the 1-hexene crude fraction through a simulated moving bed to obtain 1-hexene.

Further, step S1 includes: step S11, enabling Fischer-Tropsch synthesis oil to enter a first rectifying tower to obtain a mixed fraction containing a C ₆₊ fraction and a C ₆ fraction; step S12, the mixed fraction enters a second rectifying tower, and a C ₆ fraction is obtained at the top of the tower;

Preferably, the number of tower plates of the first rectifying tower is 20-60, the reflux ratio is 5-15, the tower top temperature is 30-45 ℃, and the tower bottom temperature is 60-100 ℃;

preferably, the theoretical plate number of the second rectifying tower is 20-60, the reflux ratio is 5-15, the tower top temperature is 50-70 ℃, and the tower bottom temperature is 110-130 ℃;

more preferably, the first rectification column and/or the second rectification column is fed at a mid-column position.

Further, step S2 includes: inputting the C ₆ fraction into an alkaline washing tower, and mixing with alkaline liquor;

preferably, the alkaline solution comprises any one or more of sodium hydroxide solution, potassium hydroxide solution and potassium carbonate solution; preferably, the concentration of the alkali liquor is 5-10wt%;

Preferably, the volume ratio of the alkali liquor to the C ₆ fraction is 4-8.

Further, step S3 includes: inputting the deacidified C ₆ fraction into a water washing tower, washing to be neutral, inputting the washed fraction into an oil-water separator, separating an oil phase, and drying;

preferably, the drying treatment is drying by adopting a drying agent, wherein the drying agent comprises silica gel, alumina, a 3A molecular sieve and a 5A molecular sieve;

preferably, the moisture content of the dried C ₆ fraction is less than 100ppm.

Further, the extractant in the step S4 comprises any one or more of methanol, ethanol, acetonitrile, dimethyl sulfoxide, azomethyl pyrrolidone, N, N-dimethylformamide and ethylene glycol; preferably, the volume ratio of the extractant to the dry C ₆ fraction is 1-8:1, and the operation temperature is 30-50 ℃;

Preferably, step S4 further includes: deoxidizing the C ₆ fraction in an adsorption tower, wherein the adsorbent selected in the adsorption tower is preferably one or more of silica gel, clay, diatomite, alumina, activated carbon, 3A molecular sieve, 5A molecular sieve, 13X molecular sieve, resin and silicate.

Further, in step S5, the catalyst for selective hydrogenation is palladium; preferably, the reaction temperature of the selective hydrogenation is 110-120 ℃.

Further, the catalyst in the step S6 is any one or more of strong acid cation exchange resin, heteropolyacid catalyst and molecular sieve catalyst;

Preferably, the lower alcohol is any one or more of methanol, ethanol and propanol, and preferably, the molar ratio of the lower alcohol to tertiary carbon olefin in the C ₆ fraction after selective hydrogenation is 2-6:1;

Preferably, the theoretical plate number of the etherification rectifying tower is 30-80, the reflux ratio is 5-15, the tower top temperature is 50-70 ℃, the tower bottom temperature is 80-150 ℃, and preferably, the feeding position of the low-carbon alcohol and the C ₆ fraction after selective hydrogenation is 20-60 th plate;

Preferably, catalysts are respectively filled in the upper section, the middle section and the lower section of the etherification reaction rectifying tower, more preferably, 2-15 theoretical plates are arranged between the tower top and the upper section catalyst bed layer, between the two adjacent sections catalyst bed layers and between the lower section catalyst bed layer and the tower bottom;

Preferably, the selectively hydrogenated C ₆ fraction and lower alcohols are fed below the lower catalyst bed.

Further, in step S8, the adsorbent of the simulated moving bed is selected from any one or more of a 5A molecular sieve, a 13X type zeolite, an LTA type zeolite, and a modified molecular sieve thereof; and/or the desorbent of the simulated moving bed is any one or more of alkane and alkene, preferably, the desorbent is a mixture of alkane and alkene, and the content of alkene is 40-60%;

Preferably, the operation temperature of the adsorption tower in the simulated moving bed is 60-150 ℃, the operation pressure is 0.45-0.55 MPa, and the catalyst-oil ratio is 0.5-4:1.

Further, the Fischer-Tropsch synthesis oil is an oil product of the middle-temperature Fischer-Tropsch synthesis of the iron-based catalyst.

According to another aspect of the present application, there is provided an apparatus for separating 1-hexene from Fischer-Tropsch synthesis oil, the apparatus comprising a rectification cutting unit, a deacidification unit, a water washing and drying unit, a deoxidization unit, a selective hydrogenation reaction unit, an etherification unit, a rectification unit and an alkylene separation unit which are connected in sequence;

The rectification cutting unit is used for rectifying and cutting the Fischer-Tropsch synthetic oil to obtain a C ₆ fraction;

The deacidification unit is used for carrying out alkali washing on the C ₆ fraction, neutralizing, and separating out an oil phase to obtain a deacidified C ₆ fraction;

The washing and drying unit is used for washing and drying the deacidified C ₆ fraction to obtain a dried C ₆ fraction;

The deoxidizing unit is used for removing oxides in the dry C ₆ fraction to obtain deoxidized C ₆ fraction;

The selective hydrogenation reaction unit is used for carrying out selective hydrogenation reaction on the deoxidized C ₆ fraction to obtain a hydrogenated C ₆ fraction;

the etherification unit is used for carrying out etherification reaction on tertiary carbon olefins in the hydrogenated C ₆ fraction and removing the tertiary carbon olefins to obtain a C ₆ fraction with tertiary carbon olefins removed;

The rectification unit is used for rectifying and removing internal olefins in the C ₆ fraction from which tertiary carbon olefins are removed to obtain a 1-hexene crude fraction;

The alkane-alkene separation unit is a simulated moving bed and is used for separating alkane from alkene to obtain 1-hexene.

According to a further aspect of the present application there is provided a 1-hexene product obtained by the process of any one of the above.

By applying the technical scheme of the application, the high-purity 1-hexene is obtained through the steps of alkali washing, water washing, drying, deacidification, deoxidization, selective hydrogenation, etherification, alkane-alkene separation and the like after Fischer-Tropsch synthetic oil is cut, wherein the selective hydrogenation can convert diene which is difficult to separate into mono-olefin, the mono-olefin is removed through rectification separation, and finally alkane-alkene separation is carried out through a simulated moving bed, so that the high-purity 1-hexene is obtained. The method is particularly suitable for separating 1-hexene from the intermediate-temperature Fischer-Tropsch synthetic oil by the iron-based catalyst, and has higher efficiency. Compared with the traditional separation process, the method has the advantages of high product purity, high yield, simple process flow, less equipment investment, simple operation, low energy consumption and the like.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

fig. 1 shows a schematic process flow diagram according to an embodiment of the invention.

Wherein the above figures include the following reference numerals: 01. an iron-based catalyst medium temperature Fischer-Tropsch synthesis oil stream; 02. a C ₆ cut stream; 03. deacidifying the C ₆ fraction stream; 04. washing the C ₆ cut stream with water; 05. drying the C ₆ cut stream; 06. extracting a deoxygenated C ₆ fraction stream; 07. adsorbing the deoxygenated C ₆ fraction stream; 08. a selectively hydrogenated C ₆ cut stream; 09. a C ₆ cut stream to remove tertiary carbon olefins; 10. a 1-hexene crude fraction stream; 11. a n-hexane stream; 12. a 1-hexene product stream; 001. a first rectifying cutting tower; 002. a second rectification cutting tower; 003. an alkaline washing tower; 004. a water washing tower; 005. an oil-water separator; 006. a dryer; 007. an extraction rectifying tower; 008. an extractant recovery column; 009. a deoxidizing adsorption tower; 010. a selective hydrogenation reactor; 011. etherification rectifying tower; 012. a super rectifying tower; 013. an adsorption tower I; 014. a rotary valve; 015. adsorption tower II; 016. a rectifying tower I; 017. rectifying column II.

Detailed Description

It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.

As analyzed in the background of the application, the problems of low purity, low yield and high running cost of separating 1-hexene from fischer-tropsch oil in the prior art are solved by the application, which provides a method and a device for separating 1-hexene from fischer-tropsch oil.

According to an exemplary embodiment of the present application, there is provided a process for separating 1-hexene from a fischer-tropsch oil, the process comprising: s1, rectifying and cutting Fischer-Tropsch synthetic oil to obtain a C ₆ fraction; step S2, carrying out alkali washing on the C ₆ fraction, neutralizing, and separating out an oil phase to obtain a deacidified C ₆ fraction; step S3, washing the deacidified C ₆ fraction with water and drying to obtain a dried C ₆ fraction; s4, feeding the dried C ₆ fraction into an extraction tower, and removing oxides in the dried C ₆ fraction and an extracting agent in a countercurrent way to obtain a deoxidized C ₆ fraction; s5, introducing the deoxidized C ₆ fraction into a selective hydrogenation reactor, and converting the diolefins in the deoxidized C ₆ fraction into monoolefins to obtain a hydrogenated C ₆ fraction; s6, inputting the hydrogenated C ₆ fraction into an etherification rectifying tower, enabling tertiary carbon olefins in the hydrogenated C ₆ fraction to carry out etherification reaction with low carbon alcohols under the action of a catalyst, and separating an etherification product to obtain a C ₆ fraction with tertiary carbon olefins removed; s7, removing internal olefins from the C ₆ fraction from which tertiary carbon olefins are removed through rectification separation to obtain a 1-hexene crude fraction; and S8, carrying out alkane-alkene separation on the 1-hexene crude fraction through a simulated moving bed to obtain 1-hexene.

The application obtains high-purity 1-hexene through steps of alkali washing, water washing, drying, deacidification, deoxidization, selective hydrogenation, etherification, alkane-alkene separation and the like after Fischer-Tropsch synthetic oil is cut, wherein the selective hydrogenation can convert diene which is difficult to separate into mono-alkene, and the mono-alkene is removed through rectification separation, and finally alkane-alkene separation is carried out through a simulated moving bed, so that the high-purity 1-hexene is obtained. The method is particularly suitable for separating 1-hexene from the intermediate-temperature Fischer-Tropsch synthetic oil by the iron-based catalyst, and has higher efficiency. Compared with the traditional separation process, the method has the advantages of high product purity, high yield, short separation flow, simple process flow, less equipment investment, simple operation, low energy consumption and the like.

The rectification cutting method of the fischer-tropsch oil in the step S1 may be according to the prior art, and in some exemplary embodiments of the present application, the step S1 includes: step S11, enabling Fischer-Tropsch synthesis oil to enter a first rectifying tower to obtain a mixed fraction containing a C ₆₊ fraction and a C ₆ fraction; step S12, the mixed fraction enters a second rectifying tower, and a C ₆ fraction is obtained at the top of the tower; preferably, the first rectification column and/or the second rectification column is fed at a mid-column position. illustratively, fischer-Tropsch oil products (the content of C ₄ -C ₁₂,C_6- fraction is 2-20%, the content of C ₆ fraction is 10-20% and the content of C ₆₊ fraction is 50-80%) are fed into the middle part of a cutting tower 1, Cutting from the top of the column to obtain a C _6- fraction, and obtaining a C ₆₊ fraction (containing a C ₆ fraction) from the bottom of the column; The C ₆₊ fraction (C ₆ fraction) from the bottom of the cutting tower 1 enters the cutting tower 2 from the middle part of the tower, the C ₆ fraction is obtained from the top of the tower, the 1-hexene content is 50-70%, and the C ₆₊ fraction (without the C ₆ fraction) is obtained from the tower bottom. Preferably, the first rectifying tower has tray number of 20-60, reflux ratio of 5-15, tower top temperature of 30-45 deg.c and tower bottom temperature of 60-100 deg.c; preferably, the theoretical plate number of the second rectifying tower is 20-60, the reflux ratio is 5-15, the tower top temperature is 50-70 ℃, and the tower bottom temperature is 110-130 ℃.

And step S2, neutralizing the C ₆ fraction with alkali liquor to remove acidic substances in the fraction. In some exemplary embodiments of the present application, step S2 includes: the C ₆ fraction is input into an alkaline washing tower and mixed with alkaline liquor, and the alkaline liquor can be better mixed with the C ₆ fraction in the tower, so that the deacidification effect is better. In some embodiments, the cut C ₆ fraction is fed to a caustic wash tower, mixed with caustic solution, and the acid value of the C ₆ fraction is 0.2-5mg/g (KOH) before caustic washing, and the acid value of the C ₆ fraction is less than 0.05mg/g (KOH) after caustic washing. Preferably, the alkali liquor comprises any one or more of sodium hydroxide solution, potassium hydroxide solution and potassium carbonate solution, wherein the sodium hydroxide solution is more preferably adopted, and the acid value of the fraction obtained after treatment is lower, the dosage is less, the price is low, the sources are rich, and the popularization and the application are convenient. Preferably, the concentration of the lye is 5 to 10wt%. Preferably, the volume ratio of the alkali liquor to the C ₆ fraction is 4-8. After the neutralization reaction is completed, the oil phase enters the subsequent water washing step.

In the step S3, the alkali or salt remaining in the deacidified C ₆ fraction is washed away by water, so that on one hand, the purity of the fraction is improved, on the other hand, the alkali or salt is prevented from remaining in the fraction, which affects the subsequent etherification reaction, reduces the activity of the etherification catalyst, and affects the separation effect, and in some embodiments of the present application, the step S3 includes: and (3) inputting the deacidified C ₆ fraction into a water washing tower, washing to be neutral, enabling the washed fraction to enter an oil-water separator, separating an oil phase for drying treatment, and preventing the activity of a catalyst in a subsequent working section from being reduced or even deactivated and prolonging the service life. In some embodiments of the application, the separated oil phase has a water content of greater than 1000ppm, and the washed C ₆ fraction is fed to a dryer to remove water from the C ₆ fraction to a water content of less than 100ppm. Preferably, the drying treatment is drying by using a drying agent, wherein the drying agent comprises silica gel, alumina, a 3A molecular sieve and a 5A molecular sieve. Preferably, the moisture content of the dried C ₆ fraction is less than 100ppm.

Step S4 above, removing the oxides from the liquid-liquid extraction column by countercurrent flow with an extractant, wherein in some embodiments of the present application, the extractant comprises any one or more of methanol, ethanol, acetonitrile, dimethyl sulfoxide, azamethylpyrrolidone, N, N-dimethylformamide, and ethylene glycol; among them, methanol is preferable, and is inexpensive and has a good extraction effect. The volume ratio of the extractant to the C ₆ fraction with tertiary carbon olefin removed is 1-8:1 (i.e. the catalyst-oil ratio), and the operation temperature is 30-50 ℃. In some embodiments, in the liquid-liquid extraction tower, the dry C ₆ fraction is reversely contacted with the extractant, sufficient space is reserved between the tower top light component section and the tower kettle recombination section in the extraction tower, sufficient residence time of liquid phase is ensured, the tower top light component section is provided with a boundary gauge, fischer-Tropsch oil is fed from the bottom of the tower body and is provided with a liquid phase distributor, the extractant is fed from the top of the tower body and is provided with the liquid phase distributor, the middle position of the tower body is provided with high-efficiency filler, and the top section and the bottom section of the filler are provided with porcelain balls and silk screens.

In some preferred embodiments of the present application, step S4 further comprises: deoxidizing the C ₆ fraction in an adsorption tower, wherein the adsorbent selected in the adsorption tower is preferably one or more of silica gel, clay, diatomite, alumina, activated carbon, 3A molecular sieve, 5A molecular sieve, 13X molecular sieve, resin and silicate. In some embodiments, the deoxidizing adsorption tower is a packed tower, the Fischer-Tropsch oil after extraction is fed from the top of the adsorption tower, a liquid phase distributor is arranged on the top of the adsorption tower, the C ₆ fraction after deep deoxidization is absorbed by the adsorption tower and is extracted from the bottom of the adsorption tower, an adsorbent is arranged in the middle of the adsorption tower, and porcelain balls and silk screens are arranged at the top and the bottom of the adsorption tower.

In some typical embodiments of the application, the dry C ₆ fraction is fed into a liquid-liquid extraction tower, the oxide content is 1-3 wt%, most of the oxide in the C ₆ fraction is removed by the action of the dry C ₆ fraction and the extractant, the oxide content is less than 1000ppm, the extractant containing the oxide is fed into an extractant recovery tower, and after regeneration, the extractant is returned to the liquid-liquid extraction tower and an etherification rectifying tower; the C ₆ fraction containing a small amount of oxide enters an adsorption tower to be subjected to deep deoxidation, and the oxide content is less than 100ppm. Preferably, the theoretical plate number of the extractant recovery tower is 20-50, the reflux ratio is 2-8, the tower top temperature is 50-70 ℃, the tower bottom temperature is 100-150 ℃, and the feeding position is the position in the tower.

Through the treatments of the steps S1 to S4, the impurities contained in the C ₆ fraction mainly include alkane, internal alkene, diene, etc., and there are technical schemes for removing tertiary alkane through etherification reaction and other alkane through simulated moving bed in the prior art, but these schemes are difficult to effectively remove diene in the C ₆ fraction, and researchers of the present application find that substances generated by polymerization of diene are easily attached to the catalyst during etherification reaction, resulting in reduced catalyst activity and even losing catalytic effect, which seriously affects catalytic efficiency of the etherification reaction. Because of the very close nature of diolefins to 1-hexene, separation by conventional methods is difficult and the purity of 1-hexene is limited. The application converts the diolefins in the C ₆ fraction into internal olefins such as 2-hexene and the like by selectively hydrogenating the diolefins, and then separates and removes the internal olefins by subsequent rectification. In some preferred embodiments of the application, in step S5, the catalyst for selective hydrogenation is palladium, which has a high selectivity and conversion to diolefins. Preferably, the temperature of the selective hydrogenation is 110-120 ℃, and the hydrogen partial pressure is 0.5-1.0 MPa. In some embodiments, the C ₆ fraction deeply deoxygenated by the adsorption column has a diolefin content of 0.05-0.5% and is fed to a selective hydrogenation reactor to convert diolefins in the C ₆ fraction to monoolefins having a diolefin content of less than 10ppm; and the C ₆ fraction subjected to selective hydrogenation is subjected to etherification reaction to remove tertiary alkane, so that the tertiary alkane removal efficiency is effectively improved.

The tertiary carbon olefin in the C ₆ fraction after selective hydrogenation is separated through etherification reaction in the step S6, the catalyst and the low carbon alcohol used can be selected in the prior art, and preferably, the catalyst in the step S4 is any one or more of strong acid cation exchange resin, heteropolyacid catalyst and molecular sieve catalyst; the strongly acidic cation exchange resin is preferably Amberlyst series products, D007, S30, or the like. In some preferred embodiments of the present application, the upper, middle and lower sections of the rectification column are filled with catalyst, respectively, and the catalyst may be packed in a packed form on the bed. More preferably, 2-15 theoretical plates are arranged between the tower top and the upper section catalyst bed layer, between the two adjacent sections catalyst bed layers and between the lower section catalyst bed layer and the tower kettle, so that the etherification and separation effects are further improved; preferably, the C ₆ fraction and the low-carbon alcohol are fed below the lower catalyst bed after selective hydrogenation, so that the catalyst of each bed is fully utilized, and the catalytic and separation effects are improved. Preferably, the lower alcohol is any one or more of methanol, ethanol and propanol; particularly, methanol is selected as low-carbon alcohol to carry out etherification reaction with tertiary carbon olefins in the C ₆ fraction, the effect improvement is more remarkable, the etherification degree of the tertiary carbon olefins is high, the separation from 1-hexene is convenient, the methanol is low in cost and easy to obtain, and the cost is controlled. Preferably, the molar ratio of the lower alcohol to the tertiary carbon olefin in the C ₆ fraction after the selective hydrogenation is 2-6:1.

Preferably, the theoretical plate number of the etherification rectifying tower is 30-80, the reflux ratio is 5-15, the tower top temperature is 50-70 ℃, the tower bottom temperature is 80-150 ℃, and preferably, the feeding position of the low-carbon alcohol and the C ₆ fraction after selective hydrogenation is 20-60 th plate. In some typical embodiments of the application, the mixture of C ₆ fraction and low-carbon alcohol after selective hydrogenation enters an etherification reaction rectifying tower from the bottom of the etherification reactor rectifying tower, wherein tertiary carbon olefin content is 0.1-1.0%, tertiary carbon olefin and low-carbon alcohol are subjected to etherification reaction under the action of a catalyst, the generated ether substances are removed from the etherification reaction rectifying tower, and C ₆ fraction with tertiary carbon olefin removed is obtained at the tower top, and the tertiary carbon olefin content is less than 0.01%.

And (3) feeding the C ₆ fraction with the tertiary carbon olefin removed into a rectifying tower for rectifying, and separating 1-hexene from internal olefin in the rectifying tower to obtain a 1-hexene crude fraction, wherein the 1-hexene content in the 1-hexene crude fraction is 55-70%, and the n-hexane content is 30-45%.

In step S8, the separation of the alkane and alkene is carried out by a simulated moving bed, and the normal hexane in the 1-hexene crude fraction is separated and removed. Illustratively, the alkylen separation is performed by a simulated moving bed using the following implementation scheme: c ₆ fraction from which internal olefins are removed enters an alkane-alkene separation system, enters an adsorption tower I through a rotary valve, olefin and part of alkane are adsorbed on an adsorbent, alkane and a desorption agent enter a rotary valve to enter raffinate, the olefin and part of alkane are pressurized to an adsorption tower II through a pump, alkane in the adsorption tower II is firstly resolved, discharged, then resolved olefin and desorption agent enter the rotary valve, and the extract is entered. The raffinate enters a rectifying tower 1 to separate n-hexane from a desorbing agent, the top of the rectifying tower is the desorbing agent, the desorbing agent returns to a rotary valve to be reused, the bottom of the rectifying tower is n-hexane, the extract enters a rectifying tower 2 to separate 1-hexene from the desorbing agent, the top of the rectifying tower is the desorbing agent, the desorbing agent returns to the rotary valve to be reused, and the bottom of the rectifying tower obtains 1-hexene as a separated product, wherein the purity of the 1-hexene is not lower than 99%, and the yield is not lower than 85%. Preferably, the operating temperature of the adsorption tower I and the adsorption tower II is 60-150 ℃, the operating pressure is 0.45-0.55 MPa, and the catalyst-to-oil ratio (i.e. the volume ratio of the adsorbent to the 1-hexene crude fraction) is 0.5-4:1.

The adsorbent and desorbent of the simulated moving bed may be selected from the prior art, preferably the adsorbent of the simulated moving bed is selected from any one or more of 5A molecular sieve, 13X zeolite, LTA type zeolite and its modified molecular sieve; preferably, the desorbent of the simulated moving bed is any one or more of alkane and alkene, more preferably, the desorbent is a mixture of alkane and alkene, and the content of alkene is 40-60%.

The method for separating 1-hexene is suitable for various Fischer-Tropsch oils in principle, and the steps S2 and S3 can remove acidic substances very efficiently, so that the effect of separating 1-hexene by taking oil products of Fischer-Tropsch synthesis at medium temperature (namely 240-280 ℃) of the iron-based catalyst as raw materials is obviously improved.

According to another exemplary embodiment of the present application, there is provided an apparatus for separating 1-hexene from fischer-tropsch synthesis oil, characterized in that the apparatus comprises a rectification cutting unit, a deacidification unit, a water washing and drying unit, a deoxidization unit, a selective hydrogenation reaction unit, an etherification unit, a rectification unit and an alkylen separation unit, which are sequentially connected; the rectification cutting unit is used for rectifying and cutting the Fischer-Tropsch synthetic oil to obtain a C ₆ fraction; the deacidification unit is used for carrying out alkali washing on the C ₆ fraction, neutralizing, and separating out an oil phase to obtain a deacidified C ₆ fraction; the washing and drying unit is used for washing and drying the deacidified C ₆ fraction to obtain a dried C ₆ fraction; the deoxidizing unit is used for removing oxides in the dry C ₆ fraction, and deeply deoxidizing by an adsorption process to obtain deoxidized C ₆ fraction; the selective hydrogenation reaction unit is used for carrying out selective hydrogenation reaction on the deoxidized C ₆ fraction to obtain a C ₆ fraction after selective hydrogenation; the etherification unit is used for carrying out etherification reaction on tertiary carbon olefins in the hydrogenated C ₆ fraction and removing the tertiary carbon olefins to obtain a C ₆ fraction with tertiary carbon olefins removed; the rectification unit is used for rectifying and removing internal olefins in the C ₆ fraction from which tertiary carbon olefins are removed to obtain a 1-hexene crude fraction; the alkane-alkene separation unit is a simulated moving bed and is used for separating alkane from alkene to obtain 1-hexene. The device for separating 1-hexene from Fischer-Tropsch synthetic oil has the advantages of high product purity, high product yield and the like.

According to yet another exemplary embodiment of the present application, there is provided a 1-hexene product prepared by any one of the methods described above. The 1-hexene product has the advantages of higher purity and lower cost due to the adoption of the preparation method, and meets the requirements of polymerization grade 1-hexene.

The advantageous effects that can be achieved by the present application will be further described below with reference to examples and comparative examples.

The example of the present application separates 1-hexene according to the schematic of the process flow shown in figure 1.

Example 1

(1) Feeding the iron-based catalyst medium temperature Fischer-Tropsch synthesis oil product stream 01 into a first rectifying and cutting tower 001, wherein the theoretical plate number of the first rectifying and cutting tower 001 is 60, the reflux ratio is 5:1, the tower top temperature is 35 ℃, the tower bottom temperature is 90 ℃, the tower pressure is normal pressure, 30 plates are fed, C _6- fractions are obtained by cutting from the tower top, and C ₆₊ fractions (containing C ₆ fractions) are obtained from the tower bottom; the C ₆₊ fraction (containing C ₆ fraction) from the bottom of the first rectifying and cutting tower 001 enters a second rectifying and cutting tower 002 from the middle part of the tower, the theoretical plate number is 60, the reflux ratio is 5:1, the tower top temperature is 63 ℃, the tower bottom temperature is 120 ℃, the tower pressure is normal pressure, 30 pieces of tower plates are fed, the C ₆ fraction stream 02 is obtained from the tower top, and the C ₆₊ fraction (without containing C ₆ fraction) is obtained from the tower bottom.

(2) C ₆ fraction flow 02 from the top of the second rectifying cutting tower 002 enters an alkaline washing tower 003, is mixed with 8% NaOH solution, the volume of alkaline liquor and C ₆ distillate oil is 2:1, and acidic substances in the C ₆ fraction are neutralized to obtain deacidified C ₆ fraction flow 03; enabling the deacidified C ₆ fraction material flow 03 to enter a water washing tower 004, washing the fraction to be nearly neutral, entering an oil-water separator, performing the oil-water separator, and separating out an upper oil phase to obtain a water washing C ₆ fraction 04 material flow; the water washed C ₆ cut stream 04 was fed to a drying column 006 containing 5A molecular sieves and dried to give a dried C ₆ cut stream 05, the water content of the dried C ₆ cut stream 05 being 47ppm.

(3) The dry C ₆ fraction stream 05 enters an extraction rectifying tower 007, the catalyst-to-oil ratio is 5, most of oxides in the C ₆ fraction are removed by the action of methanol at normal temperature, the methanol containing the oxides enters an extractant recovery tower 008, the tower plate number is 30, the reflux ratio is 4, the tower top temperature is 61-63 ℃, and the tower bottom temperature is 100-105 ℃. After regeneration, the methanol is returned to the extractive distillation column 007 and the etherification reaction distillation column 011; the extracted deoxidized C ₆ fraction stream 06 containing a small amount of methanol enters a deoxidizing adsorption tower 009 for deep deoxidization, and the adsorbent 13X molecular sieve with oxide content of 5ppm is obtained to obtain an adsorbed deoxidized C ₆ fraction stream 07.

(4) The adsorption deoxidized C ₆ fraction flow 07 enters a selective hydrogenation reactor 010, the catalyst is palladium, the reaction temperature is 115 ℃, the diolefin in the C ₆ fraction is selectively hydrogenated and converted into the monoolefin, the C ₆ fraction flow 08 after selective hydrogenation is obtained, and the diolefin content in the fraction after hydrogenation is 4ppm.

(5) The mixed material of C ₆ fraction 08 and methanol after selective hydrogenation enters an etherification reaction rectifying tower 011 from the bottom of the etherification reactor rectifying tower, theoretical plates of the etherification reaction rectifying tower 011 are 30, catalysts are filled on the 10 th, 15 th and 20 th plates, the 21 st plates are fed, the tower top temperature is 50-55 ℃, the tower bottom temperature is 100-105 ℃, under the action of a strong acid cation exchange resin Amberlyst35 catalyst, the mole ratio of the methanol to tertiary carbon olefin is 5:1, the tertiary carbon olefin and the methanol are subjected to etherification reaction, the generated ethers are removed from the etherification reaction rectifying tower 011, and the C ₆ fraction 09 with tertiary carbon olefin removed is obtained from the tower top.

(6) The C ₆ fraction flow 09 with tertiary carbon olefin removed enters a super rectifying tower 012, the pressure is normal, the temperature at the top of the tower is 59-63 ℃, the reflux ratio is 20:4, and the separation of internal olefin is realized, so that a 1-hexene crude fraction flow 10 is obtained.

(7) The 1-hexene crude fraction stream 10, which has been freed of internal olefins, enters an alkane-alkene separation system. The adsorption temperature of the adsorption tower is 50 ℃, the adsorption pressure is 0.4MPa, the crude fraction flow 10 of the catalyst-to-oil ratio of 2:1, 1-hexene enters the adsorption tower I013 through the rotary valve 014, olefin and part of alkane are adsorbed on the adsorbent, the alkane and the desorbent enter the rotary valve 014 to enter the raffinate, the olefin and part of alkane are pressurized to the adsorption tower II 015 through a pump, the alkane is firstly resolved in the adsorption tower II, discharged, then the resolved olefin and the desorbent enter the rotary valve 014, and the raffinate is entered. The raffinate enters a rectifying tower I016 to separate normal hexane and a desorbent to obtain a normal hexane stream 011, the top of the rectifying tower I016 is the desorbent, the normal hexane is returned to a rotary valve 014 for repeated use, the bottom of the rectifying tower is normal hexane, the extract enters the rectifying tower I017 to separate 1-hexene from the desorbent, the top of the rectifying tower is the desorbent, the normal hexane and the desorbent are returned to the rotary valve 014 for repeated use, and the bottom of the rectifying tower is provided with a 1-hexene product stream 012, wherein the 1-hexene purity is 99.2%, and the yield is 90%.

The principal component analysis of each stream is shown in Table 1 below, where "before 1-hexene" in Table 1 indicates the total content of compounds having a boiling point lower than 1-hexene, and the content "-" indicates that no detection was performed, and the same applies.

TABLE 1

Example 2

(1) Feeding the iron-based catalyst medium temperature Fischer-Tropsch synthesis oil product stream 01 into a first rectifying and cutting tower 001, wherein the theoretical plate number of the first rectifying and cutting tower 001 is 60, the reflux ratio is 6:1, the tower top temperature is 35 ℃, the tower bottom temperature is 90 ℃, the tower pressure is normal pressure, 30 plates are fed, C _6- fractions are obtained by cutting from the tower top, and C ₆₊ fractions (containing C ₆ fractions) are obtained from the tower bottom; the C ₆₊ fraction (containing C ₆ fraction) from the bottom of the first rectifying and cutting tower 001 enters a second rectifying and cutting tower 002 from the middle part of the tower, the theoretical plate number is 60, the reflux ratio is 6:1, the tower top temperature is 62 ℃, the tower bottom temperature is 119 ℃, the tower pressure is normal pressure, 30 pieces of tower plates are fed, the C ₆ fraction stream 02 is obtained from the tower top, and the C ₆₊ fraction (without containing C ₆ fraction) is obtained from the tower bottom.

(2) C ₆ fraction flow 02 from the top of the second rectifying cutting tower 002 enters an alkaline washing tower 003, is mixed with 10% NaOH solution, the volume of alkaline liquor and C ₆ distillate oil is 4:1, and acidic substances in the C ₆ fraction are neutralized to obtain deacidified C ₆ fraction flow 03; enabling the deacidified C ₆ fraction material flow 03 to enter a water washing tower 004, washing the fraction to be nearly neutral, entering an oil-water separator, performing the oil-water separator, and separating out an upper oil phase to obtain a water washing C ₆ fraction 04 material flow; the water washed C ₆ cut stream 04 was fed to a drying column 006 containing 5A molecular sieves and dried to give a dried C ₆ cut stream 05, the water content of the dried C ₆ cut stream 05 being 40ppm.

(3) The dry C ₆ fraction stream 05 enters an extraction rectifying tower 007, the catalyst-to-oil ratio is 8, most of oxides in the C ₆ fraction are removed by the action of methanol at normal temperature, the methanol containing the oxides enters an extractant recovery tower 008, the tower plate number is 30, the reflux ratio is 4, the tower top temperature is 61-63 ℃, and the tower bottom temperature is 100-105 ℃. After regeneration, the methanol is returned to the extractive distillation column 007 and the etherification reaction distillation column 011; the extracted deoxidized C ₆ fraction stream 06 containing a small amount of methanol enters a deoxidizing adsorption tower 009 for deep deoxidization, and the adsorbent silica gel with the oxide content of 30ppm is obtained to obtain an adsorbed deoxidized C ₆ fraction stream 07.

(4) The adsorption deoxidized C ₆ fraction flow 07 enters a selective hydrogenation reactor 010, the catalyst is palladium, the reaction temperature is 110 ℃, and the diolefin in the C ₆ fraction is selectively hydrogenated and converted into the monoolefin, so as to obtain a C ₆ fraction flow 08 after selective hydrogenation.

(5) The mixed material of C ₆ fraction 08 and methanol after selective hydrogenation enters an etherification reaction rectifying tower 011 from the bottom of the etherification reactor rectifying tower, theoretical plates of the etherification reaction rectifying tower 011 are 30, catalysts are filled on the 10 th, 15 th and 20 th plates, the 21 st plates are fed, the tower top temperature is 54-58 ℃, the tower bottom temperature is 102-107 ℃, under the action of a strong acid cation exchange resin D007 catalyst, the mole ratio of methanol to tertiary carbon olefin is 5:1, the tertiary carbon olefin and the methanol are subjected to etherification reaction, the generated ethers are removed from the etherification reaction rectifying tower 011, and the C ₆ fraction 09 with tertiary carbon olefin removed is obtained from the tower top.

(6) The C ₆ fraction flow 09 with tertiary carbon olefin removed enters a super rectifying tower 012, the pressure is normal pressure, the temperature at the top of the tower is 59-63 ℃, the reflux ratio is 20:4, and the separation of internal olefin is realized, so that a 1-hexene crude fraction flow 10 is obtained.

(7) The 1-hexene crude fraction stream 10, which has been freed of internal olefins, enters an alkane-alkene separation system. The adsorption temperature of the adsorption tower is 50 ℃, the adsorption pressure is 0.4MPa, the crude fraction flow 10 of the catalyst-to-oil ratio of 2:1, 1-hexene enters the adsorption tower I013 through the rotary valve 014, olefin and part of alkane are adsorbed on the adsorbent, the alkane and the desorbent enter the rotary valve 014 to enter the raffinate, the olefin and part of alkane are pressurized to the adsorption tower II 015 through a pump, the alkane is firstly resolved in the adsorption tower II, discharged, then the resolved olefin and the desorbent enter the rotary valve 014, and the raffinate is entered. The raffinate enters a rectifying tower I016 to separate normal hexane and a desorbent to obtain a normal hexane stream 011, the top of the rectifying tower I016 is the desorbent, the normal hexane is returned to a rotary valve 014 for repeated use, the bottom of the rectifying tower is normal hexane, the extract enters the rectifying tower I017 to separate 1-hexene from the desorbent, the top of the rectifying tower is the desorbent, the normal hexane and the desorbent are returned to the rotary valve 014 for repeated use, and the bottom of the rectifying tower is provided with a 1-hexene product stream 012, wherein the 1-hexene purity is 99.5%, and the yield is 91%.

The principal components of each stream were analyzed as follows in table 2.

TABLE 2

Comparative example 1

(1) Feeding the iron-based catalyst medium-temperature Fischer-Tropsch synthesis oil product stream 01 into a first rectifying and cutting tower, wherein the theoretical plate number of the first rectifying and cutting tower is 60, the reflux ratio is 5:1, the tower top temperature is 35 ℃, the tower bottom temperature is 90 ℃, the tower pressure is normal pressure, 30 plates are fed, C _6- fractions are obtained by cutting from the tower top, and C ₆₊ fractions (containing C ₆ fractions) are obtained from the tower bottom; c ₆₊ fraction (containing C ₆ fraction) from the bottom of the first rectifying and cutting tower enters the second rectifying and cutting tower from the middle part of the tower, the theoretical plate number is 60, the reflux ratio is 5:1, the tower top temperature is 63 ℃, the tower bottom temperature is 120 ℃, the tower pressure is normal pressure, 30 plates are fed, C ₆ fraction flow 02 is obtained from the tower top, and C ₆₊ fraction (without C ₆ fraction) is obtained from the tower bottom.

(2) C ₆ fraction 02 from the top of the second rectifying cutting tower enters an alkaline washing tower, is mixed with 8% NaOH solution, the volume of alkali liquor and C ₆ distillate is 2:1, and acidic substances in the C ₆ fraction are neutralized to obtain deacidified C ₆ fraction stream 03; enabling the deacidified C ₆ fraction material flow 03 to enter a water washing tower, washing the C ₆ fraction to be nearly neutral, entering an oil-water separator, performing the oil-water separator, separating out an upper oil phase, namely obtaining a water washing C ₆ fraction 04 material flow, and performing subsequent treatment.

(3) The water-washed C ₆ fraction 04 material flow separated from the oil-water separator enters an extraction rectifying tower, the catalyst-oil ratio is 5, most of oxides in the C ₆ fraction are removed under the action of methanol at normal temperature, the methanol containing the oxides enters a methanol recovery tower, the tower plate number is 30, the reflux ratio is 4, the tower top temperature is 61-63 ℃, and the methanol returns to the extraction rectifying tower and the etherification rectifying tower after the tower bottom temperature is 100-105 ℃; the extracted deoxidized C ₆ fraction 06 containing a small amount of methanol enters an adsorption tower to carry out deep deoxidization, thus obtaining an adsorbed deoxidized C ₆ fraction flow 07 with the oxide content of 500ppm.

(4) The mixed material of the adsorption deoxidized C ₆ fraction material flow 07 and the methanol enters an etherification reaction rectifying tower from the bottom of the etherification reactor rectifying tower, 30 theoretical plates of the etherification reaction rectifying tower are filled with catalysts on 10, 15 and 20 plates, 21 plates are fed, the tower top temperature is 50-55 ℃, the tower bottom temperature is 100-105 ℃, the mole ratio of the methanol to the tertiary carbon olefin is 5:1 under the action of a strong acid cation exchange resin A35 catalyst, the tertiary carbon olefin and the methanol are subjected to etherification reaction, the produced ethers are removed from the etherification reaction rectifying tower, and the C ₆ fraction material flow 09 with the tertiary carbon olefin removed is obtained from the tower top.

(5) Enabling a C ₆ fraction flow 09 with tertiary carbon olefins removed to enter an alkane-alkene separation system, enabling the adsorption temperature of the adsorption tower to be 50 ℃, the adsorption pressure to be 0.4MPa, the catalyst-to-oil ratio to be 2:1, enabling a C ₆ fraction subjected to deep deoxidation to enter the adsorption tower I through a rotary valve, enabling the olefins and part of alkanes to be adsorbed on an adsorbent, enabling the alkanes and the desorption agents to enter a raffinate through the rotary valve, pressurizing the olefins and part of alkanes to an adsorption tower II through a pump, enabling the alkanes to be resolved firstly in the adsorption tower II, discharging, then enabling the resolved olefins and the desorption agents to enter the rotary valve, and enabling the alkanes to enter an extracting solution. The raffinate enters a rectifying tower 1 to separate normal hexane and a desorbent to obtain a normal hexane stream 011, the top of the rectifying tower is the desorbent, the normal hexane is returned to a rotary valve for repeated use, the extract enters a rectifying tower 2 to separate 1-hexene from the desorbent, the top of the rectifying tower is the desorbent, the n-hexane is returned to the rotary valve for repeated use, and the 1-hexene product stream 012 is obtained at the bottom of the rectifying tower, wherein the 1-hexene purity is 87% and the yield is 88%.

The principal components of each stream were analyzed as follows in table 3.

TABLE 3 Table 3

Comparative example 2

(1) Feeding the iron-based catalyst medium-temperature Fischer-Tropsch synthesis oil product stream 01 into a first rectifying and cutting tower, wherein the theoretical plate number of the first rectifying and cutting tower is 60, the reflux ratio is 5:1, the tower top temperature is 35 ℃, the tower bottom temperature is 90 ℃, the tower pressure is normal pressure, 30 plates are fed, C6-fraction is obtained by cutting from the tower top, and C ₆₊ fraction (containing C ₆ fraction) is obtained at the tower bottom; the C ₆₊ fraction (containing C ₆ fraction) from the bottom of the first rectifying and cutting tower enters the second rectifying and cutting tower from the middle part of the tower, the theoretical plate number is 60, the reflux ratio is 5:1, the tower top temperature is 63 ℃, the tower bottom temperature is 120 ℃, the tower pressure is normal pressure, 30 pieces of tower plates are fed, the C ₆ fraction material flow 02 is obtained from the tower top, and the C ₆₊ fraction (without containing C ₆ fraction) is obtained from the tower bottom.

(2) Introducing the C ₆ fraction from the top of the second rectifying and cutting tower into an alkaline washing tower, mixing with 10% NaOH solution, wherein the volume of alkaline solution and C ₆ distillate is 4:1, and neutralizing acidic substances in the C ₆ fraction to obtain deacidified C ₆ fraction stream 03; enabling deacidified C ₆ fraction stream 03 to enter a water washing tower from alkaline washing tower C ₆ distillate, washing C ₆ fraction to be nearly neutral, entering an oil-water separator, performing the oil-water separator, enabling upper-layer oil phase C ₆ fraction to enter a 5A molecular sieve dryer for drying, and obtaining dry C ₆ fraction stream 05 after drying, wherein the water content in the fraction is 50ppm.

(3) The dry C ₆ fraction material flow 05 enters an extraction rectifying tower, the catalyst-to-oil ratio is 5, most of oxides in the C ₆ fraction are removed by the action of the dry C ₆ fraction material flow and the methanol at normal temperature, the methanol containing the oxides enters a methanol recovery tower, the tower plate number is 30, the reflux ratio is 4, the tower top temperature is 61-63 ℃, the tower bottom temperature is 100-105 ℃, and the methanol returns to the extraction rectifying tower and the etherification rectifying tower after being regenerated; the extracted deoxidized C ₆ fraction 06 containing a small amount of methanol enters an adsorption tower to carry out deep deoxidization, thus obtaining an adsorbed deoxidized C ₆ fraction flow 07 with the oxide content of 30ppm.

(4) The mixed material of the adsorption deoxidized C ₆ fraction material 07 and the methanol enters an etherification reaction rectifying tower from the bottom of the rectifying tower of the etherification reactor, 30 theoretical plates of the etherification reaction rectifying tower are filled with catalysts on 10, 15 and 20 plates, 21 plates are fed, the tower top temperature is 50-55 ℃, the tower bottom temperature is 100-105 ℃, the mol ratio of the methanol to the tertiary carbon olefin is 5:1 under the action of a strong acid cation exchange resin Amberlyst catalyst, the tertiary carbon olefin and the methanol are subjected to etherification reaction, the produced ethers are removed from the etherification reaction rectifying tower, and the C ₆ fraction material 09 with the tertiary carbon olefin removed is obtained from the tower top.

(5) C ₆ fraction flow 09 with tertiary carbon olefins removed enters an alkane-alkene separation system, the adsorption temperature of the adsorption tower is 50 ℃, the adsorption pressure is 0.4MPa, the catalyst-to-oil ratio is 2:1, the deeply deoxygenated C ₆ fraction enters an adsorption tower I through a rotary valve, the olefins and part of the paraffins are adsorbed on an adsorbent, the paraffins and the desorption agent enter a rotary valve to enter raffinate, the olefins and part of the paraffins are pressurized to an adsorption tower II through a pump, the paraffins are firstly resolved in the adsorption tower II, the paraffins are discharged, then the resolved olefins and the desorption agent enter the rotary valve, and the extract is entered. The raffinate enters a rectifying tower 1 to separate normal hexane and a desorbent to obtain a normal hexane material flow 011, the top of the rectifying tower is the desorbent, the normal hexane is returned to a rotary valve for repeated use, the extract enters a rectifying tower 2 to separate 1-hexene from the desorbent, the top of the rectifying tower is the desorbent, the n-hexane material flow is returned to the rotary valve for repeated use, and the 1-hexene product material flow 012 is obtained at the bottom of the rectifying tower, wherein the 1-hexene purity is 90% and the yield is 85%.

The principal components of each stream were analyzed as follows in table 4.

TABLE 4 Table 4

From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the 1-hexene has the advantages of high purity, high product yield, simple process flow, less equipment investment, simple operation, low energy consumption and the like.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for separating 1-hexene from fischer-tropsch oil, comprising:

S1, rectifying and cutting Fischer-Tropsch synthetic oil to obtain a C ₆ fraction; the Fischer-Tropsch synthesis oil is an oil product of the middle-temperature Fischer-Tropsch synthesis of an iron-based catalyst;

Step S2, alkali washing and neutralizing the C ₆ fraction, and separating out an oil phase to obtain a deacidified C ₆ fraction;

Step S3, washing the deacidified C ₆ fraction with water and drying to obtain a dried C ₆ fraction;

S4, feeding the dried C ₆ fraction into an extraction tower, and removing oxides in the dried C ₆ fraction and an extracting agent in a countercurrent way to obtain a deoxidized C ₆ fraction, wherein the extracting agent comprises any one or more of methanol, ethanol, acetonitrile, dimethyl sulfoxide, azamethylpyrrolidone, N, N-dimethylformamide and ethylene glycol; introducing the deoxidized C ₆ fraction into an adsorption tower for deoxidization;

Step S5, feeding the C ₆ fraction obtained in the step S4 into a selective hydrogenation reactor, and converting the diolefins in the deoxidized C ₆ fraction into monoolefins to obtain a hydrogenated C ₆ fraction; the catalyst for selective hydrogenation is palladium; the reaction temperature of the selective hydrogenation is 110-120 ℃;

S6, inputting the hydrogenated C ₆ fraction into an etherification rectifying tower, enabling tertiary carbon olefins in the hydrogenated C ₆ fraction to carry out etherification reaction with low carbon alcohols under the action of a catalyst, and separating an etherification product to obtain a C ₆ fraction without tertiary carbon olefins; the catalyst is any one or more of strong acid cation exchange resin, heteropolyacid catalyst and molecular sieve catalyst;

S7, rectifying and separating the C ₆ fraction from which the tertiary carbon olefins are removed to remove internal olefins, so as to obtain a 1-hexene crude fraction;

And S8, carrying out alkane-alkene separation on the 1-hexene crude fraction through a simulated moving bed to obtain 1-hexene.

2. The method according to claim 1, wherein the step S1 comprises:

Step S11, enabling Fischer-Tropsch synthesis oil to enter a first rectifying tower to obtain a mixed fraction containing a C ₆₊ fraction and a C ₆ fraction;

and step S12, the mixed fraction enters a second rectifying tower, and a C ₆ fraction is obtained at the top of the second rectifying tower.

3. The method according to claim 2, wherein the first rectifying column has a tray number of 20 to 60, a reflux ratio of 5 to 15, a column top temperature of 30 to 45 ℃ and a column bottom temperature of 60 to 100 ℃.

4. The method according to claim 2, wherein the theoretical plate number of the second rectifying column is 20-60, the reflux ratio is 5-15, the column top temperature is 50-70 ℃, and the column bottom temperature is 110-130 ℃.

5. The method according to claim 2, characterized in that the first rectification column and/or the second rectification column is fed at a mid-column position.

6. The method according to claim 1, wherein the step S2 comprises: and (3) inputting the C ₆ fraction into an alkaline washing tower, and mixing with alkaline liquor.

7. The method according to claim 6, wherein the lye comprises any one or more of sodium hydroxide solution, potassium hydroxide solution and potassium carbonate solution.

8. The method according to claim 6, wherein the concentration of the lye is 5-10wt%.

9. The method according to claim 6, wherein the volume ratio of the lye to the C ₆ fraction is 4-8.

10. The method according to claim 1, wherein the step S3 comprises: and (3) inputting the deacidified C ₆ fraction into a water washing tower, washing to be neutral, and enabling the washed fraction to enter an oil-water separator to separate an oil phase for drying treatment.

11. The method of claim 4, wherein the drying treatment is drying with a desiccant comprising silica gel, alumina, 3A molecular sieve, 5A molecular sieve.

12. The method of claim 4, wherein the moisture content of the dried C ₆ fraction is less than 100ppm.

13. The process of claim 1, wherein the volume ratio of extractant to the dry C ₆ fraction is 1-8:1 and the operating temperature is 30-50 ℃.

14. The method of claim 13, wherein the adsorbent selected from the adsorption tower is any one or more of silica gel, clay, diatomaceous earth, alumina, activated carbon, 3A molecular sieve, 5A molecular sieve, 13X molecular sieve, resin, silicate.

15. The method of claim 1, wherein the lower alcohol is any one or more of methanol, ethanol, and propanol.

16. The process according to claim 1, wherein the molar ratio of lower alcohols to tertiary olefins in the selectively hydrogenated C6 fraction is from 2 to 6:1.

17. The method according to claim 1, wherein the theoretical plate number of the rectifying column for etherification is 30-80, the reflux ratio is 5-15, the column top temperature is 50-70 ℃, and the column bottom temperature is 80-150 ℃.

18. The process of claim 1 wherein the lower alcohol is fed to the selectively hydrogenated C ₆ fraction at a point between 20 and 60 trays.

19. The method according to claim 1, wherein the etherification rectifying tower is filled with a catalyst at the upper, middle and lower stages, respectively.

20. The process of claim 19 wherein 2 to 15 theoretical plates are provided between the top of the column and the upper catalyst bed, between two adjacent catalyst beds, and between the lower catalyst bed and the bottom of the column.

21. The process of claim 19 wherein the selectively hydrogenated C ₆ fraction and the lower alcohol are fed below the lower catalyst bed.

22. The method according to claim 1, wherein in the step S8, the adsorbent of the simulated moving bed is selected from any one or more of 5A molecular sieve, 13X type zeolite and LTA type zeolite; and/or the desorbent of the simulated moving bed is any one or more of alkane and alkene.

23. The method of claim 22, wherein the desorbent is a mixture of alkanes and alkenes, the alkene content being 40-60%.

24. The method according to claim 22, wherein the operating temperature of the adsorption tower in the simulated moving bed is 60-150 ℃, the operating pressure is 0.45-0.55 MPa, and the catalyst-to-oil ratio is 0.5-4:1.

25. The device for separating 1-hexene from Fischer-Tropsch synthetic oil is characterized by comprising a rectification cutting unit, a deacidification unit, a washing and drying unit, a deoxidization unit, a selective hydrogenation reaction unit, an etherification unit, a rectification unit and an alkane-alkene separation unit which are connected in sequence;