阅读说明：本技术 费托合成油脱氧精制的方法 (Method for deoxidizing and refining Fischer-Tropsch synthetic oil ) 是由 李丽 朱豫飞 孙琦 缪平 于 2019-03-20 设计创作，主要内容包括：本发明涉及费托合成油精制领域,公开了费托合成油脱氧精制的方法,将费托合成油进行常减压分馏,得到第一段馏分、第二段馏分和第三段馏分；(2)对所述第一段馏分用甲醇水溶液进行第一萃取,得到萃取相1和萃余相1；对所述第二段馏分用乙醇水溶液进行第二萃取,得到萃取相2和萃余相2；对所述第三段馏分用乙二醇醚类的水溶液进行第三萃取,得到萃取相3和萃余相3；(3)将所述萃余相1、萃余相2和萃余相3分别进行水洗,得到脱氧精制的费托合成油。该方法不仅在脱除含氧化合物的过程中保持α-烯烃的含量,而且脱氧精制后的费托合成油中含氧化合物的含量降低到100ppm以下,且油品回收率高。(The invention relates to the field of Fischer-Tropsch synthetic oil refining, and discloses a method for deoxidizing and refining Fischer-Tropsch synthetic oil, which comprises the steps of carrying out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain a first-stage fraction, a second-stage fraction and a third-stage fraction; (2) carrying out first extraction on the first-stage fraction by using a methanol aqueous solution to obtain an extract phase 1 and a raffinate phase 1; performing second extraction on the second-stage fraction by using an ethanol aqueous solution to obtain an extract phase 2 and a raffinate phase 2; performing third extraction on the third-stage fraction by using an ethylene glycol ether aqueous solution to obtain an extract phase 3 and a raffinate phase 3; (3) and respectively washing the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 to obtain the deoxidized and refined Fischer-Tropsch synthetic oil. The method not only keeps the content of alpha-olefin in the process of removing the oxygen-containing compound, but also reduces the content of the oxygen-containing compound in the deoxidized and refined Fischer-Tropsch synthetic oil to be less than 100ppm, and has high oil recovery rate.)

1. A Fischer-Tropsch synthetic oil deoxidation refining method is characterized by comprising the following steps:

(1) carrying out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain a first-stage fraction, a second-stage fraction and a third-stage fraction, wherein,

the distillation range of the first-stage fraction is IBP-T_aThe temperature is less than or equal to 140 ℃ and T is less than or equal to_a≤170℃；

The distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 240 ℃ and T is less than or equal to_b≤300℃；

The distillation range of the third-stage fraction is more than T_b℃；

(2) Carrying out first extraction on the first-stage fraction by using a methanol aqueous solution to obtain an extract phase 1 and a raffinate phase 1; performing second extraction on the second-stage fraction by using an ethanol aqueous solution to obtain an extract phase 2 and a raffinate phase 2; performing third extraction on the third-stage fraction by using an ethylene glycol ether aqueous solution to obtain an extract phase 3 and a raffinate phase 3;

(3) washing the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 respectively to obtain deoxidized and refined Fischer-Tropsch synthetic oil;

the Fischer-Tropsch synthetic oil comprises 0.1-10 wt% of oxygen-containing compounds by total weight of the Fischer-Tropsch synthetic oil, wherein the oxygen-containing compounds comprise alcohols, ketones, aldehydes, acids and esters.

2. The process according to claim 1, wherein in step (1), the distillation range of the first stage fraction is IBP-T_aFraction at 150 ℃ or lower, wherein T is not more than 150 ℃_a≤160℃；

The distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 260 ℃ and T is more than or equal to_b≤280℃；

The distillation range of the third-stage fraction is more than T_b℃。

3. The process according to claim 1 or 2, wherein in step (2), the concentration of the aqueous methanol solution is not more than 85% by weight, preferably 60 to 75% by weight; the amount of the methanol aqueous solution is 0.5-4 times of the weight of the first-stage distillate, and preferably 0.8-2 times of the weight of the first-stage distillate.

4. The process according to claim 1 or 2, wherein in step (2), the concentration of the aqueous ethanol solution is not more than 80% by weight, preferably 60-75% by weight; the dosage of the ethanol water solution is 0.5-4 times of the weight of the second-stage distillate, and preferably 0.8-2 times.

5. The method according to claim 1 or 2, wherein in step (2) the concentration of the aqueous solution of glycol ethers is not more than 80 wt. -%, preferably 60-70 wt. -%; the dosage of the glycol ether aqueous solution is 0.5-4 times of the weight of the third-stage fraction, and preferably 0.8-2 times;

preferably, the glycol ethers are selected from one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether and diethylene glycol monobutyl ether.

6. The process according to claim 1 or 2, wherein the temperature of the first extraction is 15-50 ℃, preferably 20-50 ℃; the first extraction method is a multi-stage countercurrent extraction method; the theoretical stage number of the first extraction is 3-10 stages, and preferably 5-7 stages.

7. The process according to claim 1 or 2, wherein the temperature of the second extraction is 15-50 ℃, preferably 20-50 ℃; the second extraction method is a multi-stage countercurrent extraction method; the theoretical stage number of the second extraction is 3-10 stages, and preferably 5-7 stages.

8. The process according to claim 1 or 2, wherein the temperature of the third extraction is 15-50 ℃, preferably 20-50 ℃; the third extraction method is a multi-stage countercurrent extraction method; the theoretical stage number of the third extraction is 3-10 stages, and preferably 5-7 stages.

9. A process according to claim 1 or claim 2, wherein the fischer-tropsch synthesis oil has a boiling range of IBP to 380 ℃, preferably IBP to 350 ℃.

10. The process of claim 1 or 2, further comprising subjecting the extract phase 1, extract phase 2 and extract phase 3 to solvent separation to obtain oxygenates and recycled solvent.

Technical Field

The invention relates to the field of Fischer-Tropsch synthetic oil refining, in particular to a method for deoxidizing and refining Fischer-Tropsch synthetic oil.

Background

α -olefin is an important organic feedstock and intermediate product with a wide range of applications.1-butene, 1-hexene and 1-octene used as comonomers in Polyethylene (PE) resins can improve PE performance.C₆-C₁₀The α -olefin used for producing plasticizer alcohol, PE products added with the plasticizer alcohol have better low-temperature flexibility, processability and outdoor weather resistance, and are particularly suitable for manufacturing cables, wires, automobile accessories or decorative parts₈-C₁₀The α -olefin can be used to synthesize poly- α olefin (PAO) lubricant, PAO is high-quality synthetic lubricant C₁₁-C₁₄By hydroxylation of α -alkenes to C₁₂-C₁₅α -olefin can also be used in the production of alkylbenzene or alkylphenol to prepare lubricating oil and additive.

The fischer-tropsch synthesis reaction is a reaction in which synthesis gas is formed into a series of compounds containing alkanes, alkenes and oxygen at a certain temperature and pressure and using an iron or cobalt catalyst. The carbon chain length of the product is from 1 to more than 100, the oxygen-containing compound is mainly fatty alcohol, and a small amount of acid, ester, ketone, aldehyde and the like are also contained, 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%.

The alpha-olefin in the Fischer-Tropsch synthesis product can be used for producing PAO (polycyclic aromatic hydrocarbons), alkyl benzene and the like. However, the oxygenates must first be removed because the oxygenates have a negative effect on both of these reactions. However, currently, the removal of oxygenates in industry mainly employs a method of hydrogenating compounds containing olefins, alkanes and oxygenates. Hydrogenation processes also accompany olefin hydrosaturation during the hydrogenation removal of oxygenates, which is not a desirable result.

Other methods for separating and extracting fatty alcohol and removing oxygen-containing compounds also comprise adsorption, extraction and the like.

US3485879 discloses a process for separating alcohols from olefins and alkanes by selective adsorption on alumina, but this process has a problem of difficult industrial scale-up.

US2746984 discloses the separation of aliphatic alcohols from alcohol-hydrocarbon mixtures by reacting boric acid with the alcohol in the alcohol-hydrocarbon mixture to form an ester, followed by extraction with solvents such as methanol, ethanol, water, etc., followed by hydrolysis of the borate ester to obtain the aliphatic alcohol. However, the method is complicated in operation because of two chemical reactions, namely esterification and hydrolysis, and the content of the oxygen-containing compounds in the separated hydrocarbon is not mentioned.

US2610977 discloses the separation of alcohols from hydrocarbons and in particular discloses a process for extraction with an aqueous solution of a lower alcohol, the lower alcohol being aqueous methanol, but using an extraction phase with an oil ratio of 8-9: 1, the dosage of the extractant is large, and the recovery solvent adopts a low-carbon hydrocarbon extraction mode.

GB716131 discloses extraction with aqueous solutions of lower alcohols, but because of the wide distillation range of the feed oil, the extraction of small molecular oxygen-containing compounds and large molecular oxygen-containing compounds with the same extractant results in high hydrocarbon content in the extract, and the azeotropic distillation method is used to remove residual hydrocarbons in the alcohol, but because of the large number of components of the system, there is often multi-azeotropic and the separation effect is not good.

CN101891589B discloses a method for extracting fatty alcohol, which comprises rectifying to divide fischer-tropsch product into four-stage fractions; and respectively extracting the four fractions by using water and ethanol aqueous solutions with different concentrations. In order to reduce the hydrocarbon content in the fatty alcohol, the method also comprises the step of back-extracting the alcohol phase obtained by the extraction by using alkanes with different carbon numbers respectively. However, the recovery rate of the aliphatic alcohol was only about 95%, and it was found that the amount of the oxygen-containing compound remaining in the hydrocarbon phase was relatively large.

Both CN100575320C and CN100383096C disclose methods of extracting oxygenates from a hydrocarbon stream using a mixture of methanol and water as solvent, but the methods are directed only to C₁₀-C₁₃The oxygenate is removed from the stream of (a).

WO9958625 disclosesA process for removing oxygenate impurities from a hydrocarbon stream using a light polar solvent formed from an acetonitrile/water solvent is used. But the method is only for C₈-C₁₀The oxygenate is removed from the stream of (a).

US4686317 discloses a process for removing light hydrocarbons (C)₂To C₉) A process for the extraction of oxygenates from a hydrocarbon stream comprising extracting the oxygenates with a heavy oil polar solvent such as propylene carbonate and 2-ethanolamine, washing the extracted hydrocarbon stream with water to recover dissolved solvent and combining the extracted solvent phase with an aqueous phase in a scrubber for the recovery of the solvent by distillation. But the method is only for C₂-C₉The oxygenate is removed from the stream of (a).

The alpha-olefin content in the Fischer-Tropsch synthesis product light oil and the heavy oil is higher, and the alpha-olefins with different distillation ranges have different purposes, so that the deoxidation technology of the whole fractions of the Fischer-Tropsch light oil and the heavy oil needs to be developed, but in the prior art, the alpha-olefin content is difficult to maintain by adopting a hydrodeoxygenation method; in the methods of adsorption and extraction, some methods only perform separation of oxygen-containing compounds on a hydrocarbon stream with a narrow distillation range, and have poor separation effect on the hydrocarbon stream with a wide distillation range, even if deoxygenation refining is performed on the hydrocarbon stream with the wide distillation range, the residual amount of the oxygen-containing compounds in the hydrocarbon phase is often large, the subsequent utilization of olefin cannot be ensured, and the oil yield needs to be improved. Moreover, the prior art mostly only performs separation and extraction on alcohol in the hydrocarbon stream, but does not perform separation on ketone, aldehyde, acid and ester in the hydrocarbon stream.

Disclosure of Invention

The invention aims to overcome the problems that the content of alpha-olefin is difficult to maintain, the separation effect of oxygen-containing compounds is poor, the separation of ketone, aldehyde, acid and ester in hydrocarbon material flow is not performed, and the oil yield is required to be improved in the prior art, and provides a method for deoxidizing and refining Fischer-Tropsch synthetic oil.

In order to achieve the above object, the first aspect of the present invention provides a method for deoxygenating and refining fischer-tropsch synthetic oil, wherein the method comprises the following steps:

(1) carrying out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain a first-stage fraction, a second-stage fraction and a third-stage fraction, wherein,

the distillation range of the first-stage fraction is IBP-T_aThe temperature is less than or equal to 140 ℃ and T is less than or equal to_a≤170℃；

The distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 240 ℃ and T is less than or equal to_b≤300℃；

The distillation range of the third-stage fraction is more than T_b℃；

(2) Carrying out first extraction on the first-stage fraction by using a methanol aqueous solution to obtain an extract phase 1 and a raffinate phase 1; performing second extraction on the second-stage fraction by using an ethanol aqueous solution to obtain an extract phase 2 and a raffinate phase 2; performing third extraction on the third-stage fraction by using an ethylene glycol ether aqueous solution to obtain an extract phase 3 and a raffinate phase 3;

(3) washing the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 respectively to obtain deoxidized and refined Fischer-Tropsch synthetic oil;

the Fischer-Tropsch synthetic oil comprises 0.1-10 wt% of oxygen-containing compounds by total weight of the Fischer-Tropsch synthetic oil, wherein the oxygen-containing compounds comprise alcohols, ketones, aldehydes, acids and esters.

Preferably, in step (1), the distillation range of the first-stage fraction is IBP-T_aFraction at 150 ℃ or lower, wherein T is not more than 150 ℃_aLess than or equal to 160 ℃; the distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 260 ℃ and T is more than or equal to_bLess than or equal to 280 ℃; the distillation range of the third-stage fraction is more than T_b℃。

Preferably, in the step (2), the concentration of the methanol aqueous solution is not more than 85 wt%, preferably 60 to 75 wt%; the amount of the methanol aqueous solution is 0.5-4 times of the weight of the first-stage distillate, and preferably 0.8-2 times of the weight of the first-stage distillate.

Preferably, in the step (2), the concentration of the ethanol aqueous solution is not more than 80 wt%, preferably 60-75 wt%; the dosage of the ethanol water solution is 0.5-4 times of the weight of the second-stage distillate, and preferably 0.8-2 times.

Preferably, in the step (2), the concentration of the glycol ether aqueous solution is not more than 80 wt%, preferably 60-70 wt%; the dosage of the glycol ether aqueous solution is 0.5-4 times of the weight of the third-stage fraction, and preferably 0.8-2 times.

Preferably, the glycol ethers are selected from one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether and diethylene glycol monobutyl ether.

Preferably, the distillation range of the Fischer-Tropsch synthetic oil is IBP-380 ℃, and preferably IBP-350 ℃.

The invention carries out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain three-section fractions, and then extracts the three-section fractions respectively, wherein the distillation range is IBP-T_aFraction at 140 deg.C or less, T_a170 ℃ or less, preferably 150 ℃ or less T_aExtracting with methanol water solution at 160 deg.C or below; for distillation range greater than T_aAnd is not more than T_bFraction at 240 ℃ or lower, T_bLess than or equal to 300 ℃, preferably less than or equal to 260 ℃ and less than or equal to T_bExtracting with ethanol water solution at temperature of less than or equal to 280 deg.C; for distillation range greater than T_bThe DEG C fraction is extracted by adopting an ethylene glycol ether aqueous solution, the method not only keeps the α -olefin content in the Fischer-Tropsch synthetic oil, but also can effectively remove alcohol, ketone, aldehyde, acid and ester in the Fischer-Tropsch synthetic oil, the content of oxygen-containing compounds in the Fischer-Tropsch synthetic oil after deoxygenation refining is reduced to be below 100ppm, and the oil recovery rate is high.

Drawings

FIG. 1 is a schematic diagram of a Fischer-Tropsch synthesis oil deoxygenation refining process of the present invention.

Detailed Description

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

The invention provides a method for deoxidizing and refining Fischer-Tropsch synthetic oil in a first aspect, wherein the method comprises the following steps:

(1) carrying out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain a first-stage fraction, a second-stage fraction and a third-stage fraction, wherein,

the distillation range of the first-stage fraction is IBP-T_aThe temperature is less than or equal to 140 ℃ and T is less than or equal to_a≤170℃；

The distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 240 ℃ and T is less than or equal to_b≤300℃；

The distillation range of the third-stage fraction is more than T_b℃；

(2) Carrying out first extraction on the first-stage fraction by using a methanol aqueous solution to obtain an extract phase 1 and a raffinate phase 1; performing second extraction on the second-stage fraction by using an ethanol aqueous solution to obtain an extract phase 2 and a raffinate phase 2; performing third extraction on the third-stage fraction by using an ethylene glycol ether aqueous solution to obtain an extract phase 3 and a raffinate phase 3;

(3) washing the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 respectively to obtain deoxidized and refined Fischer-Tropsch synthetic oil;

the Fischer-Tropsch synthetic oil comprises 0.1-10 wt% of oxygen-containing compounds by total weight of the Fischer-Tropsch synthetic oil, wherein the oxygen-containing compounds comprise alcohols, ketones, aldehydes, acids and esters.

In the present invention, T_aIt means the final distillation point of the first stage fraction, and can be 140-170 deg.C, T_bThe final distillation point of the second stage fraction can be 240-300 ℃, and the final distillation point can be correspondingly carried out according to different Fischer-Tropsch synthetic oils because the components of the different Fischer-Tropsch synthetic oils are differentFractional distillation of (2) with T_aFor example, T_aThe temperature may be any value within a range of 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃ or any two of these values.

In the invention, the Fischer-Tropsch synthetic oil comes from light oil and heavy oil fractions in the Fischer-Tropsch synthetic reaction process, and the composition of the Fischer-Tropsch synthetic oil can contain alkane, olefin and oxygen-containing compounds.

In the present invention, the term "IBP" refers to the initial boiling point, i.e. the temperature recorded at the instant when the first drop of condensate falls from the end of the condenser when the distillation range of the oil is measured.

In the present invention, the raffinate phase 1, the raffinate phase 2, and the raffinate phase 3 are each washed with water to obtain a hydrocarbon phase 1, a hydrocarbon phase 2, and a hydrocarbon phase 3, and the hydrocarbon phase 1, the hydrocarbon phase 2, and the hydrocarbon phase 3 are collectively referred to as a deoxygenated and purified fischer-tropsch synthetic oil. That is, the deoxygenated refined Fischer-Tropsch oil comprises a hydrocarbon phase 1, a hydrocarbon phase 2, and a hydrocarbon phase 3.

In the present invention, the atmospheric and vacuum fractionation may be a means conventionally used in the art, and the pressure and temperature of the atmospheric and vacuum fractionation are not particularly limited, and the purpose is to obtain a fraction having a distillation range required in the present invention.

According to a preferred process of the invention, in step (1), the distillation range of the first-stage fraction is IBP-T_aThe temperature is less than or equal to 150 ℃ and T is more than or equal to_aLess than or equal to 160 ℃; the distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 260 ℃ and T is more than or equal to_bLess than or equal to 280 ℃; the distillation range of the third-stage fraction is more than T_b℃。T_aIt means the final distillation point of the first stage fraction, and can be 150-160 deg.C, T_bThe final distillation point of the second stage fraction can be 260-280 ℃, and corresponding fractionation can be carried out according to different Fischer-Tropsch synthetic oils because the components of different Fischer-Tropsch synthetic oils are different, so that the final distillation temperature is T_aFor example, T_aThe temperature may be 150 ℃, 151 ℃, 152 ℃, 153 ℃, 154 ℃, 155 ℃, 156 ℃, 157 ℃, 158 ℃, 159 ℃, 160 ℃ or any value in the range of any two of these values.

According to the method of the present invention, in the step (2), the concentration of the aqueous methanol solution may be not more than 85% by weight, and specifically, the content of methanol in the aqueous methanol solution may be not more than 85% by weight based on the total weight of the aqueous methanol solution. Preferably, the concentration of the aqueous methanol solution is 60 to 75 wt%, for example, 60 wt%, 65 wt%, 70 wt%, 75 wt%, and any value in the range of any two of these values.

According to the method of the present invention, in the step (2), the amount of the aqueous methanol solution may be 0.5 to 4 times, preferably 0.8 to 2 times, for example, 0.8 times, 0.9 times, 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, and any value in the range of any two of these values, based on the weight of the first stage fraction.

According to the method of the present invention, in the step (2), the concentration of the aqueous ethanol solution may be not more than 80% by weight, and specifically, the content of ethanol in the aqueous ethanol solution may be not more than 80% by weight, based on the total weight of the aqueous ethanol solution. Preferably, the concentration of the ethanol aqueous solution is 60 to 75 wt%, for example, 60 wt%, 65 wt%, 70 wt%, 75 wt%, and any value in the range of any two of these values.

According to the method of the present invention, the amount of the aqueous ethanol solution may be 0.5 to 4 times, preferably 0.8 to 2 times, for example, 0.8 times, 0.9 times, 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, and any value in the range of any two of these values, based on the weight of the second-stage fraction.

According to the method of the present invention, in the step (2), the concentration of the aqueous solution of glycol ethers may be not more than 80% by weight, and specifically, the content of ethanol in the aqueous solution of glycol ethers may be not more than 80% by weight based on the total weight of the aqueous solution of glycol ethers. Preferably, the concentration of the aqueous glycol ether solution is 60 to 70 wt%, for example, 60 wt%, 65 wt%, 70 wt%, or any value in the range of any two of these values.

According to the method of the invention, the glycol ethers may be selected from, but not limited to: one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether and diethylene glycol monobutyl ether.

According to the method of the present invention, the aqueous solution of glycol ethers may be used in an amount of 0.5 to 4 times, preferably 0.8 to 2 times, for example, 0.8 times, 0.9 times, 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, and any value in the range of any two of these values, based on the weight of the third fraction.

According to the method, the temperature of the first extraction can be 15-50 ℃, and preferably 20-50 ℃; the first extraction method can be a multi-stage countercurrent extraction method; the theoretical stage number of the first extraction can be 3-10 stages, and preferably 5-7 stages.

According to the method, the temperature of the second extraction can be 15-50 ℃, and preferably 20-50 ℃; the second extraction method can be a multi-stage countercurrent extraction method; the theoretical stage number of the second extraction can be 3-10 stages, and preferably 5-7 stages.

According to the method, the temperature of the third extraction can be 15-50 ℃, and preferably 20-50 ℃; the third extraction method can be a multi-stage countercurrent extraction method; the theoretical stage number of the third extraction can be 3-10 stages, and preferably 5-7 stages.

According to the method, the fraction distribution of the Fischer-Tropsch synthetic oil is wide, the heavier the fraction in the Fischer-Tropsch synthetic oil is, the lower the olefin content in an oil product is, the higher the alkane content is, the lower the content of the oxygen-containing compound is, and the olefin content of the fraction at the temperature of more than 380 ℃ is lower, so that the Fischer-Tropsch synthetic oil is fractionated before extraction to obtain the Fischer-Tropsch synthetic oil with the distillation range of IBP-380 ℃, and preferably IBP-350 ℃.

According to the method, the method further comprises the step of carrying out solvent separation on the extraction phase 1, the extraction phase 2 and the extraction phase 3 respectively to obtain an oxygen-containing compound and a circulating solvent, wherein the oxygen-containing compound refers to the organic phase 1, the organic phase 2 and the organic phase 3 in the figure 1, and the circulating solvent refers to a recyclable solvent. Specifically, taking the extraction phase 1 as an example, introducing the extraction phase 1 into a first rectification tower, obtaining methanol at the tower top of the first rectification tower, introducing a kettle bottom product of the first rectification tower into a first decanter, recovering an aqueous solvent at the bottom of the first decanter, and preparing the aqueous solution with the methanol obtained at the tower top of the first rectification tower to obtain a methanol aqueous solution with a required concentration, returning the aqueous solution to the first extraction tower for recycling as a circulating solvent, and obtaining an organic phase 1 at the top of the first decanter, wherein the organic phase 1 contains an oxygen-containing compound, olefin and paraffin stream.

According to the process of the present invention, the raffinate 1, raffinate 2 and raffinate 3 comprise a small amount of solvent alcohol (raffinate 1 comprises methanol, raffinate 2 comprises ethanol and raffinate 3 comprises glycol ethers), and thus the raffinate 1, raffinate 2 and raffinate 3 are introduced into separate water wash columns. Taking raffinate phase 1 as an example, introducing raffinate phase 1 into a first water washing tower, washing off the solvent by a water washing method, taking a hydrocarbon phase as a tower top product, and leading out the hydrocarbon phase to obtain the hydrocarbon phase 1, wherein the tower bottom product returns to the first extraction tower for recycling.

According to the method of the invention, the content of the oxygen-containing compound in the deoxidized refined Fischer-Tropsch synthetic oil can reach less than 100ppm (0.01 wt%), preferably less than 50ppm (0.005 wt%); the recovery of olefins and paraffins is higher than 95% by weight, and preferably may be higher than 98% by weight.

According to an embodiment of the invention, as shown in FIG. 1, the method for deoxidizing and refining Fischer-Tropsch synthetic oil comprises the following steps:

(1) carrying out atmospheric and vacuum fractionation on Fischer-Tropsch synthetic oil to obtain a first-stage fraction, a second-stage fraction and a third-stage fraction, wherein the distillation range of the first-stage fraction is IBP-T_aThe temperature is less than or equal to 140 ℃ and T is less than or equal to_aLess than or equal to 170 ℃; the distillation range of the second-stage fraction is more than T_aAnd is not more than T_bThe temperature is less than or equal to 240 ℃ and T is less than or equal to_bLess than or equal to 300 ℃; the distillation range of the third-stage fraction is more than T_b℃；

(2) And carrying out first extraction on the first section of fraction by using a methanol aqueous solution to obtain an extract phase 1 and a raffinate phase 1. The first fraction is fed into the first extraction column at or near the bottom of the column, and an extractant 1 comprising an aqueous methanol solution having a concentration of not more than 85% by weight, preferably 60 to 75% by weight, is fed into the first extraction column at or near the top of the column. And introducing a raffinate phase 1 at the top of the first extraction tower into a first water washing tower, wherein the raffinate phase 1 contains olefin, paraffin and a small amount of methanol. The methanol is washed away by a water washing method, a hydrocarbon phase 1 is taken out as a first water washing tower top product, a first water washing tower bottom product (methanol water solution) is returned to the first extraction tower for recycling, and the hydrocarbon phase 1 comprises more than 99 weight percent of olefin and paraffin (the content of alpha-olefin is more than 60 weight percent, and the content of n-paraffin is more than 20 weight percent) and less than 100ppm (0.01 weight percent) of oxygenated compounds, preferably less than 50ppm (0.005 weight percent) of oxygenated compounds. Extract phase 1 from the bottom of the first extraction column is introduced into a first rectification column, the overhead product from which contains more than 90 wt% methanol and small amounts of olefins and paraffins. More than 80 wt% of the olefins and paraffins in extract phase 1 are recovered in the first rectifier overhead. The method comprises the following steps of (1) obtaining methanol from the top of a first rectifying tower, introducing a kettle bottom product of the first rectifying tower into a first decanter, recovering a water solvent from the bottom of the first decanter, preparing the water solvent with the methanol obtained from the top of the first rectifying tower to obtain a methanol water solution with required concentration, returning the methanol water solution to a first extraction tower for recycling, and obtaining an organic phase 1 from the top of the first decanter, wherein the organic phase 1 contains an oxygen-containing compound, olefin and paraffin flow;

and carrying out second extraction on the second-stage fraction by using an ethanol aqueous solution to obtain an extract phase 2 and a raffinate phase 2. The second-stage fraction is conveyed into the second extraction tower at the bottom or close to the bottom of the second extraction tower, and the extracting agent 2 containing the ethanol aqueous solution is conveyed into the second extraction tower at the top or close to the top of the second extraction tower, wherein the concentration of the ethanol aqueous solution is not more than 80 wt%, and preferably 60-75 wt%. And introducing a raffinate phase 2 at the top of the second extraction tower into a second water washing tower, wherein the raffinate phase 2 contains olefin, paraffin and a small amount of ethanol. The ethanol is washed away by a water washing method, and a hydrocarbon phase 2 is taken out as a second water washing tower top product, a second water washing tower bottom product (ethanol water solution) is returned to a second extraction tower for recycling, wherein the hydrocarbon phase 2 comprises more than 99 weight percent of olefin and paraffin (the content of alpha-olefin is more than 50 weight percent, and the content of n-paraffin is more than 30 weight percent) and less than 100ppm (0.01 weight percent) of oxygenated compounds, preferably less than 50ppm (0.005 weight percent) of oxygenated compounds. The extract phase 2 from the bottom of the second extraction column is introduced into a second rectification column, the overhead product from which contains more than 90% by weight ethanol and small amounts of olefins and paraffins. More than 80 wt% of the olefins and paraffins in extract phase 2 are recovered in the second rectification column overhead product. The method comprises the following steps of obtaining ethanol or an azeotrope of ethanol and water at the top of a second rectifying tower, introducing a kettle bottom product of the second rectifying tower into a second decanter, recovering a water solvent at the bottom of the second decanter, preparing the water solvent with the ethanol or the azeotrope of ethanol and water obtained at the top of the second rectifying tower to obtain an ethanol aqueous solution with a required concentration, returning the ethanol aqueous solution to a second extraction tower for recycling, and obtaining an organic phase 2 at the top of the second decanter, wherein the organic phase 2 contains oxygen-containing compounds, olefin and paraffin flow;

and carrying out third extraction on the third-stage fraction by using an ethylene glycol ether aqueous solution to obtain an extract phase 3 and a raffinate phase 3. The third fraction is fed into the third extraction column at or near the bottom of the column, and an extractant 3 comprising an aqueous solution of glycol ethers is fed into the third extraction column at or near the top of the column, the concentration of the aqueous solution of glycol ethers being not more than 80% by weight, preferably 60-70% by weight. And introducing a raffinate phase 3 at the top of the third extraction tower into a third water washing tower, wherein the raffinate phase 3 contains olefin, paraffin and a small amount of glycol ethers. The glycol ethers are washed away by a water washing method, and a hydrocarbon phase 3 is led out as the top product of a third water washing tower, the bottom product (the water solution of the glycol ethers) of the third water washing tower returns to a third extraction tower for recycling, wherein the hydrocarbon phase 3 comprises more than 99 weight percent of olefin and paraffin (the content of alpha-olefin is more than 40 weight percent, and the content of n-paraffin is more than 40 weight percent) and less than 100ppm (0.01 weight percent) of oxygenated compounds, preferably less than 50ppm (0.005 weight percent) of oxygenated compounds. The extract phase 3 at the bottom of the third extraction column is introduced into a third rectification column, from which the overhead product contains more than 90 wt.% glycol ethers and small amounts of olefins and paraffins. More than 80 wt% of the olefins and paraffins in extract phase 3 are recovered in the third rectification column overhead product. Glycol ethers or an azeotrope of the glycol ethers and water are obtained at the top of the third rectifying tower, a kettle bottom product of the third rectifying tower is introduced into a third decanter, the water solvent is recovered at the bottom of the third decanter, and is prepared with the glycol ethers or the azeotrope of the glycol ethers and the water obtained at the top of the third rectifying tower to obtain a glycol ether aqueous solution with the required concentration, the glycol ether aqueous solution is returned to the third extraction tower for recycling, and an organic phase 3 is obtained at the top of the third decanter, wherein the organic phase 3 contains an oxygen-containing compound, olefin and paraffin stream.

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

The composition and content of the Fischer-Tropsch synthetic oil are shown in Table 1.

TABLE 1

Composition (I)	α -olefins	N-alkanes	Alcohol(s)	Aldehydes and ketones	Acids and esters
						Content by weight%	60.26	31.69	3.16	0.64	0.12