阅读说明：本技术 一种脱除费托合成油中含氧化合物的方法 (Method for removing oxygen-containing compounds in Fischer-Tropsch synthetic oil ) 是由 邹琥 葸雷 李林玥 刘欢 史军军 于 2019-10-30 设计创作，主要内容包括：本发明涉及一种脱除费托合成油中含氧化合物的方法。该方法包括脱酸处理、液液萃取、水洗和溶剂回收,其中液液萃取采用的萃取溶剂为甘醇类化合物、酰胺类化合物、吡咯烷酮类化合物或砜类化合物,或者为它们中两者或三者或四者的组合,上述萃取溶剂具有对含氧化合物选择性高、稳定性好且与费托合成油密度差大等特点。本发明的方法对含氧化合物的脱除效果好、易于操作且溶剂回收效率高；另外,该方法采用轻烃反萃工艺进行溶剂回收,回收条件温和,萃取溶剂及含氧化合物回收效率高,反萃剂、轻烃和工艺水均可循环使用,三废排放小。(The invention relates to a method for removing oxygen-containing compounds in Fischer-Tropsch synthetic oil. The method comprises deacidification treatment, liquid-liquid extraction, water washing and solvent recovery, wherein the extraction solvent adopted by the liquid-liquid extraction is a glycol compound, an amide compound, a pyrrolidone compound or a sulfone compound, or a combination of two or three or four of the glycol compound, the amide compound, the pyrrolidone compound or the sulfone compound, and the extraction solvent has the characteristics of high selectivity on oxygen-containing compounds, good stability, large density difference with Fischer-Tropsch synthetic oil and the like. The method has good effect of removing the oxygen-containing compound, is easy to operate and has high solvent recovery efficiency; in addition, the method adopts a light hydrocarbon back extraction process to recover the solvent, the recovery condition is mild, the recovery efficiency of the extraction solvent and the oxygen-containing compound is high, the back extraction agent, the light hydrocarbon and the process water can be recycled, and the discharge of three wastes is small.)

1. A method for removing oxygen-containing compounds in Fischer-Tropsch synthesis oil comprises the following steps:

contacting Fischer-Tropsch synthetic oil with deacidifying agent water solution in a deacidification tower (1) for reaction and deacidification to obtain deacidified Fischer-Tropsch synthetic oil and a water phase generated after deacidification; feeding the water phase generated after deacidification into a deacidification agent recovery tower (2) for reduced pressure distillation, discharging the separated deacidification agent from the tower top and returning to the deacidification tower (1), and discharging the acid liquid out of the deacidification agent recovery tower (2);

contacting deacidified Fischer-Tropsch synthetic oil with an extraction solvent in an extraction tower (3) for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon and an extract phase rich in oxygen-containing compounds;

contacting the raffinate phase with washing water in a washing tower (4) for washing to obtain a Fischer-Tropsch synthesis oil product with oxygen-containing compounds removed and water after washing;

enabling the extract phase and the water washed by the water to enter a solvent recovery tower (5) and to be in countercurrent contact with a back extractant to obtain a lean solvent and a back extractant rich in oxygen-containing compounds;

the lean solvent enters a solvent dehydration tower (7) for dehydration, and the dehydrated lean solvent returns to the extraction tower (3); the dehydrated water returns to the water washing tower (4) to be used as water washing water;

feeding the stripping agent rich in the oxygen compounds into a stripping agent recovery tower (6) for reduced pressure distillation, discharging the oxygen compounds from the bottom of the tower, and returning the stripping agent discharged from the top of the tower to the solvent recovery tower (5);

wherein the extraction solvent is a glycol compound, an amide compound, a pyrrolidone compound or a sulfone compound, or a combination of two, three or four of them; the stripping agent is C₅～C₇Or a hydrocarbon component having a boiling point of 80 ℃ or lower in the Fischer-Tropsch synthesis oil.

2. The method of claim 1, wherein the deacidification agent is ammonia, an ammonium salt, an amine, an alcohol amine or urea, the ammonium salt being ammonium carbonate or ammonium bicarbonate; the amine is ethylenediamine, diethylamine or triethylamine, and the alcohol amine is monoethanolamine.

3. The method according to claim 2, wherein the concentration of the deacidification agent aqueous solution is 5-40 mass%, and the mass ratio of the deacidification agent aqueous solution to the Fischer-Tropsch synthetic oil is (0.01-1): 1.

4. the method according to claim 1, wherein the operating temperature of the deacidification tower is 15-120 ℃, and the pressure is 0.1-0.5 MPa; the deacidification agent recovery tower has the operating temperature of 50-350 ℃ and the pressure of 10-80 kPa.

5. The method according to claim 1, wherein the glycol-based compound is at least one of diethylene glycol, triethylene glycol, tetraethylene glycol and pentaethylene glycol, preferably tetraethylene glycol; the amide compound is at least one of N, N-dimethylformamide, N-dimethylacetamide and formamide; the pyrrolidone compound is at least one of N-methyl pyrrolidone, 2-pyrrolidone and N-vinyl pyrrolidone; the sulfone compound is dimethyl sulfoxide and/or sulfolane.

6. A process as claimed in claim 1, wherein said raffinate phase and said extract phase are obtained from the top and bottom of said extraction column (3), respectively, by passing said deacidified fischer-tropsch synthesis oil from the lower portion into an extraction column (3) and passing said extraction solvent from the upper portion into said extraction column (3), in countercurrent contact with said deacidified fischer-tropsch synthesis oil.

7. The method of claim 1, wherein the mass ratio of the extraction solvent to the deacidified Fischer-Tropsch synthesis oil is (0.5-8): 1; the temperature of a tower kettle of the extraction tower (3) is 15-120 ℃; the pressure is 0.1-0.5 MPa.

8. The method according to claim 1, wherein the mass ratio of the water washing water to the raffinate phase is (0.05-0.5): 1; the operation temperature of the water washing tower (4) is 15-120 ℃, and the pressure is 0.1-0.5 MPa.

9. The process according to claim 1, wherein said stripping agent is introduced into said solvent recovery column (5) from the lower part, said extract phase and said water-washed water are mixed and introduced into said solvent recovery column (5) from the upper part, and are brought into counter-current contact with said stripping agent, thereby obtaining said oxygenate-rich stripping agent and said lean solvent from the top and bottom of said solvent recovery column (5), respectively.

10. The method according to claim 1, wherein the mass ratio of the stripping agent to the extract phase in the solvent recovery column (5) is (0.1-2): 1; the temperature of a tower kettle of the solvent recovery tower (5) is 15-120 ℃, and the pressure is 10-40 kPa.

11. The process according to claim 1, wherein the lean solvent is contacted with an entrainer in the solvent dehydration column (7) for azeotropic dehydration to obtain a hydrocarbon water azeotrope at the top of the column and a dehydrated lean solvent at the bottom of the column; separating the hydrocarbon-water azeotrope, returning the obtained azeotropic agent to the solvent dehydration column (7), and returning the separated water to the water washing column as water washing water (c)4) The entrainer is C₆～C₈An alkane or an arene.

12. The process according to claim 11, wherein the mass ratio of the entrainer to the lean solvent discharged from the bottom of the solvent recovery column (5) is (0.02-0.4): 1; the temperature of the solvent dehydration tower (7) is 40-100 ℃, and the pressure is 0.1-0.5 MPa.

13. The process according to claim 1, wherein the stripping agent recovery column (6) is operated at a temperature of 10 ℃ to 80 ℃ and a pressure of 10kPa to 80 kPa.

14. The method of claim 1, wherein the fischer-tropsch synthesis oil is a fischer-tropsch synthesis light oil or a fischer-tropsch synthesis full distillate; the Fischer-Tropsch synthesis light oil is a fraction of Fischer-Tropsch synthesis oil with 4-14 carbon atoms of hydrocarbons, and the Fischer-Tropsch synthesis full distillate oil is a fraction of Fischer-Tropsch synthesis oil with 4-40 carbon atoms of hydrocarbons.

15. The process according to claim 1, wherein the Fischer-Tropsch synthesis oil contains 1 to 15% by mass of an oxygen-containing compound, has a total content of normal paraffins and olefins of 20 to 90% by mass, and has a total acid value of 3 to 150 mgKOH/g.

Technical Field

The invention belongs to a separation method of impurities in indirect coal liquefaction products, and particularly relates to a method for removing oxygen-containing compounds in Fischer-Tropsch synthetic oil.

Background

Fischer-Tropsch synthesis (Fischer-Tropsch synthesis) is a coal indirect liquefaction technology, is the core composition of a coal gasification process, and the content of sulfur and nitrogen in Fischer-Tropsch synthesis products is almost zero, so that the Fischer-Tropsch synthesis products are direct raw materials for downstream oil product processing. Wherein, the olefin composition in the Fischer-Tropsch synthetic oil is mostly linear chain linear alpha-olefin (LAOs), and the LAOs serving as important petrochemical raw materials is widely applied to a plurality of fields such as comonomer, surfactant synthetic intermediate, plasticizer alcohol, synthetic lubricating oil, oil additives and the like.

The Fischer-Tropsch synthesis oil has the characteristics of wide carbon number distribution, complex composition and the like. The Fischer-Tropsch synthetic oil product contains hydrocarbon components and oxygen-containing compounds such as alcohol, aldehyde, ketone, acid, ester and the like, and the hydrocarbon and the oxygen-containing compounds can form an azeotrope and can not be effectively separated by simple rectification. Therefore, the LAOs in the fischer-tropsch oil is separated and purified by first removing the acids and oxygen-containing compounds from the fischer-tropsch oil. At present, the removal of oxygen-containing compounds in oil mainly comprises a hydrofining method, a solvent extraction method and an azeotropic distillation method.

CN102380391A discloses a selective deacidification catalyst, which comprises CuO and Al₂O₃And a metal additive selected from ZnO, NiO and Cr₂O₃The fischer-tropsch oil may be deacidified by selective hydrogenation of one or more transition metal oxides selected from MgO and BaO, one or more alkaline earth metal oxides selected from MgO and BaO and/or a noble metal selected from Pd, while about 65% of the olefins are not hydrogenated.

CN106753546A discloses a Fischer-Tropsch synthesis light distillate oil refining process, wherein Fischer-Tropsch synthesis oil is firstly subjected to solid phase adsorption unit to remove metal ion impurities and partial oxygen-containing compounds, and then a strong alkaline aqueous thionyl dimethyl methane solution is used as a composite extractant to further remove the oxygen-containing compounds. The process can treat the fraction C4-C21 of the Fischer-Tropsch synthetic oil, the content of oxygen-containing compounds in the oil product after extraction can be reduced to below 50ppm, and the extracting agent can be recycled.

CN1764619A discloses a feasible method for extracting oxygen-containing compounds from hydrocarbon streams and simultaneously ensuring the olefin content of products, which takes a mixture of methanol and water as a solvent, adopts an azeotropic distillation method to extract the oxygen-containing compounds from the hydrocarbon streams of C8-C16, and can reduce the oxygen-containing compound content in oil products to 0.2 wt%, but the total recovery rate of olefin and alkane is lower.

CN102452886A discloses a method for purifying 1-octene from Fischer-Tropsch synthesis oil, which adopts azeotropic distillation to simultaneously remove acid and other organic oxygen-containing compounds in Fischer-Tropsch synthesis C8 fraction by using an ethanol and water binary entrainer.

The hydrofining method, the solvent extraction method and the azeotropic distillation method can effectively remove the oxygen-containing compounds in the Fischer-Tropsch synthetic oil, but the process of removing the oxygen-containing compounds by hydrofining is often accompanied with olefin hydrogenation saturation, so that the loss of LAOs with high added value is caused; the azeotropic distillation needs a subsequent extractive distillation process to separate the entrainer and the hydrocarbon products, the process is more complex, and the method is suitable for removing the oxygen-containing compounds of the narrow fraction of the Fischer-Tropsch synthetic oil.

Disclosure of Invention

The invention aims to provide a method for removing oxygen-containing compounds in Fischer-Tropsch synthetic oil.

In order to achieve the above object, the first aspect of the present invention provides a method for removing oxygenates from fischer-tropsch synthesis oil, comprising:

contacting Fischer-Tropsch synthetic oil with deacidifying agent water solution in a deacidifying tower for reaction and deacidifying to obtain deacidified Fischer-Tropsch synthetic oil and a water phase generated after deacidification; feeding the water phase generated after deacidification into a deacidification agent recovery tower for reduced pressure distillation, discharging the separated deacidification agent from the tower top and returning to the deacidification tower, and discharging acid liquor from the deacidification agent recovery tower;

contacting deacidified Fischer-Tropsch synthetic oil with an extraction solvent in an extraction tower for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon and an extract phase rich in oxygen-containing compounds;

contacting the raffinate phase with washing water in a washing tower for washing to obtain a Fischer-Tropsch synthesis oil product with oxygen-containing compounds removed and water after washing;

enabling the extract phase and the water washed by the water to enter a solvent recovery tower and to be in countercurrent contact with a back extractant, so as to obtain a lean solvent and a back extractant rich in oxygen-containing compounds;

feeding the lean solvent into a solvent dehydration tower for dehydration, and returning the dehydrated lean solvent to the extraction tower; returning the dehydrated water to the water washing tower to be used as water washing water;

enabling the stripping agent rich in the oxygen compounds to enter a stripping agent recovery tower for reduced pressure distillation, discharging the oxygen compounds from the bottom of the tower, and returning the stripping agent discharged from the top of the tower to the solvent recovery tower;

wherein the extraction solvent is a glycol compound, an amide compound, a pyrrolidone compound or a sulfone compound, or a combination of two, three or four of them; the stripping agent is C₅～C₇Or a hydrocarbon component having a boiling point of 80 ℃ or lower in the Fischer-Tropsch synthesis oil.

According to the technical scheme, the Fischer-Tropsch synthetic oil is treated by the method of deacidification treatment and liquid-liquid extraction, the adopted extraction solvent has high selectivity to oxygen-containing compounds, good stability and large density difference with the Fischer-Tropsch synthetic oil, the solvent is recovered by a light hydrocarbon back extraction process, the recovery condition is mild, and in addition, the performance of the extraction solvent is improved by washing raffinate phase with water. The method has good effect of removing the oxygen-containing compounds in the Fischer-Tropsch synthetic oil, is easy to operate, has high recovery efficiency of the extraction solvent and the oxygen-containing compounds, can treat the Fischer-Tropsch synthetic full distillate oil, can recycle the used stripping agent and process water, and has small discharge of three wastes.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow chart of an embodiment of the method for removing the oxygen-containing compounds from the Fischer-Tropsch synthesis oil.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

As shown in FIG. 1, the invention provides a method for removing oxygen-containing compounds from Fischer-Tropsch synthesis oil, which comprises the following steps:

contacting Fischer-Tropsch synthetic oil with deacidifying agent water solution in a deacidification tower 1 for reaction and deacidification to obtain deacidified Fischer-Tropsch synthetic oil and a water phase generated after deacidification; feeding the water phase generated after deacidification into a deacidification agent recovery tower 2 for reduced pressure distillation, discharging the separated deacidification agent solution from the tower top and returning to the deacidification tower 1, and discharging the acid solution out of the deacidification agent recovery tower 2;

contacting deacidified Fischer-Tropsch synthetic oil with an extraction solvent in an extraction tower 3 for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon and an extract phase rich in oxygen-containing compounds;

contacting the raffinate phase with washing water in a washing tower 4 for washing to obtain a Fischer-Tropsch synthesis oil product with oxygen-containing compounds removed and water after washing;

enabling the extract phase and the water washed by the water to enter a solvent recovery tower 5 and to be in countercurrent contact with a back extractant, so as to obtain a lean solvent and a back extractant rich in oxygen-containing compounds;

the lean solvent enters a solvent dehydration tower 7 for dehydration, and the dehydrated lean solvent returns to the extraction tower 3; the dehydrated water returns to the water washing tower 4 to be used as water washing water;

the stripping agent rich in the oxygen compounds enters a stripping agent recovery tower 6 for reduced pressure distillation, the oxygen compounds are discharged from the bottom of the tower, and the stripping agent discharged from the top of the tower returns to the solvent recovery tower 5;

wherein the extraction solvent is glycol compounds, amide compounds, pyrrolidone compounds or sulfone compounds, orTwo or three or four of them in combination; the stripping agent is C₅～C₇Or a hydrocarbon component having a boiling point of 80 ℃ or lower in the Fischer-Tropsch synthesis oil.

The method of the invention firstly carries out deacidification treatment on the Fischer-Tropsch synthetic oil, and then adopts liquid-liquid extraction to remove the oxygen-containing compounds. The adopted extraction solvent has high selectivity to oxygen-containing compounds, good stability and large density difference with Fischer-Tropsch synthetic oil, the solvent recovery is carried out by adopting a light hydrocarbon back extraction method, the recovery condition is mild, and in addition, the performance of the extraction solvent is improved by utilizing water after washing raffinate phase. The method has good removal effect on the oxygen-containing compound in the Fischer-Tropsch synthetic oil, is easy to operate, has high recovery efficiency of the extraction solvent and the oxygen-containing compound solvent, can treat Fischer-Tropsch synthetic full distillate oil, can recycle the used stripping agent and process water, and has small discharge of three wastes.

According to the present invention, the deacidification treatment can be performed by a conventional method in the field, and is not limited herein, in a preferred embodiment, as shown in fig. 1, the deacidification agent can be contacted with the fischer-tropsch synthesis oil in a deacidification tower 1 for deacidification reaction, the deacidification agent is an alkaline substance to remove acid in the fischer-tropsch synthesis oil, and in an embodiment, the deacidification agent can be contacted with the fischer-tropsch synthesis oil in a countercurrent manner in the deacidification tower; for example, the Fischer-Tropsch synthesis oil can enter the deacidification tower 1 from the lower part, the deacidification agent aqueous solution can be sent to the deacidification tower 1 from the upper part, the water phase generated after deacidification can enter the deacidification agent recovery tower 2 to recover the deacidification agent, for example, the deacidification agent is separated by carrying out reduced pressure distillation in the deacidification agent recovery tower 2, the separated deacidification agent can be returned to the deacidification tower 1 for recycling, and the acid solution can be discharged from the deacidification agent recovery tower 2; the deacidified Fischer-Tropsch synthetic oil can be sent into the extraction tower 3 from the lower part, and is subjected to liquid-liquid extraction with the extraction solvent entering the extraction tower 3 from the upper part, so as to remove other oxygen-containing compounds in the deacidified Fischer-Tropsch synthetic oil. The deacidification column 1 and the deacidification agent recovery column 2 may be conventional in the art, and the present invention is not particularly limited, for example, the deacidification column may be a packed extraction column or a sieve plate extraction column, and the deacidification agent recovery column may be a distillation column such as a vacuum distillation column or a flash column.

The amount of the deacidification agent may be varied within a wide range, and in one embodiment, the deacidification agent is added to the deacidification tower in the form of an aqueous solution, and the concentration of the deacidification agent aqueous solution may be 5 to 40% by mass, preferably 10 to 40% by mass. The mass ratio of the deacidification agent aqueous solution to the Fischer-Tropsch synthetic oil can be (0.01-1): 1, preferably (0.05-1): 1. the deacidification conditions may also vary within a wide range, and in one embodiment, the operating temperature of the deacidification tower 1 may be 15 to 120 ℃, preferably 15 to 80 ℃, and the pressure of the deacidification tower 1 may be 0.1 to 0.5MPa, preferably 0.1 to 0.2 MPa. The operating conditions of the deacidification agent recovery tower can also be changed in a large range, and preferably, the operating temperature of the deacidification agent recovery tower is 50-350 ℃, more preferably 50-320 ℃, and the pressure is preferably 10-80 kPa, more preferably 10-50 kPa.

Wherein, the ammonium salt, the alcohol amine and the amine can be conventional in the field, and preferably, the ammonium salt can be at least one of ammonium carbonate and ammonium bicarbonate; the amine is preferably at least one of ethylenediamine, diethylamine and triethylamine; the alcohol amine is preferably monoethanolamine.

According to the present invention, the glycol-based compound, the amide-based compound, the pyrrolidone-based compound, and the sulfone-based compound as the extraction solvent may be of a kind conventional in the art, for example, the glycol-based compound may be selected from at least one of diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, preferably tetraethylene glycol and/or pentaethylene glycol, more preferably tetraethylene glycol; the amide compound may be selected from at least one of N, N-Dimethylformamide (DMF), N-dimethylacetamide, and formamide, preferably N, N-dimethylformamide; the pyrrolidone compound can be at least one selected from N-methylpyrrolidone (NMP), 2-pyrrolidone and N-vinyl pyrrolidone, and is preferably N-methylpyrrolidone; the sulfone compound may be selected from dimethyl sulfoxide and/or sulfolane.

In a preferred embodiment, as shown in FIG. 1, the extraction solvent and the deacidified Fischer-Tropsch synthetic oil are contacted in countercurrent in the extraction tower 3, i.e. countercurrent extraction is carried out; for example, the deacidified Fischer-Tropsch synthesis oil may be fed into the extraction column 3 from the lower part, and the extraction solvent may be fed into the extraction column 3 from the upper part, and may be counter-currently contacted with the deacidified Fischer-Tropsch synthesis oil, so that a hydrocarbon-rich raffinate phase and an extract phase containing the extraction solvent and the oxygen-containing compound may be obtained from the top and the bottom of the extraction column 3, respectively. Wherein the extraction column may be conventional in the art, the present invention is not particularly limited, for example, a packed extraction column or a sieve plate extraction column.

The dosage of the extraction solvent can be changed in a large range, and in one embodiment, the mass ratio of the extraction solvent to the deacidified Fischer-Tropsch synthetic oil can be (0.5-8): 1, preferably (0.5-5): 1. the liquid-liquid extraction conditions can also be changed within a large range, and in one embodiment, the temperature of the tower kettle of the extraction tower 3 can be 15-120 ℃, and is preferably 40-100 ℃; the operating pressure of the extraction column may be 0.1 to 0.5MPa, preferably 0.1 to 0.3 MPa.

According to the present invention, the raffinate phase from the extraction column 3 mainly contains hydrocarbons, and may contain a very small amount of oxygen-containing compounds and extraction solvent; the raffinate phase may be subjected to water washing in a water wash column to remove residual solvent. Wherein, the operation method and conditions for carrying out the water washing can be conventional in the field, and are not limited herein, and in one embodiment of the invention, the water washing water and the raffinate phase can be in countercurrent contact in a water washing tower; for example, the washing water may be fed into the washing tower from the upper part, and the raffinate phase from the extraction tower may be fed into the washing tower from the lower part, and the washing water may be counter-current contacted with the washing water, so that the raffinate phase after washing, i.e., the Fischer-Tropsch synthesis oil product without oxygen compounds, may be obtained from the top of the washing tower, and the water after washing containing a small amount of solvent may be obtained from the bottom of the washing tower.

According to the invention, the dosage of the water washing water can be changed in a large range, and preferably, the mass ratio of the water washing water to the raffinate phase can be (0.05-0.5): 1, more preferably (0.1 to 0.4): 1; the water washing conditions may include: the operation temperature of the water washing tower 4 is 15-120 ℃, and preferably 40-100 ℃; the operation pressure of the water washing tower 4 is 0.1 to 0.5MPa, preferably 0.1 to 0.3 MPa.

According to the method, the raffinate phase after washing obtained from the washing tower is the Fischer-Tropsch synthesis oil product without the oxygen-containing compounds and is the hydrocarbon compounds. The method has high yield of hydrocarbon compounds in the Fischer-Tropsch synthetic oil, and the obtained Fischer-Tropsch synthetic oil product has low acid value and low content of oxygen-containing compounds, and in one embodiment, the total acid value of the Fischer-Tropsch synthetic oil product is less than 0.03 mgKOH/g; the content of the oxygen-containing compound in the Fischer-Tropsch synthesis oil product can be less than 0.1 mass%; the yield of the hydrocarbon compound may be 95% by mass or more.

According to the invention, the extraction phase obtained from the extraction tower 3 is rich solvent, wherein the extraction phase mainly contains extraction solvent, oxygen-containing compound dissolved in the extraction solvent and a small amount of Fischer-Tropsch synthetic oil, the extraction phase can adopt light hydrocarbon back extraction technology to recover the solvent in the extraction phase so as to separate the oxygen-containing compound and the extraction solvent, and the extraction solvent obtained by separation is poor solvent and can be recycled; for example, the extract phase may be passed to a solvent recovery column 5 and stripped with a stripping agent to separate oxygenates from the rich solvent. In one embodiment of the present invention, as shown in fig. 1, the extract phase may enter the solvent recovery tower 5 from the upper part, the stripping agent enters the solvent recovery tower 5 from the lower part, and is contacted with the extraction phase for stripping, the stripping agent rich in the oxygen-containing compound may be obtained from the top of the solvent recovery tower 5, the stripping agent may be subjected to stripping agent recovery treatment to separate the oxygen-containing compound and the stripping agent, the separated stripping agent is returned to the solvent recovery tower 5 for recycling, and the obtained oxygen-containing compound may be further separated into products such as higher alcohols according to the need; from the bottom of the solvent recovery column 5, a lean solvent is obtained, which can be returned to the extraction column 3 for recycling.

Further, the water after washing obtained from the bottom of the water washing column may be also fed to the solvent recovery column, and for example, the water after washing may be mixed with the extract phase and fed to the solvent recovery column, in this embodiment, the lean solvent obtained from the bottom of the solvent recovery column contains water, and the water in the lean solvent may be further removed, and the obtained dehydrated lean solvent and water may be returned to the extraction column and the water washing column, respectively, for recycling; the dehydration method is not particularly limited, and examples thereof include distillation under reduced pressure and azeotropic distillation.

In order to further separate the water and the extraction solvent in the lean solvent, in a preferred embodiment, as shown in fig. 1, the lean solvent and the entrainer may be contacted in the solvent dehydration column 7 for azeotropic dehydration, for example, the lean solvent obtained from the bottom of the solvent recovery column 5 may be mixed with the entrainer and then enter the solvent dehydration column 7 from the lower part for azeotropic distillation, and the hydrocarbon-water azeotrope and the dehydrated lean solvent are obtained from the top and bottom of the column, respectively; the dehydrated lean solvent can be used as an extraction solvent to return to the extraction tower 3 so as to realize the recycling of the extraction solvent; the hydrocarbon-water azeotrope obtained at the top of the solvent dehydration column 7 can be further separated to separate the azeotropic agent from the aqueous phase by a method conventional in the art, such as liquid separation; in one embodiment, the hydrocarbon-water azeotrope can be sent into a liquid separation tank to be kept stand for layering, after the hydrocarbon water is separated into phases, the hydrocarbon phase is an entrainer and can be returned to the solvent dehydration tower 7 to be recycled, and the water phase can be returned to the water washing tower 4 as water washing water.

According to the invention, the operation conditions of the solvent recovery tower can be changed within a large range, and in one embodiment, the temperature of the tower kettle of the solvent recovery tower 5 can be 15-120 ℃, and preferably 30-80 ℃; the pressure of the solvent recovery tower is 10-40 kPa. The mass ratio of the stripping agent to the extract phase is (0.1-2): 1, preferably (0.1 to 1): 1.

according to the invention, the stripping agent used in the solvent recovery tower is alkane or cycloalkane with 5-7 carbon atoms, the alkane is preferably straight-chain alkane, and in a further preferred embodiment, the stripping agent is one or more of n-pentane, cyclopentane, n-hexane and cyclohexane.

In another embodiment, the stripping agent is a hydrocarbon component with an atmospheric boiling point of 80 ℃ or lower in the Fischer-Tropsch synthesis raw oil.

According to the present invention, the stripping agent recovery column is operated under reduced pressure, the operating conditions of which can vary over a wide range, and in one embodiment, the stripping agent recovery column 6 is a flash column, and the stripping agent and the oxygen-containing compound are obtained from the top and bottom of the column, respectively; the operation temperature of the stripping agent recovery tower 6 can be 10-80 ℃, preferably 30-60 ℃, and the pressure can be 10-80 kPa, preferably 15-40 kPa.

According to the present invention, the operating conditions of the solvent dehydration column can vary within a wide range, and in one embodiment, the temperature of the solvent dehydration column 7 can be 40 ℃ to 100 ℃, preferably 50 ℃ to 80 ℃, and the pressure can be 0.1MPa to 0.5MPa, preferably 0.1MPa to 0.4 MPa; when the azeotropic agent is used for dehydration, the amount of the azeotropic agent used can be changed within a wide range, and the mass ratio of the azeotropic agent to the lean solvent at the bottom of the solvent recovery tower is preferably (0.02-0.4): 1, more preferably (0.05 to 0.4): 1.

wherein the entrainer is preferably alkane or arene with carbon atom number of C6-C8; further preferably one or more of pentane, hexane, heptane and toluene, and the heptane is preferably n-heptane.

According to the method of the present invention, the Fischer-Tropsch synthesis oil raw material is not particularly limited, and in one embodiment, the Fischer-Tropsch synthesis oil raw material may be a Fischer-Tropsch synthesis light oil, for example, a Fischer-Tropsch synthesis oil fraction having 4 to 14 carbon atoms in hydrocarbon; in another embodiment, the Fischer-Tropsch synthesis oil raw material can be Fischer-Tropsch synthesis full distillate oil which is a fraction with 4-40 carbon atoms. The method has no requirement on the content of the oxygen-containing compound in the Fischer-Tropsch synthesis oil raw material, and in one embodiment, the content of the oxygen-containing compound in the Fischer-Tropsch synthesis oil raw material to be treated can be 1-15% by mass, the total content of normal alkane and olefin can be 20-90% by mass, and the total acid value can be 3-150 mgKOH/g. The oxygenate may include at least one of an alcohol, an aldehyde, a ketone, an acid, and an ester.

In one embodiment, as shown in FIG. 1, the method of the present invention may comprise the steps of:

the Fischer-Tropsch synthetic oil enters a deacidification tower 1 from the lower part through a pipeline 9, deacidification agent aqueous solution enters the deacidification tower 1 from the upper part through a pipeline 8, a water phase generated after deacidification obtained at the tower bottom enters a deacidification agent recovery tower 2 through a pipeline 10, the deacidification agent separated by reduced pressure distillation returns to the deacidification tower 1 for recycling through a pipeline 12, and acid liquor at the tower bottom is discharged through a pipeline 11; the deacidified Fischer-Tropsch synthetic oil obtained from the top of the deacidification tower enters the extraction tower 3 from the lower part through a pipeline 13, the extraction solvent enters the extraction tower 3 from the upper part through a pipeline 14, countercurrent contact extraction is carried out, a raffinate phase rich in hydrocarbon is discharged from the top of the extraction tower 3 through a pipeline 15 and enters the lower part of the washing tower 4, washing water enters the washing tower 4 from the upper part through a pipeline 16, the raffinate phase is washed with water and discharged from a pipeline 17 at the top of the washing tower 4, namely the Fischer-Tropsch synthetic oil product with oxygen-containing compounds removed, and the water after washing is discharged from the bottom of the washing tower 4 through a pipeline 18. The rich solvent (extraction phase) is discharged from the bottom of the extraction tower 3, mixed with water washed water discharged from the bottom of the water washing tower 4 through a pipeline 19, then enters the solvent recovery tower 5 from the upper part, and is in countercurrent contact with a back extractant fed into the solvent recovery tower 5 from the lower part through a pipeline 20 for back extraction, the obtained poor solvent is discharged from the bottom of the solvent recovery tower 5 through a pipeline 24, mixed with an entrainer entering through a pipeline 25, then enters the solvent dehydration tower 7 for azeotropic distillation dehydration, and the dehydrated poor solvent is discharged from the bottom of the solvent dehydration tower 7 and returns to the extraction tower 3 through a pipeline 26 for recycling; the hydrocarbon-water azeotrope evaporated from the top of the solvent dehydrating tower 7 is sent into a liquid separation tank to be kept stand for layering, after the hydrocarbon-water phase is separated, the hydrocarbon phase is an entrainer and returns to the solvent dehydrating tower 7 for recycling through a pipeline 27, and the water phase is used as water washing water and returns to the water washing tower 4 for recycling through a pipeline 28; the stripping agent discharged from the top of the solvent recovery tower 5 is rich in oxygen-containing compounds, enters the stripping agent recovery tower 6 through a pipeline 21 for flash evaporation, the oxygen-containing compounds are discharged from a tower bottom pipeline 23, products such as higher alcohols and the like are further separated according to requirements, and the stripping agent is discharged from the top of the stripping agent recovery tower 6 and returns to the solvent recovery tower 5 through a pipeline 22 for recycling.

The following examples further illustrate the invention but are not intended to limit the invention thereto.

Examples

The oxygen-containing compounds in the Fischer-Tropsch synthetic oil are removed according to the flow shown in figure 1.

The Fischer-Tropsch synthetic oil enters a deacidification tower 1 from the lower part through a pipeline 9, the deacidification agent aqueous solution enters the deacidification tower 1 from the upper part through a pipeline 8, the water phase generated after deacidification enters a deacidification agent recovery tower 2 through a pipeline 10, the deacidification agent separated by reduced pressure distillation returns to the deacidification tower 1 through a pipeline 12 for recycling, and the tower bottom acid solution is discharged through a pipeline 11; the deacidified Fischer-Tropsch synthetic oil obtained from the top of the deacidification tower enters the extraction tower 3 from the lower part through a pipeline 13, the extraction solvent enters the extraction tower 3 from the upper part through a pipeline 14, countercurrent contact extraction is carried out, a raffinate phase rich in hydrocarbon is discharged from the top of the extraction tower 3 through a pipeline 15 and enters the lower part of the washing tower 4, washing water enters the washing tower 4 from the upper part of the washing tower 4 through a pipeline 16, a raffinate phase is washed with water and then discharged from a pipeline 17 at the top of the washing tower 4, the Fischer-Tropsch synthetic oil product with oxygen-containing compounds removed is obtained, and the water after washing is discharged from the bottom of the washing tower 4 through a pipeline 18. The solvent-extract phase rich in the oxygen-containing compound is discharged from the bottom of the extraction tower 3, mixed with water discharged from the bottom of the water washing tower 4 through a pipeline 19 and then enters the upper part of a solvent recovery tower 5, and is in countercurrent contact with a back extractant fed into the lower part of the solvent recovery tower 5 through a pipeline 20, so that the oxygen-containing compound is dissolved in the back extractant and separated from the extraction solvent, the obtained lean solvent is discharged from the bottom of the solvent recovery tower 5 through a pipeline 24, mixed with an entrainer fed through a pipeline 25 and then enters a solvent dehydration tower 7, and after azeotropic distillation dehydration, the dehydrated lean solvent is discharged from the bottom of the dehydration tower and returns to the extraction tower 3 through a pipeline 26 for recycling; hydrocarbon-water azeotrope evaporated from the top of the solvent dehydration tower 7 is separated, the hydrocarbon phase is an entrainer and returns to the solvent dehydration tower 7 through a pipeline 27 for recycling, and the separated water phase returns to the water washing tower 4 through a pipeline 28 for recycling as water for washing; the stripping agent rich in oxygen-containing compounds and discharged from the top of the solvent recovery tower 5 enters a stripping agent recovery tower 6 through a pipeline 21, the oxygen-containing compounds are discharged from a tower bottom pipeline 23 through flash evaporation, products such as high-carbon alcohol and the like are further separated according to requirements, and the stripping agent is discharged from the top of the stripping agent recovery tower and returns to the solvent recovery tower 5 through a pipeline 22 for recycling.

The composition and properties of the Fischer-Tropsch synthetic oil are shown in Table 1, wherein the composition of the Fischer-Tropsch synthetic oil is tested by using a method for measuring the carbon number distribution (gas chromatography) of normal paraffin and non-normal paraffin of SH/T0653-1998 petroleum wax, and the acid value is tested by using a method for measuring the potentiometric titration of the acid value of GB/T7304-; examples and comparative example 1 the extraction solvent used for removing the oxygen-containing compounds from the Fischer-Tropsch synthesis light oil by liquid-liquid extraction and the operating conditions of the columns are shown in tables 2-1 and 2-2, and the composition, acid value and hydrocarbon compound yield of the oxygen-containing compound-removed Fischer-Tropsch synthesis light oil product obtained by extraction separation are shown in tables 3-1 and 3-2.

TABLE 1

N-alkanes,% by mass	41.344
		Olefin, mass%	40.481
Oxygen-containing compound(s)% by mass	4.603
		Others, by mass%	13.572
Acid value of mgKOH/g	6.07
		Boiling range, < DEG C	59.4～427.9

TABLE 2-1

Tables 2 to 2

The deacidification agent aqueous solution/oil mass ratio of the deacidification tower is the mass ratio of the deacidification agent aqueous solution to the fischer-tropsch synthetic oil, the agent/oil mass ratio of the extraction tower is the mass ratio of the extraction solvent to the deacidified fischer-tropsch synthetic oil, the water/oil mass ratio of the water washing tower is the mass ratio of the water washing water to the raffinate phase, the agent/oil mass ratio of the solvent recovery tower is the mass ratio of the stripping agent to the rich solvent (extract phase), and the stripping agent of the example 9 is hydrocarbon components with the boiling point of below 80 ℃ in the fischer-tropsch synthetic oil.

TABLE 3-1

Example number	1	2	3	4	Comparative example 1
						N-alkanes,% by mass	45.157	45.237	45.279	45.079	45.099
Olefin, mass%	44.825	44.765	44.664	44.564	44.844
						Oxygen-containing compound(s)% by mass	0.068	0.072	0.061	0.065	0.103
Others, by mass%	9.950	9.926	9.996	10.292	9.954
						Acid value of mgKOH/g	<0.02	<0.02	<0.02	＜0.02	0.04
Yield of hydrocarbon compound,% by mass	97.5	97.2	98.2	97.0	97.6

TABLE 3-2

The embodiment data show that the method has good removal effect on the oxygen-containing compounds in the Fischer-Tropsch synthetic oil, the total acid value of the obtained Fischer-Tropsch synthetic oil product can be reduced to be below 0.03mgKOH/g, the content of the oxygen-containing compounds can be reduced to be below 0.1 mass percent, the yield of the hydrocarbon compounds can reach more than 95 mass percent, and the extraction solvent, the stripping agent, the entrainer and the process water can be recycled.

The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.