阅读说明：本技术 一种脱除费托合成轻油中含氧化合物的方法 (Method for removing oxygen-containing compounds in Fischer-Tropsch synthesis light oil ) 是由 邹琥 刘欢 史军军 李林玥 葸雷 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轻油中含氧化合物的方法。该方法包括液液萃取、水洗和溶剂回收,其中液液萃取采用离子液体作为萃取溶剂。本发明的方法采用的萃取溶剂具有对含氧化合物选择性高、稳定性好、且与费托合成轻油密度差大等特点,该方法对含氧化合物的脱除效果好、溶剂易于回收且回收效率高。(The invention relates to a method for removing oxygen-containing compounds in Fischer-Tropsch synthesis light oil. The method comprises liquid-liquid extraction, water washing and solvent recovery, wherein the liquid-liquid extraction adopts ionic liquid as an extraction solvent. The extraction solvent adopted by the method has the characteristics of high selectivity to oxygen-containing compounds, good stability, large density difference with Fischer-Tropsch synthesis light oil and the like, and the method has good removal effect on the oxygen-containing compounds, is easy to recover and has high recovery efficiency.)

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

contacting Fischer-Tropsch synthesis light oil with an extraction solvent in an extraction tower (1) for liquid-liquid extraction to obtain a raffinate phase and an extract phase rich in oxygen-containing compounds, wherein the raffinate phase is the Fischer-Tropsch synthesis light oil without the oxygen-containing compounds;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower (2), discharging oxygen-containing compounds from the top of the tower, and returning a lean solvent discharged from the bottom of the tower to the extraction tower (1);

wherein the extraction solvent is ionic liquid, and the cation of the ionic liquid has a structure shown in a formula (I) or a formula (II);

in the formula (I), R₂、R₄And R₅Each independently is H, R₁And R₃Are respectively selected from C₁～C₄One of alkyl, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl of (a); in the formula (II), R₇、R₈、R₉、R₁₀And R₁₁Each independently is H or C₁～C₃Alkyl of R₆One selected from alkyl with 6-8 carbon atoms, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl.

2. The process of claim 1, wherein in formula (II), R₆Selected from alkyl with 6-8 carbon atoms, R₈、R₉And R₁₀Any one of them is an alkyl group having 1 to 3 carbon atoms, and the others are H.

3. The process of claim 1, wherein in formula (II), R₆Is one of aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl, R₈、R₉And R₁₀Any one of them is an alkyl group having 1 to 3 carbon atoms, and the others are H.

4. A process according to any one of claims 1 to 3, wherein the anion of the ionic liquid is BF₄ ^-、PF₆ ^-One or more of bis (trifluoromethanesulfonyl) imide, sulfonate and oxalate.

5. The process of claim 1, wherein the extraction solvent further comprises a co-solvent selected from one or more of sulfolane, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and N-methylpyrrolidone; the mass ratio of the cosolvent to the ionic liquid is 0.01-0.1.

6. The process according to claim 1, wherein the light fischer-tropsch synthesis oil is fed into an extraction column (1) from below, the extraction solvent is fed into the extraction column (1) from above, and is contacted with the light fischer-tropsch synthesis oil in a countercurrent manner, the raffinate phase is discharged from the top of the extraction column (1), and the extract phase is discharged from the bottom of the extraction column; the mass ratio of the extraction solvent to the Fischer-Tropsch synthesis light oil is (0.5-5): 1.

7. the method of claim 1, wherein the temperature of the bottom of the extraction column (1) is 20-120 ℃ and the pressure is 0.1-0.5 MPa.

8. The method according to claim 1, wherein the temperature of the bottom of the solvent recovery column (2) is 100 to 300 ℃ and the pressure is 0.01 to 0.08 MPa.

9. The method according to claim 1, wherein the Fischer-Tropsch light oil is a fraction having a hydrocarbon carbon number of 4 to 16.

10. The method according to claim 1 or 9, wherein the Fischer-Tropsch light 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 synthesis light 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 0.2w percent, 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 oxygen-containing compounds in the Fischer-Tropsch synthetic oil, but the process of hydrofining oxygen-containing compound removal 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 synthesis light oil, which can effectively remove the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil through liquid phase extraction to obtain hydrocarbon compounds.

In order to achieve the above object, the present invention provides a method for removing oxygen-containing compounds from light oil of fischer-tropsch synthesis, comprising:

contacting Fischer-Tropsch synthesis light oil with an extraction solvent in an extraction tower for liquid-liquid extraction to obtain a raffinate phase and an extract phase rich in oxygen-containing compounds, wherein the raffinate phase is the Fischer-Tropsch synthesis light oil without the oxygen-containing compounds;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower, discharging oxygen-containing compounds from the top of the tower, and returning a lean solvent discharged from the bottom of the tower to the extraction tower;

wherein the extraction solvent is ionic liquid, and the cation of the ionic liquid has a structure shown in a formula (I) or a formula (II);

in the formula (I), R₂、R₄And R₅Each independently is H, R₁And R₃Are respectively selected from C₁～C₄One of alkyl, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl of (a); in the formula (II), R₇、R₈、R₉、R₁₀And R₁₁Each independently is H or C₁～C₃Alkyl of R₆One selected from alkyl with 6-8 carbon atoms, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl.

Through the technical scheme, the ionic liquid with a proper structure is used as the extraction solvent, the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil are removed by a liquid-liquid extraction method, and the used extraction solvent has high selectivity and good stability on the oxygen-containing compounds, has large density difference with the Fischer-Tropsch synthesis light oil, has a good removal effect on the oxygen-containing compounds, is easy to recover, and has high recovery efficiency.

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 oxygenates from Fischer-Tropsch synthesis light oil of the present invention.

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 present invention provides a method for removing oxygen-containing compounds from Fischer-Tropsch synthesis light oil, comprising:

contacting Fischer-Tropsch synthesis light oil with an extraction solvent in an extraction tower 1 for liquid-liquid extraction to obtain a raffinate phase and an extract phase rich in oxygen-containing compounds, wherein the raffinate phase is the Fischer-Tropsch synthesis light oil without the oxygen-containing compounds;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower 2, discharging oxygen-containing compounds from the top of the tower, and returning a lean solvent discharged from the bottom of the tower to the extraction tower 1;

wherein the extraction solvent is ionic liquid, and the cation of the ionic liquid has a structure shown in a formula (I) or a formula (II);

in the formula (I), R₂、R₄And R₅Each independently is H, R₁And R₃Are respectively selected from C₁～C₄One of alkyl, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl of (a); in the formula (II), R₇、R₈、R₉、R₁₀And R₁₁Each independently is H or C₁～C₃Alkyl of R₆One selected from alkyl with 6-8 carbon atoms, aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl.

The method adopts the ionic liquid with the cation with the structure shown in the formula (I) or the formula (II) as an extraction solvent, and the N atom on the imidazole ring or the pyridine ring of the cation is provided with a polar group or a proper alkyl group, so that the selectivity and the solubility to oxygen-containing compounds can be improved, and the ionic liquid has good stability, large density difference with Fischer-Tropsch synthesis light oil and easy separation. The ionic liquid is used as an extraction solvent, and the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil are removed by liquid-liquid extraction, so that the removal effect is good, the operation is easy, the solvent is convenient to recover, and the recovery efficiency is high.

According to the invention, the Fischer-Tropsch synthesis light oil is a fraction with 4-16 carbon atoms. The method has no requirement on the content of oxygen-containing compounds in Fischer-Tropsch synthesis light oil, the content of the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil is 1-15% by mass, the total content of normal alkane and olefin can be 20-90% by mass, preferably 70-90% 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.

According to the invention, in formula (I), R₁And R₃Each independently may be one of an alkyl group having 1 to 4 carbon atoms, an aminoethyl group, an aminopropyl group, a carboxymethyl group, a carboxyethyl group and a carboxypropyl group. R₁And R₃May be the same or different. Wherein the alkyl group having 1 to 4 carbon atoms is at least one of methyl, ethyl, n-propyl, n-butyl and isobutyl.

According to the invention, in the formula (II), on the pyridine ring, C₁～C₃The number and position of the alkyl group of (A) are not particularly limited, R₇、R₈、R₉、R₁₀And R₁₁For example, one or two or three or four of these are H, the remainder are each C₁～C₃For example, methyl, ethyl, n-propyl or isopropyl.

In a preferred embodiment, in formula (II), R₆Is alkyl with 6-8 carbon atoms, such as n-hexyl, n-heptyl or n-octyl, R₈、R₉And R₁₀Any one of them is an alkyl group having 1 to 3 carbon atoms, and the others are H. In another embodiment, R₆Is one of aminoethyl, aminopropyl, carboxymethyl, carboxyethyl and carboxypropyl, R₈、R₉And R₁₀Any one of them is an alkyl group having 1 to 3 carbon atoms, and the others are H.

The anion of the ionic liquid described herein can be any anion capable of forming an ionic liquid. In a preferred embodiment, the anion of the ionic liquid is BF₄ ^-、PF₆ ^-At least one of bistrifluoromethanesulfonylimide, sulfonate and oxalate, more preferably BF₄ ^-Or PF₆ ^-。

In the process according to the present invention, a preferred ionic liquid may be at least one of 1-carboxyethyl-4-methylpyridine tetrafluoroborate, 1-aminoethyl-4-methylpyridine hexafluorophosphate, 1-aminoethyl-3-methylpyridine hexafluorophosphate, 1, 3-dibutylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluoroborate, 1-heptyl-4-methylpyridine hexafluorophosphate, 1-heptyl-3-methylpyridine hexafluorophosphate, 1-carboxypropyl-4-methylpyridine bistrifluoromethylsulfonylimide salt and 1-aminopropyl-4-methylpyridine p-toluenesulfonate.

According to an embodiment of the present invention, the extraction solvent may further include a cosolvent, and the cosolvent may be an amide compound, a pyrrolidone compound, or a sulfone compound, and is preferably one or more of sulfolane, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and N-methylpyrrolidone. In this embodiment, the relative content of the ionic liquid and the cosolvent in the extraction solvent can vary within a wide range, for example, the mass ratio of the cosolvent to the ionic liquid can be 0.01 to 0.1, preferably 0.02 to 0.08.

In a preferred embodiment, as shown in fig. 1, the extraction solvent and the fischer-tropsch synthesis light oil can be contacted countercurrently in the extraction column 1, i.e. countercurrent extraction is performed; for example, the Fischer-Tropsch light oil may be introduced into the extraction column 1 from the bottom, the extraction solvent may be introduced into the extraction column 1 from the top, and the extraction solvent may be brought into countercurrent contact with the Fischer-Tropsch light oil, whereby the raffinate phase may be discharged from the top of the extraction column 1, and the extract phase may be discharged from the bottom of the extraction column. The extraction column may be conventional in the art, and 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 Fischer-Tropsch synthesis light oil can be (0.5-5): 1, preferably (1-4): 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 1 can be 20-120 ℃, and is preferably 30-100 ℃; the operating pressure of the extraction tower is 0.1-0.5 MPa, preferably 0.1-0.3 MPa.

According to the present invention, the raffinate phase obtained from the extraction column 1 is a Fischer-Tropsch synthesis light oil from which oxygenates have been removed, is a hydrocarbon compound, and can be discharged as a product. The method has high yield of hydrocarbon compounds in Fischer-Tropsch synthesis light oil, and the obtained Fischer-Tropsch synthesis light oil product without oxygen compounds has low acid value and low oxygen compounds content, and in one embodiment, the total acid value of the Fischer-Tropsch synthesis light oil product is less than 0.05mgKOH/g, for example less than 0.02 mgKOH/g; the content of oxygen-containing compounds in the Fischer-Tropsch synthesis light oil product can be below 0.15 mass%; the yield of the hydrocarbon compound may be 95% by mass or more, for example 96% by mass or more.

According to the invention, the extraction phase obtained from the extraction column 1, i.e. rich solvent, mainly contains extraction solvent and oxygen-containing compound dissolved in the extraction solution, the extraction phase can be subjected to solvent recovery, the oxygen-containing compound and the extraction solvent are separated, and the extraction solvent obtained by separation is lean solvent and can be recycled; for example, in one embodiment, the extract phase may be fed to a solvent recovery column where a reduced pressure distillation process is used to separate the oxygenate from the extraction solvent in the extract phase; the operation method of performing the vacuum distillation may be conventional in the art, and is not limited herein, and in one embodiment of the present invention, as shown in fig. 1, the extract phase may enter the solvent recovery column 2 from the lower part to perform the vacuum distillation, an oxygen-containing compound may be obtained from the top of the solvent recovery column 2, the oxygen-containing compound may further be separated into higher alcohols and other products as required, a lean solvent may be obtained from the bottom of the solvent recovery column 2, and the lean solvent may be returned to the extraction column 1 for recycling.

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 2 is 100-300 ℃, preferably 150-250 ℃; the pressure of the solvent recovery tower is 0.01 to 0.08MPa, preferably 0.03 to 0.06 MPa. The solvent recovery column may be a vacuum distillation column as is conventional in the art.

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

Fischer-Tropsch synthesis light oil enters the extraction tower 1 from the lower part through a pipeline 4, an extraction solvent enters the extraction tower from the upper part through a pipeline 3, and through countercurrent extraction, a raffinate phase is discharged from the top of the extraction tower 1 through a pipeline 5, so that the Fischer-Tropsch synthesis light oil product with oxygen-containing compounds removed is obtained. The rich solvent (extract phase) rich in the oxygen-containing compound is discharged from the bottom of the extraction column, enters the lower part of the solvent recovery column 2 through a line 6, is subjected to reduced pressure distillation, the lean solvent is discharged from the bottom of the solvent recovery column and returns to the extraction column 1 through a line 7 for recycling, the oxygen-containing compound is discharged from a line 8 at the top of the solvent recovery column, and products such as higher alcohols and the like are further separated as required.

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 synthesis light oil are removed according to the flow shown in figure 1.

The Fischer-Tropsch synthesis light oil enters the extraction tower 1 from the lower part through a pipeline 4, the solvent enters the extraction tower from the upper part through a pipeline 3, and through countercurrent extraction, the raffinate phase is discharged from the top of the extraction tower 1 through a pipeline 5, so that the Fischer-Tropsch synthesis light oil product with the oxygen-containing compounds removed is obtained. The rich solvent is discharged from the bottom of the extraction tower, enters the lower part of the solvent recovery tower 2 through a pipeline 6, is subjected to reduced pressure distillation, the poor solvent is discharged from the bottom of the solvent recovery tower and returns to the extraction tower 1 for recycling through a pipeline 7, and the oxygen-containing compound is discharged from a pipeline 8 at the top of the solvent recovery tower.

The composition and properties of Fischer-Tropsch synthesis light oil are shown in Table 1, wherein the composition of Fischer-Tropsch synthesis light 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 potentiometric titration method for measuring the acid value of GB/T7304-; the extraction solvent used for removing the oxygen-containing compound by liquid-liquid extraction and the operation conditions of each column are shown in tables 2-1 and 2-2, and the composition and acid value of the Fischer-Tropsch synthesis light oil product from which the oxygen-containing compound is removed by extraction and separation and the yield of the hydrocarbon compound in the Fischer-Tropsch synthesis light oil after extraction and separation are shown in tables 3-1 and 3-2.

TABLE 1

N-alkanes,% by mass	38.032
		Olefin, mass%	41.628
Oxygen-containing compound(s)% by mass	6.791
		Others, by mass%	13.549
Acid value of mgKOH/g	5.11
		Boiling range, < DEG C	89.4～231.1

TABLE 2-1

The mass ratio of the solvent to the oil of the extraction tower is the mass ratio of the extraction solvent to the Fischer-Tropsch synthesis light oil.

Tables 2 to 2

TABLE 3-1

TABLE 3-2

Example number	8	9	10
				N-alkanes,% by mass	44.138	44.105	43.627
Olefin, mass%	47.105	47.138	47.616
				Oxygen-containing compound(s)% by mass	0.130	0.127	0.120
Others, by mass%	8.627	8.630	8.637
				Acid value of mgKOH/g	<0.02	<0.02	<0.02
Yield of hydrocarbon compound,% by mass	97.4	96.8	97.2

The data of the examples show that the method of the invention has good effect of removing the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil, the total acid value of the Fischer-Tropsch synthesis light oil product can be reduced to below 0.02mgKOH/g, the content of the oxygen-containing compounds can be reduced to below 0.14 mass percent, and the yield of the hydrocarbon compounds can reach above 96 mass percent.

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.