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 史军军 李林玥 邹琥 刘欢 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,其中液液萃取采用甘醇复合萃取溶剂。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、易于操作且溶剂回收效率高。(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 a glycol composite 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 operate and has high solvent 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 a composite extraction solvent in an extraction tower (1) for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon compounds and an extract phase rich in oxygen-containing compounds;

contacting the raffinate phase with washing water in a washing tower (2) for washing to obtain a Fischer-Tropsch synthesis light oil product with oxygen-containing compounds removed and water after washing;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower (3), returning a lean solvent obtained at the bottom of the tower to the extraction tower (1), and discharging an oxygen-containing compound from a lateral line at the upper part of the tower;

wherein the composite extraction solvent comprises a main solvent and a cosolvent; the main solvent is a glycol compound; the cosolvent is water, ammonia water, alcohol amine compounds, amide compounds or sulfone compounds.

2. The method of claim 1, wherein the glycol-based compound is triethylene glycol, tetraethylene glycol, or pentaethylene glycol, or two or more thereof.

3. The process according to claim 1 or 2, wherein the alcamines are monoethanolamine, diethanolamine, triethanolamine or azomethyldiethanolamine, or a combination of two or three or four thereof; the amide compound is N, N-dimethylformamide, N-dimethylacetamide or urea, or a combination of two or three of the N, N-dimethylformamide, N-dimethylacetamide and urea; the sulfone compound is sulfolane and/or dimethyl sulfoxide.

4. The method according to claim 1, wherein the content of the co-solvent in the composite extraction solvent is 1-10% by mass.

5. The method according to claim 1, wherein the Fischer-Tropsch synthesis light oil enters the extraction column (1) from the lower part, and the composite extraction solvent enters the extraction column (1) from the upper part, and is in countercurrent contact with the Fischer-Tropsch synthesis light oil, and the raffinate phase and the extract phase are respectively obtained from the top and the bottom of the extraction column (1).

6. The method of claim 1, wherein the mass ratio of the composite extraction solvent to the Fischer-Tropsch synthesis light oil is (1-8): 1.

7. the method of claim 1, wherein the temperature of a tower kettle of the extraction tower (1) is 30-120 ℃; the pressure is 0.1-0.5 MPa.

8. The method according to claim 1, wherein the operating temperature of the water washing tower (2) is 15-120 ℃, and the pressure is 0.1-0.5 MPa; the mass ratio of the water washing water to the raffinate phase is (0.05-1): 1.

9. the method according to claim 1, wherein the solvent recovery column (3) has a column bottom temperature of 100 to 300 ℃ and a pressure of 0.01 to 0.08 MPa.

10. The process according to claim 1, wherein light components having a low boiling point are collected from the top of the solvent recovery column (3) and are mixed with light oil from Fischer-Tropsch synthesis and returned to the lower part of the extraction column (1).

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

12. The method according to claim 1 or 11, 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 0.2 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 synthesis light oil, which can effectively remove the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil to obtain hydrocarbon compounds by separating the oxygen-containing compounds through liquid phase extraction.

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 a composite extraction solvent in an extraction tower for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon compounds 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 light oil product with oxygen-containing compounds removed and water after washing;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower, returning the lean solvent obtained at the bottom of the tower to the extraction tower, and discharging oxygen-containing compounds from the lateral line at the upper part of the tower;

wherein the composite extraction solvent comprises a main solvent and a cosolvent; the main solvent is a glycol compound; the cosolvent is water, ammonia water, alcohol amine compounds, amide compounds or sulfone compounds.

Through the technical scheme, the composite extraction solvent adopted by the invention has high selectivity to oxygen-containing compounds, good stability and large density difference with Fischer-Tropsch synthesis light oil. The liquid-liquid extraction of Fischer-Tropsch synthesis light oil by adopting the composite extraction solvent has better removal effect of oxygen-containing compounds, easy operation and high solvent 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 a composite extraction solvent in an extraction tower 1 for liquid-liquid extraction to obtain a raffinate phase rich in hydrocarbon compounds and an extract phase rich in oxygen-containing compounds;

contacting the raffinate phase with washing water in a washing tower 2 for washing to obtain a Fischer-Tropsch synthesis light oil product with oxygen-containing compounds removed and water after washing;

carrying out reduced pressure distillation on the extract phase in a solvent recovery tower 3, returning the lean solvent obtained at the bottom of the tower to an extraction tower 1, and discharging oxygen-containing compounds from the lateral line at the upper part of the tower;

wherein, the composite extraction solvent comprises a main solvent and a cosolvent; the main solvent is glycol compound; the cosolvent is water, ammonia water, alcohol amine compounds, amide compounds or sulfone compounds.

The method of the invention treats the Fischer-Tropsch synthesis light oil, the main solvent in the adopted composite extraction solvent has high selectivity to oxygen-containing compounds, good stability and large density difference with the Fischer-Tropsch synthesis light oil, and the cosolvent can increase the solubility of the main solvent and is beneficial to removing organic acid in raw materials. The method has good effect of removing the oxygen-containing compound, is easy to operate and has high solvent recovery efficiency.

According to the invention, the Fischer-Tropsch synthesis light oil is a fraction with 4-14 carbon atoms. The method has no requirement on the content of the oxygen-containing compound in the Fischer-Tropsch synthesis light oil, the content of the oxygen-containing compound in the Fischer-Tropsch synthesis light oil 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.

According to the present invention, the glycol as the main solvent may be a conventional one in the art, for example, the glycol-based compound may be selected from triethylene glycol, tetraethylene glycol or pentaethylene glycol, or any two or three thereof.

According to the invention, the cosolvent can be water, ammonia water, alcohol amine compounds, amide compounds or sulfone compounds; wherein, the amide compound can be at least one selected from N, N-Dimethylformamide (DMF), N-dimethylacetamide and urea, and is preferably N, N-dimethylformamide and/or urea; the alcamines compound is preferably monoethanolamine, diethanolamine, triethanolamine or nitrogen methyl diethanolamine, or the combination of two or three or four of the monoethanolamine, the diethanolamine, the triethanolamine or the nitrogen methyl diethanolamine; the sulfone compound can be dimethyl sulfoxide and/or sulfolane, and is preferably dimethyl sulfoxide. Wherein the mass concentration of the ammonia water is 10 to 50 mass%.

In a preferred embodiment, the main solvent is triethylene glycol or tetraethylene glycol, and the cosolvent is water, alcohol amine, ammonia water or N, N-dimethylformamide. In the preferred embodiment, the composite extraction solvent has higher selectivity and better stability to the oxygen-containing compound when performing liquid-liquid extraction, and is more favorable for separation from the fischer-tropsch synthesis light oil.

According to the invention, the relative content of the main solvent and the cosolvent in the composite extraction solvent can be changed in a large range, and the content of the cosolvent in the composite extraction solvent can be 1-10 mass%, preferably 2-8 mass%.

In a preferred embodiment, as shown in fig. 1, the composite extraction solvent and the fischer-tropsch synthesis light oil can be contacted in the extraction column 1 in a counter-current manner, i.e. the extraction is performed in a counter-current manner; for example, the light oil from Fischer-Tropsch synthesis can enter the extraction tower 1 from the lower part, the composite extraction solvent enters the extraction tower 1 from the upper part, and is in countercurrent contact with the light oil from Fischer-Tropsch synthesis, a raffinate phase mainly containing hydrocarbon compounds is obtained from the top of the extraction tower 1, and an extract phase mainly containing oxygen-containing compounds and the composite extraction solvent is obtained from the bottom of the extraction tower 1. 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 composite extraction solvent can be changed in a large range, and in one embodiment, the mass ratio of the composite extraction solvent to the Fischer-Tropsch synthesis light oil can be (1-8): 1, preferably (1-6): 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 30-120 ℃, and is preferably 35-100 ℃; the operating pressure of the extraction tower is 0.1-0.5 MPa, preferably 0.1-0.3 MPa.

According to the invention, the raffinate phase obtained from the extraction tower 1 mainly contains hydrocarbon compounds, and also can contain a very small amount of oxygen-containing compounds and composite 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 column from the upper part thereof, and the raffinate phase from the extraction column may be fed into the washing column from the lower part thereof, and the washing water may be brought into countercurrent contact therewith, whereby the raffinate phase after washing, i.e., the oxygenate-depleted Fischer-Tropsch light oil product, may be obtained from the top of the washing column, and the water after washing containing a small amount of the solvent may be obtained from the bottom of the washing column.

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 (0.05-1): 1, more preferably (0.1 to 1): 1; the operation temperature of the water washing tower 2 can be 15-120 ℃, and is preferably 40-100 ℃; the operation pressure of the water washing column 2 may be 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 light oil product without the oxygen-containing compounds, and is the hydrocarbon compounds. The method has high yield of hydrocarbon compounds in Fischer-Tropsch synthesis light oil, and the obtained Fischer-Tropsch synthesis light 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 synthesis light oil product is less than 0.03 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 96% by mass or more.

According to the invention, the extraction phase obtained from the extraction tower 1, namely the rich solvent, mainly contains the composite extraction solvent and the oxygen-containing compound dissolved therein, and also can contain a small amount of hydrocarbon, the extraction phase can be subjected to solvent recovery to separate the oxygen-containing compound and the composite extraction solvent, and the lean solvent and the cosolvent obtained by separation can be recycled; for example, the extract phase may be fed into a solvent recovery column, where the extract phase is subjected to reduced pressure distillation to separate the oxygen-containing compounds from the rich solvent; 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 3 from the lower part to perform the vacuum distillation, an oxygen-containing compound may be obtained from a side line of the solvent recovery column 3, the oxygen-containing compound may further be separated into a higher alcohol and other products as required, a lean solvent may be obtained from the bottom of the solvent recovery column 3, and the lean solvent may be returned to the extraction column 1 for recycling. In a further embodiment, light components with low boiling point may be collected from the top of the solvent recovery column 3 and returned to the extraction column 1 to further increase the yield of the hydrocarbon compound. For example, as shown in FIG. 1, the light fraction is mixed with Fischer-Tropsch light oil and returned to the lower part of the extraction column. Wherein, the light component with low boiling point is cosolvent, and the boiling point of the cosolvent is lower than that of the oxygen-containing compound.

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 3 can be 100-300 ℃, and is 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 conventional in the art, for example, a tray column or a packed column.

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

the Fischer-Tropsch synthesis light oil enters an extraction tower 1 from the lower part through a pipeline 5, a composite extraction solvent enters the extraction tower 1 from the upper part through a pipeline 4, through countercurrent extraction, raffinate rich in hydrocarbon compounds is discharged from the top of the extraction tower 1 and enters the lower part of a water washing tower 2 through a pipeline 6, water washing water enters the upper part of the water washing tower 2 through a pipeline 7, the raffinate is discharged from a pipeline 8 at the top of the water washing tower 2 after being washed with water, namely the Fischer-Tropsch synthesis light oil product without oxygenated compounds, and the water after washing is discharged from the bottom of the water washing tower 2 through a pipeline 9. The rich solvent (extraction phase) rich in the oxygen-containing compound is discharged from the bottom of the extraction tower 1, enters the solvent recovery tower 3 from the lower part through a pipeline 10, the oxygen-containing compound is discharged from a side line 13 of the solvent recovery tower through reduced pressure distillation, a high-carbon alcohol product is further separated according to needs, the poor solvent is discharged from the bottom of the recovery tower 3 and returns to the extraction tower 1 through a pipeline 11 for recycling, the light components with low boiling point are discharged from the top of the solvent recovery tower, and the light components are mixed with the Fischer-Tropsch synthesis light oil from a pipeline 5 through a pipeline 12 and then enter the lower part of the extraction tower 1.

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.

Fischer-Tropsch synthesis light oil enters the extraction tower 1 from the lower part through a pipeline 5, the composite extraction solvent enters the extraction tower from the upper part, through countercurrent extraction, raffinate rich in hydrocarbon compounds is discharged from the top of the extraction tower 1 and enters the lower part of the raffinate phase washing tower 2, washing water enters from the upper part of the washing tower 2, the raffinate is discharged from the top of the washing tower 2 after being washed, namely the Fischer-Tropsch synthesis light oil product without oxygenated compounds, and the washing water is discharged from the bottom of the washing tower. The rich solvent is discharged from the bottom of the extraction tower 1, enters the solvent recovery tower 3 from the lower part through a pipeline 10, is subjected to reduced pressure distillation, the obtained lean solvent is discharged from the bottom of the recovery tower 3 and returns to the extraction tower for recycling through a pipeline 11, the low-boiling-point components are discharged from the top of the solvent recovery tower, are mixed with Fischer-Tropsch synthesis light oil from a pipeline 5 through a pipeline 12 and then return to the extraction tower 1, and the oxygen-containing compounds are discharged from a side line 13 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 compounds from the Fischer-Tropsch synthesis light oil by liquid-liquid extraction and the operation conditions of each column are shown in tables 2-1 and 2-2, and the composition, acid value and hydrocarbon compound yield of the Fischer-Tropsch synthesis light oil products with the oxygen-containing compounds removed by extraction and separation are shown in tables 3-1 and 3-2.

Comparative example

According to the flow shown in figure 1, only the main solvent is used, no cosolvent is added, the oxygen-containing compounds in the Fischer-Tropsch synthesis light oil are removed by liquid-liquid extraction, the operation conditions of each tower are shown in a table 2-1, and the composition, the acid value and the hydrocarbon compound yield of the Fischer-Tropsch synthesis light oil product with the oxygen-containing compounds removed by extraction and separation are shown in a table 3-1.

TABLE 1

N-alkanes,% by mass	37.032
		Olefins, paraffins, and olefinsThe content of	42.628
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

Tables 2 to 2

The mass ratio of the solvent to the Fischer-Tropsch synthesis light oil is the mass ratio of the solvent to the Fischer-Tropsch synthesis light oil, and the mass ratio of the water to the oil of the water washing tower is the mass ratio of the water washing water to the raffinate phase. The content of the cosolvent is the content of the cosolvent in the composite extraction solvent (the sum of the main solvent and the cosolvent)

TABLE 3-1

TABLE 3-2

The example data 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 obtained Fischer-Tropsch synthesis light oil product can be reduced to be below 0.03mgKOH/g, the content of the oxygen-containing compounds can be reduced to be below 0.15 mass percent, and the yield of the hydrocarbon compounds can be up to more than 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.