A process for removing oxygenates from fischer-tropsch naphtha

Abstract

The application provides a method for removing oxygen-containing compounds from Fischer-Tropsch naphtha, which comprises the following steps: (1) reacting Fischer-Tropsch naphtha, a catalyst, isopropyl alcohol and glycol in a stirring reactor, and then standing and separating; (2) extracting the upper hydrocarbon phase after standing with an extractant to obtain an extraction phase and a raffinate phase; (3) recovering the solvent in a solvent recovery column, obtaining oxygen-containing compounds at the top of the column, and recycling the solvent obtained at the bottom of the column as the extractant; (4) washing the raffinate phase with water to obtain Fischer-Tropsch naphtha from which the oxygen-containing compounds are removed and washed water, recycling the washed water to the water washing column for water washing, and recycling the product at the bottom of the water recovery column as the extractant; the extractant is a mixture of ester compounds and glycol compounds, and the content of the glycol compounds is 40-70%; and the method can reduce the oxygen-containing compounds in the Fischer-Tropsch naphtha to 5 ppm, and the oil recovery rate reaches more than 95%.

Description

Technical Field

[0001] This invention relates to a method for separating impurities in hydrocarbon streams, specifically, a method for removing oxygen-containing compounds from hydrocarbon streams. Background Technology

[0002] The Fischer-Tropsch synthesis reaction involves the reaction of syngas at specific temperatures and pressures using iron or cobalt catalysts to produce a series of compounds containing alkanes, alkenes, and oxygen-containing compounds. The carbon chain lengths of the products range from 1 to over 100, with straight-chain hydrocarbons being the predominant type. The oxygen-containing compounds are mainly fatty alcohols, along with small amounts of acids, esters, ketones, and aldehydes. The presence of oxygen-containing compounds in Fischer-Tropsch synthetic oils can easily poison and deactivate catalysts in downstream processes, increasing the cost and operating expenses of subsequent product utilization and limiting the comprehensive utilization and extension of the Fischer-Tropsch synthetic oil industry chain.

[0003] Currently, the main industrial method for removing oxygen-containing compounds is to hydrogenate compounds containing alkenes, alkanes, and oxides. Other methods for separating and extracting fatty alcohols and removing oxygen-containing compounds include adsorption and extraction.

[0004] CN 112126461 A discloses a method for removing oxides from Fischer-Tropsch oil, comprising: alkaline washing of the Fischer-Tropsch oil with an alkaline aqueous solution, followed by water washing; adding an aqueous solution of bisulfite to the Fischer-Tropsch oil, reacting fully, and then removing the aqueous phase; and adding ethylene glycol or polyethylene glycol to the Fischer-Tropsch oil to remove the alcohol. This invention uses a combined reaction-extraction-adsorption process, which can remove oxides to below 1 ppm. However, this method is complex.

[0005] US2746984 discloses a method for separating aliphatic alcohols from a mixture of alcohols and hydrocarbons. First, boric acid is reacted with the alcohol in the mixture to form an ester. Then, the ester is extracted with solvents such as methanol, ethanol, or water. Finally, the boric acid ester is hydrolyzed to obtain the aliphatic alcohol. However, this method involves two chemical steps—esterification and hydrolysis—making it cumbersome, and it does not specify the content of oxygen-containing compounds in the separated hydrocarbons.

[0006] US2610977 discloses a method for separating alcohols from hydrocarbons, specifically a method for extraction using an aqueous solution of a lower alcohol, which is an aqueous methanol solution. However, the ratio of the extractant phase to the oil is 8-9:1, the amount of extractant used is large, and the solvent recovery method uses a lower hydrocarbon extraction method.

[0007] GB716131 discloses extraction using an aqueous solution of low-carbon alcohols. However, due to the wide distillation range of the feed oil, the use of the same extractant for both small-molecule and large-molecule oxygenated compounds results in a high hydrocarbon content in the extract.

[0008] CN101891589B discloses a method for extracting fatty alcohols. This method includes distillation to separate the Fischer-Tropsch product into four fractions; extracting each fraction with water and aqueous solutions of ethanol at different concentrations. To reduce the hydrocarbon content in the fatty alcohols, the method further includes back-extraction of the alcohol phase obtained from the extraction with alkanes of different carbon numbers. However, the recovery rate of fatty alcohols is only about 95%, indicating that a relatively high amount of oxygen-containing compounds remain in the hydrocarbon phase.

[0009] CN100575320C and CN100383096C both disclose methods for extracting oxygen-containing compounds from hydrocarbon streams, using a mixture of methanol and water as a solvent; however, this method is only applicable to C. 10 -C 13 Remove oxygen-containing compounds from the logistics.

[0010] WO9958625 discloses a method for removing oxide impurities from hydrocarbon streams using a light polar solvent formed from acetonitrile / water. This method is only applicable to C8-C hydrocarbons. 10 Remove oxygen-containing compounds from the logistics.

[0011] US4686317 discloses a method for removing oxide impurities from a stream of light hydrocarbons (C2 to C9). The method includes extracting the oxides using the heavy oil polar solvents propylene carbonate and 2-ethanolamine, washing the extracted hydrocarbon stream with water to recover the dissolved solvent, and combining the solvent phase obtained from the extraction with the aqueous phase in the washer and then distilling together to recover the solvent.

[0012] However, most existing technologies only target the separation and extraction of alcohols in hydrocarbon streams, and do not address the separation of ketones and aldehydes in hydrocarbon streams. Summary of the Invention

[0013] To overcome the shortcomings of the prior art, the present invention provides a commercially feasible method for removing oxygen-containing compounds from a hydrocarbon stream while maintaining the olefin content in the hydrocarbon stream.

[0014] To achieve the objectives of this invention, the following technical solution is adopted:

[0015] A method for removing oxygen-containing compounds from Fischer-Tropsch naphtha includes the following steps: (1) Fischer-Tropsch naphtha is reacted with isopropanol and glycol compounds in a stirred reactor in the presence of a catalyst, and then separated into layers after standing.

[0016] (2) The upper hydrocarbon phase after standing in step (1) is subjected to countercurrent extraction with the extractant in the extraction tower to obtain the extract phase and the raffinate phase;

[0017] (3) The extract phase is subjected to solvent recovery in the solvent recovery tower. Oxygen-containing compounds are obtained at the top of the tower, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as an extractant.

[0018] (4) The raffinate phase is washed with water in a water washing tower to obtain Fischer-Tropsch naphtha (hydrocarbon phase) and water after washing (aqueous phase) after removing oxygen-containing compounds. The water after washing enters a water recovery tower for recovery. The top product of the water recovery tower is recycled to the water washing tower for water washing, and the bottom product is recycled to the extraction tower as an extractant.

[0019] In step (2), the extractant is a composite extraction solvent of ester compounds and glycol compounds, wherein the content of glycol compounds is 40-70%. The extraction process of the present invention utilizes the coupling effect of ester compounds and glycol compounds to effectively remove ketones, aldehydes, alcohols, and ester impurities from Fischer-Tropsch naphtha. In some specific embodiments, the glycol compounds in the extractant of steps (1) and (2) are selected from diethylene glycol and / or triethylene glycol, and the ester compounds are selected from lipid compounds and / or lactone compounds, wherein the lipid compounds are preferably ethylene glycol carbonates, and the lactone compounds are preferably γ-butyrolactone.

[0020] The Fischer-Tropsch naphtha used in the preparation method of this invention is a fraction of the Fischer-Tropsch reaction condensate product, which can be a condensate product of a low-temperature or high-temperature Fischer-Tropsch reaction. Specifically, the Fischer-Tropsch naphtha can be composed of C5-11 alkanes, alkenes and C2-10 oxygen-containing compounds, with a distillation range of 30-200°C, or any fraction with a distillation range of less than 200°C, such as 30-180°C, 40-150°C, etc. The oxygenated compounds in Fischer naphtha are 0.1-15%, including ketones, aldehydes, alcohols and esters. In the specific step (1), the ratio of isopropanol to the ketones and aldehydes in Fischer naphtha is (2-10):1, for example, 3:1, 5:1, 6:1, 8:1; and the ratio of catalyst to the ketones and aldehydes in Fischer naphtha is (0.01-0.1):1, for example, 0.02:1, 0.03:1, 0.06:1, 0.07:1, 0.09:1.

[0021] In a specific embodiment of the method of the present invention, in step (1), Fischer-Tropsch naphtha reacts with isopropanol and glycol in a stirred reactor for 30–120 min, for example, 50 min, 60 min, 80 min, or 110 min; the reaction temperature is 40–60 °C, for example, 45 °C, 50 °C, or 55 °C. In some specific embodiments, the stirred reactor includes a hydrocarbon stream inlet, an isopropanol + catalyst + glycol inlet, a stirring valve, a condenser outlet, and a hydrocarbon stream outlet.

[0022] The catalyst selected in this invention is aluminum isopropoxide, aluminum triethanolamine, or aluminum tributoxide.

[0023] In some specific embodiments, the reaction solution after step (1) is allowed to stand and separate into layers. The upper hydrocarbon phase obtained after separation is drawn out for extraction reaction, while the lower phase remains in the stirred reactor. At the same time, fresh Fischer naphtha and isopropanol are added to continue the reaction under stirring.

[0024] In step (2) of the method of the present invention, the upper hydrocarbon phase and the extractant are extracted in a countercurrent manner in the extraction tower. Specifically, the extraction temperature in the extraction tower is 10 to 50°C, preferably 20 to 50°C, for example, 30°C or 40°C; the theoretical number of extraction stages in the extraction tower is 7 to 10 stages.

[0025] In some specific embodiments, the amount of extractant used is 0.5 to 4 times the weight of the upper hydrocarbon phase, preferably 0.8 to 2 times, for example, 1 time or 1.5 times.

[0026] In step (3) of the method of the present invention, the extract phase obtained after extraction is sent into a solvent recovery tower for solvent recovery. Oxygen-containing compounds are separated at the top of the tower, and the solvent obtained at the bottom of the tower is returned to the extraction tower in step (2) for recycling as an extractant. In some specific embodiments, the temperature of the solvent recovery process is 190 to 195°C, the pressure is 0.05 to 0.1 MPa, and the reflux ratio is 0.5 to 1.5.

[0027] In step (4) of the method of the present invention, the raffinate from the extraction tower is sent to the water washing tower and washed with the washing water. In some specific embodiments, the washing temperature in the water washing tower is 20-50°C, and the weight ratio of the washing water to the raffinate is (0.3-1):1. The washed water obtained after washing enters the water recovery tower for recovery. The top product of the water recovery tower is recycled to the water washing tower, and the bottom product of the water recovery tower is returned to the extraction tower in step (2) as the extractant.

[0028] The above technical solution achieves the following technical effects:

[0029] The reaction + extraction method of this invention not only maintains the α-olefin content in Fischer-Tropsch synthetic oil, but also effectively removes alcohols, ketones, aldehydes, acids and esters from the Fischer-Tropsch synthetic oil. The content of oxygenated compounds in the deoxygenated Fischer-Tropsch synthetic oil is reduced to below 5 ppm, and the oil recovery rate is high, reaching over 95%.

[0030] The method of the present invention adds glycols, which are poorly compatible with hydrocarbons, during the reaction process, which not only does not reduce the reaction activity, but also allows the catalyst in the reaction process to be reused. Attached Figure Description

[0031] Figure 1 The following is a flowchart illustrating a specific process for removing oxygen-containing compounds from Fischer-Tropsch naphtha in this embodiment of the invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0035] The raw material used in this invention, Fischer-Tropsch naphtha, is a fraction of the Fischer-Tropsch synthesis product. It is obtained by cutting the Fischer-Tropsch synthesis product and is mainly composed of C5-11 alkanes, alkenes, and C2-10 oxygen-containing compounds, with a distillation range of 33-200℃. The specific composition of the Fischer-Tropsch naphtha used in the following examples and comparative examples is shown in Tables 1 and 2.

[0036] Table 1

[0037]

[0038] Table 2

[0039]

[0040] The evaluation methods for the products obtained in the following embodiments and comparative examples are as follows:

[0041] Deoxidized naphtha recovery rate (%) = Mass of Fischer-Tropsch naphtha with oxygenated compounds removed obtained from the water washing tower / (Fischer-Tropsch naphtha feed rate × (1 - oxygenated compound content %)) × 100%

[0042] The contents of each component in Fischer-Tropsch naphtha were determined by chromatographic methods, and the contents of alcohols and esters among the oxygen-containing compounds were determined by chromatographic methods.

[0043] Determination of carbonyl oxygen content: Refer to GB / T 6324.5-2008;

[0044] Example 1

[0045] (1) Add 20kg of Fischer-Tropsch naphtha, 100g of aluminum isopropoxide, 1.0kg of isopropanol and 10kg of diethylene glycol to a stirred reactor. Stir the reaction at 50℃ for 1h. After the reaction is completed, let it stand for 30min to obtain the upper hydrocarbon phase and the lower stream.

[0046] (2) Diethylene glycol and ethylene glycol carbonate were used as a composite extraction solvent (the proportion of diethylene glycol in the composite extractant was 60%). The solvent was subjected to multi-stage countercurrent extraction with the upper hydrocarbon phase obtained after the reaction was allowed to stand in the extraction tower. The extraction temperature was 40℃, the feed rate of the composite extraction solvent was 15 g / min, and the feed rate of the upper hydrocarbon phase was 10 g / min (the ratio of the amount of composite extraction solvent to the amount of upper hydrocarbon phase was 1.5:1). The theoretical number of extraction stages was 7, and the extract phase and raffinate phase were obtained.

[0047] (3) The extract phase is introduced into the solvent recovery tower for solvent recovery. The solvent recovery temperature is 192-195℃, the pressure is 0.08MPa, and the reflux ratio is controlled at 0.5. The top of the solvent recovery tower yields oxygen-containing compounds, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as an extractant.

[0048] (4) The raffinate is introduced into the water washing tower and washed with the washing water. A small amount of extractant is washed away by the water washing method to obtain Fischer naphtha with oxygen-containing compounds removed and water after washing. The water washing temperature is 50°C and the weight ratio of water to raffinate is 0.3:1.

[0049] After washing, the water enters the water recovery tower for recycling. The temperature inside the water recovery tower is 155-160℃, and the reflux ratio is 0.5. The top product of the water recovery tower is recycled to the water washing tower for washing, and the bottom product is recycled to the extraction tower as an extractant.

[0050] 20 kg of raw naphtha was processed using the above method to obtain 18798.5 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 97.2%.

[0051] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 52.6 wt% (α-olefin retention rate 97.0%), the alcohol content in the oxygen-containing compounds was 0 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 2 ppm (by weight).

[0052] Example 2

[0053] (1) The lower layer material after the reaction in Example 1 was retained in the stirred reactor (the lower layer material contained 300g of isopropanol and 100g of aluminum isopropoxide after analysis and calculation). 20kg of Fischer-Tropsch naphtha and 700g of isopropanol were added to the reactor. The reaction was carried out at 50°C and stirred for 1 hour. After the reaction was completed, the upper hydrocarbon phase and the lower liquid were obtained after standing for 30 minutes.

[0054] (2) Diethylene glycol and γ-butyrolactone were used as a composite extraction solvent (the proportion of diethylene glycol in the composite extractant was 50%). The solvent was subjected to multi-stage countercurrent extraction with the upper hydrocarbon phase obtained after the reaction was allowed to stand in the extraction tower. The extraction temperature was 20℃, the feed rate of the composite extraction solvent was 15 g / min, and the feed rate of the upper hydrocarbon phase was 10 g / min (the ratio of the amount of composite extraction solvent to the amount of upper hydrocarbon phase was 1.5:1). The theoretical number of extraction stages was 7, and the extract phase and raffinate phase were obtained.

[0055] (3) The extract phase is introduced into the solvent recovery tower for solvent recovery. The temperature of solvent recovery is controlled at 190-193℃, the pressure is 0.08MPa, and the reflux ratio is controlled at 0.5. The top of the solvent recovery tower yields oxygen-containing compounds, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as an extractant.

[0056] (4) The raffinate is introduced into the water washing tower and washed with the washing water. A small amount of extractant is washed away by the water washing method to obtain Fischer naphtha with oxygen-containing compounds removed and water after washing. The water washing temperature is 50°C and the weight ratio of water to raffinate is 0.3:1.

[0057] After washing, the water enters the water recovery tower for recycling. The temperature inside the water recovery tower is 150-155℃, and the reflux ratio is 0.5. The top product of the water recovery tower is recycled to the water washing tower for washing, and the bottom product is recycled to the extraction tower as an extractant.

[0058] 20 kg of raw naphtha was processed using the above method to obtain 18566.4 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 96.0%.

[0059] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 52.6 wt% (α-olefin retention rate 95.7%), the alcohol content in the oxygen-containing compounds was 0 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 3 ppm (by weight).

[0060] Example 3

[0061] (1) Add 20kg Fischer-Tropsch naphtha, 30g aluminum isopropoxide, 2.0kg isopropanol and 10kg diethylene glycol to a stirred reactor. Stir the reaction at 60℃ for 1h. After the reaction is completed, let it stand for 30min to obtain the upper hydrocarbon phase and the lower stream.

[0062] (2) Diethylene glycol and ethylene glycol carbonate were used as a composite extraction solvent (the proportion of diethylene glycol in the composite extractant was 70%). The solvent was subjected to multi-stage countercurrent extraction with the upper hydrocarbon phase obtained after the reaction was allowed to stand in the extraction tower. The extraction temperature was 50℃, the feed rate of the composite extraction solvent was 10 g / min, the feed rate of the upper hydrocarbon phase was 10 g / min (the ratio of the amount of composite extraction solvent to the amount of upper hydrocarbon phase was 1:1), and the theoretical number of extraction stages was 10. The extract phase and raffinate phase were obtained.

[0063] (3) The extract phase is introduced into the solvent recovery tower for solvent recovery. The solvent recovery temperature is 192-195℃, the pressure is 0.08MPa, and the reflux ratio is controlled at 0.5. The top of the solvent recovery tower yields oxygen-containing compounds, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as an extractant.

[0064] (4) The raffinate is introduced into the water washing tower and washed with water. A small amount of extractant is washed away by water washing to obtain Fischer naphtha with oxygen-containing compounds removed and water after washing. The water washing temperature is 30°C and the weight ratio of water to raffinate is 0.3:1.

[0065] After washing, the water enters the water recovery tower for recycling. The temperature inside the water recovery tower is 155-158℃, and the reflux ratio is 0.5. The top product of the water recovery tower is recycled to the water washing tower for washing, and the bottom product is recycled to the extraction tower as an extractant.

[0066] 20 kg of raw naphtha was processed using the above method to obtain 18856.5 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 97.5%.

[0067] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 52.5 wt% (α-olefin retention rate 97.0%), the alcohol content in the oxygen-containing compounds was 0 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 3 ppm (by weight).

[0068] Example 4

[0069] (1) Add 20kg Fischer-Tropsch naphtha, 100g aluminum isopropoxide, 1.5kg isopropanol and 5kg diethylene glycol to a stirred reactor. Stir the reaction at 60℃ for 1h. After the reaction is completed, let it stand for 30min to obtain the upper hydrocarbon phase and the lower stream.

[0070] (2) Triethylene glycol and γ-butyrolactone were used as a composite extraction solvent (the proportion of triethylene glycol in the composite extractant was 40%). The solvent was subjected to multi-stage countercurrent extraction with the upper hydrocarbon phase obtained after the reaction was allowed to stand in the extraction tower. The extraction temperature was 20℃, the feed rate of the composite extraction solvent was 15 g / min, and the feed rate of the upper hydrocarbon phase was 10 g / min (the ratio of the amount of composite extraction solvent to the amount of upper hydrocarbon phase was 1.5:1). The theoretical number of extraction stages was 10, and the extract phase and raffinate phase were obtained.

[0071] (3) The extract phase is introduced into the solvent recovery tower for solvent recovery. The solvent recovery temperature is 191-194℃, the pressure is 0.08MPa, and the reflux ratio is controlled at 0.5. The top of the solvent recovery tower yields oxygen-containing compounds, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as an extractant.

[0072] (4) The raffinate is introduced into the water washing tower and washed with water. A small amount of extractant is washed away by water washing to obtain Fischer naphtha with oxygen-containing compounds removed and water after washing. The water washing temperature is 20°C and the weight ratio of water to raffinate is 0.5:1.

[0073] After washing, the water enters the water recovery tower for recycling. The temperature inside the water recovery tower is 152-158℃, and the reflux ratio is 0.5. The top product of the water recovery tower is recycled to the water washing tower for washing, and the bottom product is recycled to the extraction tower as an extractant.

[0074] 20 kg of raw naphtha was processed using the above method to obtain 17086.9 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 95.5%.

[0075] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 46.5 wt% (α-olefin retention rate 95%), the alcohol content in the oxygen-containing compounds was 0 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 4 ppm (by weight).

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that step (1) is not performed. The removal method is steps (2)-(4) in Example 1, that is, Fischer naphtha and extractant are directly subjected to countercurrent extraction in the extraction tower.

[0078] 20 kg of raw naphtha 1 was processed using the above method to obtain 18837.2 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 97.4%.

[0079] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 52.6 wt% (α-olefin retention rate 97.1%), the alcohol content in the oxygen-containing compounds was 0 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 30 ppm (by weight).

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 4 is that the extractant used in step (2) is γ-butyrolactone, while the rest is exactly the same as in Example 4.

[0082] 20 kg of raw naphtha 2 was processed according to the above method to obtain 16102.8 g of Fischer-Tropsch naphtha with oxygenated compounds removed, with a recovery rate of 90%.

[0083] Gas chromatography analysis revealed that the α-olefin content in the Fischer-Tropsch naphtha after removal of oxygen-containing compounds was 46.2 wt% (α-olefin retention rate 89.0%), the alcohol content in the oxygen-containing compounds was 10 ppm (by weight), the ester impurity content was 0 ppm, and the carbonyl oxygen content was 7 ppm (by weight).

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that in step (2), diethylene glycol and ethylene glycol carbonate are used as a composite extraction solvent (the proportion of diethylene glycol in the composite extractant is 20%). The rest is exactly the same as in Example 1.

[0086] 20 kg of raw naphtha 1 was processed using the above method to obtain 18082.9 g of oxygen-free Fischer-Tropsch naphtha, with a recovery rate of 93.5%.

[0087] Gas chromatography analysis revealed that the Fischer-Tropsch naphtha, after the removal of oxygen-containing compounds, contained 52.5 wt% α-olefins (93% α-olefin retention), 9 ppm (by weight) alcohols among the oxygen-containing compounds, 0 ppm ester impurities, and 8 ppm (by weight) carbonyl oxygen.

[0088] As can be seen from the above data, the removal method of the present invention not only maintains the content of α-olefins in Fischer-Tropsch synthetic oil, but also effectively removes alcohols, ketones, aldehydes, acids and esters from Fischer-Tropsch synthetic oil. The content of oxygenated compounds in the deoxygenated Fischer-Tropsch synthetic oil is reduced to below 5 ppm, and the oil recovery rate is high, reaching more than 95%.

Claims

1. A method for removing oxygen-containing compounds from Fischer-Tropsch naphtha, characterized in that, Includes the following steps: (1) In the presence of a catalyst, Fischer naphtha is reacted with isopropanol and glycol compounds in a stirred reactor and allowed to stand until the layers separate. (2) The upper hydrocarbon phase after settling in step (1) is subjected to countercurrent extraction with the extractant in the extraction tower to obtain the extract phase and the raffinate phase; (3) The extract phase is subjected to solvent recovery in the solvent recovery tower. The oxygen-containing compound is obtained at the top of the tower, and the solvent obtained at the bottom of the tower is recycled back to the extraction tower as the extractant. (4) The raffinate phase is washed with water in a water washing tower to obtain Fischer naphtha with oxygen-containing compounds removed and water after washing. The water after washing enters a water recovery tower for recovery. The top product of the water recovery tower is recycled to the water washing tower for water washing, and the bottom product is recycled to the extraction tower as an extractant. In step (2), the extractant is a composite extraction solvent of ester compounds and glycol compounds, wherein the content of glycol compounds is 40-70%; In step (1), the Fischer naphtha reacts with isopropanol and glycol compounds under stirring for 30-120 min at a reaction temperature of 40-60°C; the catalyst is selected from aluminum isopropoxide, aluminum triethanolamine, or aluminum tributoxide.

2. The method according to claim 1, characterized in that, The Fischer-Tropsch naphtha contains 0.1 to 15 wt% of oxygenated compounds, wherein the oxygenated compounds in the Fischer-Tropsch naphtha include ketones, aldehydes, alcohols and esters; In molar amounts, the ratio of isopropanol to the ketones and aldehydes contained in the Fischer naphtha is (2~10):1, and the ratio of the catalyst to the ketones and aldehydes contained in the Fischer naphtha is (0.01~0.1):

1.

3. The method according to claim 2, characterized in that, The Fischer-Tropsch naphtha is composed of C5-11 alkanes, alkenes, and C2-10 oxygenated compounds, with a distillation range of 30-200°C.

4. The method according to any one of claims 1 to 3, characterized in that, In step (2), the extraction temperature inside the extraction tower is 10~50℃; The theoretical number of extraction stages in the extraction tower is 7 to 10.

5. The method according to claim 4, characterized in that, The extraction temperature inside the extraction tower is 20~50℃.

6. The method according to claim 4, characterized in that, The amount of the extractant used is 0.5 to 4 times the weight of the upper hydrocarbon phase.

7. The method according to claim 6, characterized in that, The amount of extractant used is 0.8 to 2 times the weight of the upper hydrocarbon phase.

8. The method according to claim 6, characterized in that, The glycol compounds in the extractant are selected from diethylene glycol and / or triethylene glycol; The ester compounds are selected from ethylene glycol carbonates and / or γ-butyrolactone.

9. The method according to any one of claims 1 to 3, 5 to 8, wherein in step (3), the solvent recovery temperature is 190 to 195°C, the pressure is 0.05 to 0.1 MPa, and the reflux ratio is 0.5 to 1.

5.

10. The method according to any one of claims 1 to 3, 5 to 8, wherein in step (4), the temperature of the water washing is 20 to 50°C, and the weight ratio of the water washing to the raffinate is (0.3 to 1): 1; The temperature inside the water recovery tower is 150~160℃, and the reflux ratio is 0.5~1.5.

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