Method for deoxygenating Fischer-Tropsch naphtha

Abstract

The present invention provides a method for deoxygenating Fischer-Tropsch naphtha. The method comprises: adding an alkaline aqueous solution and a copper sulfate aqueous solution to the Fischer-Tropsch naphtha, extracting the first deoxygenated Fischer-Tropsch naphtha with a composite extraction solvent, washing the obtained raffinate phase, and obtaining a second deoxygenated Fischer-Tropsch naphtha; the composite extraction solvent comprises a main extraction solvent of dimethyl sulfoxide and / or cyclopentane sulfone, and an auxiliary extraction solvent of ethylene glycol carbonate and / or propylene carbonate. The present invention first performs an alkali wash to remove acids and esters, and simultaneously adds a copper sulfate aqueous solution to remove aldehyde compounds, and then uses a composite extraction solvent to remove other oxygenated compounds, which can not only effectively remove oxygenated compounds such as alcohols, ketones, aldehydes, acids and esters in the Fischer-Tropsch naphtha, but also avoid the loss of α-olefin content, is easy to operate, has low cost, and is more suitable for industrial applications.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for deoxygenating Fischer-Tropsch synthesis naphtha. Background Art

[0002] The Fischer-Tropsch synthesis reaction is a reaction in which synthesis gas is subjected to a certain temperature and pressure, using an iron or cobalt catalyst to generate a series of alkanes, olefins and oxygen-containing compounds. The carbon chain length of the product ranges from 1 to more than 100, with straight-chain hydrocarbons being the main hydrocarbons, and oxygen-containing compounds being mainly fatty alcohols, with a small amount of acids, esters, ketones and aldehydes. The presence of oxygen-containing compounds in Fischer-Tropsch synthetic oil can easily cause poisoning and deactivation of catalysts in the downstream industrial chain, resulting in an increase in the cost and operating expenses of the subsequent product utilization process, limiting the comprehensive utilization of Fischer-Tropsch synthetic oil products and the extension of the industrial chain. Therefore, it is necessary to fully remove the oxygen-containing compounds in Fischer-Tropsch synthetic oil.

[0003] At present, the removal of oxygen-containing compounds in industry mainly adopts the method of hydrogenating compounds containing olefins, alkanes and oxides. Other methods for separating and extracting fatty alcohols and removing oxygen-containing compounds include adsorption, extraction, etc. However, in the prior art, it is difficult to maintain the content of α-olefins by the method of hydrodeoxygenation; when using the extraction method, some patents use low-boiling low-carbon alcohols as extractants. Since the entire extractant needs to be evaporated during recovery, the recovery cost of the extractant is relatively high, and the boiling points of methanol, ethanol, and isopropanol are included in the distillation range of Fischer-Tropsch oil, and cannot be removed by distillation, which causes more difficulties in separation. Moreover, most of the prior art only separates and extracts alcohols in hydrocarbon streams, but does not separate ketones and aldehydes in hydrocarbon streams.

[0004] Patent CN 112126461 A discloses a method for removing oxygenates from Fischer-Tropsch oil, using a combined process of reaction-extraction-adsorption, adding a bisulfite aqueous solution to the Fischer-Tropsch oil after alkali washing and water washing, and removing the aqueous phase after sufficient reaction; adding ethylene glycol or polyethylene glycol to the Fischer-Tropsch oil to remove the alcohol therein, and the oxygenates can be removed to less than 1ppm, but the process is complicated and the practicality is not high. Patent US2746984 discloses a method for separating aliphatic alcohols from an alcohol-hydrocarbon mixture, first reacting boric acid with the alcohol in the alcohol-hydrocarbon mixture to generate esters, and then extracting with solvents such as methanol, ethanol, and water, and then hydrolyzing the boric acid ester to obtain aliphatic alcohols. However, this method is cumbersome to operate because it involves two-step chemical reactions of esterification and hydrolysis, and it does not mention whether the content of oxygenated compounds in the hydrocarbons after separation reaches a low level, and the operability is poor. Patent US2610977 discloses a method for separating alcohols from hydrocarbons, specifically a method for extracting with an aqueous solution of low-carbon alcohols, wherein the low-carbon alcohol is a methanol aqueous solution, but the ratio of the extraction phase to the oil is 8 to 9:1, the amount of extractant used is too much, and it is also necessary to use low-carbon hydrocarbons to extract and recover the solvent, which is costly. Patent GB716131 discloses a method for extracting with an aqueous solution of low-carbon alcohols, but since the distillation range of the raw oil is very wide, the use of the same extractant for small molecular oxygen-containing compounds and large molecular oxygen-containing compounds will result in a high content of hydrocarbons in the extract, and the removal effect of oxygen-containing compounds is poor.

[0005] Patent CN101891589B discloses a method for extracting fatty alcohols, including distilling the Fischer-Tropsch product into four fractions; extracting the four fractions with water and ethanol aqueous solutions of different concentrations. In order to reduce the hydrocarbon content in the fatty alcohol, the method also includes stripping the alcohol phase obtained by the above extraction with alkanes of different carbon numbers. However, the recovery rate of fatty alcohol is only about 95%, and there are still many residual oxygen-containing compounds in the hydrocarbon phase. Patents CN100575320C and CN100383096C both disclose methods for extracting oxygenates from hydrocarbon streams, using a mixture of methanol and water as a solvent, but the method is only for removing oxygen-containing compounds from C10-C13 streams. Patent WO9958625 discloses a method for removing oxide impurities from hydrocarbon streams using a light polar solvent formed by acetonitrile / water solvent. This method is only for removing oxygen-containing compounds from C8-C10 streams. Patent US4686317 discloses a method for removing oxide impurities from a light hydrocarbon (C2-C9) hydrocarbon stream, which comprises extracting oxides using heavy oil polar solvents propylene carbonate and 2-ethanolamine, washing the extracted hydrocarbon stream with water to recover the dissolved solvent, and combining the extracted solvent phase with the water phase in the scrubber and then distilling to recover the solvent. However, the above methods are relatively narrow in applicability. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for deoxygenating Fischer-Tropsch naphtha, so as to solve the problems in the prior art that the deoxygenation effect of Fischer-Tropsch naphtha is poor and the α-olefin content is reduced after deoxygenation.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for deoxygenating Fischer-Tropsch naphtha is provided, wherein the Fischer-Tropsch naphtha comprises 0.1 to 10% oxygen-containing compounds by weight, and the oxygen-containing compounds comprise alcohols, ketones, aldehydes, acids and esters, and the method comprises the following steps: step S1, adding an alkaline aqueous solution to the Fischer-Tropsch naphtha for alkaline washing, and adding an aqueous copper sulfate solution for oxidation to obtain a first deoxygenated Fischer-Tropsch naphtha; step S2, extracting the first deoxygenated Fischer-Tropsch naphtha with a composite extraction solvent to obtain an extraction phase and a raffinate phase; step S3, washing the raffinate phase with water to obtain a second deoxygenated Fischer-Tropsch naphtha; wherein the composite extraction solvent comprises a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent comprises dimethyl sulfoxide and / or cyclopentane sulfone, and the auxiliary extraction solvent comprises ethylene glycol carbonate and / or propylene carbonate.

[0008] Furthermore, the composite extraction solvent comprises, by weight, 50 to 90 parts of a main extraction solvent, 10 to 50 parts of an auxiliary extraction solvent and 0 to 10 parts of water.

[0009] Furthermore, the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha is (0.5-4):1, preferably (0.8-2):1.

[0010] Furthermore, in step S1, the alkaline aqueous solution is an aqueous solution containing KOH and / or NaOH, and the mass concentration of the alkaline aqueous solution is 5-20%; preferably, the weight ratio of Fischer-Tropsch synthesis naphtha to the alkaline aqueous solution is 1:(0.5-2).

[0011] Furthermore, in step S1, the mass concentration of the copper sulfate aqueous solution is 30-50%; preferably, the weight ratio of Fischer-Tropsch synthesis naphtha to the copper sulfate aqueous solution is 10:(0.5-2).

[0012] Furthermore, the alkali washing time is 0.5 to 2 hours, and / or the oxidation time is 0.5 to 1 hour.

[0013] Furthermore, in step S2, the extraction temperature is 10 to 50°C, preferably 20 to 50°C; preferably, the extraction is a multi-stage countercurrent extraction, and the theoretical number of stages is 5 to 15, more preferably 8 to 12.

[0014] Furthermore, step S3 also includes: recovering the extraction phase to obtain a reused organic solvent and reused water, returning the reused organic solvent to the extraction process, and returning the reused water to the washing process.

[0015] According to another aspect of the present invention, a device for deoxygenating Fischer-Tropsch naphtha is provided, which comprises, in terms of the material flow direction, an alkali washing-oxidation unit having a Fischer-Tropsch naphtha inlet, an alkali aqueous solution inlet, a copper sulfate aqueous solution inlet, a first deoxygenated Fischer-Tropsch naphtha outlet and a first aqueous phase outlet, wherein the alkali washing-oxidation unit is used to add an alkali aqueous solution and a copper sulfate aqueous solution to the Fischer-Tropsch naphtha for alkali washing and oxidation; an extraction unit having a first deoxygenated Fischer-Tropsch naphtha inlet, a composite extraction solvent inlet, an extraction phase outlet and a raffinate phase outlet, and the first deoxygenated Fischer-Tropsch naphtha inlet, a composite extraction solvent inlet, an extraction phase outlet and a raffinate phase outlet. The naphtha inlet is connected to the first deoxygenated Fischer-Tropsch naphtha outlet, and the extraction unit is used to add a composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha for extraction; the water washing unit has a raffinate phase inlet, a water inlet, a second deoxygenated Fischer-Tropsch naphtha outlet and a second water phase outlet, the raffinate phase inlet is connected to the raffinate phase outlet, and the water washing unit is used to wash the raffinate phase with water; wherein the composite extraction solvent includes a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent includes dimethyl sulfoxide and / or cyclopentane sulfone, and the auxiliary extraction solvent includes ethylene glycol carbonate and / or propylene carbonate.

[0016] Furthermore, it also includes a recovery unit. According to the material flow direction, the recovery unit includes a solvent recovery tower, a decanter and a water recovery tower, wherein the solvent recovery tower has an extraction phase inlet, a reused organic solvent outlet and an aqueous organic matter outlet, the extraction phase inlet is connected to the extraction phase outlet of the extraction unit, the reused organic solvent outlet is connected to the composite extraction solvent inlet of the extraction unit, and the solvent recovery tower is used to recover the solvent from the extraction phase; the decanter has an aqueous organic matter inlet, a first organic phase outlet and a third aqueous phase outlet, the aqueous organic matter inlet is connected to the aqueous organic matter outlet of the solvent recovery tower, and the decanter is used to decant the aqueous organic matter; the water recovery tower has a third aqueous phase inlet, a second organic phase outlet and a reused water outlet, the reused water outlet is connected to the water inlet of the water washing unit, the third aqueous phase inlet is connected to the third aqueous phase outlet of the decanter, and the water recovery tower is used to recover the third aqueous phase; wherein the water recovery tower is a distillation tower or a stripping tower.

[0017] The technical scheme of the present invention is applied, and alkali washing is first performed to remove acids and esters, and a copper sulfate aqueous solution is added to remove aldehyde compounds, and then a composite extraction solvent is used to remove oxygenated compounds from Fischer-Tropsch synthesis naphtha by a liquid-liquid extraction method. The method can not only effectively remove oxygenated compounds such as alcohols, ketones, aldehydes, acids and esters in Fischer-Tropsch synthesis naphtha, but also avoid the loss of α-olefin content and maintain a higher α-olefin content in Fischer-Tropsch synthesis naphtha. The content of oxygenated compounds in the deoxygenated Fischer-Tropsch synthesis naphtha is reduced to below 10ppm, and the recovery rate of oil products containing olefins and paraffins is high, reaching more than 94%, and an extraction solvent with high selectivity for oxygenated compounds, good stability, high boiling point, low toxicity, and easy separation is used in the extraction step, and no new impurities are introduced, and the product does not affect the various downstream application requirements of Fischer-Tropsch oil at all. The method of the present invention is simple to operate, low in cost, and more suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A schematic diagram of a Fischer-Tropsch synthesis naphtha deoxygenation device according to an embodiment of the present invention is shown.

[0020] The above drawings include the following reference numerals:

[0021] 1. Alkali washing-oxidation unit; 2. Extraction unit; 3. Water washing unit; 4. Recovery unit; 41. Solvent recovery tower; 42. Decanter; 43. Water recovery tower; a. Fischer-Tropsch naphtha; b. Alkaline aqueous solution; c. Copper sulfate aqueous solution; d. First aqueous phase; e. First deoxygenated Fischer-Tropsch naphtha; f. Composite extraction solvent; g. Raffinate phase; h. Extraction phase; i. Water; j. Second deoxygenated Fischer-Tropsch naphtha; k. Second aqueous phase; l. Recycled organic solvent; m. Water-containing organic matter; n. First organic phase; o. Third aqueous phase; p. Second organic phase; q. Recycled water. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] It should be noted that the Fischer-Tropsch synthesis naphtha described in the present invention is typically a fraction of the condensate product of the Fischer-Tropsch reaction, which can be a condensate product of a low-temperature or high-temperature Fischer-Tropsch reaction, and can contain alkanes, olefins and oxygen-containing compounds, with the hydrocarbons being mainly straight-chain hydrocarbons, and the oxygen-containing compounds being mainly fatty alcohols, and also having a small amount of acids, esters, ketones and aldehydes, etc. Its distillation range is relatively wide, and can be 30-200°C, or any fraction less than 200°C, such as 30-130°C, 40-120°C, etc.

[0025] As described in the background of the present invention, there are problems in the prior art that the deoxygenation effect of Fischer-Tropsch oil is poor and the content of α-olefins is reduced after deoxygenation. In order to solve the above problems, in a typical embodiment of the present invention, a method for deoxygenating Fischer-Tropsch naphtha is provided, in which the Fischer-Tropsch naphtha includes 0.1 to 10% oxygen-containing compounds by weight, and the oxygen-containing compounds include alcohols, ketones, aldehydes, acids and esters. The method includes the following steps: Step S1, adding an alkaline aqueous solution to the Fischer-Tropsch naphtha for alkaline washing, and adding a copper sulfate aqueous solution for oxidation to obtain a first deoxygenated Fischer-Tropsch naphtha; Step S2, extracting the first deoxygenated Fischer-Tropsch naphtha with a composite extraction solvent to obtain an extraction phase and a raffinate phase; Step S3, washing the raffinate phase with water to obtain a second deoxygenated Fischer-Tropsch naphtha; wherein the composite extraction solvent includes a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent includes dimethyl sulfoxide and / or cyclopentane sulfone, and the auxiliary extraction solvent includes ethylene glycol carbonate and / or propylene carbonate.

[0026] With respect to the above-mentioned Fischer-Tropsch naphtha raw material, the inventor unexpectedly discovered through extraction experiments during the research process that the removal of aldehydes among its oxygen-containing compounds is the most difficult. The present invention first adds an alkaline aqueous solution to the Fischer-Tropsch naphtha for alkaline washing, converts the acidic substances into salts that are easily soluble in water, and hydrolyzes the esters to remove the acids and esters; at the same time, an aqueous copper sulfate solution is added to oxidize the aldehyde substances into acids with the help of the alkaline environment created by the alkaline aqueous solution, and the oxidized acids are further converted into salts by the alkaline aqueous solution for removal, and after the reaction is completed, the reaction is allowed to stand for stratification, thereby removing the aldehyde compounds that are difficult to remove by extraction, and obtaining the first deoxygenated Fischer-Tropsch naphtha, without adding additional equipment, which can greatly reduce costs.

[0027] After obtaining the first deoxygenated Fischer-Tropsch naphtha, it is extracted with a composite extraction solvent to obtain an extraction phase and a raffinate phase containing olefins, paraffins and a small amount of extraction solvent; finally, the raffinate phase is washed with water to remove the extraction solvent to obtain a second deoxygenated Fischer-Tropsch naphtha, which contains more than 99% olefins and paraffins by weight, and less than 10 ppm of oxygen-containing compounds. The composite extraction solvent includes a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent includes dimethyl sulfoxide and / or cyclopentane sulfone, the auxiliary extraction solvent includes an ester compound, the ester compound includes a carbonate compound, and the carbonate compound includes ethylene glycol carbonate and / or propylene carbonate.

[0028] The method of the present invention can not only effectively remove oxygen-containing compounds such as alcohols, ketones, aldehydes, acids and esters in Fischer-Tropsch naphtha, but also maintain a relatively high content of α-olefins in Fischer-Tropsch naphtha. The content of oxygen-containing compounds in the deoxygenated Fischer-Tropsch naphtha is reduced to below 10 ppm, and the oil recovery rate is high, reaching more than 94%. In addition, an extraction solvent with high selectivity for oxygen-containing compounds, good stability, high boiling point, low toxicity, and easy separation is used in the extraction step, and no new impurities are introduced, and the product does not affect various downstream application requirements of Fischer-Tropsch oil at all. The method of the present invention is easy to operate, low in cost, and more suitable for industrial applications.

[0029] In a preferred embodiment, the composite extraction solvent includes, by weight, 50 to 90 parts of a main extraction solvent, 10 to 50 parts of an auxiliary extraction solvent and 0 to 10 parts of water, which can further improve the extraction effect of oxygen-containing compounds such as alcohols and ketones in Fischer-Tropsch synthesis naphtha, and can further ensure that the loss rate of α-olefins after deoxygenation is low.

[0030] Typically, but not limiting, by weight, the composite extraction solvent comprises 50 parts of a main extraction solvent and 50 parts of a co-extraction solvent; or the composite extraction solvent comprises 70 parts of a main extraction solvent and 30 parts of a co-extraction solvent; or the composite extraction solvent comprises 70 parts of a main extraction solvent, 20 parts of a co-extraction solvent and 10 parts of water; or the composite extraction solvent comprises 50 parts of a main extraction solvent, 45 parts of a co-extraction solvent and 5 parts of water; or the composite extraction solvent comprises 50 parts of a main extraction solvent, 40 parts of a co-extraction solvent and 10 parts of water; or the composite extraction solvent comprises 90 parts of a main extraction solvent and 10 parts of a co-extraction solvent.

[0031] The amount of the composite extraction solvent can vary within a wide range. In a preferred embodiment, the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha is (0.5-4):1, preferably (0.8-2):1. The amount of the composite extraction solvent includes but is not limited to the above range. When within the range, the extraction effect of oxygenated compounds in the Fischer-Tropsch oil can be further improved without causing excessive use of the extraction solvent, which will lead to subsequent separation difficulties and increased costs.

[0032] Typically but not limiting, the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha is 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or a range consisting of any two of them.

[0033] Alkali washing is carried out under stirring conditions or in a static mixing device, which can be an alkali washing kettle, an alkali washing tank or an alkali washing tower. The alkali aqueous solution can use a conventional alkaline solution in the field. In a preferred embodiment, in step S1, the alkali aqueous solution is an aqueous solution containing KOH and / or NaOH, and the mass concentration of the alkali aqueous solution is 5-20%, which can further reduce the cost and facilitate large-scale application; preferably, the weight ratio of Fischer-Tropsch synthesis naphtha and the alkali aqueous solution is 1: (0.5-2), and the weight ratio of Fischer-Tropsch synthesis naphtha and the alkali aqueous solution includes but is not limited to the above range, and within the range, the acidic substances can be converted into salts more quickly and efficiently, and the lipids can be hydrolyzed to remove acids and esters, and a more suitable alkaline environment can be provided for the oxidation reaction of copper sulfate and aldehyde compounds.

[0034] Typically but not limiting, the weight ratio of Fischer-Tropsch synthesis naphtha to the alkali aqueous solution is 1:0.5, 1:1, 1:1.5, 1:2 or a range consisting of any two of them.

[0035] In a preferred embodiment, in step S1, the mass concentration of the copper sulfate aqueous solution is 30-50%; preferably, the weight ratio of Fischer-Tropsch naphtha and the copper sulfate aqueous solution is 10:(0.5-2), and the weight ratio of Fischer-Tropsch naphtha and the copper sulfate aqueous solution includes but is not limited to the above range, and within the range, the removal efficiency and removal effect of aldehyde compounds can be further improved.

[0036] Typically but not limiting, the weight ratio of Fischer-Tropsch synthesis naphtha to copper sulfate aqueous solution is 10:0.5, 10:0.8, 10:1, 10:1.2, 10:1.5, 10:1.8, 10:2 or a range consisting of any two of them.

[0037] The time of alkali washing and oxidation can be specifically adjusted according to the composition of the feedstock oil. In a preferred embodiment, the time of alkali washing is 0.5 to 2 hours, and / or the time of oxidation is 0.5 to 1 hour, which is more universal.

[0038] The operation method for liquid-liquid extraction can be conventional in the art. To further improve the extraction effect, in a preferred embodiment, in step S2, the extraction temperature is 10 to 50°C, preferably 20 to 50°C; preferably, the extraction is a multi-stage countercurrent extraction with a theoretical number of 5 to 15 stages, more preferably 8 to 12 stages.

[0039] In a preferred embodiment, step S3 also includes: recovering the extraction phase to obtain a reused organic solvent and reused water, returning the reused organic solvent to the extraction process, and returning the reused water to the washing process, so that the materials in the treatment process are more fully utilized and the cost is further reduced.

[0040] In another typical embodiment of the present invention, a Fischer-Tropsch synthesis naphtha deoxygenation device is also provided, such as Figure 1 As shown, according to the material flow direction, it includes an alkali washing-oxidation unit 1, which has a Fischer-Tropsch synthesis naphtha inlet, an alkali aqueous solution inlet, a copper sulfate aqueous solution inlet, a first deoxygenated Fischer-Tropsch synthesis naphtha outlet and a first water phase outlet, and the alkali washing-oxidation unit 1 is used to add an alkali aqueous solution and a copper sulfate aqueous solution to the Fischer-Tropsch synthesis naphtha to perform alkali washing and oxidation; an extraction unit 2, which has a first deoxygenated Fischer-Tropsch synthesis naphtha inlet, a composite extraction solvent inlet, an extraction phase outlet and a raffinate phase outlet, a first deoxygenated Fischer-Tropsch synthesis naphtha inlet and a first deoxygenated Fischer-Tropsch synthesis naphtha outlet. The synthetic naphtha outlet is connected, and the extraction unit 2 is used to add a composite extraction solvent to the first deoxygenated Fischer-Tropsch synthetic naphtha for extraction; the water washing unit 3 has a raffinate phase inlet, a water inlet, a second deoxygenated Fischer-Tropsch synthetic naphtha outlet and a second water phase outlet, the raffinate phase inlet and the raffinate phase outlet are connected, and the water washing unit 3 is used to wash the raffinate phase with water; wherein the composite extraction solvent includes a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent includes dimethyl sulfoxide and / or cyclopentane sulfone, and the auxiliary extraction solvent includes ethylene glycol carbonate and / or propylene carbonate.

[0041] Specifically, Fischer-Tropsch naphtha a and alkaline aqueous solution b are first introduced into the alkaline washing-oxidation unit 1 to perform alkaline washing to remove acids and esters, and then copper sulfate aqueous solution c is added during the alkaline washing process to remove aldehyde compounds to obtain the first aqueous phase d, the first deoxygenated Fischer-Tropsch naphtha e, and the alkaline washing-oxidation unit 1 can be an alkaline washing kettle, an alkaline washing tank or an alkaline washing tower. The first deoxygenated Fischer-Tropsch naphtha e and the composite extraction solvent f are introduced into the extraction unit 2 together for extraction, and the extraction unit 2 can be an extraction tower. At this time, the first deoxygenated Fischer-Tropsch naphtha e is transported to the extraction tower at the bottom of the extraction tower or near the bottom of the tower, and the composite extraction solvent f is transported to the tower at the top of the extraction tower or near the top of the tower to obtain the extraction phase h and the raffinate phase g. The raffinate phase g contains a small amount of organic solvent, so the raffinate phase g at the top of the extraction tower is introduced into the water washing unit 3, which can be a water washing tower, to wash away the extractant by passing water i through water washing, and the second deoxygenated Fischer-Tropsch synthesis naphtha j is used as the deoxygenated hydrocarbon phase and is drawn out as the top product of the water washing tower, which contains more than 99% of olefins and paraffins, and less than 10 ppm of oxygen-containing compounds by weight percentage, and the second water phase k is drawn out from the bottom of the tower.

[0042] The use of the above-mentioned device for deoxygenation of Fischer-Tropsch naphtha can not only effectively remove oxygenated compounds such as alcohols, ketones, aldehydes, acids and esters in Fischer-Tropsch naphtha, but also maintain a relatively high content of α-olefins in Fischer-Tropsch naphtha. The content of oxygenated compounds in the deoxygenated Fischer-Tropsch naphtha is reduced to below 10ppm, and the oil recovery rate is high, reaching more than 94%. In addition, an extraction solvent with high selectivity for oxygenated compounds, good stability, high boiling point, low toxicity, and easy separation is used in the extraction, and no new impurities are introduced. The product does not affect the various downstream application requirements of Fischer-Tropsch oil at all. The above-mentioned device is easy to operate, low in cost, and more suitable for industrial applications.

[0043] In a preferred embodiment, the device also includes a recovery unit 4, which includes a solvent recovery tower 41, a decanter 42 and a water recovery tower 43 according to the material flow direction, wherein the solvent recovery tower 41 has an extraction phase inlet, a reused organic solvent outlet and an aqueous organic matter outlet, the extraction phase inlet is connected to the extraction phase outlet of the extraction unit 2, the reused organic solvent outlet is connected to the composite extraction solvent inlet of the extraction unit 2, and the solvent recovery tower 41 is used to recover the solvent from the extraction phase; the decanter 42 has an aqueous organic matter inlet, a first organic phase outlet and a third aqueous phase outlet, the aqueous organic matter inlet is connected to the aqueous organic matter outlet of the solvent recovery tower 41, and the decanter 42 is used to decant the aqueous organic matter; the water recovery tower 43 has a third aqueous phase inlet, a second organic phase outlet and a reuse water outlet, the third aqueous phase inlet is connected to the third aqueous phase outlet of the decanter 42, the reuse water outlet is connected to the water inlet of the water washing unit 3, and the water recovery tower 43 is used to recover the third aqueous phase; wherein the water recovery tower 43 is a distillation tower or a stripping tower.

[0044] Specifically, the extraction phase h is first introduced into the solvent recovery tower 41, and the water-containing organic matter m, including oxygen-containing compounds, water, and a small amount of olefins and paraffins, is obtained at the top of the tower, and the recycled organic solvent l is drawn out from the bottom of the tower; the top product is introduced into the decanter 42 for decantation, and the top product of the decanter 42 is the first organic phase n that is insoluble in water, mainly oxygen-containing compounds and a small amount of hydrocarbons. The bottom of the decanter 42 is the third water phase o, which is mainly water and oxygen-containing compounds soluble in water, which is introduced into the water recovery tower 43, which can be a distillation tower or a stripping tower, and the second organic phase p, mainly some oxygen-containing compounds, is obtained at the top of the distillation tower or the stripping tower, and the recycled water q is obtained at the bottom of the tower and circulated to the water washing unit 3.

[0045] The bottom water of the water washing unit 3 and a small amount of extraction solvent can be further mixed with the recovery solvent obtained at the bottom of the solvent recovery tower 41 to prepare the extraction solvent of the required concentration, and return to the extraction unit 2 for recycling. If the amount of water is excessive relative to the prepared extractant, the bottom water of the water washing unit 3 needs to enter the solvent recovery tower 41 together with the bottom material of the extraction unit 2 for further recovery.

[0046] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0047] Unless otherwise specified, in the following examples and comparative examples, "%" refers to weight percentage.

[0048] Unless otherwise specified, the following examples and comparative examples are all Figure 1 The device shown.

[0049] Unless otherwise specified, in the following examples and comparative examples, the raw material is the following Fischer-Tropsch synthesis naphtha, the composition and content of which are shown in Table 1, and the distillation range is IBP-170°C; the content of each component is measured by chromatography, wherein the content of carbonyl oxygen is determined according to GB / T6324.5-2008.

[0050] Table 1

[0051] Element α-Olefins Normal alkanes alcohol Carbonyl oxygen content% 69.9 23.7 2.2 0.64

[0052] Example 1

[0053] Step S1, introducing Fischer-Tropsch naphtha and 10% NaOH aqueous solution into an alkaline washing kettle at a weight ratio of 1:1 to perform alkaline washing for 1 hour to remove acids and esters, and then adding 40% copper sulfate aqueous solution at a weight ratio of 10:1 during the alkaline washing process to perform oxidation for 1.5 hours to remove aldehyde compounds, thereby obtaining a first deoxygenated Fischer-Tropsch naphtha;

[0054] Step S2, the composite extraction solvent is 70 parts of dimethyl sulfoxide and 30 parts of ethylene glycol carbonate, and the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthesis naphtha is 1.5:1. Multi-stage countercurrent extraction is carried out in the extraction tower, the extraction temperature is 20°C, the theoretical number of extraction stages is 10, the feed rate of the first deoxygenated Fischer-Tropsch synthesis naphtha is 10g / min, and the feed rate of the extractant is 15g / min, to obtain an extract phase and a raffinate phase;

[0055] Step S3, introducing the raffinate phase at the top of the extraction tower into a water washing tower, washing off a small amount of extractant by water washing, and drawing out the hydrocarbon phase as the top product, introducing the extract phase at the bottom of the extraction tower into a solvent recovery tower, obtaining oxygen-containing compounds and a small amount of hydrocarbons at the top of the solvent recovery tower, returning the extractant at the bottom of the solvent recovery tower to the extraction tower for recycling, introducing the top of the tower into a decanter, obtaining a water-insoluble organic phase, mainly oxygen-containing compounds and a small amount of hydrocarbons, at the top, obtaining water and water-soluble oxygen-containing compounds at the bottom, introducing the bottom product of the decanter into a distillation tower, obtaining oxygen-containing compounds at the top of the tower, obtaining recycled water at the bottom of the tower, and circulating to the water washing tower.

[0056] Example 2

[0057] Step S1, introducing Fischer-Tropsch naphtha and 5% NaOH aqueous solution into an alkali washing kettle at a weight ratio of 1:2 to perform alkali washing for 0.5 h to remove acids and esters, and then adding 30% copper sulfate aqueous solution at a weight ratio of 10:2 during the alkali washing process to perform oxidation for 0.5 h to remove aldehyde compounds, thereby obtaining a first deoxygenated Fischer-Tropsch naphtha;

[0058] Step S2, the composite extraction solvent is 50 parts of dimethyl sulfoxide, 45 parts of propylene carbonate and 5 parts of water, and the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthesis naphtha is 4:1. Multi-stage countercurrent extraction is carried out in the extraction tower, the extraction temperature is 10°C, the theoretical number of extraction stages is 5, the feed rate of the first deoxygenated Fischer-Tropsch synthesis naphtha is 10g / min, and the feed rate of the extractant is 40g / min, to obtain an extract phase and a raffinate phase;

[0059] Step S3, introducing the raffinate phase at the top of the extraction tower into a water washing tower, washing off a small amount of extractant by water washing, and drawing out the hydrocarbon phase as the top product, introducing the extract phase at the bottom of the extraction tower into a solvent recovery tower, obtaining oxygen-containing compounds and a small amount of hydrocarbons at the top of the solvent recovery tower, returning the extractant at the bottom of the solvent recovery tower to the extraction tower for recycling, introducing the top of the tower into a decanter, obtaining a water-insoluble organic phase, mainly oxygen-containing compounds and a small amount of hydrocarbons, at the top, obtaining water and water-soluble oxygen-containing compounds at the bottom, introducing the bottom product of the decanter into a distillation tower, obtaining oxygen-containing compounds at the top of the tower, obtaining recycled water at the bottom of the tower, and circulating to the water washing tower.

[0060] Example 3

[0061] Step S1, introducing Fischer-Tropsch naphtha and 10% NaOH aqueous solution into an alkaline washing kettle at a weight ratio of 1:1 to perform alkaline washing for 1 hour to remove acids and esters, and then adding 40% copper sulfate aqueous solution at a weight ratio of 10:1 during the alkaline washing process to perform oxidation for 1.5 hours to remove aldehyde compounds, thereby obtaining a first deoxygenated Fischer-Tropsch naphtha;

[0062] Step S2, the composite extraction solvent is 80 parts of dimethyl sulfoxide, 5 parts of water and 15 parts of ethylene glycol carbonate, and the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthesis naphtha is 2:1. Multi-stage countercurrent extraction is carried out in the extraction tower, the extraction temperature is 40°C, the theoretical number of extraction stages is 8, the feed rate of the first deoxygenated Fischer-Tropsch synthesis naphtha is 10g / min, and the feed rate of the extractant is 20g / min, to obtain an extract phase and a raffinate phase;

[0063] Step S3, introducing the raffinate phase at the top of the extraction tower into a water washing tower, washing off a small amount of extractant by water washing, and drawing out the hydrocarbon phase as the top product, introducing the extract phase at the bottom of the extraction tower into a solvent recovery tower, obtaining oxygen-containing compounds and a small amount of hydrocarbons at the top of the solvent recovery tower, returning the extractant at the bottom of the solvent recovery tower to the extraction tower for recycling, introducing the top of the tower into a decanter, obtaining a water-insoluble organic phase, mainly oxygen-containing compounds and a small amount of hydrocarbons, at the top, obtaining water and water-soluble oxygen-containing compounds at the bottom, introducing the bottom product of the decanter into a distillation tower, obtaining oxygen-containing compounds at the top of the tower, obtaining recycled water at the bottom of the tower, and circulating to the water washing tower.

[0064] Example 4

[0065] Step S1, introducing Fischer-Tropsch naphtha and 10% NaOH aqueous solution into an alkaline washing kettle at a weight ratio of 1:1 to perform alkaline washing for 1 hour to remove acids and esters, and then adding 40% copper sulfate aqueous solution at a weight ratio of 10:1 during the alkaline washing process to perform oxidation for 1.5 hours to remove aldehyde compounds, thereby obtaining a first deoxygenated Fischer-Tropsch naphtha;

[0066] Step S2, the composite extraction solvent is 50 parts of sulfolane, 10 parts of water and 40 parts of propylene carbonate, and the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthesis naphtha is 0.8:1. Multi-stage countercurrent extraction is carried out in the extraction tower, the extraction temperature is 50°C, the theoretical number of extraction stages is 15, the feed rate of the first deoxygenated Fischer-Tropsch synthesis naphtha is 10g / min, and the feed rate of the extractant is 8g / min, to obtain an extract phase and a raffinate phase;

[0067] Step S3, introducing the raffinate phase at the top of the extraction tower into a water washing tower, washing off a small amount of extractant by water washing, and drawing out the hydrocarbon phase as the top product, introducing the extract phase at the bottom of the extraction tower into a solvent recovery tower, obtaining oxygen-containing compounds and a small amount of hydrocarbons at the top of the solvent recovery tower, returning the extractant at the bottom of the solvent recovery tower to the extraction tower for recycling, introducing the top of the tower into a decanter, obtaining a water-insoluble organic phase, mainly oxygen-containing compounds and a small amount of hydrocarbons, at the top, obtaining water and water-soluble oxygen-containing compounds at the bottom, introducing the bottom product of the decanter into a distillation tower, obtaining oxygen-containing compounds at the top of the tower, obtaining recycled water at the bottom of the tower, and circulating to the water washing tower.

[0068] Example 5

[0069] Step S1, introducing Fischer-Tropsch naphtha and 20% NaOH aqueous solution into an alkaline washing kettle at a weight ratio of 1:0.5 to perform alkaline washing for 2 hours to remove acids and esters, and then adding 50% copper sulfate aqueous solution at a weight ratio of 10:0.5 during the alkaline washing process to perform oxidation for 1 hour to remove aldehyde compounds, thereby obtaining a first deoxygenated Fischer-Tropsch naphtha;

[0070] Step S2, the composite extraction solvent is 90 parts of sulfolane and 10 parts of ethylene glycol carbonate, and the weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthesis naphtha is 1.5:1. Multi-stage countercurrent extraction is carried out in the extraction tower, the extraction temperature is 40°C, the theoretical number of extraction stages is 12, the feed rate of the first deoxygenated Fischer-Tropsch synthesis naphtha is 10g / min, and the feed rate of the extractant is 15g / min, to obtain an extract phase and a raffinate phase;

[0071] Step S3, introducing the raffinate phase at the top of the extraction tower into a water washing tower, washing off a small amount of extractant by water washing, and drawing out the hydrocarbon phase as the top product, introducing the extract phase at the bottom of the extraction tower into a solvent recovery tower, obtaining oxygen-containing compounds and a small amount of hydrocarbons at the top of the solvent recovery tower, returning the extractant at the bottom of the solvent recovery tower to the extraction tower for recycling, introducing the top of the tower into a decanter, obtaining a water-insoluble organic phase, mainly oxygen-containing compounds and a small amount of hydrocarbons, at the top, obtaining water and water-soluble oxygen-containing compounds at the bottom, introducing the bottom product of the decanter into a distillation tower, obtaining oxygen-containing compounds at the top of the tower, obtaining recycled water at the bottom of the tower, and circulating to the water washing tower.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 1 is that in step S1, copper sulfate aqueous solution is not used for oxidation.

[0074] Comparative Example 2

[0075] The difference between Comparative Example 2 and Example 1 is that in step S2, dimethyl sulfoxide is first used to extract the first deoxygenated Fischer-Tropsch naphtha for a period of time, and then polycarbonate is used for the remaining extraction.

[0076] The 100-min top product of the water washing tower was taken for material balance in Examples 1 to 5 and Comparative Examples 1 to 2. The results are shown in Table 2.

[0077] Table 2

[0078]

[0079] As can be seen from the above, compared with the comparative example, the method of each embodiment of the present invention first performs alkaline washing to remove acids and esters, and at the same time adds a copper sulfate aqueous solution to remove aldehyde compounds, and then uses a composite extraction solvent to remove other oxygen-containing compounds, which can not only effectively remove oxygen-containing compounds such as alcohols, ketones, aldehydes, acids and esters in Fischer-Tropsch synthesis naphtha, but also avoid the loss of α-olefin content, and is simple to operate, low in cost, and more suitable for industrial application. In addition, it can be seen that when each process parameter is within the preferred range of the present invention, the effect is better.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for deoxygenating Fischer-Tropsch naphtha, characterized in that: The Fischer-Tropsch synthesis naphtha comprises 0.1-10% oxygen-containing compounds by weight, wherein the oxygen-containing compounds include alcohols, ketones, aldehydes, acids and esters, and the method comprises the following steps: Step S1, adding an alkali aqueous solution to the Fischer-Tropsch synthesis naphtha for alkali washing, and adding a copper sulfate aqueous solution for oxidation to obtain a first deoxygenated Fischer-Tropsch synthesis naphtha; Step S2, extracting the first deoxygenated Fischer-Tropsch synthesis naphtha with a composite extraction solvent to obtain an extract phase and a raffinate phase; Step S3, washing the raffinate phase with water to obtain a second deoxygenated Fischer-Tropsch synthesis naphtha; Wherein, the composite extraction solvent comprises a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent comprises dimethyl sulfoxide and / or sulfolane, and the auxiliary extraction solvent comprises ethylene glycol carbonate and / or propylene carbonate; The alkaline aqueous solution is an aqueous solution containing KOH and / or NaOH, and the mass concentration of the alkaline aqueous solution is 5-20%, and the weight ratio of the Fischer-Tropsch synthesis naphtha to the alkaline aqueous solution is 1:(0.5-2); The mass concentration of the copper sulfate aqueous solution is 30-50%, and the weight ratio of the Fischer-Tropsch synthesis naphtha to the copper sulfate aqueous solution is 10:(0.5-2).

2. The method according to claim 1, characterized in that In parts by weight, the composite extraction solvent comprises 50 to 90 parts of the main extraction solvent, 10 to 50 parts of the auxiliary extraction solvent and 0 to 10 parts of water.

3. The method according to claim 1 or 2, characterized in that: The weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha is (0.5-4):

1.

4. The method according to claim 3, characterized in that: The weight ratio of the composite extraction solvent to the first deoxygenated Fischer-Tropsch naphtha is (0.8-2):

1.

5. The method according to claim 1 or 2, characterized in that: The alkali washing time is 0.5 to 2 hours, and / or the oxidation time is 0.5 to 1 hour.

6. The method according to claim 1 or 2, characterized in that: In step S2, the extraction temperature is 10-50°C.

7. The method according to claim 6, characterized in that In step S2, the extraction temperature is 20-50°C.

8. The method according to claim 1 or 2, characterized in that: The extraction is a multi-stage countercurrent extraction with a theoretical number of stages of 5 to 15.

9. The method according to claim 8, characterized in that The extraction is a multi-stage countercurrent extraction with a theoretical number of stages of 8 to 12.

10. The method according to claim 1 or 2, characterized in that: The step S3 further comprises: The extraction phase is recovered to obtain a reused organic solvent and reused water. The reused organic solvent is returned to the extraction process, and the reused water is returned to the water washing process.

11. A device for deoxygenating Fischer-Tropsch naphtha, characterized in that: According to the material flow direction, including An alkali washing-oxidation unit (1) has a Fischer-Tropsch synthesis naphtha inlet, an alkali aqueous solution inlet, a copper sulfate aqueous solution inlet, a first deoxygenated Fischer-Tropsch synthesis naphtha outlet and a first aqueous phase outlet, wherein the alkali washing-oxidation unit (1) is used to add an alkali aqueous solution and a copper sulfate aqueous solution to the Fischer-Tropsch synthesis naphtha to perform alkali washing and oxidation; An extraction unit (2), comprising a first deoxygenated Fischer-Tropsch synthetic naphtha inlet, a composite extraction solvent inlet, an extraction phase outlet and a raffinate phase outlet, wherein the first deoxygenated Fischer-Tropsch synthetic naphtha inlet and the first deoxygenated Fischer-Tropsch synthetic naphtha outlet are connected, and the extraction unit (2) is used to add the composite extraction solvent to the first deoxygenated Fischer-Tropsch synthetic naphtha to perform extraction; A water washing unit (3), comprising a raffinate phase inlet, a water inlet, a second deoxygenated Fischer-Tropsch synthesis naphtha outlet and a second water phase outlet, the raffinate phase inlet and the raffinate phase outlet being connected, and the water washing unit (3) is used to wash the raffinate phase with water; The composite extraction solvent comprises a main extraction solvent and an auxiliary extraction solvent, the main extraction solvent comprises dimethyl sulfoxide and / or cyclopentane sulfoxide, and the auxiliary extraction solvent comprises ethylene glycol carbonate and / or propylene carbonate.

12. The device according to claim 11, characterized in that It also includes a recovery unit (4). According to the material flow direction, the recovery unit (4) includes a solvent recovery tower (41), a decanter (42) and a water recovery tower (43), wherein: The solvent recovery tower (41) has an extraction phase inlet, a recycled organic solvent outlet and a water-containing organic matter outlet, the extraction phase inlet is connected to the extraction phase outlet of the extraction unit (2), the recycled organic solvent outlet is connected to the composite extraction solvent inlet of the extraction unit (2), and the solvent recovery tower (41) is used to recover the solvent from the extraction phase; The decanter (42) has an aqueous organic matter inlet, a first organic phase outlet and a third aqueous phase outlet, the aqueous organic matter inlet is connected to the aqueous organic matter outlet of the solvent recovery tower (41), and the decanter (42) is used to decant the aqueous organic matter; The water recovery tower (43) has a third water phase inlet, a second organic phase outlet and a recycled water outlet, the recycled water outlet is connected to the water inlet of the water washing unit (3), the third water phase inlet is connected to the third water phase outlet of the decanter (42), and the water recovery tower (43) is used to recover the third water phase; Wherein, the water recovery tower (43) is a distillation tower or a stripping tower.

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