Application of extraction agent in removal of isohydrocarbon in Fischer-Tropsch synthetic oil

Abstract

The invention relates to the technical field of separation of impurities in coal indirect liquefaction products, and discloses an application of an extraction agent in removal of isohydrocarbons in Fischer-Tropsch synthetic oil, the extraction agent is an ionic liquid composed of cations and anions, and C1-C4 alkoxy groups exist on N atoms on bipyridine rings of the cations. After 2-5 times of extraction, the extraction agent adopted by the method can effectively remove the isohydrocarbon, an excellent isohydrocarbon removal effect is provided, and the extraction agent has relatively good stability and is easy to prepare and recover.

Description

Technical Field

[0001] The invention relates to the technical field of separation of impurities in coal indirect liquefaction products, and in particular to the application of an extractant in removing isomeric hydrocarbons in Fischer-Tropsch synthetic oil. Background Art

[0002] Fischer-Tropsch synthesis is a coal indirect liquefaction technology and a core component of the coal gasification process. Fischer-Tropsch synthesis is a coal indirect liquefaction process that converts the synthesis gas (CO, H2) produced by coal gasification into gasoline, diesel and other hydrocarbon products in the presence of a catalyst. The crude reaction products are mainly light oil, heavy oil and heavy wax. Among them, the main substances in light oil are normal alkanes and normal olefins, and the olefin components are mostly α-olefins. When conventional naphtha and diesel are the main products, olefins need to be hydrogenated. If the required α-olefin components can be separated from the products by appropriate methods to further produce high-value products, the economic benefits of the process will be greatly improved. At present, China does not have the ability to separate and purify α-olefins from FT synthetic oil. Only Sasol in South Africa has such technology in the world. Therefore, if the separation and purification technology of α-olefins can be developed, it will not only achieve the purpose of value-added utilization of Fischer-Tropsch synthesis light oil, but also have a significant impact on the global α-olefin production capacity and market.

[0003] Fischer-Tropsch synthetic oil has the characteristics of wide carbon number distribution and complex composition. Fischer-Tropsch synthetic oil is mainly composed of straight-chain olefins and straight-chain alkanes, and also contains a small amount of isoolefins, isoalkanes, and oxygen-containing compounds such as organic acids, alcohols, aldehydes, ketones, esters and alkyl acids. Among them, straight-chain olefins are important petrochemical raw materials and are widely used in many fields such as comonomers, surfactant synthesis intermediates, plasticizers, synthetic lubricants and oil additives, and can be used as direct raw materials for downstream oil processing.

[0004] Normal hydrocarbons include normal olefins and normal alkanes, which can usually be used directly or indirectly to produce wax, chemical products, gasoline and diesel, etc. The presence of isohydrocarbons will affect the application of normal hydrocarbons. For example, when used as gasoline blending materials, isohydrocarbons will affect the ethylene yield. Therefore, in order to more effectively utilize the Fischer-Tropsch synthetic oil resources, it is necessary to separate the normal hydrocarbons and isohydrocarbons in the Fischer-Tropsch oil to improve the utilization value of the Fischer-Tropsch oil. At present, the main methods for separating normal and isohydrocarbons in industry include distillation, adsorption and membrane separation.

[0005] Since normal hydrocarbons and isohydrocarbons with the same number of carbon atoms have similar boiling points, distillation separation requires a large number of theoretical plates, a large reflux ratio, and high energy consumption; complex extraction and complex adsorption are relatively mature for the separation of short-chain hydrocarbons, but there are many technical barriers for separating long-chain hydrocarbons, such as high energy consumption for desorbent recovery and difficulty in regeneration; membrane separation technology for normal and isohydrocarbons is still in the research and development stage, and there are problems such as difficulty in selecting membrane materials and high cost, and it is still a long way from industrialization.

[0006] A Chinese invention patent (publication number: CN112745888B, publication date: 2022.05.03) discloses a method for removing oxygenated compounds from Fischer-Tropsch light oil. The method includes liquid-liquid extraction, water washing and solvent recovery, wherein the liquid-liquid extraction uses an ionic liquid as an extraction solvent. In the ionic liquid, the N atom on the imidazole ring or pyridine ring of the cation has a polar group or a suitable alkyl group, which can increase the selectivity and solubility of oxygenated compounds. The ionic liquid has good stability and a large density difference with the Fischer-Tropsch light oil, making it easy to separate.

[0007] A Chinese invention patent (publication number: CN103732587B, publication date: 2015.09.03) discloses a dual-center bipyridyl cationic ionic liquid, which synthesizes a dialkyl bipyridyl halide by reacting bipyridyl with an alkyl halide, and then converts the halogen ions in the dialkyl pyridyl halide into target anions by an ion exchange reaction, and finally obtains the target ionic liquid. The electrochemical window of the dual-center bipyridyl cationic ionic liquid exceeds 4V, has good electrochemical stability, and is not easy to decompose under high voltage. Summary of the invention

[0008] In view of the deficiencies of the prior art, the present invention provides application of an extractant in removing isomeric hydrocarbons from Fischer-Tropsch synthetic oil.

[0009] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0010] Application of an extractant in removing isomeric hydrocarbons from Fischer-Tropsch synthetic oil, wherein the extractant is an ionic liquid composed of cations and anions;

[0011] The cation adopts the structural formula shown below:

[0012]

[0013] Among them, R3-R 10 independently selected from hydrogen atoms or C1-C 10 An alkyl group, R1 and R2 are selected from C1-C3 alkoxy groups.

[0014] Preferably, the anion includes, but is not limited to, nitrate, sulfonate, oxalate, methylsulfate, tetrafluoroaluminate, tetrafluoroborate, heptachlorodialuminate, hexafluorophosphate, bis(trifluoromethylsulfonyl)imide and pure halogen.

[0015] Preferably, the weight ratio of the extractant to the Fischer-Tropsch oil is (15:85)-(40:60), preferably (30:70)-(40:60), and more preferably 30:70.

[0016] Preferably, the method comprises the following steps: mixing the extractant with the Fischer-Tropsch synthetic oil, stirring and then letting it stand, and then performing liquid separation to obtain a supernatant which is the target product.

[0017] Preferably, the stirring temperature after the extractant and the Fischer-Tropsch synthetic oil are mixed is 50-85°C, preferably 60-85°C, more preferably 75-85°C.

[0018] Preferably, the stirring time after the extractant and the Fischer-Tropsch synthetic oil are mixed is 0.5-4 h, the stirring speed is 400-1200 r / min, and the standing time after stirring is 0.5-1 h.

[0019] Preferably, the extraction number of times of extracting the Fischer-Tropsch synthetic oil with the extractant is 1-5 times, preferably 4-5 times, more preferably 5 times.

[0020] Preferably, the supernatant obtained by the treatment can be further centrifuged to obtain an upper supernatant, the centrifugation time is 10-30 minutes, and the standing time after centrifugation is 10-30 minutes.

[0021] The extractant provided by the present invention can effectively remove isomeric hydrocarbons after 2-5 extractions, providing an excellent isomeric hydrocarbon removal effect, and the extractant has good stability and is easy to prepare and recycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the GC-MS spectrum of Fischer-Tropsch synthetic oil.

[0023] Figure 2 This is the GC-MS spectrum of the supernatant after extraction in Example 1.

[0024] Figure 3 This is the GC-MS spectrum of the supernatant after extraction in Example 2.

[0025] Figure 4 This is the GC-MS spectrum of the supernatant after extraction in Comparative Example 1. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The Fischer-Tropsch synthetic oil used in this application comes from Shaanxi Future Energy Chemical Co., Ltd., and the gas chromatogram is shown in the attached Figure 1 The composition analysis is shown in Table 1 and Table 2.

[0028] Table 1 GC-MS detailed analysis of Fischer-Tropsch synthetic oil composition (wt%)

[0029]

[0030]

[0031]

[0032] Table 2 Classification and statistics of Fischer-Tropsch synthetic oil composition

[0033]

[0034] The preparation method of the extractant of the present invention refers to the Chinese invention patent CN103732587B: 4,4'-bipyridine or 2,2'-bipyridine compounds are reacted with halogenated hydrocarbons to obtain dialkoxypyridinium salts, which are then reacted with acids or salts to finally generate ionic liquids. Alternatively, 4,4'-bipyridine or 2,2'-bipyridine compounds are reacted with organic or inorganic strong acids to generate ionic liquids.

[0035] Preparation of ionic liquid iL-1

[0036] 156.18 g of 4,4'-bipyridine and 198.53 g of chloromethyl ether were added to a 500 mL round-bottom flask, and the temperature was raised to 75°C under nitrogen atmosphere, and the reaction was stirred for 20 hours. After cooling to room temperature, the mixture was washed three times with ethyl acetate and dried in vacuo at 70°C to obtain dialkoxy 4,4'-bipyridine chloride with a yield of 78.7%.

[0037] Add 172.23 g of dialkoxy 4,4'-bipyridyl chloride, 109.79 g of sodium fluoroborate and 120 mL of deionized water to a 500 mL flask and stir at room temperature for 8 h. After the reaction is complete, extract with dichloromethane three times, concentrate by rotary evaporation, and dry in vacuo at 70 ° C to obtain ionic liquid iL-1, with the structural formula:

[0038] Do it 1H-NMR (solvent CDCl3) structural characterization results are:

[0039] 1 H-NMR ((CD3)2CO, 400MHz, ppm): 9.28(d,4H), 8.6(d,4H), 3.41(d,4H), 3.39(s,4H), 1.15(d,6H).

[0040] Preparation of ionic liquid iL-2

[0041] 156.18 g of 4,4'-bipyridine and 261.60 g of 2-methoxyethoxymethyl chloride were added to a 500 mL round-bottom flask, and the temperature was raised to 75°C under nitrogen atmosphere, and the mixture was stirred for 20 hours. After cooling to room temperature, the mixture was washed three times with ethyl acetate and dried under vacuum at 70°C to obtain a dialkoxy 4,4'-bipyridine chloride salt with a yield of 76.6%.

[0042] Add 200.23 g of dialkoxy 4,4'-bipyridyl chloride, 109.79 g of sodium fluoroborate and 120 mL of deionized water to a 500 mL flask and stir at room temperature for 8 h. After the reaction is completed, extract with dichloromethane three times, concentrate by rotary evaporation, and dry in vacuum at 70 ° C to obtain ionic liquid iL-2, with the structural formula:

[0043] Do it 1 H-NMR (solvent CDCl3) structural characterization results are:

[0044] 1 H-NMR ((CD3)2CO, 400MHz, ppm): 9.35 (d, 4H), 8.62 (d, 4H), 3.58 (s, 4H), 3.44 (m, 8H), 3.23 (s, 6H).

[0045] Preparation of ionic liquid iL-3

[0046] 80.09 g of pyrazine and 198.53 g of chloromethyl ether were added to a 500 mL round-bottom flask, and the temperature was raised to 75°C under nitrogen atmosphere, and the mixture was stirred for 20 h. After cooling to room temperature, the mixture was washed with ethyl acetate three times and dried in vacuo at 70°C to obtain dialkoxypyrazine chloride with a yield of 79.0%.

[0047] Add 134.18 g of dialkoxypyrazine chloride, 109.79 g of sodium fluoroborate and 120 mL of deionized water to a 500 mL flask and stir at room temperature for 8 h. After the reaction is complete, extract with dichloromethane three times, concentrate by rotary evaporation, and dry in vacuo at 70 ° C to obtain ionic liquid iL-3, with the structural formula:

[0048] Do it 1 H-NMR (solvent CDCl3) structural characterization results are:

[0049] 1 H-NMR((CD3)2CO,400MHz,ppm):8.68(m,4H),,3.48(d,4H),3.4(s,4H),1.16(d,6H).

[0050] The Fischer-Tropsch synthetic oil is extracted using the ionic liquid extractant prepared above.

[0051] Example 1 A method for removing oxygen-containing compounds and isomerized hydrocarbons from Fischer-Tropsch synthetic oil: 14.0012 g of extractant and 21.0084 g of Fischer-Tropsch synthetic oil are weighed and mixed in a weight ratio of 40:60, the mixture is heated to 85°C, stirred at 600 r / min for 4 hours, and then transferred to a separatory funnel and allowed to stand for stratification. After stratification, the mixture is separated and the supernatant is the Fischer-Tropsch synthetic oil after the oxygen-containing compounds and isomerized hydrocarbons are removed.

[0052] In this example, the extraction was repeated twice, and the extractant was the ionic liquid iL-1.

[0053] Example 2 A method for removing oxygen-containing compounds and isomerized hydrocarbons from Fischer-Tropsch synthetic oil: The extractant and Fischer-Tropsch synthetic oil are mixed in a weight ratio of 30:70, the temperature is raised to 85°C, stirred at 600 r / min for 4 hours, then transferred to a separatory funnel and allowed to stand for 1 hour to separate the layers, and then separated after separation. The supernatant is the Fischer-Tropsch synthetic oil after the oxygen-containing compounds and isomerized hydrocarbons are removed.

[0054] In this example, the extraction was repeated twice, and the extractant was the ionic liquid iL-2.

[0055] Comparative Example 1 A method for removing oxygen-containing compounds and isomerized hydrocarbons from Fischer-Tropsch synthetic oil: mixing an extractant and Fischer-Tropsch synthetic oil in a weight ratio of 30:70, heating to 85°C, stirring at 600 r / min for 4 hours, then transferring to a separatory funnel and standing to separate layers, and performing liquid separation after separation. The supernatant is the Fischer-Tropsch synthetic oil after the oxygen-containing compounds and isomerized hydrocarbons are removed.

[0056] In this example, the extraction was repeated 5 times, and the extractant was the ionic liquid iL-3.

[0057] Performance testing

[0058] The supernatant obtained in the embodiment was subjected to component test analysis, and the GC-MS integration conditions were as follows (peak area): number of peaks 5, slope 600 / min, half-peak width 3 sec, drift 0 / min, variable parameter time 1000 min, minimum peak area / peak height 50000, smoothing times 1, and smoothing half-peak width 7 points.

[0059] Table 3 GC-MS analysis results of Example 1

[0060]

[0061]

[0062] By comparing Table 3, Figure 2 The GC-MS analysis results show that after two extractions, no isoolefins and isoparaffins were detected in the supernatant. The supernatant components are normal olefins and normal paraffins, with contents of 45.70% and 54.30% respectively.

[0063] Table 4 GC-MS analysis results of Example 2

[0064]

[0065] By comparing Table 4, Figure 3 The GC-MS analysis results show that after two extractions, no isoolefins and isoparaffins were detected in the supernatant. The supernatant components are normal olefins and normal paraffins, with contents of 46.32% and 53.68% respectively.

[0066] Table 5 GC-MS analysis results of Comparative Example 1

[0067]

[0068]

[0069]

[0070] By comparing Table 5, Figure 4 The GC-MS analysis results show that after 5 extractions, isoolefins and isoparaffins are still present in the supernatant. The contents of normal olefins and normal paraffins in the supernatant are 45.45% and 49.10%, respectively.

[0071] The above is a description of the embodiments of the present invention. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed herein.

Claims

1. Application of an extractant in removing isomeric hydrocarbons from Fischer-Tropsch synthetic oil, wherein the extractant is an ionic liquid composed of cations and anions; The cation adopts the structural formula shown below: （Ⅰ） ； in, R3-R 10 independently selected from hydrogen atoms or C1-C 10 An alkyl group, R1 and R2 are selected from C1-C3 alkoxy groups.

2. The use according to claim 1, characterized in that: The anions include, but are not limited to, nitrate, sulfonate, oxalate, methylsulfate, tetrafluoroaluminate, tetrafluoroborate, heptachlorodialuminate, hexafluorophosphate, bistrifluoromethylsulfonimide and pure halogen.

3. The use according to claim 1, characterized in that: The weight ratio of the extractant to the Fischer-Tropsch oil is (15:85)-(40:60), preferably (30:70)-(40:60), and more preferably 30:

70.

4. The use according to claim 1, characterized in that: The method comprises the following steps: mixing the extractant with the Fischer-Tropsch synthetic oil, stirring and then standing the mixture, and then performing liquid separation to obtain a supernatant liquid which is the target product.

5. The use according to claim 4, characterized in that: The stirring temperature after the extractant and the Fischer-Tropsch synthetic oil are mixed is 50-85°C, preferably 60-85°C, and more preferably 75-85°C.

6. The use according to claim 4, characterized in that: The stirring time after the extractant and the Fischer-Tropsch synthetic oil are mixed is 0.5-4h, the stirring speed is 400-1200r / min, and the standing time after stirring is 0.5-1h.

7. The use according to claim 4, characterized in that: The extraction times of the Fischer-Tropsch synthesis oil with the extractant are 1 to 5 times, preferably 4 to 5 times, and more preferably 5 times.

8. The use according to claim 4, characterized in that: The supernatant obtained by the treatment can be further centrifuged to obtain an upper supernatant, the centrifugation time is 10-30 minutes, and the standing time after centrifugation is 10-30 minutes.

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