Ionic liquid catalysts, methods of making and using the same

Abstract

This invention relates to an ionic liquid catalyst, its preparation method, and its application. The preparation method of the ionic liquid catalyst includes the following steps: S11, reacting a reaction system containing imidazole, ethylene oxide, and a solvent to obtain reaction product I; S12, contacting reaction product I with an alkyl chloride to obtain reaction product II; S13, contacting reaction product II with a solution containing X to obtain reaction product III containing the ionic liquid catalyst. The ionic liquid catalyst provided by this invention, while ensuring catalytic performance, also enables direct separation of the product from the ionic liquid catalyst and the recycling of the ionic liquid catalyst.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and more specifically, to an ionic liquid catalyst, its preparation method, and its application. Background Technology

[0002] Carbonylation of formaldehyde and its derivatives is an important research direction in C1 chemistry. This route uses formaldehyde and its derivatives derived from coal, natural gas, or biomass as raw materials to produce ethylene glycol, and is one of the important alternatives to existing ethylene glycol processes. One of the carbonylation products, methyl methoxyacetate, is a highly valuable intermediate that can be used for the kinetic resolution of chiral amines, the synthesis of vitamin B6 and sulfonamide-5-pyrimidine, and as an ionic liquid catalyst in polymerization reactions. It can also be used to produce ethylene glycol through hydrogenation and hydrolysis.

[0003] Currently, there are two routes for carbonylation reactions: homogeneous catalysis and heterogeneous catalysis. The traditional homogeneous method mainly uses inorganic liquid acids as ionic liquid catalysts, such as concentrated sulfuric acid, hydrofluoric acid, and fluorosulfonic acid. DuPont disclosed in USP2152852 and USP2285448 the catalytic carbonylation of formaldehyde and CO using sulfuric acid as an ionic liquid catalyst at 200°C and 90 MPa, which was used for the commercial production of ethylene glycol, but production ceased in 1968. Chevron disclosed in USP3911003 the carbonylation of formaldehyde using HF as an ionic liquid catalyst at 22-50°C and 6.89-13.78 MPa. Due to the strong corrosiveness and severe pollution caused by inorganic acids, production was discontinued shortly after its launch. Patents CN201210205619.7 and EP19820305617 indicate that the production of methyl methoxyacetate by catalytic carbonylation of methyl acetal under liquid conditions using strong acids presents problems such as difficulty in product separation and corrosion of the equipment by the liquid acid. While various developed solid acids (such as molecular sieves, heteropoly acids, and ion exchange resins) offer advantages such as low corrosivity and easy separation, their catalytic activity and recyclability still need improvement.

[0004] Due to the severe pollution caused by inorganic acid ionic liquid catalysts, and the fact that the formaldehyde liquid-phase carbonylation reaction requires high-pressure conditions, the separation of ionic liquid catalysts and products is difficult, costly, and corrodes equipment. Therefore, developing new ionic liquid catalysts and processes has become a key research focus in formaldehyde carbonylation. Ionic liquids, with their numerous advantages over traditional solvents and their application as green solvents in the synthesis of organic and polymeric substances, are attracting increasing attention and being used in some carbonylation reactions. For example, in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, methylbenzenesulfonic acid and CF3SO3Ag can be used as ionic liquid catalysts to synthesize methyl glycolate. However, in such reaction systems, problems remain regarding unsatisfactory product selectivity and the difficulty in separating and recovering ionic liquid catalysts. How to effectively combine the high activity of homogeneous acid ionic liquid catalysts with the easy recovery of heterogeneous ionic liquid catalysts to develop novel ionic liquid catalysts that ensure mass transfer efficiency while achieving simple separation and recovery of ionic liquid catalysts has become a key focus of carbonylation research. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the inventors of this invention, through extensive and in-depth research, have provided an ionic liquid catalyst, its preparation method, and its application. For example, one objective of this invention is to provide an ionic liquid catalyst that, while ensuring catalytic performance, also enables direct separation of the product from the ionic liquid catalyst and the recycling of the ionic liquid catalyst. Another objective of this invention is to provide the application of the above-mentioned ionic liquid catalyst in the synthesis of methyl methoxyacetate, resulting in a high yield of methyl methoxyacetate, non-corrosive reaction equipment, and easy separation and recovery of the carbonylation solvent and the ionic liquid catalyst.

[0006] To achieve the above objectives, the first aspect of the present invention provides an ionic liquid catalyst, the structure of which is as follows:

[0007]

[0008] In formula (I), n = 7 to 55, R1 is selected from C1 to C6 alkyl, preferably C1 to C6 straight-chain alkyl, more preferably C3 to C5 straight-chain alkyl, and X is selected from one or more of the anions having the structure shown in formula (II) or formula (III);

[0009]

[0010] In formula (II), R2 is selected from hydrogen, C1-C5 straight-chain alkyl, C3-C5 branched alkyl, C2-C5 straight-chain alkenyl, C2-C5 branched alkenyl, C2-C5 straight-chain alkynyl and C2-C5 branched alkynyl, preferably selected from hydrogen and C1-C5 straight-chain alkyl, more preferably hydrogen or methyl;

[0011] In formula (III), R3 is selected from trifluoromethyl, perfluorobutyl and perfluorohexyl, preferably trifluoromethyl.

[0012] According to the present invention, the value of n can be calculated by the product weight gain method.

[0013] A second aspect of the present invention provides a method for preparing an ionic liquid catalyst according to the first aspect of the present invention, comprising the steps of:

[0014] S11. React the reaction system containing imidazole, ethylene oxide and solvent to obtain reaction product I;

[0015] S12. Contact the reaction product I with an alkyl chloride to obtain reaction product II;

[0016] S13. Contact the reaction product II with a solution containing X to obtain the reaction product III containing an ionic liquid catalyst.

[0017] In some embodiments of the present invention, the preparation method may optionally include the steps of: S14, removing HCl from the reaction product III to obtain the ionic liquid catalyst; or, S14 removing HCl from the reaction product III and solvent from the solution containing X to obtain the ionic liquid catalyst. In some embodiments of the present invention, steps S11 to S13 are carried out in an inert gas atmosphere, preferably nitrogen, helium, neon, or argon, more preferably nitrogen.

[0018] In some embodiments of the present invention, the solvent in step S11 is selected from one or more of n-hexane and anhydrous ethanol; the reaction conditions in step S11 include: a reaction temperature of 60°C to 90°C; and a reaction time of 4 to 10 hours.

[0019] According to the present invention, in step S11, the molar ratio of imidazole to ethylene oxide in the reaction system is 0.01 to 1. For example, the content of imidazole in the reaction system is 2 to 10 g, and the content of ethylene oxide is 9 to 70 ml.

[0020] According to the present invention, in step S11, the content of solvent in the reaction system is not fixed or strictly limited, and those skilled in the art can flexibly select according to the actual situation.

[0021] In some embodiments of the present invention, in step S11, the content of imidazole in the reaction system is 2-10g; the content of ethylene oxide is 9-70ml; and the content of solvent is 5-20ml.

[0022] In some embodiments of the present invention, a step of removing the solvent from the reaction product I is included before step S12.

[0023] According to the present invention, the solvent in the reaction product I can be removed by vacuum distillation.

[0024] In some embodiments of the present invention, in step S12, the contact conditions include: a pressure of 4.5 MPa to 5.5 MPa; a reaction temperature of 90°C to 120°C; and a reaction time of 9 to 24 h. The alkyl group in the alkyl chloride is selected from C1-C6 alkyl groups, preferably C1-C6 straight-chain alkyl groups, and more preferably C3-C5 straight-chain alkyl groups.

[0025] According to the present invention, in step S12, the molar ratio of the reaction product II to the alkyl chloride is 0.5 to 2:1.

[0026] In some embodiments of the present invention, in step S13, the solution containing X is selected from one or more of benzenesulfonic acid solution, p-toluenesulfonic acid solution, trifluoromethanesulfonic acid solution, perfluorobutylsulfonic acid solution and perfluorohexylsulfonic acid, preferably selected from one or more of benzenesulfonic acid solution, p-toluenesulfonic acid solution or trifluoromethanesulfonic acid solution, more preferably benzenesulfonic acid solution or p-toluenesulfonic acid solution.

[0027] According to the present invention, the reaction product III can be brought into contact with the solution containing X by slowly adding the solution containing X dropwise to the reaction product III. For example, the solution containing X can be slowly added dropwise using a constant pressure dropping funnel to bring it into contact with the reaction product III.

[0028] According to the present invention, in step S13, the solution containing X can be obtained by weighing the substance containing X and then dissolving it in a small amount of solvent (such as deionized water); or the solution containing X is in a liquid state, so there is no need to dissolve it with a solvent. For example, the solution containing X is trifluoromethanesulfonic acid.

[0029] According to the present invention, in step S13, the molar ratio of the reaction product III to the solution containing X is 0.6 to 3:1.

[0030] According to the present invention, in step S14, the removal of HCl from the reaction product III and the solvent from the solution containing X can be carried out by vacuum distillation.

[0031] In some embodiments of the present invention, the preparation method includes the following steps:

[0032] (i) In a high-pressure reactor under a nitrogen atmosphere, imidazole and ethylene oxide are added using n-hexane and / or anhydrous ethanol as solvents and reacted at a constant temperature of 60℃~90℃ for 4~10h to obtain reaction product I.

[0033] (ii) Remove the solvent from reaction product I to obtain reaction product II;

[0034] (iii) Add alkyl chloride to the autoclave, and stir at a constant temperature of 90℃~120℃ for 9~24h under a nitrogen atmosphere of 5MPa to obtain reaction product III;

[0035] (iv) Slowly add the solution containing X dissolved in a small amount of deionized water, heat and stir at a constant temperature to obtain reaction product IV containing the ionic liquid catalyst;

[0036] (v) Remove HCl and water under reduced pressure to obtain the ionic liquid catalyst.

[0037] According to the present invention, if the solution containing X is a liquid, then step (iv) does not require dissolving the solution containing X with a small amount of deionized water, and step (v) does not require dehydration under reduced pressure.

[0038] According to the present invention, there is no fixed or strict temperature after heating in step (iv). Preferably, the temperature can be heated to 75°C to 85°C before constant temperature stirring.

[0039] The third aspect of the present invention provides the application of the ionic liquid catalyst prepared by the ionic liquid catalyst according to the first aspect of the present invention and / or the preparation method according to the second aspect of the present invention in carbonylation reactions, especially in the synthesis of methyl methoxyacetate.

[0040] In some embodiments of the present invention, the ionic liquid catalyst is used in the synthesis of methyl methoxyacetate. The synthesis of methyl methoxyacetate includes the following steps: S21, contacting formaldehyde source, carbon monoxide, solvent and the ionic liquid catalyst to carry out a carbonylation reaction to obtain an intermediate reaction solution; S22, contacting the intermediate reaction solution with methanol to obtain the methyl methoxyacetate.

[0041] According to the present invention, after contacting formaldehyde source, carbon monoxide, solvent and said ionic liquid catalyst to carry out carbonylation reaction, methoxyacetic acid is generated; methoxyacetic acid is then contacted with methanol to carry out esterification reaction to generate methyl methoxyacetate.

[0042] In some embodiments of the present invention, the formaldehyde source is selected from one or more of formaldehyde or substances that can generate formaldehyde in situ in the synthesis reaction system; preferably selected from one or more of trioxymethylene, paraoxymethylene and formaldehyde.

[0043] In some embodiments of the present invention, the solvent in step S21 is a mixture of an organic solvent and an organic acid. Preferably, the organic solvent is selected from one or more of sulfolane, dioxane, formamide, pyrrolidone, and toluene; and the organic acid is selected from one or more of acetic acid, propionic acid, and isobutyric acid. Preferably, the molar ratio of the organic acid to the organic solvent in the solvent is 1:2 to 1:10, more preferably 1:5 to 1:10.

[0044] In some embodiments of the present invention, in step S21, the reaction conditions include: a temperature of 80°C to 140°C; a pressure of 4 MPa to 8 MPa; and the amount of the ionic liquid catalyst used is 0.1 mol% to 1 mol% of the formaldehyde source feed.

[0045] In some embodiments of the present invention, in step S22, the reaction conditions include: a reaction temperature of 80°C to 120°C and a reaction time of 1 to 4 hours.

[0046] Compared with the prior art, the present invention includes at least one of the following beneficial effects:

[0047] 1) The ionic liquid catalyst provided by this invention improves the structure of existing ionic liquids and has the characteristics of high-temperature homogeneity and low-temperature biphase;

[0048] 2) When the ionic liquid catalyst provided by this invention is used in carbonylation reactions, especially in the synthesis of methyl methoxyacetate, it can achieve direct separation of the product from the ionic liquid catalyst and recycling of the ionic liquid catalyst while ensuring catalytic performance.

[0049] 3) When the ionic liquid catalyst provided by this invention is used in the synthesis of methyl methoxyacetate, it has the advantages of high methyl methoxyacetate yield, non-corrosive reaction equipment, and easy separation and recovery of carbonylation solvent and ionic liquid catalyst.

[0050] 4) When the ionic liquid catalyst provided by this invention is used in the synthesis of methyl methoxyacetate, after the carbonylation reaction is completed, the organic solvent phase and the ionic liquid phase containing the product methyl methoxyacetate can be obtained separately by simple phase separation, which eliminates the product separation step, and the ionic liquid phase can be directly recycled. Detailed Implementation

[0051] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0052] Unless otherwise specified in the examples, the conditions shall be performed under conventional conditions or conditions recommended by the manufacturer. Raw materials, reagents, or instruments whose manufacturers are not specified are all commercially available products or prepared according to publicly disclosed methods.

[0053] In the examples, the yield of methyl methoxyacetate was calculated as follows:

[0054] Methyl methoxyacetate yield (%) = (molar amount of methyl methoxyacetate produced / molar amount of formaldehyde in the raw material) × 100%.

[0055] Example 1

[0056] 1. Preparation of ionic liquid catalysts

[0057] 3.1 g of imidazole and 20 ml of ethylene oxide were added to a high-pressure reactor. The reactor was reacted for 6 h at 80 °C under a nitrogen atmosphere with 10 ml of anhydrous ethanol as the solvent. The anhydrous ethanol was then removed by vacuum distillation. 16 ml of n-chlorobutane was added, and the reactor was purged with 5 MPa of nitrogen and stirred at 90 °C for 9 h. 7.2 g of benzenesulfonic acid was weighed, dissolved in a small amount of deionized water, and slowly added to the above reaction solution through a constant pressure dropping funnel. The reactor was stirred at 80 °C for 6 h and the water and HCl were removed by vacuum distillation to obtain ionic liquid catalyst I.

[0058] The obtained ionic liquid catalyst I has the following structure:

[0059]

[0060] In the formula, n is 12, R1 is n-butyl, and X is benzenesulfonate ion.

[0061] 2. Carbonylation reaction

[0062] In a 100 mL stainless steel high-pressure reactor, 3 g of trioxymethylene (0.1 mol HCHO) and 30 mL of a mixed solvent of sulfolane and acetic acid (mol / mol) = 5:1 were added. 0.21 g of the previously prepared ionic liquid catalyst I (CAT / HCHO = 0.2 mol%) was weighed and added to the reactor. The mixture was stirred thoroughly, the reactor was sealed, and the air in the reactor was replaced three times with CO. High-pressure CO was then introduced until the pressure inside the reactor reached 8 MPa. The reaction was carried out at 120 °C for 3 h. After the reaction was completed, the reactor was cooled to room temperature, and all the reaction solution was removed and placed in a separatory funnel, allowing it to stand until the layers separated. The upper layer was filtered through a microporous membrane to obtain a light brownish-yellow carbonylated product, which was reserved for later use; the lower layer was the recyclable ionic liquid catalyst.

[0063] 3. Esterification reaction

[0064] The carbonylated product obtained after filtration was added to a reaction vessel, along with 15 mL of methanol and 1 g of Amberlyst 15 resin. The reaction vessel was sealed and reacted at 100 °C with stirring for 2 h. After the reaction was completed, the reaction vessel was cooled to room temperature, and the liquid in the vessel was removed. The product was analyzed by gas chromatography and high performance liquid chromatography. The yield of methyl methoxyacetate is shown in Table 1.

[0065] The carbonylation and esterification reactions were repeated using the recycled ionic liquid catalyst. The yields of the product methyl methoxyacetate after repeated use are shown in Table 1 below.

[0066]

[0067] Therefore, it can be seen that ionic catalysts can be recycled multiple times and can achieve a good yield of methyl methoxyacetate.

[0068] Example 2

[0069] Example 2 is essentially the same as Example 1, except that 1-chlorooctane is used instead of the chlorobutane in Example 1. Under otherwise identical conditions, ionic liquid catalyst II is prepared.

[0070] The obtained ionic liquid catalyst II has the following structure:

[0071]

[0072] In the formula, n is 13, R1 is n-octyl, and X is benzenesulfonate ion.

[0073] The product methyl methoxyacetate was obtained in 68.0% by using the same carbonylation and esterification reactions as in Example 1, with the aid of ionic liquid catalyst II.

[0074] Example 3

[0075] Example 3 is essentially the same as Example 1, except that trifluoromethanesulfonic acid is used instead of benzenesulfonic acid in Example 1. Under otherwise identical conditions, ionic liquid catalyst III is prepared.

[0076] The obtained ionic liquid catalyst III has the following structure:

[0077]

[0078] In the formula, n is 12, R1 is n-butyl, and X is trifluoromethanesulfonate ion.

[0079] The product methyl methoxyacetate was obtained in 67.5% by using the same carbonylation and esterification reactions as in Example 1, with the aid of ionic liquid catalyst III.

[0080] Example 4

[0081] Example 4 was essentially the same as Example 1, except that 55 mL of ethylene oxide was added to the autoclave. Under otherwise identical conditions, ionic liquid catalyst IV was prepared.

[0082] The obtained ionic liquid catalyst IV has the following structure:

[0083]

[0084] In the formula, n is 45, R1 is n-butyl, and X is benzenesulfonate ion.

[0085] Using the same carbonylation and esterification reactions as in Example 1, the yield of methyl methoxyacetate was 68.9% with ionic liquid catalyst IV. The yield of methyl methoxyacetate was 68.7% after the catalyst was recycled twice.

[0086] Comparative Example 1

[0087] In this comparative example, the ionic liquid 1-butyl-3-methylimidazolium trifluorosulfonate was used as the catalyst.

[0088] 1. Carbonylation reaction

[0089] In a 100 mL stainless steel high-pressure reactor, 2 g of 1-butyl-3-methylimidazolium trifluorosulfonate, 20 mL of a mixed solvent of cyclohexane and acetic acid in a molar ratio of 5:1, and 3 g of paraformaldehyde (0.1 mol HCHO) were added sequentially. The reactor was sealed, and the air inside was replaced with CO three times. High-pressure CO was then introduced until the pressure inside the reactor reached 8 MPa. The reaction was carried out at 110 °C for 3 h. After the reaction was completed, the reactor was cooled to room temperature, and all the reaction solution was removed and placed in a separatory funnel. The liquids did not separate into layers.

[0090] 2. Esterification reaction

[0091] All the liquid after the carbonylation reaction was put into the reaction vessel, 20 mL of methanol and 1 g of Amberlite IR120 resin were added, the reaction vessel was sealed, and the reaction was carried out at 100 °C for 2 h with stirring. After the reaction was completed, the reaction vessel was cooled to room temperature, and the liquid in the vessel was taken out for chromatographic analysis. The yield of the product methyl methoxyacetate is shown in Table 2.

[0092] Comparative Example 2

[0093] This comparative example uses homogeneous acid trifluoromethanesulfonic acid as a catalyst.

[0094] 1. Carbonylation reaction

[0095] In a stainless steel high-pressure reactor, add 0.3 g of paraformaldehyde (0.1 mol HCHO) and 30 mL of a mixed solvent of cyclohexane:acetic acid = 10:1 (molar ratio). Pipette 200 μL of trifluoromethanesulfonic acid into the reactor. After thorough mixing, seal the reactor and replace the air in the reactor three times with CO. Then, purge with high-pressure CO until the pressure inside the reactor reaches 7 MPa. React at 110 °C for 3 hours. After the reaction is complete, cool the reactor to room temperature and remove all the reaction solution into a separatory funnel. The liquids do not separate into layers.

[0096] 2. Esterification reaction

[0097] All the liquid after the carbonylation reaction was put into the reaction vessel, 20 mL of methanol was added, the reaction vessel was sealed, and the reaction was carried out at 100 °C for 2 h with stirring. After the reaction was completed, the mixture was cooled to room temperature, and the liquid in the vessel was taken out for analysis. The yield of the product methyl methoxyacetate is shown in Table 2.

[0098] Comparative Example 3

[0099] This comparative example uses HZSM-5 molecular sieve as a catalyst.

[0100] 1. Carbonylation reaction

[0101] In a 100 mL stainless steel high-pressure reactor, 3 g of paraformaldehyde (0.1 mol HCHO), 2 g of HZSM-5 molecular sieve, and 20 mL of a mixed solvent of sulfolane and acetic acid in a 1:1 molar ratio were added. After thorough mixing, the reactor was sealed, and the air inside was replaced with CO three times. High-pressure CO was then introduced until the pressure inside the reactor reached 8 MPa, and the reaction was carried out at 110 °C for 3 h. After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was filtered out as the carbonylation product for later use. The filtered HZSM-5 molecular sieve was recovered.

[0102] 2. Esterification reaction

[0103] The carbonylation product was added to a reaction vessel, along with 20 mL of methanol and 1 g of Amberlite IR 120 resin. The reaction vessel was sealed and reacted at 100 °C with stirring for 2 h. After the reaction was completed, the reaction vessel was cooled to room temperature, and the liquid in the vessel was removed. The product was analyzed by gas chromatography and high performance liquid chromatography. The yield of methyl methoxyacetate is shown in Table 2.

[0104]

[0105]

[0106] According to Table 2 and Comparative Example 1, when using 1-butyl-3-methylimidazolium trifluorosulfonate ionic liquid, which does not have a post-reaction separation effect, as a catalyst, the carbonylation product does not separate into layers. The carbonylation product and solvent must all enter the next esterification reaction together, increasing the throughput of the esterification step and subsequent distillation operations. In addition, after purification steps such as distillation and methanol washing, some methanol is mixed into the solvent (acetic acid, propionic acid, or isobutyric acid), making it difficult to recycle the solvent.

[0107] As shown in Table 2 and Comparative Example 2, the product yield is low after carbonylation reaction using a homogeneous catalyst, and the product does not separate into layers. The carbonylation product and solvent must all be carried into the next esterification reaction together. The processing volume of the esterification step and subsequent distillation operations is about 3-4 times that of Example 1. In addition, after purification steps such as distillation and methanol washing, methanol is mixed into the solvent, which makes it difficult to recycle the solvent.

[0108] As shown in Table 2 and Comparative Example 3, although the use of solid acid catalysts (such as HZSM-5) can achieve catalyst recovery, the reaction efficiency is low and the product yield is not ideal due to the limited mass transfer in the gas-liquid-solid three-phase reaction.

[0109] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An application of an ionic liquid catalyst in a carbonylation reaction, wherein the structure of the ionic liquid catalyst is as follows: Equation (I) In formula (I), n = 7~55, R1 is selected from C1~C6 alkyl or n-octyl, and X is selected from one or more anions having the structure shown in formula (II) or formula (III); Equation (II) Equation (III) In formula (II), R2 is selected from hydrogen, C1~C5 straight-chain alkyl, and C3~C5 branched alkyl; In formula (III), R3 is selected from trifluoromethyl, perfluorobutyl and perfluorohexyl.

2. The application according to claim 1, characterized in that, In formula (I), R1 is selected from C1~C6 straight-chain alkyl or n-octyl; In and / or in formula (II), R2 is selected from hydrogen and C1~C5 straight-chain alkyl groups; In and / or in formula (III), R3 is trifluoromethyl.

3. The application according to claim 2, characterized in that, In formula (I), R1 is selected from C3~C5 straight-chain alkyl or n-octyl; In and / or in formula (II), R2 is hydrogen or methyl.

4. The application according to any one of claims 1 to 3, characterized in that, The preparation method of the ionic liquid catalyst includes the following steps: S11. React the reaction system containing imidazole, ethylene oxide and solvent to obtain reaction product I; S12. Contact the reaction product I with an alkyl chloride to obtain reaction product II; S13. Contact the reaction product II with a solution containing X to obtain the reaction product III containing an ionic liquid catalyst; as well as Optionally, in step S14, HCl and, optionally, solvent from a solution containing X are removed from reaction product III to obtain the ionic liquid catalyst.

5. The application according to claim 4, characterized in that, Steps S11 to S13 are carried out in an inert gas atmosphere.

6. The application according to claim 5, characterized in that, The inert gas is nitrogen, helium, neon, or argon.

7. The application according to claim 6, characterized in that, The inert gas is nitrogen.

8. The application according to claim 4, characterized in that, The solvent in step S11 is selected from one or more of n-hexane and anhydrous ethanol; the reaction conditions in step S11 include: a reaction temperature of 60℃~90℃; and a reaction time of 4~10h.

9. The application according to claim 4, characterized in that, In step S12, the contact conditions include: a pressure of 4.5 MPa to 5.5 MPa; a reaction temperature of 90°C to 120°C; a reaction time of 9 to 24 h; and / or the alkyl group in the alkyl chloride is selected from C1-C6 alkyl groups.

10. The application according to claim 9, characterized in that, The alkyl group in the alkyl chloride is selected from C1-C6 straight-chain alkyl groups.

11. The application according to claim 10, characterized in that, The alkyl group in the alkyl chloride is selected from C3-C5 straight-chain alkyl groups.

12. The application according to claim 4, characterized in that, In step S13, the solution containing X is selected from one or more of benzenesulfonic acid solution, p-toluenesulfonic acid solution, trifluoromethanesulfonic acid, perfluorobutylsulfonic acid solution, and perfluorohexylsulfonic acid.

13. The application according to claim 12, characterized in that, In step S13, the solution containing X is selected from one or more of benzenesulfonic acid solution, p-toluenesulfonic acid solution, or trifluoromethanesulfonic acid.

14. The application according to claim 13, characterized in that, In step S13, the solution containing X is selected from benzenesulfonic acid solution or p-toluenesulfonic acid solution.

15. The application according to any one of claims 1 to 3, characterized in that, The application is in the synthesis of methyl methoxyacetate.

16. The application according to claim 15, characterized in that, Including the following steps: S21. Formaldehyde source, carbon monoxide, solvent and ionic liquid catalyst are brought into contact to carry out carbonylation reaction to obtain intermediate reaction solution; S22. Contact the intermediate reaction solution with methanol to obtain the methyl methoxyacetate.

17. The application according to claim 16, characterized in that, The formaldehyde source is selected from one or more of formaldehyde or substances that can generate formaldehyde in situ in the synthesis reaction system; The solvent mentioned in step S21 is a mixture of organic solvent and organic acid.

18. The application according to claim 17, characterized in that, The formaldehyde source is selected from one or more of trioxymethylene, paraoxymethylene, and formaldehyde; and / or The organic solvent is selected from one or more of sulfolane, dioxane, formamide, pyrrolidone, and toluene; and / or The organic acid is selected from one or more of acetic acid, propionic acid, and isobutyric acid; and / or The molar ratio of organic acid to organic solvent in the solvent is 1:2 to 1:

10.

19. The application according to claim 18, characterized in that, The molar ratio of organic acid to organic solvent in the solvent is 1:5 to 1:

10.

20. The application according to claim 16, characterized in that, In step S21, the reaction conditions include: a temperature of 80℃~140℃; a pressure of 4MPa~8MPa; and / or The amount of the ionic liquid catalyst used is 0.1 mol% to 1 mol of the formaldehyde source feed.

21. The application according to claim 16, characterized in that, In step S22, the reaction conditions include: a reaction temperature of 80℃~120℃ and a reaction time of 1~4h.

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