A preparation method of ethyl methyl carbonate

Abstract

The present invention provides a preparation method of ethyl methyl carbonate, belonging to the technical field of chemical synthesis, which comprises the following steps: (1) dehydrating ethanol to obtain dehydrated ethanol; (2) mixing the dehydrated ethanol obtained in the step (1) with dimethyl carbonate and a catalyst, and carrying out transesterification reaction to obtain ethyl methyl carbonate; the catalyst comprises molecular sieve and ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent. The present invention first dehydrates ethanol to reduce the water content of ethanol and improve the yield of ethyl methyl carbonate; the molecular sieve in the catalyst itself has a catalytic effect, and an ionic liquid is grafted onto its surface. The ionic liquid also has a catalytic effect, and there is a synergistic effect between the two, which can further improve the yield of ethyl methyl carbonate. The results of the examples show that the yield of ethyl methyl carbonate prepared by the preparation method of the present invention reaches more than 95%.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical synthesis, and particularly relates to a preparation method of ethyl methyl carbonate. Background Art

[0002] Ethyl methyl carbonate is a widely used asymmetric carbonate compound, containing active reaction groups such as methyl, ethyl and carbonyl groups, and is mainly used as a solvent and an intermediate in organic synthesis. Due to its low viscosity, large dielectric constant, strong solubility for lithium salts, safety and stability, it can well improve the energy density and charge-discharge capacity of batteries, and can further improve the safety performance and service life of batteries, and can alleviate the domestic demand for electrolytes to a certain extent.

[0003] At present, the synthesis method of ethyl methyl carbonate is mainly the transesterification method, and the commonly used catalysts are mostly alkali metal hydroxides, alcoholates or carbonates, strong base resins, etc., but the yields of the prepared ethyl methyl carbonate are all relatively low (below 80%).

[0004] Therefore, how to further improve the yield of ethyl methyl carbonate has become a difficult problem in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of ethyl methyl carbonate. The ethyl methyl carbonate prepared by the preparation method provided by the present invention has a higher yield.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of ethyl methyl carbonate, comprising the following steps:

[0008] (1) Dehydrating ethanol to obtain dehydrated ethanol;

[0009] (2) Mixing the dehydrated ethanol obtained in the step (1) with dimethyl carbonate and a catalyst, and then carrying out a transesterification reaction to obtain ethyl methyl carbonate; the catalyst comprises a molecular sieve and an ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent.

[0010] Preferably, the mass content of water in the dehydrated ethanol in the step (1) is less than or equal to 0.1%.

[0011] Preferably, the preparation method of the catalyst in the step (2) comprises the following steps:

[0012] a. Mixing the molecular sieve with a silane coupling agent and a solvent, and then carrying out an etherification reaction to obtain an intermediate;

[0013] b. Mixing the intermediate obtained in the step a with a carboxyl group-containing ionic liquid and a solvent, and then carrying out a condensation reaction to obtain the catalyst.

[0014] Preferably, the mass ratio of the molecular sieve to the silane coupling agent in step a is (2-10):1.

[0015] Preferably, the temperature of the etherification reaction in step a is 80-120°C, and the time of the etherification reaction is 5-30 h.

[0016] Preferably, the mass ratio of the intermediate to the ionic liquid with a carboxyl group in step b is (1-5):1.

[0017] Preferably, the molar ratio of dehydrated ethanol to dimethyl carbonate in step (2) is (0.3-3):1.

[0018] Preferably, the mass ratio of the catalyst to dimethyl carbonate in step (2) is (0.001-0.5):1.

[0019] Preferably, the temperature of the transesterification reaction in step (2) is 50-150°C.

[0020] Preferably, the time of the transesterification reaction in step (2) is 5-24 h.

[0021] The present invention provides a method for preparing ethyl methyl carbonate, comprising the following steps: (1) dehydrating ethanol to obtain dehydrated ethanol; (2) mixing the dehydrated ethanol obtained in step (1) with dimethyl carbonate and a catalyst, and then carrying out a transesterification reaction to obtain ethyl methyl carbonate; the catalyst comprises a molecular sieve and an ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent. The present invention first dehydrates ethanol to reduce the water content of ethanol and improve the yield of ethyl methyl carbonate; the molecular sieve in the catalyst itself has a catalytic effect, and an ionic liquid is grafted onto its surface. The ionic liquid also has a catalytic effect, and there is a synergistic effect between the two, which can further improve the yield of ethyl methyl carbonate. The results of the examples show that the yield of ethyl methyl carbonate prepared by the preparation method of the present invention reaches more than 95%. Detailed Embodiments

[0022] The present invention provides a method for preparing ethyl methyl carbonate, comprising the following steps:

[0023] (1) Dehydrating ethanol to obtain dehydrated ethanol;

[0024] (2) Mixing the dehydrated ethanol obtained in step (1) with dimethyl carbonate and a catalyst, and then carrying out a transesterification reaction to obtain ethyl methyl carbonate; the catalyst comprises a molecular sieve and an ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent.

[0025] Unless otherwise specified, the present invention does not particularly limit the sources of the various components, and commercially available products or products prepared by conventional preparation methods well known to those skilled in the art can be used.

[0026] The present invention dehydrates ethanol to obtain dehydrated ethanol.

[0027] In the present invention, the mass content of water in the dehydrated ethanol is preferably less than or equal to 0.1%. By limiting the mass content of water in the dehydrated ethanol within the above range, the present invention can avoid the influence of water on the transesterification reaction and further improve the yield of ethyl methyl carbonate.

[0028] In the present invention, the dehydration is preferably carried out by adding a water-absorbing resin or zeolite to ethanol and then filtering. The present invention does not particularly limit the addition amount of the water-absorbing resin or zeolite and the dehydration time, as long as the mass content of water in the dehydrated ethanol is within the above range.

[0029] In the present invention, the dehydration can reduce the water content in the raw material ethanol and avoid the adverse effect of water on the transesterification.

[0030] After obtaining the dehydrated ethanol, the present invention mixes the dehydrated ethanol with dimethyl carbonate and a catalyst and then carries out a transesterification reaction to obtain ethyl methyl carbonate.

[0031] In the present invention, the catalyst includes a molecular sieve and an ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent.

[0032] In the present invention, the molecular sieve preferably includes ZSM-5 molecular sieve or β molecular sieve.

[0033] In the present invention, the silane coupling agent is preferably 3-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

[0034] In the present invention, the ionic liquid is preferably an imidazole-based or pyridine-based ionic liquid. In the present invention, the structural formula of the imidazole-based ionic liquid is preferably as shown in Formula 1:

[0035]

[0036] Among them, X is preferably Cl, Br or I; R2 is preferably ethyl, propyl or butyl.

[0037] In the present invention, the structural formula of the pyridine-based ionic liquid is preferably as shown in Formula 2:

[0038]

[0039] Among them, X is preferably Cl, Br or I; R1 is preferably ethyl, propyl or butyl.

[0040] By limiting the structure of the ionic liquid within the above range, the present invention can endow it with a suitable structure, excellent catalytic performance, and further improve the yield of ethyl methyl carbonate.

[0041] In the present invention, the molecular sieve in the catalyst has a porous structure, which can promote the diffusion of raw materials and products during the catalytic reaction, enabling the raw materials to come into full contact with the molecular sieve and the ionic liquid, giving full play to the catalytic effects of both and having a synergistic effect, and further improving the yield of ethyl methyl carbonate.

[0042] In the present invention, the preparation method of the catalyst preferably includes the following steps:

[0043] a. Mix the molecular sieve, silane coupling agent, and solvent, and then carry out an etherification reaction to obtain an intermediate;

[0044] b. Mix the intermediate obtained in step a with the carboxyl group-containing ionic liquid and solvent, and then carry out a condensation reaction to obtain the catalyst.

[0045] The present invention preferably mixes the molecular sieve, silane coupling agent, and solvent and then carries out an etherification reaction to obtain an intermediate.

[0046] In the present invention, the mass ratio of the molecular sieve to the silane coupling agent is preferably (2 - 10):1, more preferably (3 - 8):1, and most preferably (5 - 6):1. By limiting the mass ratio of the molecular sieve to the silane coupling agent within the above range, the content of the silane coupling agent on the surface of the molecular sieve can be adjusted, and then the content of the ionic liquid in the catalyst can be adjusted, enabling both the molecular sieve and the ionic liquid to fully exert their catalytic effects and further improving the yield of ethyl methyl carbonate.

[0047] In the present invention, the solvent is preferably toluene. In the present invention, the mass ratio of the molecular sieve to the solvent is preferably 1:(10 - 50), more preferably 1:(20 - 40). By limiting the mass ratio of the molecular sieve to the solvent within the above range, the raw materials can be dispersed more fully and uniformly.

[0048] The present invention has no special limitation on the operation of mixing the molecular sieve, silane coupling agent, and solvent, and the technical solutions for material mixing well-known to those skilled in the art can be adopted.

[0049] In the present invention, the temperature of the etherification reaction is preferably 80 to 120 °C, more preferably 90 to 110 °C, and most preferably 100 °C; the time of the etherification reaction is preferably 5 to 30 h, more preferably 10 to 25 h, and most preferably 15 to 20 h. In the present invention, the etherification reaction is preferably carried out in an argon atmosphere. In the present invention, during the etherification reaction, the hydroxyl groups on the surface of the molecular sieve react with the silane coupling agent and are grafted onto the surface of the molecular sieve. By limiting the temperature and time of the etherification reaction within the above ranges in the present invention, the etherification reaction can proceed sufficiently.

[0050] After the etherification reaction is completed, the present invention preferably cools, filters, washes, and dries the product of the etherification reaction in sequence to obtain an intermediate.

[0051] The present invention has no special limitation on the operations of cooling, filtering, washing, and drying, and the technical solutions of cooling, filtering, washing, and drying well-known to those skilled in the art can be adopted.

[0052] After obtaining the intermediate, the present invention preferably mixes the intermediate with an ionic liquid with a carboxyl group and a solvent and then carries out a condensation reaction to obtain a catalyst.

[0053] In the present invention, the mass ratio of the intermediate to the ionic liquid with a carboxyl group is preferably (1 to 5):1, more preferably (2 to 4):1, and most preferably 3:1. By limiting the mass ratio of the intermediate to the ionic liquid with a carboxyl group within the above ranges in the present invention, the content of the ionic liquid on the surface of the molecular sieve can be adjusted, enabling both to fully exert their catalytic performance and further improving the yield of ethyl methyl carbonate.

[0054] In the present invention, the solvent is preferably toluene. In the present invention, the mass ratio of the intermediate to the solvent is preferably 1:(10 to 50), more preferably 1:(20 to 40). By limiting the mass ratio of the intermediate to the solvent within the above ranges in the present invention, each raw material can be dispersed more fully and evenly.

[0055] The present invention has no special limitation on the operation of mixing the intermediate with the ionic liquid with a carboxyl group and the solvent, and the technical solutions of material mixing well-known to those skilled in the art can be adopted.

[0056] In the present invention, the temperature of the condensation reaction is preferably 80 to 120 °C, more preferably 90 to 110 °C; the time of the condensation reaction is preferably 5 to 12 h, more preferably 6 to 10 h, and most preferably 7 to 9 h. In the present invention, during the condensation reaction, the amino group in the silane coupling agent reacts with the carboxyl group in the ionic liquid, and then the ionic liquid is grafted onto the surface of the molecular sieve. By limiting the temperature and time of the condensation reaction within the above ranges in the present invention, the condensation reaction can proceed sufficiently.

[0057] After the condensation reaction is completed, the present invention preferably cools, filters, washes, and dries the product of the condensation reaction in sequence to obtain a catalyst.

[0058] The present invention has no special limitation on the operations of cooling, filtering, washing, and drying, and the technical solutions of cooling, filtering, washing, and drying well-known to those skilled in the art can be adopted.

[0059] In the present invention, both the molecular sieve and the ionic liquid in the catalyst have catalytic effects, and a synergistic effect can be generated between the two to further improve the catalytic performance.

[0060] In the present invention, the molar ratio of the dehydrated ethanol to the dimethyl carbonate is preferably (0.3 - 3):1, more preferably (0.3 - 1):1, and most preferably (0.5 - 0.8):1. By limiting the molar ratio of the dehydrated ethanol to the dimethyl carbonate within the above range, the two can fully react to form ethyl methyl carbonate.

[0061] In the present invention, the mass ratio of the catalyst to the dimethyl carbonate is preferably (0.001 - 0.5):1, more preferably (0.005 - 0.4):1, and most preferably (0.01 - 0.2):1. By limiting the mass ratio of the catalyst to the dimethyl carbonate within the above range, the catalyst can fully exert its catalytic performance and further improve the yield of ethyl methyl carbonate.

[0062] In the present invention, the temperature of the transesterification reaction is preferably 50 - 150 °C, more preferably 80 - 120 °C; the time of the transesterification reaction is preferably 5 - 24 h, more preferably 10 - 20 h, and most preferably 10 - 15 h. By limiting the temperature and time of the transesterification reaction within the above range, ethanol and dimethyl carbonate can fully react to generate ethyl methyl carbonate.

[0063] After the transesterification reaction is completed, the present invention preferably post-treats the product of the transesterification reaction. The present invention has no special limitation on the operation of the post-treatment, and the technical solutions of post-treatment well-known to those skilled in the art can be adopted.

[0064] The present invention first dehydrates ethanol to reduce the water content of ethanol, improves the yield of ethyl methyl carbonate, and controls process parameters such as the composition of the catalyst and the dosage of each component, reaction temperature, and time to further improve the yield of ethyl methyl carbonate.

[0065] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0066] Example 1

[0067] (1) Add water-absorbing resin to ethanol for dehydration treatment to obtain dehydrated ethanol, with the mass content of water being 0.08%.

[0068] (2) Mix ZSM-5 molecular sieve with 3-aminopropyltriethoxysilane and toluene (the mass ratio of ZSM-5 molecular sieve to 3-aminopropyltriethoxysilane is 5:1, and the mass ratio of ZSM-5 molecular sieve to toluene is 1:30). Heat to 80 °C under an argon atmosphere and react for 6 h. After cooling, filter, wash with water, and dry to obtain an intermediate. Then mix the intermediate with toluene and 1-ethyl-2-methyl-4-carboxypyridinium bromide (the mass ratio of the intermediate to 1-ethyl-2-methyl-4-carboxypyridinium bromide is 2:1, and the mass ratio of the intermediate to toluene is 1:30). React at 100 °C for 5 h. After cooling, filter, wash with water, and dry to obtain a catalyst.

[0069] (3) Mix dimethyl carbonate with the treated ethanol and the catalyst (the molar ratio of dehydrated ethanol to dimethyl carbonate is 0.5:1, and the mass ratio of the catalyst to dimethyl carbonate is 0.002:1). React at 80 °C for 10 h to obtain ethyl methyl carbonate.

[0070] Example 2

[0071] Replace the mass ratio of the catalyst to dimethyl carbonate in step (3) of Example 1 with 0.005:1, and other parameters are the same as those in Example 1.

[0072] Comparative Example 1

[0073] Replace the catalyst in step (3) of Example 1 with ZSM-5 molecular sieve, and other parameters are the same as those in Example 1.

[0074] Comparative Example 2

[0075] Replace the catalyst in step (3) of Example 1 with 1-ethyl-2-methyl-4-carboxypyridinium bromide, and other parameters are the same as those in Example 1.

[0076] Test the yields of ethyl methyl carbonate in Examples 1-2 and Comparative Examples 1-2, and the results are listed in Table 1.

[0077] Table 1 Yields of ethyl methyl carbonate in Examples 1-2 and Comparative Examples 1-2

[0078] Yield of ethyl methyl carbonate % Example 1 95％ Example 2 96.2％ Comparative Example 1 71％ Comparative Example 2 78％

[0079] As can be seen from Table 1, at the same catalyst dosage, the yields of ethyl methyl carbonate are both relatively low when ZSM-5 molecular sieve and 1-ethyl-2-methyl-4-carboxylpyridinium bromide are used as catalysts. However, after grafting and compounding the two, the yield of ethyl methyl carbonate is significantly improved, indicating a synergistic effect between them.

[0080] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing ethyl methyl carbonate, comprising the following steps: (1) Dehydrate ethanol to obtain dehydrated ethanol; (2) Mix the dehydrated ethanol obtained in step (1) with dimethyl carbonate and a catalyst, and carry out a transesterification reaction to obtain ethyl methyl carbonate; the catalyst is composed of a molecular sieve and an ionic liquid grafted onto the surface of the molecular sieve through a silane coupling agent, and the ionic liquid is 1-ethyl-2-methyl-4-carboxyl pyridinium bromide; the molecular sieve is a ZSM-5 molecular sieve; In step (2), the mass ratio of the catalyst to dimethyl carbonate is (0.001~0.005):1; the temperature of the transesterification reaction in step (2) is 80°C, and the time of the transesterification reaction is 10 h; The preparation method of the catalyst in step (2) includes the following steps: a. Mix the molecular sieve with a silane coupling agent and a solvent, and carry out an etherification reaction to obtain an intermediate; b. Mix the intermediate obtained in step a with a carboxyl-containing ionic liquid and a solvent, and carry out a condensation reaction to obtain a catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass content of water in the dehydrated ethanol is less than or equal to 0.1%.

3. The preparation method according to claim 1, characterized in that, In step a, the mass ratio of the molecular sieve to the silane coupling agent is (2~10):

1.

4. The preparation method according to claim 1, characterized in that, In step a, the temperature of the etherification reaction is 80~120°C, and the time of the etherification reaction is 5~30 h.

5. The preparation method according to claim 1, characterized in that, In step b, the mass ratio of the intermediate to the carboxyl-containing ionic liquid is (1~5):

1.

6. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of the dehydrated ethanol to dimethyl carbonate is (0.3~3):1.

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