A method for continuously preparing methylal using a microchannel reaction device

Abstract

The present application belongs to the field of fine chemical industry, and relates to a method for continuously preparing methylal by using a micro-channel reaction device. The micro-channel reaction device is adjusted, a solution prepared by mixing methanol, formaldehyde and a catalyst is punched into the reaction system, and the product methylal is synthesized after micro-channel reaction; the micro-channel reaction device adopts a multi-module structure, and the connection mode and the number of modules between the modules can be assembled according to requirements. The present application has the following advantages: 1) the micro-channel reaction device is used, compared with a conventional reactor, a great breakthrough is made in technology, the reaction conditions can be accurately controlled, and a larger heat exchange area can greatly improve the mass transfer and heat transfer efficiency; 2) the on-line continuous reaction can break the intermittent operation mode of the conventional reactor, and reduce the test error caused by the intermittent operation; 3) the ionic liquid catalyst is used, the reaction conditions are mild, and a better reaction effect can be achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical industry, and relates to a method for continuously preparing methylal by using a micro-channel reaction device. BACKGROUND

[0002] Methylal is also called dimethoxy methane (DMM), has the advantages of low toxicity, low boiling point and good solubility, is an environmentally friendly solvent with excellent performance, and is also an important chemical intermediate. Polyformaldehyde produced by using methylal is an engineering plastic widely used in the automobile industry. The mass fraction of oxygen in methylal is as high as 42.1%, and there is no C-C bond in the molecule, so methylal can be used as an oil additive. By adding 5% to 10% of methylal in diesel, the combustion performance of the engine can be effectively improved, and the content of hydrocarbons and carbon monoxide in the exhaust gas can be reduced. As a high-value-added product downstream of methanol and formaldehyde, methylal has wide application and can be applied to cosmetics, medicines, household products, industrial and automotive products, pesticides, leather polishing agents, rubber industry, paints and inks and the like.

[0003] There are mainly the following methods for synthesizing methylal: methanol and formaldehyde condensation method, one-step methanol oxidation method, dimethyl ether oxidation method, and formaldehyde and polyformaldehyde reaction method. At present, the more mature synthesis method is to prepare methylal by condensation reaction of methanol and formaldehyde under the catalysis of acid. The current research focus of this process is to optimize the suitable catalyst and the process flow of catalytic reaction distillation.

[0004] An ionic liquid is usually composed of an organic cation and an inorganic or organic anion, is a substance composed of ions completely, and is in a liquid state at room temperature and adjacent temperatures. The ionic liquid has the advantages of zero vapor pressure, non-volatilization at high temperature, wide temperature range of liquid existence, non-combustion, non-explosion, non-oxidation, high thermal stability, low viscosity, large heat capacity, easy handling, relatively low cost, and controllable physicochemical properties by adjusting the anion and cation.

[0005] CN102211981A discloses a reaction for synthesizing an alkoxyl ether compound by using methylal, ethylal, methanol or ethanol and a water solution of trioxymethylene, trioxymethylal, formaldehyde or acetaldehyde as a catalyst under the condition of a tetraalkyl guanidine ionic liquid. CN107413386A uses a halogenated copper and an ionic liquid composition as a catalyst to react methanol and oxygen to synthesize methylal. The reaction processes in the above two inventions are intermittent reactions and cannot be continuously operated. SUMMARY

[0006] The purpose of the present application is to provide a method for continuously preparing methylal by using a micro-channel reaction device, which is simple in process and environmentally friendly.

[0007] The application is implemented by using a micro-channel reaction device to continuously prepare methylal, characterized by using the micro-channel reaction device to perform the following steps: adjusting the micro-channel reaction device, feeding a solution prepared by mixing methanol, formaldehyde and a catalyst into the reaction system, and synthesizing the product methylal after micro-channel reaction.

[0008] Generally, the module connection mode is parallel or series, and the number of modules is 1-20.

[0009] The module material is special glass.

[0010] The catalyst is an ionic liquid, the cation of the ionic liquid is one or more of imidazole type ions, pyridine type ions and quaternary ammonium salt ions, and the anion is hydrogen sulfate ion.

[0011] The ionic liquid is N - methyl imidazole hydrogen sulfate, 1-ethyl-3-methyl imidazole hydrogen sulfate, 1-butyl-3-methyl imidazole hydrogen sulfate, 1-methyl-3-sulfonic acid imidazole hydrogen sulfate, 1-methyl-3-propyl sulfonic acid imidazole hydrogen sulfate, N - butyl pyridine hydrogen sulfate, N - ethyl pyridine hydrogen sulfate, N , N - dimethyl cyclohexyl ammonium hydrogen sulfate, N , N - dimethyl benzyl ammonium hydrogen sulfate.

[0012] The methanol, formaldehyde and catalyst are fed by using a mixed solution, and the flow rate of the mixed solution is 10-75 g / min.

[0013] The mass fraction of the catalyst is 3%-7%, based on the total mass of the mixed solution.

[0014] The molar ratio of methanol to formaldehyde is 2.2:1-2.8:1.

[0015] The reaction temperature is 40-90℃.

[0016] The method of the application mixes formaldehyde, methanol and ionic liquid catalyst in a certain proportion, and the mixed solution is reacted in the micro-channel reaction device. The reaction product is subjected to vacuum distillation, and methylal is separated.

[0017] Compared with the prior art, the method has the advantages that: 1) the micro-channel reaction device is adopted, compared with a conventional reactor, a breakthrough is made in technology, reaction conditions can be accurately controlled, and a larger heat exchange area can greatly improve mass transfer and heat transfer efficiency; 2) on-line continuous reaction can break the intermittent operation mode of the conventional reactor, and reduce test errors caused by intermittent operation; and 3) the ionic liquid catalyst is adopted, and the reaction condition is mild, and good reaction effect can be achieved. DETAILED DESCRIPTION

[0018] The method of the present application is described in detail below in combination with examples.

[0019] In the following examples, the micro-channel reaction device adopts a multi-module structure, the connection mode between the modules and the number of modules can be assembled according to needs, the connection mode is parallel or series, the number of modules is 1-20, and the module material is special glass. By setting the reaction parameters of the micro-channel reaction device, formaldehyde, methanol and ionic liquid catalyst are mixed in a certain proportion, the mixed solution is reacted in the micro-channel reaction device, and the reaction product is separated by vacuum distillation to obtain methylal.

[0020] Example 1

[0021] After adjusting the temperature of the constant temperature system to the reaction temperature 40℃, the molar ratio of methanol to formaldehyde is 2.2:1, N - the mass fraction of butylpyridine hydrogen sulfate ionic liquid catalyst is 3%, methanol, formaldehyde and ionic liquid catalyst are pumped into the micro-channel reaction device for reaction, the mixed solution at the reaction outlet is sampled and analyzed, the formaldehyde conversion rate is 75.6%, and the methylal selectivity is 99.7%.

[0022] Example 2

[0023] After adjusting the temperature of the constant temperature system to the reaction temperature 40℃, the molar ratio of methanol to formaldehyde is 2.5:1, N - the mass fraction of methyl imidazole hydrogen sulfate ionic liquid catalyst is 5%, methanol, formaldehyde and ionic liquid catalyst are pumped into the micro-channel reaction device for reaction, the mixed solution at the reaction outlet is sampled and analyzed, the formaldehyde conversion rate is 78.5%, and the methylal selectivity is 99.6%.

[0024] Example 3

[0025] After adjusting the temperature of the constant temperature system to the reaction temperature 40℃, the molar ratio of methanol to formaldehyde is 2.8:1, N - the mass fraction of ethylpyridine hydrogen sulfate ionic liquid catalyst is 5%, methanol, formaldehyde and ionic liquid catalyst are pumped into the micro-channel reaction device for reaction, the mixed solution at the reaction outlet is sampled and analyzed, the formaldehyde conversion rate is 87.5%, and the methylal selectivity is 99.7%.

[0026] Example 4

[0027] After adjusting the temperature of the constant temperature system to the reaction temperature of 65℃, the molar ratio of methanol to formaldehyde was 2.5:1, and the mass fraction of 1-ethyl-3-methylimidazolium hydrogen sulfate ionic liquid catalyst was 3%. Methanol, formaldehyde, and ionic liquid catalyst were pumped into the microchannel reaction device for reaction. The mixture at the reaction outlet was sampled and analyzed. The formaldehyde conversion rate was 81.4%, and the selectivity of methylal was 99.5%.

[0028] Example 5

[0029] After adjusting the temperature of the constant temperature system to the reaction temperature of 65℃, the molar ratio of methanol to formaldehyde was 2.2:1, and the mass fraction of 1-butyl-3-methylimidazolium hydrogen sulfate ionic liquid catalyst was 5%. Methanol, formaldehyde, and ionic liquid catalyst were pumped into the microchannel reaction device for reaction. The mixture at the reaction outlet was sampled and analyzed. The formaldehyde conversion rate was 83.2%, and the selectivity of methylal was 99.3%.

[0030] Example 6

[0031] After adjusting the temperature of the constant temperature system to the reaction temperature of 65℃, the molar ratio of methanol to formaldehyde is 2.8:1. N , N -dimethyl- N- The (3-sulfonic acid)cyclohexane ammonium hydrogen sulfate ionic liquid catalyst had a mass fraction of 7%. Methanol, formaldehyde, and the ionic liquid catalyst were pumped into a microchannel reaction device for reaction. The mixture at the reaction outlet was sampled and analyzed. The formaldehyde conversion rate was 87.7%, and the selectivity of methyl acetal was 99.4%.

[0032] Example 7

[0033] After adjusting the temperature of the constant temperature system to the reaction temperature of 85℃, the molar ratio of methanol to formaldehyde was 2.8:1, and the mass fraction of 1-methyl-3-sulfonic acid imidazolium hydrogen sulfate ionic liquid catalyst was 3%. Methanol, formaldehyde, and ionic liquid catalyst were pumped into the microchannel reaction device for reaction. The mixture at the reaction outlet was sampled and analyzed. The formaldehyde conversion rate was 85.8%, and the selectivity of methyl acetal was 99.1%.

[0034] Example 8

[0035] After adjusting the temperature of the constant temperature system to the reaction temperature of 85℃, the molar ratio of methanol to formaldehyde is 2.2:1. N , N -dimethyl- N-The 3-(sulfonic acid) propyl benzyl ammonium hydrogen sulfate ionic liquid catalyst mass fraction was 5%, methanol, formaldehyde, and the ionic liquid catalyst were pumped into the micro-channel reaction device to react, the mixed liquid at the reaction outlet was sampled and analyzed, the formaldehyde conversion rate was 82.9%, and the methylal selectivity was 98.9%.

[0036] Example 9

[0037] After the constant temperature system temperature was adjusted to the reaction temperature 85℃, the methanol and formaldehyde molar ratio was 2.5:1, the 1-methyl-3-propyl sulfonic acid imidazole hydrogen sulfate ionic liquid catalyst mass fraction was 7%, methanol, formaldehyde, and the ionic liquid catalyst were pumped into the micro-channel reaction device to react, the mixed liquid at the reaction outlet was sampled and analyzed, the formaldehyde conversion rate was 80.7%, and the methylal selectivity was 98.4%.

Claims

1. A method for the continuous preparation of methylal using a microchannel reaction device, characterized in that... The microchannel reaction apparatus is used according to the following steps: The microchannel reaction apparatus is adjusted, and a solution prepared from methanol, formaldehyde, and a catalyst is introduced into the reaction system. After passing through the microchannel reaction, the product methylal is synthesized. The reaction temperature is 40-85℃. The microchannel reaction apparatus adopts a multi-module structure. The catalyst is an ionic liquid. N 1-Methyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-methyl-3-sulfonic acid imidazolium hydrogen sulfate, 1-methyl-3-propanesulfonic acid imidazolium hydrogen sulfate, N -Butylpyridine hydrogen sulfate, N 1-Ethylpyridine hydrogen sulfate, N , N -Dimethylcyclohexane ammonium hydrogen sulfate, N , N - One or a combination of dimethylbenzylammonium hydrogen sulfates.

2. The method as described in claim 1, characterized in that... The multi-module structure is configured such that the modules are connected in parallel or in series, and the number of modules ranges from 1 to 20.

3. The method as described in claim 1 or 2, characterized in that... The module is made of special glass.

4. The method as described in claim 1, characterized in that... The methanol, formaldehyde, and catalyst are fed as a mixed solution with a flow rate of 5-80 g / min.

5. The method as described in claim 1 or 4, characterized in that... The catalyst mass fraction is 3% to 7% based on the total mass of the mixture.

6. The method as described in claim 1 or 4, characterized in that... The molar ratio of methanol to formaldehyde is 2.2:1 to 2.8:1.