CN114481171A

CN114481171A - Method for preparing methylal from methanol by electrochemical method

Info

Publication number: CN114481171A
Application number: CN202210042151.8A
Authority: CN
Inventors: 王强; 张政委; 张乐涛
Original assignee: Xinjiang Technical Institute of Physics and Chemistry of CAS
Current assignee: Xinjiang Technical Institute of Physics and Chemistry of CAS
Priority date: 2022-01-14
Filing date: 2022-01-14
Publication date: 2022-05-13
Anticipated expiration: 2042-01-14
Also published as: CN114481171B

Abstract

The invention relates to a method for preparing methylal from methanol by an electrochemical method, wherein an alternating current power supply is selected as a power supply of the method, two graphite electrode pairs are used, a mixed solution of acid and industrial methanol is used as an electrolyte, and the methylal is obtained by performing electrochemical reaction under the conditions of alternating current voltage of 2-3 volts, frequency of 50-10000 Hz, waveform of sine wave, reaction temperature of 20-25 ℃ and reaction pressure of normal pressure. The method has the advantages of mild reaction conditions, low price and easy obtaining of materials required by the reaction and high product selectivity.

Description

Method for preparing methylal from methanol by electrochemical method

Technical Field

The invention relates to a method for synthesizing methylal by an electrochemical method, in particular to a method for preparing methylal by taking methanol as a raw material by the electrochemical method.

Background

Methylal (Methylal) with a structural formula of CH₃OCH₂CH₃O, also known as Dimethoxymethane (DMM), is one of the important downstream products of methanol. The methylal has the advantages of low toxicity, good solubility and low boiling point, is an ideal novel environment-friendly solvent, and can be widely applied to a plurality of industries such as medicine, rubber, cosmetics, paint and the like. By using methylal as a raw material, methoxy ethyl acetate, glycol and a clean diesel additive poly-methoxy dimethyl ether with high additional value can be synthesized.

In the industrial synthesis of methylal, an aldol condensation technology using methanol and formaldehyde as raw materials is mainly adopted. The technical process is mature, and the production process comprises two steps: the first step, methanol is oxidized to prepare formaldehyde; in the second step, methanol is condensed with formaldehyde to produce methylal. The process has the advantages of complex flow, high reaction temperature, low catalyst activity and serious equipment corrosion.

At present, the research is mostly carried out on the technology for preparing methylal by one-step oxidation of methanol, and the used catalysts are heteropolyacid catalysts, noble metal Ru-based catalysts, Re-based catalysts and non-noble metal V-based catalysts. The technology firstly converts methanol into formaldehyde at the oxidation site of a catalyst, and then formaldehyde and methanol generate methylal at the acid site. The technology omits the procedure of preparing formaldehyde by oxidizing methanol, shortens the process flow and reduces the investment and production cost. But the heteropolyacid catalyst has higher operation temperature, is easy to decompose, the noble metal is expensive, and the V-based catalyst has higher vanadium source toxicity.

Disclosure of Invention

The invention aims to provide a method for preparing methylal from methanol by an electrochemical method, wherein an alternating current power supply is selected as a power supply of the method, two graphite electrode pairs are used for forming the power supply, a mixed solution of acid and industrial methanol is used as an electrolyte, and the electrochemical reaction is carried out under the conditions of alternating current voltage of 2-3 volts, frequency of 50-10000 Hz, waveform of sine wave, reaction temperature of 20-25 ℃ and reaction pressure of normal pressure to obtain the methylal. The method has the advantages of mild reaction conditions, low price and easy obtaining of materials required by the reaction and high product selectivity.

The invention relates to a method for preparing methylal from methanol by an electrochemical method, which takes methanol as a raw material and adopts the electrochemical method to prepare methylal, and the method comprises the following specific operation steps:

a. the power supply of the electrochemical reaction adopts an alternating current power supply, and the electrodes are electrode pairs consisting of two graphites;

b. mixing an acid solution and industrial methanol according to the volume ratio of 1:19-1:9, adding the mixture into an electrolytic cell to serve as electrolyte, and placing a graphite electrode pair into the electrolyte, wherein the acid solution is concentrated hydrochloric acid or concentrated sulfuric acid;

c. and respectively connecting the graphite electrode pair with the output end of a power supply through a lead, starting the power supply, controlling the voltage of alternating current to be 2-3 volts, the frequency to be 50-10000 Hz, and the waveform to be sine wave, controlling the reaction temperature to be 20-25 ℃, and reacting for 4-8 hours under normal pressure to obtain the methylal.

Drawings

FIG. 1 is a gas chromatogram of the electrolyte after the electrochemical reaction in example 1 of the present invention.

FIG. 2 is a gas chromatogram of the electrolyte after the electrochemical reaction in example 2 of the present invention.

FIG. 3 is a gas chromatogram of the electrolyte after the electrochemical reaction in example 3 of the present invention.

FIG. 4 is a gas chromatogram of the electrolyte after the electrochemical reaction in example 4 of the present invention.

Detailed Description

Example 1

b. mixing concentrated hydrochloric acid and industrial methanol according to the volume ratio of 1:9, adding the mixture into an electrolytic cell to serve as electrolyte, and placing a graphite electrode pair into the electrolyte;

c. connecting graphite electrode pair with output end of power supply via wires, turning on the power supply, regulating AC voltage to 3V, frequency of 5000 Hz, waveform of sine wave, reaction temperature of 25 deg.C, reaction pressure of normal pressure, and reaction time of 6

Analytical results table

From table 1, it follows: the conversion rate of methanol is 42.35%, the selectivity of methylal is 100%, and no by-product is produced in the reaction.

Example 2

b. mixing concentrated sulfuric acid and industrial methanol according to the volume ratio of 1:9, adding the mixture into an electrolytic cell to serve as electrolyte, and placing a graphite electrode pair into the electrolyte;

c. and respectively connecting the graphite electrode pair with the output end of a power supply through a lead, starting the power supply, regulating the alternating current voltage to 2 volts, controlling the frequency to 10000 Hz, forming a sine wave, controlling the reaction temperature to be 20 ℃, controlling the reaction pressure to be normal pressure, and reacting for 4 hours to obtain the methylal.

After the electrochemical reaction is finished, the electrolyte after the reaction is taken for gas chromatographic analysis, and a gas chromatogram is shown in figure 2, wherein the result analysis in figure 2 is shown in table 2:

TABLE 2 analytical results Table

From table 2, it follows: the conversion rate of methanol is 50.64%, the selectivity of methylal is 100%, and no by-product is produced in the reaction.

Example 3

a. The power supply of the electrochemical reaction adopts an alternating current power supply, and the electrodes are an electrode pair consisting of two graphites;

c. and respectively connecting the graphite electrode pair with the output end of a power supply through a lead, starting the power supply, regulating the alternating current voltage to 3 volts, controlling the frequency to be 1000 Hz, and controlling the reaction temperature to be 20 ℃, the reaction pressure to be normal pressure, and the reaction time to be 8 hours to obtain the methylal.

After the electrochemical reaction is finished, the electrolyte after the reaction is taken for gas chromatographic analysis, and a gas chromatogram is shown in fig. 3, wherein the result analysis in fig. 3 is shown in table 3:

TABLE 3 analytical results Table

From table 3, it follows: the conversion rate of methanol is 49.86%, the selectivity of methylal is 100%, and no by-product is produced in the reaction.

Example 4

b. mixing concentrated sulfuric acid and industrial methanol according to the volume ratio of 1:19, adding the mixture into an electrolytic cell to serve as electrolyte, and placing a graphite electrode pair into the electrolyte;

c. and respectively connecting the graphite electrode pair with the output end of a power supply through a lead, starting the power supply, regulating the alternating current voltage to 3 volts, controlling the wave form to be sine wave, the frequency to be 10000 Hz, controlling the reaction temperature to be 25 ℃, controlling the reaction pressure to be normal pressure, and reacting for 6 hours to obtain the methylal.

After the electrochemical reaction is finished, the electrolyte after the reaction is taken for gas chromatographic analysis, and the gas chromatogram is shown in fig. 4, wherein the result analysis in fig. 4 is shown in table 4:

TABLE 4 analytical results Table

From table 4, it follows: the conversion rate of methanol is 51.50%, the selectivity of methylal is 100%, and no by-product is produced in the reaction.

Claims

1. A method for preparing methylal from methanol by an electrochemical method is characterized in that the method takes methanol as a raw material and adopts the electrochemical method to prepare methylal, and the specific operation steps are as follows:

c. and respectively connecting the graphite electrode pair with the output end of a power supply through a lead, starting the power supply, controlling the voltage to be 2-3 volts, the frequency to be 50-10000 Hz, and the waveform to be sine wave, controlling the reaction temperature to be 20-25 ℃, and reacting for 4-8 hours under normal pressure to obtain the methylal.