Preparation method of trimethyl orthoformate

Trimethyl orthoformate is a colorless and irritating odor liquid, flammable, decomposed in contact with water, soluble in ethanol, ether, etc. It is an important organic synthesis intermediate used in the synthesis of various medicines, dyes and fragrances.

Trimethyl orthoformate is a hypothetical compound that does not actually exist, so it is impossible to generate trimethyl orthoformate and other compounds through the reaction of methyl orthoformate. The manufacturing technology of orthoformic acid is mainly divided into the old method using chloroform as raw material and the new route using hydrocyanic acid as raw material. The technical route of ethyl chloroform as raw material is divided into two-step method and one-step method. The two-step process is short, the investment is low, and the technology is mature, but there are many wastes and pollution to the environment. One-step technology is a clean production technology.

(1) Two-step technology: two-part synthesis of trimethyl orthoformate with chloroform and sodium methoxide as raw materials. The first is the reaction of methanol and sodium metal, or the reaction of methanol and sodium hydroxide can generate sodium methoxide. The reaction is as follows:

2CH3OH + 2Na → 2CH3ONa + H2

CH3OH + NaOH → CH3ONa + H2O

In the second step, chloroform reacts with sodium methoxide to form trimethyl orthoformate. The reaction formula is as follows:

CHCl3 + 3CH3ONa → HC (OCH3) 3 + 3NaCl

The actual production process is carried out in the methanol solution of sodium methoxide and chloroform. The reaction is carried out at about 60 ° C under full reflux at a pressure of 0.12~ 0.15MPa. The reaction product is cooled, the NaCl is centrifuged and filtered out, distilled, and the 100~ 105 ° C fraction is intercepted., to obtain the trimethyl orthoformate product with a total yield of more than 97% and a purity of more than 99.8% based on chloroform.

(2) One-step technology: One-step method uses chloroform, methanol, and sodium hydroxide as raw materials, and tributylbenzyl ammonium chloride (PTC) is used as the phase transfer catalyst, that is, to realize the transfer between solid and liquid phases, and to generate trimethyl formate in one step. Some industrial plants have adopted this technology for production.

(3) Hydrocyanic acid method: This method is to react with anhydrous methanol, hydrocyanic acid and hydrochloric acid, and then continue to react with methanol to obtain trimethyl orthoformate. This method can use hydrocyanic acid by-product of other products as an advantage, and has the characteristics of saving investment. However, the process uses highly toxic hydrocyanic acid as raw material, which requires a refrigeration device, which requires high safety requirements for equipment sealing and production process. There is no domestic use, and Kay Fries in the United States uses this technology to produce trimethyl orthoformate.

Trimethyl orthoformate quality reference index:

Trimethyl orthoformate content ≥ 99%

Methanol content ≤ 0.3%

Methyl formate ≤ 0.2%

Other impurity content ≤ 0.05%