This invention relates to a new process for the production of lower alkyl alkoxyacetates, preferably methyl methoxyacetate, from di(lower alkoxy)methanes, preferably dimethoxymethane, that is carried out in the gas phase and at atmospheric or near-atmospheric conditions. Methyl methoxyacetate is an ether/ester of glycolic acid, and can be converted to glycolic acid and ultimately ethylene glycol by hydrogenation and hydrolysis, or reduced directly to ethylene glycol monomethyl ether, an important industrial solvent.
Acid-catalyzed formaldehyde carbonylation has been investigated as a means for producing carbon-carbon bonds for over sixty years. The product of this reaction, glycolic acid and its esters/ethers can be converted to ethylene glycol, an important industrial chemical used in polyester synthesis. Until now, such efforts have been carried out exclusively in the liquid-phase, typically requiring pressures of tens to hundreds of atmospheres of carbon monoxide to overcome its low solubility. The reaction proceeds by the Koch mechanism, in which protonated formaldehyde reacts with carbon monoxide to form an acyl carbocation, which is then hydrated to the carboxylic acid or ester product.
Production of methyl methoxyacetate by the reaction of dimethoxymethane with carbon monoxide has been described in several U.S. patents. In U.S. Pat. No. 2,273,269 (Johnson), the reaction is carried out at temperatures of from about room temperature to about 300° C. and pressures ranging from 5 and 1500 atmospheres, preferably 30-700 atmospheres. U.S. Pat. No. 3,948,977 (Suzuki) describes a process for carrying out this reaction using hydrogen fluoride as a catalyst, with carbon monoxide partial pressure of between 10 and 4000 psig. U.S. Pat. No. 4,501,917 (Schmidt et al.) used organic ion exchange materials as the catalyst, carrying out the process in an autoclave under pressure. In all of these processes, the reaction is conducted in liquid phase at elevated pressures.
Some other processes for production of methyl methoxyacetate include reaction of methanol with carbon monoxide in the presence of a hydrogen fluoride catalyst and an oxidizing agent (Threlkel, U.S. Pat. No. 4,482,735) and reaction of methoxy chloroacetate with an alkali metal methoxide (Kleemiss et al., U.S. Pat. No. 6,143,920). However, the first of these is a high pressure, batch liquid phase process and the second uses very expensive raw materials and involves complex processing.