Methylal Synthesis over Cs_xH_(3-x)PW_(12)O_(40) (x = 1,1.5,2,2.5, and 3) Salts and Cs_(2.5)H_(0.5)PW_(12)O_(40)/SiO_2 Catalysts

摘要

Methylal, or dimethoxymethane, is generally used as reaction or extraction solvent in organic synthesis and as a fuel additive for smoke reduction. By methylal oxidation, more than 70 % formaldehyde is obtained. Methylal can be synthesized from methanol and formaldehyde in the presence of inorganic acid such as sulfuric acid and hydrofluoric acid. Since these liquid acids are corrosive and produce a large amount of waste, replacement of the liquid catalysts with solid acid catalysts is desirable for developing environmentally benign processes. It has been known that cesium salts of 12-tungstophosphoric acid, Cs_xH_(3-x)PW_(12)O_(40), are insoluble in water and polar solvent, called as versatile green catalysts. It has been demonstrated that many organic reactions can be effectively catalyzed by the cesium salts. In this study, we prepared Cs_xH_(3-x)PW_(12)O_(40) ( x = 1, 1.5, 2, 2.5, and 3) salts and Cs_(2.5)H_(0.5)PW_(12)O_(40)/SiO_2 catalysts and then first evaluated their catalytic activities in synthesis of methylal.