Dehydrogenation of Methanol to Formaldehyde by ZnO–SiO2 and Zn2SiO4 Catalysts

To develop a new process for non–aqueous formaldehyde (FA) production, vapor phase dehydrogenation of methanol over zinc-based catalysts was studied. Silica-supported ZnO catalyst, prepared by calcining SiO2 impregnated with zinc nitrate, exhibited a FA selectivity of 90% at a methanol conversion of 50%. The main side reaction was the decomposition to carbon monoxide and hydrogen; mechanistic studies indicated that the decomposition proceeds via FA. ZnO was gradually reduced causing deterioration of the catalyst. Zinc silicate, Zn2SiO4, prepared from zinc nitrate and ammonium silicate and calcined at 1000°C exhibited a stable activity, with a little lower FA selectivity, for more than 500 hours owing to the greater resistance to the reduction.