PRODUCTION OF FORMALDEHYDE

PURPOSE:To obtain, in the subject production of formaldehyde by excess methanol method, a by-product gas mainly composed of nitrogen and hydrogen and almost free from oxygen becoming a problem in purification at a low cost by improving the grain size of the catalyst and the reaction conditions. CONSTITUTION:In production of formaldehyde by reaction between respectively prescribed amounts of gasified air and methanol in the presence of a silver catalyst, the grain size of the whole silver catalyst is controlled to 10 mesh pass so that 20-32 mesh pass and 32 mesh pass may be contained respectively in an amount of 30-40wt.% and 40-50wt.%. The specific surface area of the grains having 32 mesh pass grain size is regulated to 100-250cm /g, preferably 150-180cm /g. The reaction is carried out in conditions of 30-60sec, preferably 40-50sec space velocity, 600-650 deg.C, preferably 620-640 deg.C reaction temperature 0.1-0.6kg/cm -G, preferably 0.2-0.4kg/cm -G reaction pressure, thus affording a by-product gas substantially free from oxygen and useful as a raw material capable of readily producing high-purity nitrogen and hydrogen.