VERFAHREN ZUR HERSTELLUNG ALIPHATISCHER ISOCYANATE DURCH OXIDATIVE DEHYDRIERUNG VON FORMAMIDEN

摘要

1. A process for the preparation of isocyanic acid or aliphatic isocyanates by reacting formamides of the formula R-NH-CHO where R is hydrogen or alkyl of 1 to 8 carbon atoms, with oxygen or an oxygen-containing gas in the gas phase over a catalyst consisting of copper or silver crystals, and subsequent rapid cooling, wherein the reaction is carried out at a temperature of from 300 to 700 degrees C over a catalyst which is arranged in a plurality of layers and whose copper or silver crystals have a particle size of from 0.1 to 5.0 mm, the mean residence time being from 0.0005 to 0.1 sec, and the copper or silver crystals being so arranged according to their particle size that the particle size is smaller in the upper layer or layers.