| abstract |
Disclosed is a method for preparing an isocyanate in a gaseous phase, comprising feeding, in the presence or absence of an inert gas, an amine-containing gas stream and a phosgene-containing gas stream into a reaction region, allowing the amine and the phosgene to contact in gaseous forms and undergo a phosgenation reaction in the reaction region, thus preparing the target isocyanate in a gaseous form in the reaction region. The phosgene-containing stream is subjected to preheating and warming before being fed into the reaction region, and the phosgene-containing stream comprises a substance A at a mass fraction of < 1% before being subjected to the preheating and warming up, the substance A being a NCO group-containing substance and/or an olefinic double bond-containing substance. The method of the present invention can reduce the formation of clogging matter in a heat exchanger and a vessel during the preheating and warming of the phosgene and during the reaction process. Accordingly, clogging can be effectively ameliorated, a longer run cycle can be achieved, the frequency of overhaul of the phosgene-containing system can be reduced, and the safety in apparatus operation can be enhanced. |