CPC C07C 263/10 (2013.01) [C07C 265/06 (2013.01)] | 18 Claims |
1. A method for preparing an isocyanate in a gas phase, comprising: feeding an amine-containing gas stream and a phosgene-containing stream into a reaction zone in the presence or absence of an inert gas, allowing the amine and the phosgene to contact in gaseous forms and undergo a phosgenation reaction in the reaction zone, thus preparing the isocyanate in the reaction zone; wherein the phosgene-containing stream is preheated before entering the reaction zone and the phosgene-containing stream comprises a substance A with a mass fraction smaller than 0.5% before being preheated, wherein the substance A is a substance containing non-target isocyanate (NCO) groups and olefinic double bonds;
where before preheated, the phosgene-containing stream is treated through one or a combination of at least two of rectification, adsorption, and scrubbing such that the mass fraction of the substance A contained in the phosgene-containing stream is controlled.
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