Patent ID: 8981145
Filing Date: 2015-03-17
Classification: C07C

Abstract:
1. A process for preparing isocyanates, comprising (a) the reaction of at least one amine with phosgene in the gas phase in a reaction zone and (b) the subsequent cooling of the reaction gases, from the temperature at which the reaction gases leave the reaction zone to a temperature which is below the temperature at which the reaction gases leave the reaction zone, in a cooling zone by means of indirect cooling, the cooling medium which absorbs the heat of the reaction gases being conducted in countercurrent to the product stream at least in the region of the highest temperature in the cooling zone, wherein the cooling is from the temperature at which the reaction gases enter the cooling zone down to a temperature which is 50° C. above the dew point of the reaction gases, with a cooling time of from 0.01 to 10 seconds, and wherein the heat absorbed by the cooling medium in step (b) is utilized at least partly for indirect heat transfer to at least one reactant stream of the reaction in step (a).