Patent ID: 8288584

Claim:
A process for preparing a diisocyanate by reacting the corresponding diamine with phosgene in a stoichiometric excess of phosgene in at least one reaction zone, comprising: mixing at least one stream comprising gaseous phosgene with at least one stream comprising gaseous diamine, and converting this mixture at a temperature of from 200 to 600Â° C. in the at least one reaction zone, mixing the resulting reaction mixture, which consists essentially of isocyanate, phosgene and hydrogen chloride, with at least one liquid while lowering the temperature to from 100 to 200Â° C., such that the isocyanate present in the reaction mixture is transferred at least partly to the liquid by condensation, while phosgene and hydrogen chloride remain in the gas phase, working up the condensed isocyanate with evaporation of the phosgene and hydrogen chloride present in the condensed phase, separating the combined gaseous streams comprising essentially hydrogen chloride and phosgene into a stream comprising predominantly phosgene and a stream comprising predominantly hydrogen chloride, recycling the thus obtained stream comprising predominantly phosgene into the mixing, wherein the phosgene present in the process stages is present essentially in gaseous form.