| 摘要 |
The present invention relates to a method for producing isocyanates by reacting amines with phosgene in liquid phase, involving the following method steps: (a) mixing a liquid amine-containing reactant flow (1) and a liquid phosgene-containing reactant flow (2) so as to obtain a reactant mixture; (b) reacting the reactant mixture in a dwell time reactor (R) so as to obtain a reaction mixture (3); (c) reacting the reaction mixture (3) in a reaction column (K1) so as to obtain a head flow (4) and an bottom flow (5), which is fed to a phosgene/hydrogen chloride stripping column (K2); (d) separating by distillation phosgene and hydrogen chloride via the head flow (6) of the phosgene/hydrogen chloride stripping column (K2), a bottom flow (7) being obtained in the phosgene/hydrogen chloride stripping column (K2), containing the isocyanate and the solvent, from which in method step (e) the valuable product isocyanate is obtained by separating the solvent by distillation, and in method step (f) a hydrogen-chloride-containing vapour flow (13) and a bottom flow (14), which contains phosgene and solvent and which is recycled into method step (a), are obtained by thermally fractionating the vapours from the phosgene/hydrogen chloride stripping column (K2) in a separation column (K3) overhead, characterised in that the thermal fractionation in method step (f) is performed at a higher head pressure in the separation column (K3) relative to the head pressure in the phosgene/hydrogen chloride stripping column (K2). |
