Method for the preparation of isocyanate by partially adiabatic phosgenation of the corresponding amine

Abstract

The present invention relates to a process for preparing an isocyanate by reacting a primary amine with phosgene, comprising I) providing an amine solution and adjusting its temperature in a heat exchanger, II) providing a phosgene solution and adjusting its temperature in a heat exchanger, III) mixing the amine solution with the phosgene solution in a mixing unit, followed by IV) further conversion in an adiabatically operated reaction zone and the removing of the gas phase formed as a result of the chemical reaction in a separation zone, V) expanding the remaining liquid phase, VI) further conversion of the liquid phase remaining after expansion in an indirectly heated reaction zone and VII) isolating the isocyanate from the reaction solution obtained therein, in which the temperature inthe reaction zone and separation zone is adjusted by fixing a target value within a range from 110 DEG C to 145 DEG C. for the temperature of the reaction mixture from step III) and using the actualtemperature of the reaction mixture from step III) measured continuously or at intervals for closed-loop control of the temperature of the solution of the primary amine provided in step I) and / or of the temperature of the solution of phosgene provided in step II) by means of the heat exchangers used to adjust the temperature of each of these solutions.

Description

technical field [0001] The present invention relates to a process for the preparation of isocyanates by reacting primary amines with phosgene comprising I) providing an amine solution and tempering it in a heat exchanger, II) providing a phosgene solution and tempering it in a heat exchanger , III) mixing of the amine solution with the phosgene solution in the mixing unit, followed by IV) further reaction in the adiabatically operated reaction zone and separation of the gaseous phase formed as a result of the chemical reaction in the separation zone, V) depressurization of the remaining liquid phase , VI) further reacting the liquid phase remaining after decompression in an indirectly heated reaction zone and VII) separating the isocyanate from the reaction solution obtained here, wherein the temperature in the reaction zone and the separation zone is adjusted as follows: The temperature of the reaction mixture of step III) specifies a target value in the range of 110° C. to 1...

AI Technical Summary

Problems solved by technology

Regulating the temperature in an adiabatically operated reactor by means of a targeted closed-loop control of the reactant temperature is not disclosed in EP 1 616 857 A1