Separation of ammonium chloride from the gas phase of an isocyanate production process

摘要

Isocyanates are produced in the gas phase and by-products such as ammonium halides are selectively separated from the gas phase by desublimation.

主权项

1. A process for producing an isocyanate comprising:
(a) feeding an amine and phosgene to a reactor wherein the amine is phosgenated in the gas phase to produce a gas phase isocyanate-containing reaction mixture, (b) feeding the gas phase isocyanate-containing reaction mixture and a quenching agent to a scrubber to separate the isocyanate from the gas stream; (c) feeding the gas stream from the scrubber to a condenser to produce a gas stream free of liquid constituents or constituents condensable to liquid form; (d) feeding the gas stream produced by the condenser to a scrubber that separates the gas stream into a waste gas stream and a phosgene stream; and (e) feeding the phosgene produced by the scrubber to the phosgene that is fed to the reactor, wherein the process further comprises separating a by-product from a gas stream subsequent to (a) by desublimating the by-product as a solid at a point in the process subsequent to the condenser, and wherein the desublimation is carried out in one or more plate-type heat exchangers operated with a heat transfer medium that has a temperature of from 100° C to −40° C.