Patent ID: 9714215
Date: 2017-07-25
CPC Classifications: C07C,Y02P

Claim:
1. A method of producing an isocyanate, from using an organic primary amine, urea and an organic hydroxy compound as raw materials, comprising: a carbamation step of generating an N-substituted carbamate from the organic primary amine, the urea and the organic hydroxy compound according to a carbamation reaction, and then recovering a first gaseous phase component comprising the urea and/or a compound having a carbonyl group derived from the urea, the organic hydroxy compound, and ammonia; a condensation step of condensing the first gaseous phase component with a condenser; an isocyanate production step of producing an isocyanate by subjecting the N-substituted carbamate to pyrolysis; an ammonia absorption step of absorbing a second gaseous phase component recovered as a gaseous phase component from the condenser by absorption water to generate gas-absorbed water, wherein an ammonia stripping step of heating the gas-absorbed water to separate the ammonia from the gas-absorbed water; an organic hydroxy compound separation step of separating an organic hydroxy compound and a water phase, both contained in a liquid phase component obtained after the separation of the ammonia in the ammonia stripping step; and a liquid phase blow-down step of substituting a portion of an aqueous solution obtained in the organic hydroxy compound separation step with water.