| abstract |
The present invention provides an isocyanate production method including an ammonia recovery step capable of recovering ammonia generated in a carbamate reaction. An isocyanate production method using an organic primary amine, urea, and an organic hydroxy compound as raw materials, the N-substitution of the organic primary amine, urea, and organic hydroxy compound by a carbamation reaction. A carbamate step for producing a carbamate and recovering a first gas phase component containing urea and / or a compound having a carbonyl group derived from urea, an organic hydroxy compound, and ammonia; A condensation process for condensing by a condenser, an isocyanate production process for producing isocyanate by thermally decomposing N-substituted carbamate, and a second gas phase component mainly composed of ammonia extracted from the condenser into sulfuric acid water And an ammonia absorption step of absorbing to produce ammonium sulfate. [Selection figure] None |