METHOD OF PRODUCING ISOCYANATES Russian patent published in 2012 - IPC C07C263/10 C07C265/14 

FIELD: chemistry.

SUBSTANCE: method involves reaction of corresponding primary amines with phosgene, in which a) primary amines are evaporated and heated to reaction temperature, phosgene and amines react in a reaction space at temperatures higher than the boiling point of amines and during average contact time of 0.05-15 s, in adiabatic conditions and b) the gaseous mixture from the reaction space is cooled in order to condense the formed isocyanate. The method is characterised by that c) cooling at step b) takes place in a single step by direct cooling at a cooling section while feeding at least one liquid coolant, in two or more successively lying cooling zones, wherein only one common condensation mixture is obtained from two or more cooling zones, and d) the uncondensed isocyanate is separated from the gaseous mixture by washing with a washing liquid. Direct cooling at step c) is carried out such that the coolant fed into the first zone is a solvent-containing liquid coolant at temperature 50-200°C, which contains solvent in amount of 80-100 wt % with respect to weight of the liquid coolant, and also the isocyanate obtained at step a) in amount of 20-0 wt % with respect to weight of the liquid coolant. The liquid coolant fed into the second and, if necessary, subsequent zones, is a mixture at temperature 100-200°C, obtained as a bottom product of the cooling section, which contains solvent in amount of 30-90 wt % with respect to weight of the liquid coolant, and also isocyanate obtained at step a) in amount of 70-10 wt % with respect to weight of the liquid coolant.

EFFECT: method enables to reduce formation of by-products and reduce power consumption on separating isocyanate from the gaseous mixture.

6 cl, 2 ex