Preparation and recovery of n-hydrocarbylthiophosphoric triamides or

Abstract

A reaction mixture containing N-hydrocarbylthiophosphoric triamide or N-hydrocarbylphosphoric triamide ('Triamide') is formed by reacting ammonia with N-hydrocarbylaminothiophosphoryl dichloride or N-hydrocarbylaminophosphoryl dichloride in a liquid organic medium, in proportions of at least 16 moles of ammonia per mole of such dichloride and that keep in solution the ammonium chloride co-product formed in the reaction. The temperature of the reaction mixture is kept high enough to keep ammonium chloride-ammonia complex from forming a solid phase in the reaction mixture, but low enough to avoid significant reduction in Triamide yield. The reaction mixture is then caused/allowed to separate into an inorganic phase comprising ammonia, ammonium chloride and co-product thiophosphoric triamide or phosphoric triamide, and an organic phase comprising Triamide, liquid organic medium, dissolved ammonia and, usually, phosphorus impurities. These phases are separated from each other. The ammonia is removed from the organic phase to leave a concentrated solution of Triamide in residual liquid organic medium usually also containing phosphorus impurities. The Triamide is separated or recovered from this residual mixture by continuously introducing a stream of the liquid mixture into a wiped film evaporator operating at a temperature of about 60.degree.-140.degree. C., and at a pressure that avoids solids formation on the heating surface of the wiped film evaporator, and continuously collecting the Triamide product. Triamides are urease inhibitors for use with urea-based fertilizers.