GB721620A - Improvements in the production of guanidine sulphamate - Google Patents

Abstract

Guanidine sulphamate is prepared by reacting at a temperature above 200 DEG C. in a closed reaction zone at least one compound selected from the group consisting of urea, biuret and cyanuric acid with ammonium sulphamate in the presence of added ammonia and under a pressure of ammonia greater than atmospheric, the reactants being substantially free from water and the ammonium sulphamate being present in the mol. ratio equivalent to at least about 2 mols. ammonium sulphamate per mol. urea and recovering guanidine sulphamate from the reaction mixture. The added ammonia is preferably introduced in the liquid state with the other reactants into the reaction vessel; in general, sufficient is used to provide a pressure of 200 to 4000 p.s.i. or higher. Preferred reaction temperatures are from about 250 DEG to 330 DEG C., the reaction time being insufficient to form substantial amounts of heterocyclic compounds such as melamine and ammeline which are otherwise formed. Normally, ammonium sulphamate is reacted with urea but all or part of the latter may be replaced by biuret and/or cyanuric acid. The process, which may be operated batch-wise or continuous should be carried out in apparatus lined with corrosion-resistant material. The recovery of the guanidine sulphamate may be effected by cooling the reaction mixture, suitably to just above 125 DEG C., evaporating off the free ammonia under lowered pressure, then filtering to remove ammonium sulphate and heterocyclic products and separating the guanidine sulphamate from the filtrate, for example, by crystallization. The unreacted materials may be recycled to the reaction zone. Numerous comparative experiments are described, illustrating the reaction p of ammonium sulphamate with urea in molar proportions of 0.5 to 5.0 mols. per mol. urea in the presence of various amounts of added ammonia and in absence of ammonia and in the presence of nitrogen, at various temperatures. Other experiments show the use of ammonium sulphamate and cyanuric acid in a 6 : 1 molar ratio and of ammonium sulphamate and biuret in a 4.2 : 1 ratio, in the presence of added ammonia.