GB639940A - Improvements in or relating to the production of guanidine nitrate - Google Patents

Abstract

Guanidine nitrate is obtained by dissolving ammonium thiocyanate and at least one equimolar weight of ammonium nitrate in ammonia, heating the so-formed solution in an enclosed vessel to a temperature between 170 DEG and 210 DEG C. and recovering guanidine nitrate from the reaction product. The preferred temperature range is 175 DEG to 185 DEG C. and the pressure is preferably between 200 and 300 pounds per square inch. the yield is improved by eliminating hydrogen sulphide at intervals from the reaction mass. This may be effected by interrupting the heating at intervals, venting the reaction vessel and sweeping anhydrous ammonia through the reaction melt to carry out the hydrogen sulphide while at the same time maintaining a protective blanket of ammonia in the reaction vessel to prevent risk of explosion. The ammonia and hydrogen sulphide are separated and the ammonia recycled to the reaction zone. Another method to eliminate the hydrogen sulphide is to use an excess of ammonium nitrate whereby the hydrogen sulphide is oxidized to elemental sulphur which is insoluble in the reaction melt. The process may be carried out batchwise or continuously. In the continuous process ammonium thiocyanate and ammonium nitrate are dissolved in anhydrous ammonia and the solution pumped under pressure through a pipe still or heated coil, the mixture being continuously discharged into a flash chamber under a lower pressure than that in the pipe still. Gaseous ammonia and hydrogen sulphide are allowed to escape from the flash chamber and further quantities of ammonia are injected through the reaction mass in the flash chamber until the effluent gases are substantially free of hydrogen sulphide. Unreacted salts and ammonia are then recycled to the pipe still in admixture with fresh reactants. Guanidine nitrate is withdrawn from the chamber at an average rate equivalent to the rate of its continuous production. In both batch and continuous processes the charge can batch and continuous processes the charge can be poured out into a mixture of ice and water to crystallize the guanidine nitrate, and after filtration to remove the crystals, residual ammonium thiocyanate and ammonium nitrate are returned to the process. In examples, ammonium nitrate and ammonium thiocyanate are placed in a vessel cooled below room temperature and gaseous ammonia passed through the mixture to form a solution of the salts in liquid ammonia. This mixture is then heated in an autoclave, to the appropriate temperature, to form guanidine nitrate. In one of the examples, two moles. of ammonium nitrate are used per mole. of the thiocyanate and a comparative example is also given to show that no guanidine nitrate is obtained when the reaction temperature is 120 DEG C. The Specification as open to inspection under Sect. 91 refers to the use of any temperature above 120 DEG C. This subject-matter does not appear in the Specification as accepted.