Reactions of cyanamide, dicyandiamide and related cyclic azines in high temperature water

Cyanamide, dicyandiamide, and the related cyclic azines (melamine, ammeline, ammelide, and cyanuric acid) were reacted in water at 100-300 degrees C in a sealed 316 SS tube (275 bar) for the purpose of characterizing the hydrothermolysis chemistry of cyanamide. The conversion of cyanamide to dicyandiamide dominates at 100-175 degrees C. At 175-250 degrees C, when the reaction times are shorter than 15 min, the major pathway is hydrolysis of the cyanamide-dicyandiamide mixture to CO2 and NH3. A minor pathway is cyclization to higher azines (melamine, ammeline, ammelide and cyanuric acid). Above about 225 degrees C, hydrolysis of these cyclic azines to aqueous NH3 and CO2 occurs in a relative ratio which depends on the particular cyclic azine, and, to an extent, which increases with temperature. At 300 degrees C the conversion of all compounds to CO2 and NH3 is complete in 10 min. The hydrothermolysis chemistry of cyanamide and urea are compared. (C) 1997 Elsevier Science B.V.