Determination and correlation for solubilities of urea and cyanuric acid in organic solvents from 300.75 K to 369.45 K

In order to choose the suitable solvent for the synthesis of cyanuric acid from urea through the liquid phase pyrolysis method, the solubilities of urea and cyanuric acid in eight kinds of pure solvents, N,N -dimethyl formamide, cyclohexanol, N,N -dimethyl acetamide, 1,2-propanediol, N -methylpyrrolidone, 2-methyl-1,3-propanediol, formamide and tetramethylene sulfone, were determined in the temperature ranging from 300.75 K to 369.45 K using the laser assisted-dynamic method under atmospheric pressure. The modified Apelblat model, van’t Hoff model and λh model were employed to correlate the solubilities of urea and cyanuric acid respectively, in which the Apelblat equation was better with the relative average deviation 0.18∼1.95 %. In addition, the thermodynamic properties of the dissolution processes were calculated and discussed based on the Apelblat equation, indicating that the dissolution process is an endothermic non-spontaneous entropy-driven process. Finally, formamide, 1,2-propanediol and 2-methyl-1,3-propanediol were selected as solvent for the synthesis of cyanuric acid from urea.