Equilibrium of Urea Synthesis. I.

A test of the equilibrium conversion of CO2 to urea was carried out using a batch autoclave. Some results different from those reported by Frèjacques were obtained, as was expected from the latest data on commercial urea plants. The equilibrium conversion reached its maximum value at about 195°C by 5–15% higher than that reported by Frèjacques. On the contrary, at temperatures above 200°C the value was lower, and falled rapidly with the raise of temperature. This phenomenon may be due to the mechanism of the equilibrium of urea synthesis, and not to the experimental method, as our sampling was made directly from the liquid phase. The equilibrium conversion, x, may be expressed with respect to NH3/CO2, a, H2O/CO2, b, and temperature, t, as (Remark: Graphics omitted.) Therefore, a limited conversion exists in the conventional urea process.