Heat effects of NTO synthesis in nitric acid solution

The heat effects in the case of manufacture process of nitration 1,2,4-triazol-5-one (TO) in nitric acid solution were distinguished and determined using the calorimeters of DSC200F3, C80 and E856; the influence of these heats on the total exothermic effect during manufacture process was examined. Five kinds of thermal effects were differentiated and measured: the heat of process of dosing TO (ΔH_TO,dosing), the heat of dissolution TO (ΔH_{TO,dissolution}), the heat of reaction (ΔH_r), the heat of crystallization of NTO (ΔH_{NTO,crystallization}) and the heat (ΔHHNO3) caused by changes in concentration of nitric acid. The data on dissolution heats of TO and NTO in nitric acid with different concentrations in the 0–98.4 % range and isobaric heat capacity of TO over the temperature range of 0–90 °C are determined. The main results of examination showed: The ΔH_r was the main contribution to the total exothermic effect during synthesis processes in 66–96 % HNO₃; the contribution ability rank of other four thermal effects varied based on the concentration of HNO₃ adopted.