Thermal hazard characteristics and essential mechanism study of 1-hydroxybenzotriazole: Thermodynamic study combined DFT simulation

1-Hydroxybenzotriazole (HOBT) as an important fine chemical has been used as reactants, reagents or catalysts in over 6 million chemical synthesis reactions. The thermal decomposition characteristics of HOBT in non-isothermal, isothermal and adiabatic conditions were investigated through differential scanning calorimetry, thermogravimetric analyzer, and accelerating rate calorimeter. The apparent activation energy, thermal safety parameters, and the decomposition reaction pattern of HOBT pyrolysis were obtained based on adiabatic accelerating calorimeter experimental data. HOBT pyrolysis is a rapid exothermic process with large amounts of gas produced, and HOBT can decompose at a temperature substantially lower than the onset temperature. The severity and probability of HOBT runaway reaction were assessed. The pyrolysis mechanism paths of HOBT were explored by using TG-MS and TG-FTIR experiments couple with density functional theory calculations. The main decomposition products of HOBT were N2, NO, C2H2, C6H6, CO, HCN, and CO2 gases. This study provides guidance for safe production and application of HOBT, and formulating emergency plans for related hazards.