Thermal runaway mechanisms and kinetics of benzene nitrification system based on microcalorimetry experiments and ReaxFF molecular dynamics simulation

Abstract

The thermal runaway reaction mechanisms and kinetics of nitrification process under abnormal conditions remain incompletely understood. In this study. C600 microcalorimetry experiments combined with GC/MS characterization and IR analysis of the intermediates indicated that the secondary thermal runaway of benzene nitrification system was preferentially initiated by the decomposition of nitrobenzene sulfonated by-products rather than that of nitrobenzene products. This was further verified by the ReaxFF MD simulations and DFT calculations of the microscopic decomposition thermal runaway mechanisms of typical product and by-product. Furthermore, the model-free kinetic models were compared and evaluated from the perspective of reaction mechanism. The results showed that although the models of Kissinger, FWO and Friedman could obtain feasible kinetic parameters, Friedman model had a good match with the microscopic kinetics and thermodynamic mechanisms, and could reasonably approximate the intrinsic thermokinetics. Finally, the thermal hazards under adiabatic conditions with different thermal inertia factors (φ) were discussed, the results provide a reference for the optimization of safety and economy.