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p-Nitrotoluene is a toxic, flammable, and explosive nitro-hazardous chemical in process industries. However, the combustion reaction mechanism is still unclear, and kinetic data on chemical reactions is lacking. This work investigated the combustion reaction pathways of p-nitrotoluene through ReaxFF molecular dynamics simulations and calculated the reaction rate constants at the M062X/6–31+g**//CCSD(T)/cc-PVTZ theoretical level. A combustion reaction kinetic model for p-nitrotoluene was proposed, which included 367 species and 2509 reactions, thereby exploring the initial pathways and mechanisms of the p-nitrotoluene combustion reaction. Reaction force field molecular dynamics simulations and high-precision quantum chemical density functional theory calculations showed that the key intermediate products of p-nitrotoluene combustion are mainly C6H5CH3, C6H6, and C6H4CH3OH. Hydrogen extraction from CH3·was the main hydrogen extraction pathway initiating the chain reaction, while NO2·tended to depart from the benzene ring and participate in hydrogen abstraction reactions. Through sensitivity analysis of these three key intermediate products, the initial reaction pathways of combustion were elucidated. This research provides theoretical guidance for the process safety and risk engineering of nitro-hazardous chemicals.

The study of the pyrolysis/combustion kinetics and kinetic modelling of methyl ethyl ketone peroxide (MEKPO) is of great significance for its potential engineering applications. The pyrolysis and combustion mechanisms of MEKPO are studied in this work by ReaxFF MD simulation, DFT calculations and modelling simulations. The potential energy surface (PES) of the primary pathways in MEKPO pyrolysis and combustion are established at M06–2X/6–31 +G* *// CCSD(T)/cc-PVTZ level, and the rate constants are obtained via TST/VTST. The identified pathways and rate constants are integrated to a novel kinetic model. The results of ReaxFF MD simulation and modelling simulation both indicate that MEKPO will rapidly pyrolyze into butanone primarily in the way of MEKPO→·C4H9O3→butanone. The most crucial intermediate species in the process of MEKPO combustion are C2H4, H2O2, CH2O, CH2CO and H2. Although a large amount of ·HO2is generated during the pyrolysis of MEKPO, the key radicals for MEKPO combustion are ·H, ·O and ·OH, which can be attributed to the energy barriers for ·H, ·O and ·OH attacking H atoms are relatively low. For instance, the average energy barriers for ·HO2,·H, ·O, ·OH attacking H atoms of butanone are 26.5, 14.7, 11.5 and 8.4 kcal/mol, respectively. However, the ·HO2generated during pyrolysis has the effect of promoting the H2-O2sub-mechanism, while also facilitating the combustion of MEKPO. The study can facilitate a deeper understanding of the chemical processes occurring in the formation of air pollutants (CO/ CO2/C2H2/CH2O) in MEKPO combustion, and the threats to the environment and human health.