Detailed mechanism study of volatile organic compound decomposition and oxidation removal based on a ReaxFF MD method

Abstract

Volatile organic compounds (VOCs) are typical air pollutants as well as gaseous wastes that contain energy. Utilization and disposition of VOCs is currently an important research hotspot in the field of atmospheric environment. In this paper, the thermal cracking and oxidation reaction processes of typical VOCs components were modelled and analyzed by combining molecular dynamics and detailed reaction mechanisms, focusing on the effects of temperature, oxygen and other conditions on the conversion of VOCs. The results of molecular dynamics studies show that improving temperature and reaction time benefit the decomposition of VOCs. High temperatures under an inert atmosphere can sufficiently crack the VOCs themselves, but other by-products are generated, which in turn cause secondary pollution. The activation energies derived by ReaxFF-MD calculation are 328 kJ mol⁻¹, 147 kJ mol⁻¹ and 121 kJ mol⁻¹ for toluene, styrene and benzaldehyde respectively, which is consistent with experimental results. Under the oxygen atmosphere, the conversion rate of VOCs is greatly increased and the reaction temperature is significantly reduced. Meanwhile, the oxidation reaction fully converts VOCs into non-polluting products such as CO₂ and H₂O. Detailed kinetic studies show that initial oxidation of toluene molecules raised by hydrogen abstraction reaction is the dominant step during toluene oxidation, which significantly improved the decomposition efficiency of toluene.