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Initial Reaction Mechanism of Bio-oil High-Temperature Oxidation Simulated with Reactive Force Field Molecular Dynamics

Liu, Xiaolong, Li, Xiaoxia, Nie, Fengguang, Guo, Li
Energy & Fuels 2017 v.31 no.2 pp. 1608-1619
biofuels, chemical bonding, combustion, energy use and consumption, kinetics, models, molecular dynamics, oxygen, superoxide anion, temperature
The high-temperature reaction pathways of bio-oil oxidation were investigated by simulations of a 24-component bio-oil model using reactive force field (ReaxFF) molecular dynamics. Evolution profiles of fuel, O₂, and major products, including radicals, with time and temperature during the initial stage of bio-oil oxidation were obtained. Major products generated during the simulations are consistent with observations reported in the literature. A kinetic model obtained from the simulated bio-oil oxidation is able to predict a long-time evolution trend of fuel consumption. Reaction networks of five representative components of the bio-oil model were revealed. The bio-oil oxidation is initiated by a series of homolysis and H-abstraction reactions and then propagation reactions involving H-shift, H-abstraction, and β-scission reactions. Oxidation of the unsaturated C–C bond, ring reduction of the phenolic radical, and abscission of the −CO structure (decarbonylation) appear frequently. Reaction pathways obtained from the comprehensive observations of simulation results employing VARxMD are in broad agreement with the literature. This work demonstrated a methodology that ReaxFF molecular dynamic simulations combined with the capability of VARxMD for reaction analysis can provide useful insights into the reaction pathway of bio-oil combustion.