Computational Study on Kinetics of Conversion of Bio-oil Model Compound - Anisole, to Platform Chemicals

Abstract

With the rise in the need of clean and renewable energy source, lignocellulosic biomass has gained significant attention across the globe. The major reason for its use as a fuel is the compatibility of biomass derived bio-oil with the conventional energy infrastructure. But the derived bio-oil contains over 300-400 components, most of which are not viable to be used as fuel due to the presence of oxy groups which decrease the energy density of the fuel. Thus, the bio-oil needs to be deoxygenated in order to increase its calorific value. In this study, anisole is taken as a model component representing phenolic fraction of the bio-oil. First, a bond dissociation energy (BDE) calculation is performed on optimized anisole structure to understand the energy requirement of breakage of bonds present in it. Consequently, three different pathways are proposed to convert anisole to benzene, phenol and toluene. Since the reaction is occurring in aqueous phase, direct hydrogenation of anisole is also proposed in an additional pathway. The proposed pathways are studied under the density functional theory (DFT) framework using B3LYP functionals with 6-311+g(d,p) basis set in aqueous phase with SMD solvation model. Finally, the thermochemical parameters are calculated for 298 K to 698 K temperature range. It is observed that the anisole can be reduced to benzene with lowest energy requirement among the proposed pathways. In general, increase in temperature cause decrease in Gibb's free energy change and enthalpy change of the reactions, thereby increasing reaction favourability.