A Mechanistic Formation of Phenolic and Furan-Based Molecular Products from Pyrolysis of Model Biomass Components

Herein, we critically present theoretical modeling of toxic molecular compounds from biomass pyrolysis using the density functional theory formalism at the B3LYP level of theory coupled to 3-21G basis set. Detailed molecular modeling – geometry optimization, global hardness, and chemical potentials of the selected phenols and furans are reported. The thermal energy changes and reactivity are estimated from Gaussian’09 and Chemissian computational platforms. The formation of phenol and cresols are attributed to the thermally induced fragmentation of tyrosine via the rapture of the C-C bond (β-fission) which occurs via an endethermicity of +231.58 kJ/mol. The decarboxylation of tyrosine proceeds exothermally following an energy release of -14.36 kJ/mol. Subsequently, furans were formed from radical recombination during the thermal fragmentation of monomeric cellulose and tyrosine. The mechanistic formation of toxic molecular species from the thermal degradation of representative biomass materials has been proposed. From the global hardness data, it was noted that p-cresol was more reactive compared to phenol whereas alkylated benzofurans were more reactive than benzofuran because of their lower HOMO-LUMO energy gaps.