Exploring the combustion chemistry of a novel lignocellulose-derived biofuel: cyclopentanol. Part I: quantum chemistry calculation and kinetic modeling

Biomass derived chemicals may offer sustainable alternatives to petroleum derived hydrocarbons, while also enhancing engine combustion performance with co-optimization of fuels and engines. This paper presents a numerical study on the oxidation and combustion of a novel biofuel compound, cyclopentanol. Its reaction kinetics and thermochemistry are first explored using ab initio quantum chemistry methods. Thermochemical properties are calculated for cyclopentanol and a set of its key oxidation intermediates. C-H bond dissociation energies of cyclopentanol are computed for different carbon sites. For the fuel radicals, the energy barriers of their ring-opening reactions and the potential energy surfaces of their oxidation reactions are determined. Based on the theoretical results, a chemical kinetic mechanism is proposed to describe the oxidation of cyclopentanol at low and high temperatures. The model is compared against data obtained from shock tube, rapid compression machine, combustion vessel, and counterflow burner experiments over a range of initial conditions. Furthermore, reaction pathway analysis is performed using the present mechanism to give insights into the underlying oxidation chemistry of cyclopentanol. It is found that the α-radical of cyclopentanol undergoes preferably an alcohol-specific HO2 elimination reaction to form stable cyclopentanone and this reaction can strongly retard reactivity. The major reaction pathways of β- and γ-radicals are similar to those of cyclopentyl radicals that are the sequential and formally direct reactions of fuel radicals with O2 to form cyclopentenols and HO2 radicals. The existence of the hydroxy moiety affects the bond dissociation energies and reaction barriers, slightly favoring the chain-branching channel for γ-radicals at low temperatures.