Computational investigation of isoeugenol transformations on a platinum cluster—II: Deoxygenation through hydrogenation to propylcyclohexane

Abstract

The debate on climate change and the future of our Planet has brought to general attention the problem of fossil fuels (coal, oil and natural gas), among the main causes of pollution on Earth. At the same time, the necessity to encourage research and development of alternative and renewable energy resources has become increasingly relevant. In this context, biomass is an attractive option to produce biofuels and chemicals currently derived from petroleum. The hydrodeoxygenation process of bio-oils, produced by the rapid pyrolysis of biomass, is the most effective strategy for obtaining biofuels, hence the reason for the investigation of its mechanism on model biomass compounds. Having investigated the direct deoxygenation (DDO) mechanims in the first paper of this series, the present work aims to illustrate the deoxygenation-through-hydrogenation (HYD) mechanism, by which isoeugenol, a compound chosen as a model of bio-oils, is converted into propylcyclohexane on a ten-atom platinum cluster. DFT calculations highlight, from kinetic and thermodynamic perspectives, how the formation of propylcyclohexane takes place through 4-propyl-2-methoxycyclohexane-1-ol, the removal of –OCH3 as methanol and then of the –OH group as water. Microkinetic analysis, performed by joining findings on both DDO and HYD routes, reveals that the isoeugenol DDO mechanism is favored at any selected temperatures.