Study on the pyrolysis mechanism of unsaturated fatty acid: A combined density functional theory and experimental study

Abstract

In this study, oleic acid was used as a model compound to discuss the mechanism of thermal conversion of unsaturated fatty acids to hydrocarbons, so as to promote the goal of obtaining renewable chemicals and fuels from unsaturated fatty acids. In-situ detection techniques such as TG-FTIR and Py-GC/MS combined with density functional theory were applied to study the reaction mechanism of oleic acid molecules in the conditions of slow pyrolysis and fast pyrolysis. As the temperature rises, the hydrogen bond is broken, and the vibration peak of oleic acid shows obvious dehydrogenation under slow pyrolysis, and the same situation exists under fast pyrolysis. As the temperature increases, the pyrolysis process of oleic acid molecules changed from the dominant role of bimolecular mutual catalysis to that of free radical reaction. The results of Py-GC/MS showed that methyl, ethyl, and hydrogen radicals are the main active substances under the conditions of high temperature and fast pyrolysis of unsaturated fatty acid. This work demonstrates the feasibility of producing renewable hydrocarbons by pyrolysis of unsaturated fatty acids and proposed influenced factors to control product distribution. Novelty Statement Density functional theory (DFT) combined with experiments was used in present study to supplement the understanding of the pyrolysis mechanism of fatty acids in bio oil pyrolysis, and the control factors of controlling the distribution of fatty acid pyrolysis products were proposed.