Exploring the mechanism of alkali‑oxygen oxidation of Yilan oil shale to carboxylic acids using a combined experimental and theoretical method

Abstract

The alkali‑oxygen oxidation of oil shale is a useful method to study the structural characteristics and produce carboxylic acids (CAs). However, this approach usually only obtains the average structural parameters and just examines oxidation product distribution. The information regarding reaction pathway and mechanism is not discussed in detail. In this study, a combination of experimental and computational methods was applied to investigate the alkaline‑oxygen oxidation mechanism of Yilan oil shale. In the oxidation process, 56.1 wt% yield of CAs can be obtained. By characterizing degradation pathway of organic carbon in oil shale, the degradation pathway was concluded. By analyzing molecular dynamics simulation trajectories, intermediates and elementary reactions involved in carbon structure were tracked. The ReaxFF results showed that the reaction followed a chain-reaction pathway, which included side-chain oxidation, aromatic carbon oxidation, and decarboxylation steps. Formaldehyde and carbonyl/phenolic hydroxyl groups were the active sites for carboxyl group formation.