Alkanolysis simulation of lignite-related model compounds using density functional theory

Abstract

Benzyloxybenzene (BOB), phenethoxybenzene (PEB), oxydibenzene (ODB), and anisole were selected as lignite-related model compounds (LRMCs). Theoretical simulation on the LRMC alkanolysis was conducted to understand the mechanism for lignite alkanolysis using density functional theory in terms of bond order, transition state (TS), charge distribution of TS, bond length, and activation energy (AE). The alkanolysis includes nucleophilic attack of the oxygen atom in an alkanol on the carbon atom in the oxygen-containing bridged bond (OCBB) of a LRMC, hydrogen transfer from OH in the alkanol to oxygen atom in the OCBB, and subsequent cleavage of the OCBB. According to the calculated AE, under the same conditions, the reactivities of the LRMCs toward alkanolysis decrease in the order: BOB>anisole>PEB>ODB; for the same LRMC, ethanolysis proceeds much easier than methanolysis. The rate constant of BOB ethanolysis is ten times more than that of BOB methanolysis at the same temperature.