Transesterification mechanism of soybean oil to biodiesel catalyzed by calcined sodium silicate

Solid calcined sodium silicate (CSS) was successfully used to produce biodiesel from vegetable oil, but its transesterification mechanism is still not well-understood. In this work, stability tests confirmed that some active basic species were leached into methanol from CSS. FT-IR spectra and density functional theory were employed to deduce the mechanistic route of transesterification reactions catalyzed with CSS. It was confirmed that alkaline active species were formed from the ion-exchange between CSS and CH3OH. Deactivated CSS can be reused by regenerating the active sites using a simple method found by us.