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

► The mechanistic route of the transesterification catalyzed with calcined sodium silicate (CSS) was firstly elucidated. ► Density functional theory were employed to deduce the mechanism of transesterification reactions catalyzed with CSS. ► The alkaline active species of CSS were formed from the ion-exchange between CSS and CH3OH. ► A simple method was used to regenerate the catalyst that performed good activity and reproducibility.