Modified mesoporous graphitic carbon nitride: a novel high-performance heterogeneous base catalyst for transesterification reaction

Abstract

Mesoporous graphitic carbon nitride (g-C₃N₄) was modified with thermal grafting of Oryza sativa (rice) bran ash (OBA) and Triticum aestivum (wheat) bran ash (TBA). These novel catalysts were employed in transesterification reaction for upgrading triglycerides (TAG) of lipids into fatty acid methyl ester (FAME) with alcohol for biodiesel production at room temperature. The catalysts were systematically characterized with analytical techniques such as XRF, XRD, SEM, EDAS, TEM, TGA, XPS, BET and CO₂-TPD. These basic green heterogeneous catalytic procedures exclude aqueous quenching, neutralization and saponification steps, tedious catalyst separation, and prevent corrosion in the reactor and engine. Introduction of otherwise decent transesterification catalysts OBA and TBA into graphitic carbon nitride nanosheets significantly enhances activity and reusability in the transesterification process. This increased activity of the nanostructured heterojunctions is attributed to the enhanced basicity, mesoporosity and surface area upon incorporation of OBA/TBA over graphitic carbon nitride nanosheets as confirmed by CO₂-TPD and BET analysis. The obtained biodiesel samples were further characterized by ¹H NMR and GC MS analysis. The biodiesel samples were tested for important physico-chemical properties to ensure their practical use.