Cordierite honeycomb monoliths coated with zirconia and its modified forms for biodiesel synthesis from Pongamia glabra

This study investigates the use of cordierite honeycomb monoliths coated with solid acids such as zirconia, Mo(VI)/ZrO₂ and Pt-SO₄^2-/ZrO₂ and solid bases like zirconia-calcia, zirconia-magnesia mixed oxides in the synthesis of biodiesel from oil (PG-oil). Solid acids were used for the esterification of free fatty acids in PG-oil with methanol to reduce the percentage of free fatty acids in the oil followed by transesterification of PG-oil over solid bases to synthesize biodiesel. The oxide catalysts were coated on honeycombs by an impregnation technique and characterized for their surface acidity/basicity, crystallinity and morphology. The effect of the molar ratio of PG-oil/methanol in esterification and transesterification was studied. Reactivation and reusability of both solid acid and solid base catalysts was investigated. The catalysts were also prepared in their powder forms and their activity was compared with that of honeycomb coated forms. A two-fold increase in the yield of biodiesel was obtained when the catalysts were used in honeycomb coated forms. The results revealed that the honeycombs coated with mixed oxides such as zirconia-calcia and zirconia-magnesia were economical, efficient and eco-friendly (3e concept) for biodiesel production with ∼95% yield.