Effect of Metal Oxides on the Catalytic Activities of Sulfonated Graphene Oxide for the Esterification of Oleic Acid and Conversion of Waste Cooking Oil to Biodiesel

Nanocomposites of metal oxides with graphene oxide and other carbon materials have shown superior catalytic activities in many important chemical reactions. A systematic investigation of the effect of oxides of Fe, Co, Ni, Cu, and Zn, on the catalytic activities of sulfonated graphene oxides (GO) is detailed in the present paper. The nanocomposites of GO with the metal oxides were prepared under carefully chosen conditions so that the metal content in the nanocomposites remains similar. The nanocomposites were sulfonated and used as solid acid catalysts in the esterification of oleic acid and trans-esterification of waste cooking oil. Paramagnetic transition metal oxides showed superior catalytic activities over non-magnetic ones with the nanocomposite containing iron oxide being the most active. The so called 'super acidic' acid sites on the paramagnetic metal oxides could be the reason for enhanced catalytic activities of their nanocomposites. [GRAPHICS] .