Bi-functional Catalyst Derived from Waste Biomass for the Sustainable Production of Biodiesel from Waste Cooking Oil

A potential replacement for non-renewable energy sources derived from fossil fuels is bio-diesel. The expensive price of feedstocks and catalysts, however, prevents its widespread industrial application. From this angle, it is an unusual endeavour to use garbage as a source for both the synthesis of catalysts and the feedstock for bio-diesel. Waste rice husk was investigated as a starter material for making rice husk char (RHC). In order to create bio- diesel, highly acidic waste cooking oil (WCO) was simultaneously esterified and transesterified using sulfonated RHC as a bi-functional catalyst. The combination of the sulfonation procedure with ultrasonic irradiation was shown to be a successful method for creating a high acid density in the sulfonated catalyst. The synthesized catalyst with a surface area of 144 m²/g and sulfonic and total acid densities of 4.18 and 7.58 mmol/g, respectively. The catalyst loading was 3.5 weight percent, the reaction time was 50 minutes, the methanol to oil ratio was 13:1, and the ultrasonic amplitude was 51%. These parameters resulted in an optimal bio-diesel yield of 96%. The developed catalyst demonstrated better stability for up to five cycles and an above-average bio-diesel output of 80%.