Utilization of Alpinia nigra leaves as a sustainable source of highly efficient heterogeneous catalyst for biodiesel production from waste cooking oil

This study encompasses development of an affordable and highly effective heterogeneous solid base catalyst from Alpinia nigra leaves for biodiesel production from waste cooking oil (WCO). XRD and EDX analyses of the developed catalyst revealed K (potassium) as the dominant element (48.40 wt%) in the form of oxide and carbonate. The catalyst obtained is mesoporous in nature with BET surface area of 4.808 m 2 /g and pore diameter of 4.33 nm. It is highly basic (calculated basic strength is 1.67 mmol/g and pH value is 13.14 at 1:10 w/v dilution). The catalyst delivered a maximum 98.03 % biodiesel conversion in 30 min in presence of 7 wt% catalyst loading, MTOR (methanol to oil ratio) of 6:1 at 65 °C. Reaction is found proceeding through a pseudo first order kinetics. From the Arrhenius equation, activation energy was determined as 62.85 kJmol -1 . Catalyst was remained effective up to 4th cycle, giving a maximum 88.88 % biodiesel conversion. The fuel properties of the produced biodiesel met the standard limits authorised by the international standard ASTM D6751 and EN 14214. The estimated 1 kg cost of the catalyst is $ 2.37/kg. • Synthesised a solid base catalyst from Alpinia nigra leaves. • Catalyst contains K in the highest amount, exhibits BET surface area of 4.808 m 2 /g. • Biodiesel was successfully produced from waste cooking oil. • Maximum 98.03 % conversion of waste cooking oil was achieved in 30 min using CAL550. • Optimal reaction condition found was MTOR = 6:1, catalyst loading = 7 wt%, temperature = 65 °C.