Phosphomolybdic acid/graphene oxide as novel green catalyst using for biodiesel production from waste cooking oil via electrolysis method: Optimization using with response surface methodology (RSM)

Abstract

In this study, biodiesel (FAME) was prepared using a novel heterogeneous catalyst of phosphomolybdic acid (H3PMo12O40, HPMo)/support graphene oxide (GO). The characterization of the catalyst was evaluated by SEM, EDX, Map analysis, TEM, FT-IR, and Raman analyses. The production of biodiesel from waste cooking oil (WCO) was carried out by the electrolysis method. The process of the trans-esterification reaction was optimized by applying the response surface methodology (RSM) based on the central composite design (CCD) approach. The effects of four independent variables of methanol to oil molar ratio (6–12 mol:mol), catalyst weight (0.5–1.5 wt%), time (8–24 h), and voltage (30–70 V) were examined. The highest biodiesel yield was 90.39% at optimum conditions of room temperature, the catalyst weight of 0.85 wt%, the voltage of 60 V, time of 15 h, methanol to oil, and THF to methanol molar ratios of 6:1 and 0.5:1, respectively. Based on the obtained results, all studied variables had significant impacts on the FAME yield. The catalyst was used four times in the trans-esterification reaction without any significant reduction in the yield. The quality of biodiesel was confirmed by H-NMR and FT-IR analyses, and its physicochemical properties were in agreement with the ASTM standard.