Optimization of Biodiesel Production from Waste Cooking Oil Using S–TiO2/SBA-15 Heterogeneous Acid Catalyst

Abstract

The aim of this research was to synthesize, characterize, and apply a heterogeneous acid catalyst to optimum biodiesel production from hydrolyzed waste cooking oil via an esterification reaction, to meet society’s future demands. The solid acid catalyst S–TiO2/SBA-15 was synthesized by a direct wet impregnation method. The prepared catalyst was evaluated using analytical techniques, X-ray diffraction (XRD), Scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET) method. The statistical analysis of variance (ANOVA) was studied to validate the experimental results. The catalytic effect on biodiesel production was examined by varying the parameters as follows: temperatures of 160 to 220 °C, 20–35 min reaction time, methanol-to-oil mole ratio between 5:1 and 20:1, and catalyst loading of 0.5%–1.25%. The maximum biodiesel yield was 94.96 ± 0.12% obtained under the optimum reaction conditions of 200 °C, 30 min, and 1:15 oil to methanol molar ratio with 1.0% catalyst loading. The catalyst was reused successfully three times with 90% efficiency without regeneration. The fuel properties of the produced biodiesel were found to be within the limits set by the specifications of the biodiesel standard. This solid acid catalytic method can replace the conventional homogeneous catalyzed transesterification of waste cooking oil for biodiesel production.