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Due to rapid changes in food habits, a substantial amount of waste fat and used oils are generated each year. Due to strong policies, the disposal of this material into nearby sewers causes ecological and environmental problems in many parts of the world. For efficient management, waste cooking oil, a less expensive, alternative and promising feedstock, can be used as a raw material for producing biofuel. In the present study, we produced a biodiesel from hydrolyzed waste cooking oil with a subcritical methanol process using a synthesized solid super acid catalyst, a sulfated zirconium oxide supported on Santa Barbara Amorphous silica (S-ZrO2/SBA-15). The characterization of the synthesized catalyst was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and the Brunauer-Emmett-Teller (BET) method. The catalytic effect on biodiesel production was examined by varying the parameters: temperatures of 120 to 200 °C, 5-20 min times, oil-to-methanol mole ratios between 1:5 to 1:20, and catalyst loadings of 1-2.5%. The maximum biodiesel yield was 96.383%, obtained under optimum reaction conditions of 140 °°C, 10 min, and a 1:10 oil-to-methanol molar ratio with a 2.0% catalyst loading. We successfully reused the catalyst five times without regeneration with a 90% efficiency. The fuel properties were found to be within the limits set by the biodiesel standard. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]