Accelerating transesterification reaction with biodiesel as co-solvent: A case study for solid acid sulfated tin oxide catalyst

Solid acid catalysts are normally used to catalyze the transesterification of oil with high free fatty acid (FFA) to biodiesel. However, the immiscible phases of methanol-oil-catalyst in the initial reaction mixture usually lead to slow reaction rate and long reaction time. One possible way to overcome this limitation is by using co-solvent that has high solubility in oil and methanol. Therefore, in the present study, the use of biodiesel as co-solvent for transesterification reaction catalyzed by SO42-/SnO2–SiO2 (solid acid catalyst) was investigated. It was found that with the use of biodiesel as co-solvent, a high FAME yield of 88.2% (almost 30% higher than without using co-solvent) can be obtained in a shorter reaction time (1.5 h) using the following reaction conditions; reaction temperature of 150 °C, methanol to oil ratio of 15 and catalyst loading of 6 wt.% (weight of oil).