Enhanced biodiesel production from oleic acid using TiO2-decorated magnetic ZIF-8 nanocomposite catalyst and its utilization for used frying oil conversion to valuable product

Abstract

In this study, a new recyclable TiO2-decorated magnetic ZIF-8 (Fe3O4@ZIF-8/TiO2) nanocomposite catalyst was first synthesized and its structural and morphological properties were characterized through different techniques such as XRD, FT-IR, TEM, EDX, TPD, and VSM. Then, biodiesel was produced using the Fe3O4@ZIF-8/TiO2 catalyst through the esterification of oleic acid in the presence of ethanol. Response surface methodology (RSM) was also employed to achieve the optimum experimental operating variables affecting the yield of biodiesel production. Significant variables like the amount of catalyst, the molar ratio of alcohol to fatty acid, reaction time, and temperature were optimized through RSM to achieve the highest yield of biodeisel production. The results indicated that the highest biodiesel yield is obtained at the reaction temperature of 50 °C, the reaction time of 62.5 min, the alcohol to oleic acid molar ratio 30:1, and 0.2 g (6 %wt) amount of catalyst. In this condition, the highest yield of biodiesel production was found 80% and 93% using ethanol and methanol, respectively; around 40% higher than pristine TiO2 and magnetic ZIF-8. Subsequently, the biodiesel production in optimum conditions was evaluated from frying oil by using the as-prepared catalyst. The result from 1H NMR and GC–MS analyses confirmed the efficient conversion of frying oil wastes to valuable biofuel product.