(582b) Preparation of Biodiesel from Waste Cooking Oil Via Lithium Metasilicate Catalyzed Transesterification Reaction

In this study, biodiesel was produced from transesterification of waste soybean oil in excess methanol with lithium metasilicate (Li₂SiO₃) catalysts prepared from diatomite Lithium metasilicate was synthesized via hydrothermal processes by using diatomite in starting gel material with an addition of LiOH_(aq) at 150°C for one day. After the hydrothermal reaction, the solids were rinsed by deionized water and calcined at 500°C. The properties of solid catalysts were characterized with XRD, FTIR, solid-state NMR, SEM, BET and TPD. The acid values of the waste soybean oil collected ranged from ca. 0.5 mg KOH/g oil to 1.5 mg KOH/g oil. Hence, oleic acid was employed to spike soybean oil to obtain an acid value of 0.54 mg KOH/g oil and 1.5 mg KOH/g oil to simulate the waste cooking oils (WCO). Variables in transesterification process were studied to optimize the reaction condition. Consequently, the yields of biodiesel were above 95% in an hour by using lithium metasilicate catalysts under the optimal condition. The activation energy of the catalyzed transesterification using lithium metasilicate is near 61.65 kJ/mol. Furthermore, the spent catalysts of could be recycled and reused for at least for 19^th cycles without significant deactivation observed in catalysis. With a decreasing loading of catalyst-to-oil to 25wt%, the yield of biodiesel could still reach ca. 85% in four hours at 60°C.