| Summary: | 碩士 === 國立成功大學 === 化學工程學系 === 106 === In this study, lithium metasilicate (Li2SiO3) prepared from fumed silica was used as a heterogeneous base catalyst to catalyze the transesterification reaction of waste cooking oil (WCO) in excess methanol for biodiesel production. Waste cooking oil collected from the local restaurant contained an acid value measured at 1.91 mg KOH/g oil. Li2SiO3 catalyst was synthesized via a hydrothermal process by using fumed silica as a starting material with an addition of LiOH(aq) at 150oC for 2 h. After the hydrothermal reaction, the products were washed thoroughly with de-ionized water, dried in the oven, and then calcined at 500oC in the air for 6 h. The catalysts were characterized by XRD, TGA, FTIR, SEM, BET and ssNMR. Its basicity was also measured. The factors influencing the yield of biodiesel such as reaction temperature, reaction time, alcohol quantity, and catalyst amount were studied. The yield of biodiesel achieved 90% under the following optimal conditions: methanol to oil molar ratio 54:1, catalyst amount 10 wt% at 65oC for 4 h. After reused of lithium metasilicate for 5 cycles, the yield could still reach 48%. According to Arrhenius equation, the activation energy of transesterification reaction using lithium metasilicate is near 75.50 kJ/mol. Furthermore, the properties of biodiesel such as acid value, density and viscosity were found to be within the limits of ASTM standards.
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