Guo-Wei Yu,Jing Nie,Lin-Guang Lu,Shen-Peng Wang,Zu-Guang Li,Maw-Rong Lee
Microwave and ultrasound have been demonstrated to be outstanding process intensification techniques for transesterification of oil. According to their mechanisms, simultaneous effects can surely bring about better enhancement than sole microwave or ultrasound. Therefore, this study aimed to investigate the important factors and their suitable levels in the KOH-catalyzed transesterification of soybean oil with methanol by using synergistic assistance of microwave-ultrasound (CAMU). The feasibility of application of CAMU in transesterification of oil was demonstrated. When the dosage of methanol, soybean oil and KOH were 15.4 g, 34.7 g (with methanol-to-oil molar ratio of 12:1) and 1 g, respectively, and the microwave power, ultrasonic power, ultrasonic mode, reaction temperature and reaction time were 700 W, 800 W, 1:0, 65 °C and 6 min, respectively, the transesterification reached 98.0% of yield, being the highest yield among all the results obtained; while by using 600 W of microwave plus stirring instead of CAMU, only 57.4% of yield could be obtained. Compared with other reaction techniques, the transesterification by applying novel CAMU was found to have remarkable advantages. Furthermore, by monitoring the variation of real-time temperature and microwave power during transesterification reactions with different microwave operation time and by taking comparison of the corresponding yield, it was demonstrated that the main reason for the acceleration of microwave-assisted transesterification was the polarization and further activation of reactants caused by microwave irradiation, but not the factor of fast heating.
Liu Yueyu,Yin Zhili,Wang Ziqing,Mou Ronglin,Wei Zhong
High surface area ZrO 2 –KOH sample was prepared and used the catalyst for the synthesis of glycerol carbonate (GC) from dimethyl carbonate (DMC) and glycerol. The structure properties of ZrO 2 –KOH were characterized by XRD, BET, CO 2 -TPD, XPS, and ICP-OES. It was found that the strong basicity of ZrO 2 –KOH might be attributed to the oxygen vacancies as well as the big surface area. Experiments were developed to evaluate the effects of catalysis loading, proportion of reactants, temperature and reaction time on the conversion of glycerol to GC. The consequences showed that ZrO 2 –KOH was a highly efficient basic catalyst for synthesis of GC from glycerol. The catalytic performance of ZrO 2 –KOH is much better than that of ZrO 2 –KOH–CP, ZrO 2 –NH 4 OH, and some reported heterogeneous catalysts. And the higher performance of ZrO 2 –KOH was ascribed to the strong basicity. 99.43% conversion was obtained in a particular situation of catalyst/glycerol weight ratio of 3 wt%, DMC/glycerol molar ratio of 3:1, reaction temperature of 80 °C, and reaction time of 2 h. The plausible reaction mechanism for the transesterification on the strong basic active sites was discussed.
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