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A solid base catalyst (K2SiO3/C) capable of microwave absorption was used for the transesterification of soybean oil under microwave radiation. The K2SiO3/C catalyst was prepared by an impregnation method that loaded K2SiO3 on carbon particles (1-3.5 mm diameter) followed by drying at 120 °C. The catalysts were characterized by X-ray diffraction, scanning electron microscopy-energy dispersive spectrometry, and the Hammett indicator method. K2SiO3 was well distributed on the support. The effects of reaction variables such as catalyst loading, molar ratio of methanol to oil, and reaction time (under microwave radiation and conventional heating) were studied. When the conventionally heated reaction was carried out at 65 °C with a methanol/oil molar ratio of 30:1 and a catalyst concentration of 24 wt%, the biodiesel conversion was 96.5% after 2.5 h reaction time. The same reaction reached equilibrium after 1.5 h under microwave radiation, and the conversion of biodiesel was 96.7%. |
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