Comparative assessment of the ability of a microwave absorber nanocatalyst in the microwave-assisted biodiesel production process

摘要

In this study, a carbon-supported KOH/Ca_(12)Al_(14)O_(33) nanocomposite was fabricated via the microwave combustion method, in which dextrose was used as a carbon source, and its activity in the microwave-assisted transesterification reaction as a microwave absorption material was assessed. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, BrunauereEmmetteTeller (BET), field-emission scanning electron microscopy, and energy dispersive X-ray analyses. The results showed that the carbonate and noncarbonate samples had a calcium aluminate (Ca_(12)Al_(14)O_(33)) structure as a support. Different carbon groups were formed during preparation of the carbon-supported KOH/Ca_(12)Al_(14)O_(33) nanocomposite, which improved its surface area and porosity. Although the samples presented similar basicity, the carbonated nanocomposite exhibited twice as much activity as the KOH/Ca_(12)Al_(14)O_(33) nanocatalyst for conversion of canola oil to biodiesel in the microwave-assisted transesterification reaction at 270 W microwave power. The nanocomposite with a larger pore size made active sites easily accessible and exhibited higher catalytic ability where the conversion of 98.8% was obtained under the optimized conditions of 270 W microwave power, methanol/oil molar ratio of 15, 4 wt% of the nanocomposite, and 30 min of reaction time. The carbonsupported nanocatalyst can be reused for at least four times with less reduction in activity. Furthermore, the obtained biodiesel showed that it met the standard values (EN 14214 and ASTM D-6751) with respect to the density, kinematic viscosity at 40 °C, acid number, and flash point.