Influence of carbon source content on the structure and performance of KOH/Ca12Al14O33[sbnd]C nanocatalyst used in the transesterification reaction via microwave irradiation

Abstract

KOH/Ca12Al14O33 nanocatalyst as solid base nanocatalyst was utilized in the microwave-assisted transesterification reaction that it was modified with carbon group to enhance its ability for absorption of microwave irradiation. The nanocatalyst was fabricated via microwave combustion method using dextrose as fuel and carbon source, and the effect of carbon amount (fuel-to-oxidizer ratio) on its activity was evaluated. The samples were characterized by XRD, FTIR, TG/DTA, FESEM, EDX analyses. The results indicated that the nanocatalyst prepared by stoichiometric amount of fuel showed appropriate textural properties and basicity for conversion of canola oil to biodiesel. However, carbon groups were not observed in the sample prepared by less amount of fuel, although high crystallinity, surface area and well element distribution were discerned. On the other hand, the sample prepared by higher amount of fuel showed low crystallinity, surface area and active phase content that resulted low activity. The best nanocatalyst prepared by stoichiometric amount of dextrose to oxidizer converted 98.8% of canola oil to biodiesel under the conditions of 270 W of microwave power, 15 M ratio of methanol-to-oil, 4 wt.% of catalyst and 30 min reaction time. The sample also preserved its activity at least for five times that makes it suitable for industrial application. The results explained that the combustion method is a simple and appropriate method for fast preparation of carbonated nanocatalysts.