Fabrication of carbonated alumina doped by calcium oxide via microwave combustion method used as nanocatalyst in biodiesel production: Influence of carbon source type

Carbonated alumina doped by calcium oxide was successfully synthesized by a simple, cost effective and rapid microwave combustion method (MCM) and the effect of fuel type on the structural and performance of the sample in the microwave-assisted transesterification reaction were examined. For this purpose, five kinds of fuel as carbon source such as citric acid, starch, triethylene glycol, sorbitol and dextrose were utilized for fabrication of carbonated calcium aluminate and then active phase of KOH was dispersed on the surface of samples by impregnation method. The results of TG/DSC, XRD, FTIR, BET-BJH, FESEM and EDX analyses mentioned that the sample synthesized by dextrose, sorbitol and triethylene glycol presented well-crystalline structure, surface area, pore size and activity, respectively. While, the sample prepared by citric acid and starch showed insufficient physicochemical properties that can be assigned to flash point, auto-ignition temperature and proportion of oxygen to carbon of the fuel. Assessment the activity of the sample prepared by dextrose exhibited that 98.8% of canola oil was converted to biodiesel at the conditions of 270 W microwave power, 15 M ratios of methanol/oil, 4 wt% of catalyst and 30 min reaction time. Moreover, the sample presented the highest stability compared to those prepared by other fuels such that its activity reduced only 3.4% and 6.1% after second and third uses, while 9.2%, 16.6%, 15.6% and 27.8% reduction in the activity were respectively observed for carbonated calcium aluminate prepared by sorbitol, triethylene glycol, starch and citric acid as fuel.