Synthesis, characterization and application of a novel carbon-doped mix metal oxide catalyst for production of castor oil biodiesel

Abstract

A novel carbon-doped CaO–MgO catalyst had been successfully synthesized via co-precipitation method, and was utilized for the production of castor oil biodiesel through the transesterification of oil with methanol. The conditions of carbon-doped CaO–MgO catalyst preparation were optimized, and the optimal preparation parameters were as follows: urea amount of 6 wt%, calcium/magnesium molar ratio of 1:1, calcination temperature of 800 °C and calcination time of 5 h. The TGA, XRD, SEM, EDS, Basicity, BET and XPS were used for the characterization of prepared catalyst. The effects of transesterification reaction parameters on biodiesel production have been investigated, and the conversion ratio of 91.1% was achieved under the optimal conditions: methanol to oil molar ratio of 21:1, catalyst dosage of 8 wt%, reaction temperature of 70 °C and reaction time of 4 h. Meanwhile, the kinetics and thermodynamics studies indicated that the transesterification of castor oil followed the pseudo-first-order kinetics and was a non-spontaneous, endothermic reaction. Furthermore, the characterization analysis results showed that the excellent catalytic activity of composite catalyst was due to the textural property, the basicity of composite and the doped carbon in the prepared catalyst. Meanwhile, the possible reaction mechanism involved in the transesterification catalyzed by carbon-doped CaO–MgO catalyst was presented. The results of turnover frequency, environmental factor and process mass index showed that the transesterification of castor oil to synthesize biodiesel catalyzed by the prepared efficient catalyst possessed the distinct characteristic of environmentally friendly process.