Preparation and application of binary acid–base CaO–La2O3 catalyst for biodiesel production

• The mixed metal CaO–La2O3 catalyst comprised of bifunctional acid–base properties.
• CaO–La2O3 able to catalyzed esterification & transesterification simultaneously.
• High yield of biodiesel (99%) was produced from low quality Jatropha oil via CaO–La2O3 reaction.
• High reusability of CaO–La2O3 catalyst with less leaching of active Ca2+ ion in biodiesel product.
• Jatropha-based biodiesel was comply with biodiesel standard EN 14103 & ASTM D6751.

A simple method was developed for biodiesel production from non-edible Jatropha oil which contains high free fatty acid using a bifunctional acid–base catalyst. The acid–base catalyst comprising CaO and La2O3 mixed metal oxides with various Ca/La atomic ratios were synthesized via co-precipitation method. The effects of Ca/La compositions on the surface area, acidity–basicity and transesterification activity were investigated. Integrated metal–metal oxide between Ca and La enhanced the catalytic activity due to well dispersion of CaO on composite surface and thus, increased the surface acidic and basic sites as compared to that of bulk CaO and La2O3 metal oxide. Furthermore, the transesterification reactions resulted that the catalytic activity of CaO–La2O3 series were increased with Ca/La atomic ratio to 8.0, but the stability of binary system decreased by highly saturated of CaO on the catalyst surface at Ca/La atomic ratio of 10.0. The highest biodiesel yield (98.76%) was achieved under transesterification condition of 160 °C, 3 h, 25 methanol/oil molar ratio and 3 wt.%. In addition, the stability of CaO–La2O3 binary system was studied. In this study, Ca–La binary system is stable even after four cycles with negligible leaching of Ca2+ ion in the reaction medium.

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