Effect of single metal loading on CaO/AL2O3 pellet catalyst for biodiesel production

Abstract

Biodiesel is a sustainable biofuel mainly derived from transesterification of vegetable oil or animal fat. Transesterification is increasingly being catalyzed by heterogeneous catalysts in recent years. As a result of a high-pressure drop, solid base catalysts in a powder form are not suitable for a continuous process. A pellet catalyst is more convenient, but it has lower surface per volume as well as lower in its catalytic activity for transesterification. This research aims at studying the effect of metal oxides loading on CaO/Al2O3 pellet catalyst for improvement of catalytic activity of transesterification. The 20 wt.% single metal loading of metal oxides on CaO/Al2O3 pellet catalysts including Li-CaO/Al2O3, K-CaO/Al2O3, Sr-CaO/Al2O3, and Fe-CaO/Al2O3 were synthesized by incipient impregnation method. The K-CaO/Al2O3 pellet catalyst gave the highest biodiesel yield (95.5%) under 12:1 methanol to oil molar ratio, 65 °C, 10 wt.% catalysts and 6 h reaction time. Its total basicity was found to be 2.40 mmol/g. The initial TOF was determined and found the relationship between the basicity and its catalytic activity. In addition, the mechanical strength of K-CaO/Al2O3 pellet catalyst was increased when compared with the bare CaO/Al2O3 pellet catalyst. Unfortunately, the leaching problem of K-CaO/Al2O3 pellet catalyst was observed during the transesterification.