CaO catalyst is a heterogeneous catalyst used in biodiesel synthesis. Modification of the CaO catalyst with porous materials such as silica (SiO2) was carried out to increase its catalytic activity. The aim of this research is to synthesis the CaO-SiO2 catalyst using the wet impregnation method with variations in the weight of silica to CaO, namely 3%, 5%, and 7% (w/w). The CaO catalyst was obt…