Enhancement of biodiesel synthesis from soybean oil by potassium fluoride modification of a calcium magnesium oxides catalyst

Transesterification of soybean oil with methanol was carried out in the presence of CaO–MgO and KF-modified CaO–MgO catalysts at atmospheric pressure. While the methyl ester yield for the CaO–MgO catalyst with a ratio of 8:2 (CaO:MgO) was 63.6%, it was 97.9% for the KF-modified catalyst at a 2% catalyst to the reactants (methanol/oil mixture) weight ratio, a temperature of 65 °C, a methanol–soybean oil ratio of 9:1 and a reaction time of 2.5 h. The KF/CaO–MgO catalyst still yielded 86.7% after four successive uses. The catalytic performance of the KF/CaO–MgO catalyst was attributed to the formation of active KCaF3 and K2MgF4 centers.