Polyoxometalate-MgF2 hybrids as heterogeneous solid acid catalysts for efficient biodiesel production

Abstract

A series of highly active and stable Keggin heteropolyacid catalysts were prepared through mixing of 12-tungstophosphoric acid (TPA) with magnesium fluoride (MgF₂). Among those acidic catalysts, the Mg₂₀F₃₉TPA-1.0 hybrid with moderate acidity (0.96 mmol g⁻¹) and good dispersion of active sites presented pronounced catalytic performance in esterification of oleic acid (up to 95% oleic acid conversion). Particularly, Mg₂₀F₃₉TPA-1.0 was also efficient for the transesterification of Jatropha oil with a high acid value, giving biodiesel in 93% yield. Moreover, the catalyst showed good durability and reusability for at least five consecutive cycles.