Tungsten oxide zirconia as solid superacid catalyst for esterification of waste acid oil (dark oil)

Biodiesel is a renewable fuel which can be produced through an esterification reaction. The cost of feedstock which resulted in that of biodiesel is a large problem to be resolved. Dark oil from industrial process can be a better alternative for biodiesel production because of its low price. In spite of this, the study of biodiesel production using the dark oil has not been reported. This study provides technical information and catalytic properties on this system. Among the several catalysts, WO₃/ZrO₂ catalyst was the most effective catalyst in the esterification of the dark oil to fatty acid methyl esters (FAMEs). The catalytic reaction parameters were optimized that 20 wt.% WO₃/ZrO₂ has a high FFA conversion of 96% at 150 °C, 0.4 g/ml (oil), 1:9 (oil to alcohol, molar ratio) and 2 h reaction time. The physical and chemical properties of the catalyst were characterized by XRD, Raman spectrometer, BET and NH₃-TPD.