Sodium Impregnated Zinc Oxide as a Solid Catalyst for Biodiesel Preparation from a Variety of Triglycerides

In the present work, a series of sodium impregnated zinc oxide catalysts were prepared by a wet impregnation method followed by calcinations at different temperatures. The prepared catalysts were characterized by powder X-ray diffraction, Hammett indicator test, scanning electron, and transmission electron microscopic studies. The catalysts prepared by impregnating 5 wt% of sodium in ZnO and calcined at 400 degrees C were used for the virgin cotton seed oil transesterification with methanol. The selected catalysts were able to yield the complete transesterification of the oil to biodiesel, and the catalytic activity was found to depend on (i) the impregnated sodium amount, (ii) the calcination temperature, (iii) methanol to oil molar ratio, (iv) reaction temperature, and (v) the amount of free fatty acid contents in feedstock. The selected catalyst was also used for the transesterification of a variety of feedstock (virgin cottonseed oil, used cotton seed oil, mutton fat, karanja oil, and jatropha oil) having free fatty acid contents in the range of 0.1-8.5 wt% and found to complete the transesterification when free fatty acids were less than 1 wt% in feedstock used.