SnSO₄ as Catalyst for Simultaneous Transesterification and Esterification of Acid Soybean Oil

Biodiesel is an alternative biodegradable and non-toxic biofuel produced from renewable resources. Industrially, it is produced by catalytic transesterification of refined vegetable oil with methanol or ethanol. Biodiesel production costs can be reduced by using non-refined feedstocks whose market prices are lower than those of refined vegetable oils. This work studied the use of tin(II) sulfate (SnSO₄), as catalyst for the simultaneous transesterification and esterification of model acid oil containing high levels of free fatty acids. The influence of experimental parameters, catalyst leaching as well as its reusability was investigated. For a model feedstock containing 70 wt. % of free fatty acids (oleic acid), the highest biodiesel yield (92%) was obtained at 100 ºC, under autogenous pressure, using 5 wt. % of SnSO₄ in excess of ethanol after 3 h of reaction. The catalyst was reused ten times without significant decrease in biodiesel yield.

biodiesel; esterification; model acid oil; SnSO₄; tin catalysts