Heterogeneous transesterification of castor oil for biodiesel production by Al2O3, Al2O3-NiO and Al2O3-CoO modified bentonite as catalyst

Abstract

Bentonite clay from Maghnia (Algeria), very rich in montmorillonite (~ 90 %) purified and intercalated with pillars Al2O3, Al2O3-NiO and Al2O3-CoO, was applied as catalyst for the conversion of a mixture of castor oil-ethanol to biodiesel. The pillared clay with Al2O3-CoO (10%) led to 98% ester conversion. The highest yield of biodiesel production was obtained at 1/15 molar ratio of oil/ethanol, a temperature of 250 °C and 7.5 wt% of catalyst. This behaviour was ascribed to a synergetic effect of the largest surface area developed in the clay and the highest catalytic activity of cobalt in basic medium. The catalysts re-usability experiments revealed that the pillared clays were safely re-used three times without losing their original catalytic effectiveness. The kinetics calculations demonstrated that the transesterification of castor oil in an excess of alcohol using the pillared clay as catalyst followed a pseudo first order kinetics. The biodiesel produced exhibited comparable fuel properties as those of classical fossil diesel.