Improving heterogeneously catalyzed transesterification reaction for biodiesel production using ultrasound energy and petro-diesel as cosolvent

Abstract

ABSTRACT Heterogeneously catalyzed transesterification process has by far been one of the most popular methods of biodiesel production particularly for the oil feedstock containing large amount of free fatty acid. However, the major constraint of the method is the poor yield of biodiesel and a long reaction time that increased its production cost. With an objective to increase the product yield in lesser time, the current work investigated the effect of addition of ultrasound and addition of cosolvent in the heterogeneously catalyzed transesterification reaction. Three commonly used solid catalyst – calcium oxide (CaO), calcined sodium silicate (CSS) and sulfated zirconia (SZ) were chosen for study. The results suggested that there was a remarkable increase in the yield of biodiesel in comparison to the conventional mechanically stirred process. CSS showed the best catalytic activity both in first use and in repeated uses. It gave a maximum yield of 97% biodiesel in 120 minutes with 9:1 molar ratio of alcohol to oil 3 wt.% of catalyst and 10 wt.% of catalyst. For CaO and CSS a noticeable difference in biodiesel yield was observed upon addition of cosolvent. CaO gave 76% yield with cosolvent and 65% without it. SZ gave 73% biodiesel with cosolvent and 61% without. Since petrodiesel was used as the cosolvent it was not required to remove the cosolvent from biodiesel during the purification process.