Biodiesel production from vegetable oils in presence of heterogenous catalysts

Abstract

The world is presently confronted with the twin crisis of fossil fuel depletion and environmental degradation. All countries including India and China are grappling with the problem of meeting the ever increasing demand of transport fuels within the constraints of international commitments, legal requirements, environmental concerns and limited resources. Currently a dual step process has been used for biodiesel preparation from high FFA containing materials. The first step of the process is to reduce the FFA content in the oil by esterification with methanol to methyl esters catalyzed by solid acid, followed by the transesterification process, in which the triglyceride present in pretreated oil is converted into methyl esters in presence of a solid base catalyst. In the present study two different non-edible oils which are available in plenty in India, which possess high calorific value and are under utilized such as Neem (Azadirachta indica) and Pinnai (Calophyllum inophyllum) have been selected for the production of biodiesel. The results of Thermo Gravimetric Analysis (TGA) indicate the increased hydrophobicity due to phosphoric acid modification, and hence the adsorption of FFA on the surface of phosphoric acid modified catalyst is high which leads to higher conversion of FFA. Kinetic studies revealed that the solid acid catalyzed esterification reaction and the solid base catalyzed transesterification reaction follow pseudo first order kinetics. Kinetic constants were computed from the kinetic plots obtained. From the kinetic constant values it was clear that the forward reactions occur to higher extent, in comparison to the reverse reactions. To check the reusability of both solid acid catalysts, esterification was repeated with the use of phosphoric acid modified zeolites for thrice. In all the three, 75-85% conversion was obtained; thus establishing the absence of catalyst deactivation. While checking the reusability of solid base catalyst, no catalyst deactivation was observed similar to the above case.