Calcium diglyceroxide catalyzed biodiesel production from waste cooking oil in the presence of microwave: Optimization and kinetic studies

The present paper reports the microwave assisted intensification of biodiesel production from waste cooking oil using heterogeneous base catalyst - calcium diglyceroxide. Initially, experiments were carried out by varying various parameters such as reaction temperature, catalyst loading, and methanol to waste cooking oil (WCO) molar ratio using one factor at a time (OFAT) approach, to estimate the best condition. Response surface methodology (RSM) was applied to optimize the process variables, using the BoxBehnken model with three level and three factor. Under the optimized reaction conditions of methanol (MeOH) to WCO molar ratio of 7.46:1, catalyst loading of 1.03% (w/w of WCO) and temperature of 62 degrees C in the presence of microwave, a maximum biodiesel yield of 94.86% was obtained, whereas in the conventional heating method showed 42.59% yield for the similar reaction time of 15 min. Reusability of the catalyst was also tested, after the first run catalytic activity of calcium diglyceroxide was decreased for consecutive cycles. The transesterification of WCO followed pseudo first-order kinetics model. The activation energy and per-exponential factor were found to be 26.56 kJ mol(-1) and 1.65 x 103 min(-1), respectively. The fuel properties of biodiesel matched with the American Society for Testing and Materials (ASTM-D6751) standards. (C) 2018 Elsevier Ltd. All rights reserved.