Optimization, kinetic and thermodynamic studies on sustainable biodiesel production from waste cooking oil: An Indian perspective

In India, the biodiesel industry is promising and growing at a rapid rate. Several attempts have been made using non edible feedstock to develop the commercial and sustainable biodiesel industry. In this perspective, this study has aimed to optimize four main factors; catalyst quantity, methanol: waste cooking oil molar ratio, mixing intensity and reaction time, which would influence the conversion of waste cooking oil to biodiesel. Response surface methodology integrated with desirability function approach was used to determine the best operative conditions. The optimal reaction parameters for maximum biodiesel yield (90 +/- 0.25%) were identified as 0.6%w/w catalyst loading, 10.6:1 methanol to waste cooking ratio, 559 rpm mixing intensity and 63 min reaction time. The study of reaction kinetics revealed that the experimental data followed the first order reaction kinetics and the energy required to activate the molecules to undergo chemical transformation was calculated as 57.82 kJ/mol. The important thermodynamic parameters such as enthalpy (Delta H), entropy (Delta S), and the Gibbs free energy (Delta G) were estimated to assess the characteristics of the transesterification process. The values of the thermodynamic parameters were found to be Delta H = 55.09 kJ/mol, Delta S =-0.103 kJ/mol K and Delta G = 89.90 kJ/mol, respectively.