Application of response surface methodology for optimization of biodiesel production parameters from waste cooking oil using a membrane reactor

Abstract

In light of the growing concerns over depleting energy resources, alternative renewable fuels such as biodiesel have been identified as a possible means of addressing this crisis. In biodiesel production, waste cooking oil (WCO) is seen as the ideal alternative feedstock to vegetable oils, which are part of the food chain. The need to obtain high quality biodiesel at minimal cost has driven the idea to use membrane reactors, which offers the ability to achieve both reaction and separation processes simultaneously. Design and optimization studies were conducted using sulphated zirconia pre-treated WCO as feed stock. Response surface methodology modelling was used to investigate the effect of reaction temperature, catalyst concentration and circulation flow rate in biodiesel production using membrane reactors. This is because limited data is available, particularly considering circulation flow rate effect on biodiesel production using membrane reactors. Experimental results also show that the higher the catalyst to WCO ratio the higher the free fatty acids (FFA) content. A maximum biodiesel yield of 92. 6 mole % was obtained at a temperature of 61°C, circulation flow rate of 26 mL/min using KOH catalyst concentration of 1.3 wt % over a TiO2/Al2O3 membrane. Upon membrane optimization, a biodiesel yield of 94.03 mol % was obtained at 58.5 °C, circulation flow rate of 18.78 ml/min and catalyst concentration of 1.24 wt %. This analysis clearly shows that RSM can be successfully used to model reacting membranes using temperature, catalyst concentration and circulation flow rate to achieve higher yields for biodiesel production.