One-pot synthesis of biodiesel from high FFA shea butter in an optimisation study using response surface methodology

Abstract

Optimisation of biodiesel production from high free fatty acids (FFA) of 6.86% shea butter (SB) using a base catalyst, potassium hydroxide, was studied. Response surface methodology (RSM) was employed as a model for the optimisation of the process by varying temperature, agitation speed, mole ratio and catalyst loading in the range of 40–60 C, 200–1400 rpm, 8:1–12:1 (w/w) and 1–2% (w/w) respectively. The significance of the variables in both linear and nonlinear forms of the model was analysed by analysis of variance (ANOVA). The ANOVA results showed that the temperature, agitation speed, mole ratio and catalyst loading had a significant effect on the shea biodiesel yield with a p-value of < 0.0001 for each of the variables, adjusted R2 of 0.9517 and predicted R2 of 0.8625. The maximum %yield of shea biodiesel obtained was 90.83% at optimal operating temperature of 50 C, agitation speed of 800 rpm, mole ratio of 12:1 (w/w) and catalyst loading of 1% (w/w). This showed that the RSM optimised the one-pot synthesis of biodiesel from high FFA SB, an indication that it can be adopted successfully in the industry to maximise the yield of biodiesel from high FFA SB.