Process optimization of super phosphoric acid-catalyzed esterification of palm fatty acid distillate using response surface methodology

Abstract

The present study reports the findings of experiments carried out to optimize super phosphoric acid-catalyzed esterification of palm fatty acid distillate—a low-cost by-product of the palm oil refining process for biodiesel production. The main objectives were to develop an approach that would enable us to better understand the relationships between the governing variables, i.e., oil to methanol ratio, temperature and catalyst concentration, and the response (conversion of the biodiesel), and to obtain the optimum conditions for biodiesel production using central composite design (CCD) and response surface methodology (RSM). All the three variables significantly affected the acid value of the product, oil to methanol ratio being the most effective followed by temperature and catalyst concentration. Using response surface methodology, a quadratic polynomial equation was obtained for acid value by multiple regression analysis. Verification experiments confirmed the validity of the predicted model. Various properties of the biodiesel were evaluated and compared in relation to that of conventional petro-diesel. The prepared biodiesel blended with different proportion of petro-diesel was then subjected to performance and emission tests at varying loads in order to evaluate its actual performance, when used as a diesel engine fuel.