Response surface method and genetic algorithm assisted optimal synthesis of biodiesel from high free fatty acid sal oil (Shorea robusta) using ion-exchange resin at high temperature

•Synthesis of biodiesel from high free fatty acid sal oil at high temperature and pressure.•Sal oil biodiesel and recycling of ion-exchange catalyst.•Optimal synthesis of biodiesel using CCD assisted RSM.•Comparison RSM results with simple genetic algorithm.•Multi-objective optimization for biodiesel synthesis.

In this study, response surface methodology (RSM) and genetic algorithm (GA) were used for the optimal synthesis of biodiesel from high free fatty acid sal oil using an acidic ion-exchange resin catalyst at high temperature and pressure. The conversion of sal oil to sal oil methyl ester (SOME) biodiesel was studied by varying catalyst loading, methanol–oil ratio, reaction time and temperature. The maximum trans-esterification temperature was set by the onset degradation temperature of sal oil, SOME biodiesel and catalyst. Analysis of variance was used to determine the significance of individual operating variables and their interacting effects on biodiesel yield. A quadratic polynomial model was obtained through multiple regression analysis using RSM to predict biodiesel yield. A multi-objective optimization problem was formulated involving conflicting objectives (i.e., maximization of biodiesel yield and minimization of trans-esterification time) and solved using non-dominated sorting genetic algorithm. Sets of non-dominated (equally good) Pareto solutions are obtained for the problem studied. The validity of optimal solutions obtained from RSM and GA was confirmed by the series of experimental results through quantification of sal oil, SOME biodiesel and free fatty acid by Fourier transformed infra red analysis. Activity of fresh and recycled resin catalyst was determined by ion-exchange capacity, scanning electron microscopy and measuring the biodiesel yield after several recycling of the catalyst. Finally, biodiesel was analyzed by the ASTM’s method.

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