Bentonite-enhanced biodiesel production by NaOH-catalyzed transesterification: Process optimization and kinetics and thermodynamic analysis

Abstract The use of bentonite as a water adsorbent to remove moisture from the biodiesel synthesis reaction system could produce an important enhancement to the transesterification process. The influence of concentration of NaOH, methanol/oil molar ratio, amount of bentonite, agitation rate, reaction temperature and reaction time was investigated. Based on the results of single factor experiments, response surface methodology central composite design (RSMCCD) was applied to optimize the process parameters of the bentonite-enhanced transesterification reaction. The maximum FAME yield of 98.56% was achieved under the optimized conditions of 7.47:1 methanol/oil molar ratio, 0.77 wt% concentration of NaOH, 1.76 wt% amount of bentonite and 57.8 °C reaction temperature. This study also examined the kinetics and evaluated the thermodynamic activation parameters for the bentonite-enhanced transesterification reaction, and the following results are obtained: the activation energy ( E a ) was 31.03 kJ mol −1 , Δ G  > 0, Δ H  > 0 and Δ S