Powder XRD study was performed to establish the
To study the kinetics of the reaction, the percent conversion of FFA into respective ester was determined  by substituting the Hesperadin values in equation (1).equation(1)%X=100× (ai−at)/ai %X=100× (ai−at)/ai where X is the conversion of FFA into ester, ai and at are the initial and final acid values (at time t) of the reaction mixture, respectively. All results are an average of three experiments with a relative standard deviation of ±2%.
Acid values of the reaction mixture at given point of time were determined  by following equation (2).equation(2)a=(V×1000×MW×C)/Wa=(V×1000×MW×C)/Wwhere a = acid value (mg of KOH/g of sample); V = volume of solution employed for titration (ml); MW = molecular weight of KOH; C = molar concentration of the KOH solution used for titration (0.01 M in present case); and W = weight (in mg) of the reaction mixture to be analyzed.
The TOF (moles of fatty acid converted per mole of acidic sites per hour) of the catalyst is calculated from equation (3) (at ∼25% conversion levels) following the literature reported procedure .equation(3)TOF=molactual/t×fmTOF=molactual/t×fmwhere molactual is the moles of fatty acid methyl or ethyl esters produced, t is time in hour, and fm is total surface acidic sites (in mmol/g) of catalyst calculated by Hammett indicator-amine titration method.