Biofuels and additives: Comparative kinetic study of Amberlite IR 120-catalyzed esterification of ethanol with acetic, propanoic and pentanoic acids to produce eco-ethyl-esters

•Effect of temperature on reaction kinetics is linked to the steric hindrance around the alpha carbon of the carboxylic acid.•Amberlite IR 120 is effective for the esterification of ethanol with acetic and propanoic acids.•Catalyst efficiency decreases exponentially with increase in the acid molar volume.•Highest initial reaction rate observed is in the ethanol feed ratio range of 0.3–0.6.•Surface reaction between acid in the bulk phase and adsorbed ethanol is found to be the rate limiting step. The effect of reaction time and operating parameters like temperature, catalyst loading and feed ratios on Amberlite IR 120-catalyzed esterification of ethanol with acetic, propanoic and pentanoic acids is studied. All three esterifications are slightly endothermic. The kinetic results are presented in the form of surface response plots. Relative increase in initial rates with increase in temperature depends on the steric hindrance around the carboxylic group. Ethanol feed ratios ranging from 0.3 to 0.6 exhibit the fastest initial rates. Catalyst efficiency is found to decrease significantly with increase in carboxylic acid chain length. Modified UNIFAC (Dortmund) model is used to predict system non idealities. An Eley Rideal mechanism, with surface reaction between adsorbed ethanol and acid in the bulk as the limiting step, best correlates the kinetic data.