Ultrasound assisted synthesis of methyl butyrate using heterogeneous catalyst

• Ultrasound assisted synthesis of methyl butyrate using amberlyst-15 catalyst.
• Optimization of various parameters was done to obtain maximum conversion.
• Ultrasound helps to reduce the reaction time compared with conventional process.
• Reaction was well predicated using Langmuir–Hinshelwood–Hougen–Watson models.

Ultrasound assisted esterification of butyric acid with methanol was investigated in an ultrasound irradiated isothermal batch reactor using acid ion-exchange resin (amberlyst-15) as a catalyst. Effect of parameters such as temperature (323–353 K), catalyst loading (0–8.5% w/w), alcohol to acid ratio, M (2–6), ultrasound power (0–145 W), duty cycle (0–85%) and amount of molecular sieves added (0–11% w/w) on the rate of reaction was studied. At optimized parameters, a maximum conversion of 91.64% was obtained in 120 min in presence of ultrasound. Experimental kinetic data were correlated by using Eley–Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW) models taking into account reverse reaction. Studies showed that single site LHHW with reactants and products both adsorbing on catalyst surface was most suited for the obtained experimental data. Activation energy determined based on heterogeneous kinetics was in the range 49.31–57.54 kJ/mol while it was 18.29 kJ/mol using homogeneous model.