Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

The kinetics of the esterification reaction between propionic acid and methanol, ethanol, and 1‐butanol over the ion exchange resin, Amberlyst 15, was investigated. Experiments were conducted using a fixed‐bed plug flow reactor over the temperature range of 298–328 K. Acid to alcohol molar ratios of 3:1, 1:1, and 1:3 were employed. For each esterification system, the equilibrium conversion of propionic acid was found to increase with increasing reaction temperature. Several kinetic models were tested to correlate the collected data under kinetically controlled conditions; the pseudo‐homogeneous (P‐H), Eley–Rideal (E–R), Langmuir–Hinshelwood (L–H), and Pöpken (P‐P) models. In all cases, the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of the reactants and products. The P‐P model was found to best represent the kinetic data of the investigated esterification systems with a total average error of less than 3%. The increase of alcohol chain length had a negative impact on the conversion of propionic acid due to steric hindrance. The activation energy of the esterification reaction is influenced by the chain length of the alcohol used. The adsorption equilibrium constants estimated by the P‐P model and the solubility parameters reported by AICHE DIPPER® followed the same trend; ester < acid < alcohol < water. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 432–448, 2009