Adsorption and Kinetic Parameters for Synthesis of Methyl Nonanoate over Heterogeneous Catalysts

Methyl nonanoate was synthesized in a batch reactor by esterification of nonanoic acid with methanol catalyzed by the cation exchange resins, Dowex 50Wx2, Amberlyst 35, and Amberlyst 15. The effect of various parameters such as speed of agitation, catalyst loading, molar ratio, and reaction temperature on degree of conversion has been reported. The conversion of nonanoic acid to methyl nonanoate was found to increase with an increase in temperature in the range of 303.15–333.15 K and the increase was appreciable with an excess use of methanol in the reaction mixture. Nonideality of the liquid phase was taken into account by using activities instead of concentration. The activity coefficients were calculated using the UNIFAC group contribution method. The possible mechanism of reaction was mathematically treated using theories of the Eley–Rideal model based on inhibition by water and methanol on the Amberlyst 15. The reaction rate constants and the adsorption coefficients for methanol and water were determined from the experimental data established at three different temperatures for the effect of initial concentration of acid and alcohol. The kinetics reported in this study was obtained under conditions free of both external and internal mass transfer resistance. Activation energy and pre-exponential factor of the reaction were found to be 47.6 kJ mol–1 and 3.2 × 104 L2 g–1 mol–1 h–1, respectively.