Parametric optimization and rate laws determination for the conversion of 4-tert-butylbenzoic acid to methyl 4-tert-butylbenzoate

Abstract

The esterification of 4-tert-butylbenzoic acid has been studied to produce methyl 4-tert-butylbenzoate, having its widespread applications in the pharmaceuticals, perfumes, flavor, cosmetics, and fragrance industries. The limiting nature of the reaction is catalyzed with methane sulphonic acid, a green catalyst. The study focused on optimization of the experimental parameters to achieve higher conversion of acid with the aid of statistical analysis based on the Taguchi technique. An L₉ array, S/N ratios, and ANOVA have been used with catalyst concentration, molar ratio and time as the process parameters with acid conversion as the response variable. Parametric optimization based on Taguchi method suggest a combination of optimal parameters as 10% catalyst concentration, 5:1 methanol to acid molar ratio and 2 h at a refluxing temperature of 67°C. A kinetic investigation for the esterification is also conducted to define the rate equations that govern the overall progress of reaction and the results established that the reaction follows irreversible pseudo second order rate in the initial phase followed by the reversible second order rate. The proposed model is found to be in good agreement with the experimental results.