Kinetics of esterification of aromatic carboxylic acids over zeolites Hβ and HZSM5 using dimethyl carbonate

Esterification of benzoic acid and substituted benzoic acids has been carried out efficiently over zeolite HP and HZSM5 in an autoclave using dimethyl carbonate (DMC) as the methylating agent. The wide applicability of this esterification method to esterify, a wide range of aromatic carboxylic acids has been demonstrated. This method is a viable and safe alternative to other esterification processes, involving harmful alkylating agents and chemicals. Strong acid sites are responsible for the reaction. The reaction proceeds inside as well as outside the pores of the zeolites. The pore architecture of the zeolites and mass transfer limitations come into play only when the molecular diameter of the reactant molecules is greater than the pore size of the zeolites. Kinetic study shows that the reaction is first-order with respect to acid concentration. (C) 2003 Elsevier Science B.V. All rights reserved.