Heteropoly acid supported on clay: An effective catalyst for esterification of formic acid with n-Butyl alcohol and kinetic modelling

In this study, a series of catalysts having 10%, 20% and 30% loadings of DTP on Bentonite were synthesized, the samples were characterized by using XRD, FT-IR, BET method and the catalytic activities of the catalysts were examined by esterification of formic acid with butyl alcohol.The XRD and FT-IR analyses of Tonsil earth, pure HPA and syntesized catalyst show that there is an interaction between the tonsil and heteropoly acid. The surface area, pore volume and pore size distibution were measured by using the BET method. The surface area and pore volume of Tonsil were reduced considerably by loading of different HPAs on tonsil. The adsorption?desorption isotherms of HPAs were found to agree with the isotherm of Type IV, which was a characteristic of a mesoporous solid.It has been indicated that the reaction between formic acid-butyl alcohol, conducted without catayst, follows a simple second order reversible reaction mechanism. Temperature dependency of the forward reaction rate constant was calculated.The 20% DTP on tonsil showed the highest catalytic activity. Therefore the reaction was studied in the presence of this catalyst. The experiments has been carried out in a stirred batch reactor. The effects of reactant molar ratio, reaction temperature, stirring speed and catalyst loading on the reaction rate have been determined.It was shown that the reaction rate increases linearly with the catalyst loading. And it has been observed that the stirring speed has no effect on the reaction rate. The experimental results showed that the reaction follows the Eley-Rideal mechanism. The kinetics model depending on this mechanism has been developed aswhere T is absolute temperture in K.Keywords: Esterification, Heteropoly acid, Heterogeneous catalysis, Kinetic modelling