Surface acidity and catalytic activity of aged SO42-/SnO2 catalyst supported with WO3

New solid acid was prepared by loading of aged 15 wt.% SO42-/SnO2 catalyst with 15 and 35 wt.% WO3. The catalysts were calcined at 400 and 650 degrees C. The surface areas of the catalysts were determined by the data of N-2 adsorption at -196 degrees C. The surface acidity was measured potentiometricaly using n-butylamine solution in acetonitrile. The types of acidic sites were determined by FT-IR spectra of adsorbed pyridine. The catalytic activities of the catalysts were tested toward esterification of propionic acid (PA) with n-butanol (B). The S-BET values of the ISS were decreased with an increase in the calcination temperature, whereas, the S-BET of the loaded catalysts was maximum at 400 degrees C. The results reveal that the used catalysts possess very strong acid sites and contain both Bronsted and Lewis acidic sites. The acid strength, total surface acidity and the conversion of PA were maxima for 400 degrees C products. The effect of the reaction parameters was also studied, and shows that the PA conversion was increased with an increase in the reaction temperature and the catalyst weight. The reactant molar ratio shows a maximum conversion at PA:B = 1:2. The kinetics study indicates that the catalytic esterification of PA with B obey first order kinetics equation. The results were compared with previously prepared non-aged catalysts. The comparison reveals that the aging of the support would causes a decrease in S-BET, acid strength and catalytic activity, but increases the acid amount of the catalyst. (C) 2013 Elsevier B.V. All rights reserved.