Silicotungstic acid supported zirconia: An effective catalyst for esterification reaction

Abstract

A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt% of silicotungstic acid on hydrous zirconia (ZSTA). The prepared catalysts were characterized by PXRD, FTIR, UV-vis DRS, EPMA, BET surface area, acid sites, etc. IFTIR and UV-vis DRS studies indicate that the material retain the Keggin-type structure of silicotungstic acid up to 500 degrees C. The suitability of the materials was studied for acid catalysed esterification reactions using formic, acetic, propionic, n-butyric acid and n-butyl alcohol (NBA), isobutyl alcohol (IBA) and sec-butyl alcohol (SBA). Material with 15 wt% STA on hydrous zirconia having high surface area and acid sites acts as better catalyst for esterification reactions. The esterification of acids with NBA was found to be higher than IBA and SBA. In all the cases, the selectivity for the corresponding esters is nearly 100%. The straight-line plot of -ln(1 - conversion) versus reaction time for the reactions carried out at 98 degrees C supports that the esterification reaction obeys first order kinetics with respect to acid concentration. The reusability study justifies that the catalyst is stable and active. (c) 2007 Elsevier B.V All rights reserved.