FUNCTIONAL SILICA-SUPPORTED POLYMERS .4. SYNTHESIS AND CATALYTIC ACTIVITY OF SILICA-GRAFTED SULFONATED POLYPHENYLSILSESQUIOXANE

The ladder polymer, polyphenylsilsesquioxane, has been grafted onto porous silica and sulfonated to obtain catalysts of high stability with enhanced site accessibility and increased number of sites, as well as high acidity level. The catalytic behaviour, even at a low level of capacity, has shown excellent esterification and phenol alkylation activity, with, in the latter case, excellent selectivity, as compared to classical ion exchangers or highly acidic Nafion material. In batch reaction, hydration of the support leads to partial deactivation; activity may be partly recovered and the rate constant is still higher than that obtained with the reference catalyst.