Acylation of B15C5 crown ether by acetic anhydride in the absence of solvent, on sulfated zirconias prepared in different conditions Original Research Article

The surface properties have been compared for sulfated zirconia (SZr) prepared either by one-step sol–gel process using different solvents or impregnation of zirconia by sulfuric acid. The solvent used in the preparation affects the amount of sulfur and surface area of the resulting solid. The number of acid sites of these samples varies from 0.3 to 0.9 meq. g−1 due to the preparation. The infrared spectrum of the activated catalyst contains two bands attributed to sulfates: one at 1400 cm−1 more intense on the most acidic solids prepared by a one-step process and a second one at 1380 cm−1 observed on all solids. Only the first band, attributed to disulfates, is shifted by interaction with benzene, suggesting that these species are responsible for stronger acidity. The catalytic properties have been measured for the acylation of benzo-15-crown-5 (B15C5) crown ether by acetic anhydride in the absence of solvent. The yield in acylated compound reaches 70% in 2 h using a sulfated zirconia prepared in one step by sol–gel. The reaction is catalyzed by H+ and inhibited by the products of reaction. The surface heterogeneity has no effect on the initial rate which is roughly correlated with the total number of acid sites determined by NH3 adsorption.