Dealuminated H-Y zeolites: Influence of the number and type of acid sites on the catalytic activity for isopropanol dehydration

The effect of the number and type of acid sites of H-Y catalysts dealuminat ed by different techniques on the dehydration of 2-propanol has been studie d in this work. The increase in the number of acid sites generally increase s the activity for the formation of both main products, propene and diisopr opyl ether. The presence of different types of extraframework phases genera ted by steaming or treatment by SiCl4 or by (NH4)(2)SiF6 treatment affects the activity and selectivity in different ways. The yield of propene is alw ays higher than that of ether but shows a minimum at 95 degrees C in the ca talysts with few acid sites and Si-Al amorphous phases formed by dealuminat ion with SiCl4. Highly crystalline catalysts with relatively high acidity ( parent or dealuminated by (NH4)(2)SiF6 or steaming/EDTA) give propene yield s higher than ether's only at temperatures higher than 95 degrees C. The pr esence of extraframework Al generated by relatively low-temperature steamin g reduces the catalyst activity for both products. A statistical analysis o f the turnover frequency at different temperatures showed that all acid sit es of the crystalline zeolitic phase participate in the formation of both p roducts, while the catalytic sites of the amorphous phase formed by SiCl4 c ontribute at relatively low temperatures with propene as the main product. A common compensation effect for the formation of both products exists for all the tested crystalline dealuminated H-Y catalysts.