Publications
Two pairs of Brønsted acid sites have been identified in H,Na-Y zeolite, located in the supercage and in the sodalite cage, which upon ultrastabilization (dealumination) are transformed into pairs of Brønsted and Lewis acid sites. This mild postsynthetic modification step is an important process for converting this material into an active catalyst for large-scale commercial reactions. Pairing structures and their transformations have been investigated using 1H double-quantum NMR experiments for dehydrated zeolite, H,Na-Y, and its ultrastabilized form, H,Na-USY. This enables the detection of pairs of Brønsted and Lewis acid sites with unprecedented 1H resolution and distinguish them from isolated acid sites. The dealumination is also observed by static, ultrawideline 27Al solid-state NMR experiments.