INFLUENCE OF ZRO2 CRYSTALLINE-STRUCTURE AND SULFATE ION CONCENTRATIONON THE CATALYTIC ACTIVITY OF SO42- ZRO2

The catalytic behavior of SO42--ZrO2 in the n-butane isomerization rea ction was studied. Both ZrO2 crystalline structure and SO42- concentra tion were analyzed. ZrO2 samples were obtained from ZrCl4 in different reaction media, thus allowing us to obtain tetragonal and monoclinic phases separately. The SO42- concentration over ZrO2 was the same by s ulfating amorphous or crystalline materials. The sulfate addition over amorphous Zr(OH)(4) generated strong acid sites, which are active in n-butane isomerization. The catalytic activity showed a maximum at cal cination temperatures between 873 and 893 K, where the Lewis acidity i s higher. The tetragonal phase is present under these conditions, as s hown by XRD patterns. The same results were obtained with samples synt hesized from another precursor. Coke deposition or water presence prod uced catalyst deactivation. (C) 1995 Academic Press, Inc.