Monoclinic and tetragonal high surface area sulfated zirconias in butane isomerization: CO adsorption and catalytic results

In the present study high surface area monoclinic and tetragonal sulfated z irconia samples both active in n-butane isomerization were prepared from th e same hydroxide precursor in a navel one-step hydrothermal process. The pr ocess is studied via analysis of intermediate stages of the product formati on. The monoclinic samples show a catalytic activity in n-butane isomerizat ion lower by about a factor of 4 compared to the tetragonal samples, althou gh the acidity as analyzed by CO adsorption was found to be similar. This s uggests, that it is not only the acidity of sulfated zirconia that determin es the catalytic performance. The results support the bimolecular mechanism , for which a favorable arrangement of surface groups is necessary. The sur face structure of tetragonal zirconia seems to be better suited than that o f the monoclinic zirconia, although the presented monoclinic zirconia perfo rms substantially better than claimed in many publications, where the monoc linic phase is typically assumed to be inactive. (C) 2001 Academic Press.