The Balance Between Reactivity and Stability of Modified Oxide Surfaces Illustrated by the Behavior of Sulfated Zirconia Catalysts

The stability of a series of sulfated zirconia catalysts, promoted with up to 2 wt% iron or manganese, in their calcined state was investigated. Phase composition, nature of surface sulfate species, degree of hydroxylation, and butane isomerization activity changed during aging over months in various atmospheres and during milling. The metastability of small oxide particles is discussed, including literature data on alumina, titania and other oxides. Catalytically active fractions of a material easily transition into more stable, less active forms

The role of the "glow phenomenon" in the preparation of sulfated zirconia catalysts

During the calcination procedure that is necessary to obtain sulfated zirconia catalysts from hydroxide precursors an exothermic reaction occurs in the heat-up period which can lead to a rapid overheating ('glow') of the sample bed; the batch size is identified as a critical parameter that influences heat transfer and thus the extent of the temperature overshoot and the catalytic activity of the product