Improvement of the catalytic isomerization performance for sulfated zirconias by use of templating techniques

Abstract

Abstract New sulfated zirconias covering a wide range of pore diameters from micropores to macropores have been prepared by a combined use of two different structure-directing templates. The catalytic performance of these sulfated zirconias for the n -butane isomerization could be improved significantly compared to a standard displaying a maximum rate of isomerization of 1490 μmol/g h at 423 K. The materials remained their high activity even at 348 K. Moreover, deactivated materials could be reactivated to the original activity in an air-flow at 673 K several times. The newly designed materials were fully characterized by XRD, XPS, TPD of ammonia, IR spectroscopy and N 2 adsorption to describe the formation of active surface centres and their morphology. The formation of active pyrosulfates with sulfate bands above 1400 cm −1 was followed by DRIFTS. An increased ratio of Bronsted-to-Lewis centres could be detected which can be accounted for the unexpected high activity.