Alumina-promoted sulfated zirconia system: structure and microstructure characterization

The Al2O3 promotion of ZrO2/SO4 has been shown to influence n-butane isomerization activity. In this paper we report a study of the influence of a small addition of Al2O3 (0.6-10.3 wt %) onto the ZrO2 structure and microstructure. The addition of alumina is related to an increase of the surface area. A detailed X-ray diffraction analysis by the use of the modified Rietveld method allowed us to follow the changes in the crystalline phases and to quantify the amount of amorphous phase. When the Al2O3 content is increased, a decrease of the ZrO2 particle sizes is observed, paralleled by an increase of the amorphous phase. When the Al2O3 content is larger than 3.7 wt %, only amorphous phase can be detected. No crystalline peaks of Al2O3 were ever observed. These data were supported also by TEM and Raman measurements.