Alumina-Promoted Sulfated Zirconia System:  Structure and Microstructure Characterization

The Al 2 O 3 promotion of ZrO 2 /SO 4 has been shown to influence n -butane isomerization activity. In this paper we report a study of the influence of a small addition of Al 2 O 3 (0.6−10.3 wt %) onto the ZrO 2 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 Al 2 O 3 content is increased, a decrease of the ZrO 2 particle sizes is observed, paralleled by an increase of the amorphous phase. When the Al 2 O 3 content is larger than 3.7 wt %, only amorphous phase can be detected. No crystalline peaks of Al 2 O 3 were ever observed. These data were supported also by TEM and Raman measurements.