Effect of perchlorate ion on the textural and catalytic activity of zirconia

Abstract

Synthesis and physico-chemical characterization of hydrous zirconia gel were carried out. The perchlorate sorption properties of hydrous zirconia were found to be appreciable and a loading of about 9 wt% was possible in an equilibrium solution of 0.1 M HClO4. Formation of perchlorated zirconia has been investigated using XRD, TG/DTA and FTIR. Nitrogen adsorption desorption isotherms at liquid nitrogen temperature were used to explore the surface area and porosity of the samples. The nitration of chlorobenzene was used as the test reaction. It was observed that finely divided zirconia with mesoporous texture can be prepared using preshaped precipitating medium. The XRD patterns revealed that perchlorate ion stabilizes the tetragonal phase of zirconia. TG/DTA and FTIR studies supported the presence of perchlorate moiety in the sample. The surface acidity measurement using different organic bases irreversibly adsorbed on zirconia surface showed that perchlorated samples are highly acidic up to a temperature of 250 degrees C, which drastically decreased on further heating. The material modified with perchlorate ion was found to be an efficient and selective catalyst for solvent-free mononitration of chlorobenzene. (C) 1999 Elsevier Science B.V. All rights reserved.