Studies on PO4 (3-)/ZrO2 .1. Effect of H3PO4 on textural and acidic properties of ZrO2

Abstract

A series of PO43-/ZrO2 samples with PO43- loading in the range 2.24 to 37.5 wt% have been prepared (by impregnation of H3PO4 with Zr(OH)4 and calcination) and characterized by chemical analysis, XRD, FTIR, nitrogen adsorption-desorption isotherms, and acid sites. XRD pattern and FTIR spectra confirm the formation of quasi-amorphous tetragonal zirconia at 400 degrees C and a well-crystallized tetragonal phase at 600 degrees C. Nitrogen adsorption-desorption studies at liquid nitrogen temperature show that samples prepared without and with 37.5 wt% PO43- possess mesopores in the range 5.2 to 5.9 mn, while samples prepared in the range 2.24 to 32.9 wt% PO43- have large surface areas and contain predominantly micropores (in the range 0.6 to 0.7 mn) along with some mesopores. While the loading of 2.74 less than or equal to [PO43-] less than or equal to 37.5 wt% stabilizes the tetragonal phase, its presence up to 19.87 wt% increases the surface area and number of acid sites. (C) 1996 Academic Press, Inc.