CHARACTERIZATION OF MOO3-P2O5-ZRO2 CATALYSTS - AN OXIDE-SUPPORTED MIXED-OXIDE

P2O5/ZrO2, MoO3/ZrO2 and MoO3-P2O5/ZrO2 samples have been prepared by impregnation of a commercial zirconia support with ammonium phosphate and/or heptamolybdate aqueous solutions. The structural and morphologi cal properties have been studied by XRD diffraction, nitrogen adsorpti on-desorption experiments and skeletal FT-LR and FT-Raman spectra. Ori ginal zirconia is in monoclinic phase with traces of tetragonal phase. Only Mo and P amount higher than the theoretical monolayer molybdite is observed. The incorporation of P and/or Mo causes a slight decrease in the value of the specific surface area with respect to pure suppor t. All samples are mesoporous, whose texture can be described by tubul ar pores with widened parts. Surface MexOy (where Me = P or Mo) groups have been detected. Fourier transform infrared spectra of adsorbed am monia and carbon dioxide show that the addition of Mo and/or P on zirc onia causes a relevant increase of the surface acidity and destroys th e surface nucleophilic oxygen present on the pure support. (C) 1998 El sevier Science S.A. All rights reserved.