STABILITY OF SURFACE CHROMATE - A PHYSICOCHEMICAL INVESTIGATION IN RELEVANCE TO ENVIRONMENTAL RESERVATIONS ABOUT CALCINED CHROMIA CATALYSTS

The present investigation presents and correlates observed and reporte d characterization results of calcined, supported and unsupported chro mias obtained via various precursor compounds. Studies performed emplo yed a range of surface and bulk analytical techniques, in hopes of a p roper assessment of the stability of surface chromate (Cr(VI)-O) speci es thus generated to thermal decomposition, hydrolysis and reduction. Impacts on the redox catalytic activity were probed towards the decomp osition of H2O2 solutions and the CO oxidation in the gas phase. The r esults have revealed that chromate species established on bulk and dis persed alpha-Cr2O3 particles enjoy high stability against thermal and chemical treatments, and yet contribute to the formation of surface si tes that are catalytically active in redox reactions. This should help lessening environmental reservations about the industrial application of calcined chromia catalysts. (C) 1998 Elsevier Science B.V. All rig hts reserved.