Chromia supported on titania. V. Preparation and characterization of supported CrO{sub 2}, CrOOH, and Cr{sub 2}O{sub 3}
- Swiss Federal Inst. of Technology, Zuerich (Switzerland); and others
Chromium dioxide, CrO{sub 2}, supported on titania was prepared by impregnation of the carrier with chromium(III) nitrate (10 wt% Cr{sub 2}O{sub 3} on TiO{sub 2}) followed by its thermal decomposition and calcination under oxygen at 573 K. X-ray amorphous CrO{sub 2} (ca. 95%) was found to be present after calcination. The chemical and structural changes of the supported CrO{sub 2} phase during thermal treatment in hydrogen, oxygen, air, argon, and ammonia, and under SCR conditions (selective catalytic reduction of NO by NH{sub 3} in excess oxygen) were investigated by thermoanalytical methods, (ferro)magnetic resonance, XRD, and UV-visible and IR spectroscopy. Supported CrO{sub 2} is reversibly reduced under hydrogen, producing antiferromagnetic CrOOH on titania. Reoxidation to CrO{sub 2} occurs at temperatures above 520 K in air, under oxygen, and under SCR conditions (NO + NH{sub 3} + O{sub 2}). CrOOH and CrO{sub 2} were decomposed at T {approx}770 K under argon to antiferromagnetic Cr{sub 2}O{sub 3}; the decomposition is complete only at T > 1000 K. The composition and thermal stability of the supported oxides are compared to the corresponding bulk phases CrO{sub x}. 35 refs., 11 figs., 1 tab.
- OSTI ID:
- 224003
- Journal Information:
- Journal of Catalysis, Vol. 157, Issue 2; Other Information: PBD: Dec 1995
- Country of Publication:
- United States
- Language:
- English
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