Chromia supported on titania. VI. Properties of different chromium oxide phases in the catalytic reduction of NO by NH{sub 3} studied by in situ diffuse reflectance FTIR spectroscopy
- Swiss Federal Inst. of Technology, Zuerich (Switzerland); and others
Chromia on titania catalysts containing different chromium oxide phases, ie., CrO{sub 2}, CrOOH, and Cr{sub 2}O{sub 3}, have been prepared and tested for the low-temperature selective catalytic reduction of nitric oxide by ammonia (SCR). The different chromium oxide phases (10 wt% total chromium oxide content) differ in their activity and selectivity to N{sub 2}. Supported CrOOH is oxidized to CrO{sub 2} under SCR conditions above 570 K. The highest activity paired with a high selectivity to N{sub 2} (>90%) is found for amorphous Cr{sub 2}O{sub 3} supported on titania prepared by decomposition of CrOOH/TiO{sub 2} under mild conditions. Crystallization of Cr{sub 2}O{sub 3} induced at higher temperatures reduces the activity significantly. The surface adsorption sites for the components of the SCR feed gas were investigated using temperature-programmed desorption combined with in situ diffuse reflectance FTIR spectroscopy. NO, which is adsorbed as a nitrate species, is most abundant on CrO{sub 2}, and seems to be responsible for the formation of undesired N{sub 2}O at temperatures below 400 K over catalysis containing this chromium oxide. 26 refs., 6 figs., 2 tabs.
- OSTI ID:
- 224004
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 157; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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