Catalytic reduction of NO by CO over rhodium catalysts. 2. Effect of oxygen on the nature, population, and reactivity of surface species formed under reaction conditions

Journal Article · Sat Apr 01 04:00:00 EST 2000 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1999.2785· OSTI ID:20030513

Kondarides, D I; Chafik, T; Verykios, X E

The effect of oxygen on the nature, population, and reactivity of surface species formed during reduction of NO by CO over Rh/TiO{sub 2} catalysts has been examined employing FTIR and transient MS techniques. It has been found that the activity of Rh is hindered by accumulation of surface oxygen originating from NO decomposition and gas-phase oxygen in the feed. Adsorbed CO and reduced TiO{sub 2{minus}x} species in the vicinity of Rh particles act as oxygen atom scavengers and, under fuel-rich conditions, remove atomic oxygen from the surface and restore the catalytic properties. Results of the present study provide additional evidence that production of N{sub 2} is related to dissociation of adsorbed Rh-NO{sup {minus}} while production of N{sub 2}O is related to the presence of Rh(NO){sub 2}. The presence of reduced RH{sup 0} sites is necessary for the formation of both reduction products. In the absence of oxygen in the feed, surface isocyanate species are also observed under reaction conditions. Their formation requires the presence of adjacent Rh{sup 0}-CO and reduced Rh{sup 0} sites. Although these species are favored under conditions in which NO conversion to reduction products is observed, there is no evidence that they are catalytically active species.

• Research Organization: Univ. of Patras (GR)
• OSTI ID: 20030513
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 119; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
33 ADVANCED PROPULSION SYSTEMS
54 ENVIRONMENTAL SCIENCES
CARBON MONOXIDE
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
NITRIC OXIDE
OXYGEN
RHODIUM
SELECTIVE CATALYTIC REDUCTION