Temperature-programmed desorption/reaction and in situ spectroscopic studies of vanadia/titania for catalytic reduction of nitric oxide

Journal Article · Fri May 01 04:00:00 EDT 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90283-N· OSTI ID:6915630

Srnak, T Z; Dumesic, J A ^[1]; Clausen, B S; Toernqvist, E; Topsoee, N -Y ^[2]

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1. Univ. of Wisconsin, Madison (United States)
2. Haldor Topsoee Research lab., Lyngby (Denmark)

Temperature-programmed desorption (TPD) and temperature-programmed reaction (TPR) studies were conducted to probe the catalytic chemistry of nitric oxide reduction by ammonia on thin films of titania, vanadia, and vanadia/titania at vacuum conditions, as well as on powdered catalysts under flow conditions. The activation energies and enthalpies of ammonia desorption estimated in vacuum and powder TPD studies, respectively, are comparable, consistent with nonactivated ammonia adsorption. The enthalpies of ammonia desorption range from about 18 to 26 kcal/mol over vanadia, vanadia/titania, and titania, with the enthalpy increasing with decreasing vanadia content. In situ IR measurements of the surface ammonia coverages under reaction conditions for the selective catalytic reduction (SCR) of nitric oxide suggest that ammonia adsorption on Lewis acid sites is stronger than on Broensted acid sites and ammonia adsorption is not rate determining for the SCR reaction. Significant amounts of adsorbed NO are not present on vanadia/titania surfaces under SCR reaction conditions. Vacuum and powder TPR studies indicate that the activation energy for the formation of N[sub 2] from NO and NH[sub 3] is about 20 kcal/mol, independent of whether the NO species is strongly adsorbed (under vacuum TPR conditions) or weakly adsorbed (under powder TPR conditions).

• OSTI ID: 6915630
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 135:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
AIR POLLUTION CONTROL
AMMONIA
BROENSTED ACIDS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CONTROL
DENITRIFICATION
DESORPTION
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY
ENTHALPY
HYDRIDES
HYDROGEN COMPOUNDS
INFRARED RADIATION
INORGANIC ACIDS
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NITROGEN
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
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OXIDES
OXYGEN COMPOUNDS
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RADIATIONS
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SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM OXIDES