AES and TDS study of the adsorption of NH sub 3 and NO on V sub 2 O sub 5 and TiO sub 2 surfaces: Mechanistic implications

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90135-8· OSTI ID:6832586

Odriozola, J A; Heinemann, H; Pereira, P ^[1]; Somorjai, G A ^[2]; de la Banda, J F.G. ^[3]

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1. Lawrence Berkeley Laboratory, CA (USA)
2. Univ. of California, Berkeley (USA)
3. Instituto de Catalisis y Petroleoquimica, Madrid (Spain)

The adsorption of NH{sub 3} and NO on pure V{sub 2}O{sub 5} and on TiO{sub 2} samples at pressures (ca. 25 Torr) and temperatures (room temperature to 675 K) close to those used in industry with V{sub 2}O{sub 5}/TiO{sub 2} catalysts to carry out the NO reduction with NH{sub 3} has been studied by Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS), using a UHV chamber equipped with a built-in high pressure cell (up to 1 atm). NH{sub 3} adsorption takes place over the whole range of temperatures studied on TiO{sub 2} and on V{sub 2}O{sub 5} as well as on reduced V{sub 2}O{sub 5} surfaces. NO adsorption occurs only on TiO{sub 2} and on reduced V{sub 2}O{sub 5} but not on oxidized V{sub 2}O{sub 5} surfaces. It is shown that NH{sub 3} reduces the vanadium pentoxide surface resulting in the production of N{sub 2}O. The presence of N{sub 2}O, NO, and O{sub 2} results in the reoxidation of the vanadium surface with the nitrogen oxides being converted into N{sub 2}. No evidence for the NO + NH{sub 3} reaction has been obtained on the TiO{sub 2} surface. However, NO adsorption on TiO{sub 2} appears to be a main factor for the catalyst effectiveness in V{sub 2}O{sub 5}TiO{sub 2} samples since it may provide a source of NO at the interface of vanadia islands on TiO{sub 2} in the actual catalyst. Finally, from TDS and AES data a reaction mechanism is suggested that may explain the reduction of NO to N{sub 2} as well as the side reaction responsible for the production of N{sub 2}O.

• OSTI ID: 6832586
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 119:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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