FTIR studies of adsorption of NO, NO2 and N2O on layered V2O5/ZrO2

Abstract

The adsorption of NO, NO, and N 2 0 at various temperatures on mono-and multi-layered V20,/Zr0, catalysts prepared by t h e gas-phase method h a s been investigated by IR spectroscopy. On t h e reduced samples of both mono-and multi-layer catalysts, NO is adsorbed giving mono-and di-nitrosylic species. On t h e oxidized form of t h e monolayer catalyst, only nitrite and nitrate species are formed and no nitrosylic species are formed. NO2 adsorbed on reduced multilayer catalysts exhibits IR bands due to nitrate species together with minor amounts of nitrosylic species. The surface nitrosylic species were less readily formed on the monolayer catalyst than on multilayer catalysts. Quantitative analysis of the V=O band in t h e region 1100-900 cm-' indicates that only the surface V=O species in t h e top layer of the catalyst interacts with the adsorbed species. Both NO and NO, reoxidize t h e catalyst surface at higher temperatures and the monolayer catalyst was less readily oxidized than t h e multilayer catalyst.

Redox Properties of Vanadium Ions in SBA-15-Supported Vanadium Oxide: An FTIR Spectroscopic Study

“…Miyata et al 31 , which they assigned to bridged, bidentate, and monodentate species, respectively. These authors 30 believe that the respective nitrato species form after interaction of NO 2 with oxygen from the vanadyl groups. By analogy to these results, we can assign the bands at 1639 and 1573 cm -1 in our spectra to the ν as -(NO 2 ) stretching modes of bridged and bidentate NO 3 -complexes.…”

“…18 Summarizing, these results show that CO is a good probe molecule for determination of the oxidation state, but not the coordination state of surface vanadium ions. Previous studies on NO adsorption on supported vanadia have shown that both V 4+ and V 3+ ions can form dinitrosyls, 17,[29][30][31][32] and it was concluded that NO is a better probe molecule for determining the coordination state of vanadium sites. 29 For a detailed understanding of catalyst properties, the use of materials with well-defined structure is necessary.…”

FTIR Spectroscopic Characterization of NOxSpecies Adsorbed on ZrO2and ZrO2−SO42-

“…Some authors [10][11][12] have reported that nitrosylic species cannot form on pure zirconia, whereas others [13][14][15] have observed coordination of NO to Zr 4+ sites. Mononitrosyl species have been found on sulfated zirconia.…”

“…However, interpretations of the bands in this region are quite contradictory. A typical example is the band at 1180-1190 cm -1 , which has been assigned to nitrite 10,13,15 or nitrate 12 species. Greater amounts of NO x species (mainly nitrates and nitrites) on ZrO 2 are observed when NO and O 2 are coadsorbed at room temperature.…”

“…Mononitrosyl species have been found on sulfated zirconia. 11 The adsorption of NO on pure [10][11][12][13][14][15] and sulfated zirconia 11 at room temperature gives rise to bands in the nitrito-nitrato region. However, interpretations of the bands in this region are quite contradictory.…”