Infrared studies of CO and/or NO adsorption on reduced W/Al sub 2 O sub 3 catalysts

Journal Article · Sun Sep 01 00:00:00 EDT 1991 · Journal of Catalysis; (United States)

OSTI ID:5757783

Yan, Yushan; Xin, Qin; Jiang, Shaocong; Guo, Xiexian ^[1]

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1. Dalian Inst. of Chemical Physics (China)

Infrared spectroscopy (IR) has been used to investigate CO and/or NO adsorption on reduced W/Al{sub 2}O{sub 3} catalysts. The effect of reduction temperature and tungsten-loading was studied. Three different kinds of surface W-sites were identified according to the IR spectra (possibly W{sup 5+}, W{sup 4+} (I), and W{sup 4+} (II)). Up to three IR bands at 2,198, 2,176, and 2,154 cm{sup {minus}1} for adsorbed CO, which are best assigned to W{sup 5+} (CO), W{sup 4+} (I) (CO), and W{sup 4+} (II) (CO), respectively, were observed. Only two kinds of surface complexes, W{sup 5+} (NO) with a single band at 1,843 cm{sup {minus}1} and W{sup 4+} (I and II) (NO){sub 2} with coupled bands at 1,780 and 1,691 cm{sup {minus}1}, were formed upon NO contact. In the case of CO + NO and NO + CO (added in sequence) coadsorption, a surface complex in the form of (CO) W{sup 4+} (I) (NO){sub 2}, which gave three IR bands at about 2,117, 1,801, and 1,725 cm{sup {minus}1}, was evidenced in the spectra in addition to W{sup 5+} (CO) and W{sup 4+} (II) (NO){sub 2} on the surface. These observations suggest that W{sup 4+} (I)-sites differ from W{sup 4+} (II)-sites in the coordination state and the coadsorption of CO + NO or NO + CO allows more information about the surface W-sites to be achieved than the corresponding CO or NO single adsorption in IR studies. The adsorption and desorption mechanisms are discussed for the surface complex of (CO) W{sup 4+} (I) (NO){sub 2}. Laser Raman spectroscopy (LRS) and temperature-programmed reduction (TPR) were also employed as complementary techniques to characterize the W/Al{sub 2}O{sub 3} catalysts. The results from these two measurements are in good agreement with the IR results.

• OSTI ID: 5757783
• Journal Information: Journal of Catalysis; (United States), Vol. 131:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON MONOXIDE
ADSORPTION
NITRIC OXIDE
TUNGSTEN
SORPTIVE PROPERTIES
SURFACE PROPERTIES
ABSORPTION SPECTROSCOPY
ALUMINIUM OXIDES
CARBONYLS
CATALYST SUPPORTS
CATALYSTS
DENITRIFICATION
DESORPTION
DESULFURIZATION
INFRARED RADIATION
INFRARED SPECTRA
LASER SPECTROSCOPY
QUANTITY RATIO
RAMAN SPECTROSCOPY
REDUCTION
TEMPERATURE CONTROL
TEMPERATURE DEPENDENCE
TUNGSTEN COMPLEXES
VALENCE
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
CONTROL
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SORPTION
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties