Surface coverage of WO3/ZrO2 catalysts measured by ion scattering spectroscopy and low temperature CO adsorption

Vaidyanathan, Nithya; Houalla, Marwan; Hercules, David M.

doi:10.1002/(sici)1096-9918(19980515)26:6<415::aid-sia375>3.0.co;2-c

Cited by 26 publications

(3 citation statements)

References 6 publications

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“…The surface density was, thus, expressed as the number of atoms of Nb or W per nm 2 of the titania support. For WO x /TiO 2 , the theoretical coverage was calculated assuming that a full monolayer corresponds to 4.9 W atom nm À2 [24,25]. For NbO x /TiO 2 , the theoretical coverage was estimated considering that each Nb 2 O 5 unit occupies 0.32 nm 2 [26].…”

Section: Preparation Of the Catalystsmentioning

confidence: 99%

Acidity of titania-supported tungsten or niobium oxide catalystsCorrelation with catalytic activity

Onfroy

Clet

Bukallah

et al. 2006

Applied Catalysis A: General

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The acidity of catalytic systems based on tungsten oxide or niobium oxide supported on titania was compared. Two series with metal contents up to 3.6 atom nm À2 were prepared by incipient wetness impregnation of the titania support with ammonium metatungstate or niobium oxalate solutions. Characterization of both systems by X-ray diffraction and Raman spectroscopy studies did not show evidence of bulk metal oxide formation. The acidity was monitored by adsorption of 2,6-dimethylpyridine (2,6-lutidine) followed by infrared spectroscopy. The catalytic activity was tested for the reaction of isopropanol dehydration.At a reaction temperature of 403 K, WO x /TiO 2 catalysts were inactive for a surface density of W 1.2 W atom nm À2 . Above this loading, the activity increased progressively with increasing W content. Similar evolution was observed for the abundance of relatively strong Brønsted acid sites (i.e. able to retain lutidine at 573 K). In contrast, NbO x /TiO 2 catalysts were essentially inactive at this reaction temperature and a higher reaction temperature (473 K) was required to reach a comparable catalytic activity. No threshold of Nb loading for the development of catalytic activity was observed. Similar behavior was evidenced for the abundance of medium strength Brønsted acid sites (able to retain lutidine at 523 K). For both systems, a direct correlation between the catalytic activity and the abundance of Brønsted acid sites was observed. #

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Section: Preparation Of the Catalystsmentioning

confidence: 99%

Acidity of titania-supported tungsten or niobium oxide catalystsCorrelation with catalytic activity

Onfroy

Clet

Bukallah

et al. 2006

Applied Catalysis A: General

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show abstract

“…For this reason, many researchers have examined the system with various spectroscopic techniques, such as photoelectron spectroscopy (X‐ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy), infrared spectroscopy, etc. Those techniques have provided valuable results, such as chemical state change of metal atoms, bonding between adsorbed CO molecules and Cu atoms, adsorption site, coverage, etc. However, there has been no information on any modification of atomic and/or electronic geometry of the Cu surface that might happen with CO adsorption.…”

Section: Introductionmentioning

confidence: 99%

An X‐ray absorption spectroscopic study of carbon monoxide‐adsorbed Cu surface

Kim

Tian

Kim³

et al. 2014

Surface & Interface Analysis

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a Adsorption/interaction of Carbon monoxide (CO) on a catalytic surface is the key step in electrochemical conversion of CO2 for environmental consideration. Copper (Cu) is known to be the most efficient catalyst for this purpose. Thus, this paper investigates effects of CO adsorption on the electronic/atomic state of polycrystalline Cu surface by using x-ray absorption spectroscopy (XAS). X-ray absorption near-edge structure (XANES) tells that the Cu K-edge shift +0.2 eV on adsorbing CO. Extended x-ray absorption fine structure (EXAFS) analysis informs that CO adsorption disturbs Cu surface, i.e. increase of Cu-Cu bonding distance and decrease of the coordination number of the first nearest neighbor. Both the results of XANES and EXAFS imply decrease of d-electron density of Cu on the adsorption. Demonstrated is that XAS is very useful in studying the surface phenomena of a catalyst but requires further efforts.

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“…Similar to the influence of other doping metals, the interaction between tungsten oxide and zirconia hinders the crystallization of zirconia from the amorphous status and further transition from tetragonal to monoclinic phase. ,, The dispersion of tungsten on the zirconia surface can affect its acidity and activity dramatically; thus, a lot of research focused on the structure of WO x domains in TZ. ,− Iglesia and co-workers proposed a three-stage growth of the WO x domain with the increase of tungsten concentration as shown in Figure . , …”

Section: Zirconia As a Catalyst Supportmentioning

confidence: 99%

Zirconia-Based Solid Acid Catalysts for Biomass Conversion

et al. 2021

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Biomass conversion is of great importance in the sustainable manufacturing of green chemicals, and it is well known as a viable way to deal with the shortage of fossil fuels and carbon emissions. Most biomass conversions are often governed by carbocation chemistry, which requires acidic active sites on the catalysts. Solid acid catalysts are considered as one of the most popular heterogeneous catalysts and are widely applied in biomass conversion. Among them, zirconia-based catalysts have received vast attentions as either a catalyst itself or a catalyst support owing to their desirable catalytic properties. This review presents bare zirconia and zirconia-based support catalysts for their wide applications in biomass conversion reactions. Various aspects of zirconia-based acid catalysts including synthesis methods, catalyst structures, acidities, reaction mechanisms, and applications are discussed. Thanks to their strong acidity, remarkable stability, versatility of modification, high catalytic performances, easy catalyst recovery and reusability, and environmentally friendliness, it is believed that zirconia and zirconia-based catalysts are one of the most practical and multifunctional solid acid catalysts in many acid-catalyzed biomass conversions.

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Surface coverage of WO3/ZrO2 catalysts measured by ion scattering spectroscopy and low temperature CO adsorption

Cited by 26 publications

References 6 publications

Acidity of titania-supported tungsten or niobium oxide catalystsCorrelation with catalytic activity

Acidity of titania-supported tungsten or niobium oxide catalystsCorrelation with catalytic activity

An X‐ray absorption spectroscopic study of carbon monoxide‐adsorbed Cu surface

Zirconia-Based Solid Acid Catalysts for Biomass Conversion

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