WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies (Articolo in rivista)

Type

• Prodotto della ricerca (Classe)
• Articolo in rivista (Classe)

Label

• WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies (Articolo in rivista) (literal)

Anno

• 2003-01-01T00:00:00+01:00 (literal)

Alternative label

• G. Ferraris, S. De Rossi, D. Gazzoli, I. Pettiti, M. Valigi, M. Magnacca, C. Morterra (2003)
  WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies
  
  (literal)

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• G. Ferraris, S. De Rossi, D. Gazzoli, I. Pettiti, M. Valigi, M. Magnacca, C. Morterra (literal)

Pagina inizio

• 119 (literal)

Pagina fine

• 128 (literal)

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• Impact factor 2.258 (literal)

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• 240 (literal)

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• The rationalization of the catalytic activity of supported catalysts requires a knowledge of the dispersion of the active species in order to draw a correlation between active metal content and catalytic behavior. Many studies have therefore investigated the surface coverage of the support by the active species for various catalytic reactions. The surface coverage can be studied by various techniques, notably spectroscopy and volumetric adsorption analysis. These two methods, based on the chemisorption of probe molecules either on the free portion of the support surface or on the supported species, are complementary in that the former identifies the surface adduct whereas the latter provides overall quantitative data. These studies are here applied to the W/ZrO2 system, active for the isomerization of light hydrocarbons, and show that the high activation temperature (1073 K) causes an interaction between tungsten oxide and zirconia. This interaction affects some support behaviours, such as crystallization and sintering, and the dispersion of tungsten species. By leaching the catalysts with an ammonia solution, we removed crystalline WO3 and tungsten species not directly anchored to the support, and determined the fraction of the tungsten interacting with ZrO2. It has so developed a reliable method to determine the surface coverage of the support by the active tungsten species. (literal)

Note

• ISI Web of Science (WOS) (literal)

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• - 1: CNR IMIP Section MICE - 2 : University \"La Sapienza\" Roma, 3 : University of Turin (literal)

Titolo

• WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies (literal)

Abstract

• The adsorption of CO at 77K on zirconia-supported tungsten oxide (ZW) samples prepared by equilibrium adsorption or by impregnation and with tungsten content up to 12.4 W atoms nm-2 was studied with the aim of determining the coverage of ZrO2 surface by the supported tungsten oxospecies. As an essential background for quantitative volumetric measurements,ZW samples were investigated by FT-IR spectroscopy to identify the surface sites responsible for theCOadsorption. FT-IR showed that CO adsorbed selectively and irreversibly on Zr4+ cus centers of the support surface, but not on W6+ cus sites. By volumetric determinations, the coverage of the zirconia surface by tungsten oxospecies was about 50% at maximum, irrespective of the preparation procedure and of the support crystallographic modification (monoclinic or tetragonal). Zirconia coverage remained significantly unchanged after leaching with a NH3 solution that removed tungsten oxospecies not directly interacting with the zirconia surface. This finding indicates that ZrO2 support coverage depends mainly on the tungsten species strongly anchored to the zirconia surface. (literal)

Prodotto di

• Istituto di Nanotecnologia (NANOTEC) (Istituto)
• Dinamica dei processi atomici e molecolari (MD.P03.026.001) (Modulo)

Autore CNR

• SERGIO DE ROSSI (Persona)
• GIOVANNI FERRARIS (Unità di personale interno)

Insieme di parole chiave

• Keywords of "WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies" (Insieme di parole chiave)

Incoming links:

Prodotto

• Istituto di Nanotecnologia (NANOTEC) (Istituto)
• Dinamica dei processi atomici e molecolari (MD.P03.026.001) (Modulo)

Autore CNR di

• SERGIO DE ROSSI (Persona)
• GIOVANNI FERRARIS (Unità di personale interno)

Insieme di parole chiave di

• Keywords of "WOx/ZrO2 Catalysts. Part 3. Surface coverage as investigated by low temperature CO adsorption: FT-IR and volumetric studies" (Insieme di parole chiave)