Raman spectroscopic study of V/θ-Al 2O 3 catalysts: Quantification of surface vanadia species and their structure reduced by hydrogen

Zili Wu, Peter C Stair, Sreekala Rugmini, S. David Jackson

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Two interesting topics about supported vanadia catalysts were studied using in situ UV and visible Raman and UV-vis diffuse reflectance spectroscopy (DRS): The quantification of different surface vanadia species and the hydrogen reduction of these vanadia species. Using the diffuse reflectance value as an external standard, we could correct the Raman intensity measurements of V/θ-Al 2O 3 for the self-absorption effect. On the basis of the ability to selectively detect monovanadate (UV-excited), polyvanadate (visible-excited), and V 2O 5 (visible-excited) in the Raman measurements, the distribution of monovanadate, polyvanadate, and V 2O 5 present on dehydrated V/θ-Al 2O 3 samples was successfully quantified as a function of surface VO x density. It is shown that monovanadate species are present at all surface VO x densities studied but are the dominant species at low surface VO x density. Polyvanadate and V 2O 5 are also present and predominate on the surface at intermediate and high surface VO x density. The UV- and visible-excited Raman studies of the V/θ-Al 2O 3 samples reduced in hydrogen show that polyvanadate and V 2O 5 are more easily reduced than monovanadate species. UV Raman is better able to obtain information on reduced vanadia species than visible Raman, mainly because of a decrease in self-absorption and resonance enhancement in the UV region. Comparison of the UV Raman spectra from reduced V/θA1 2O 3 with bulk vanadium oxide compounds suggests that reduced VO x species can assume a V 2O 3-like form. The reduced VO x species redisperse on the support surface upon reoxidation.

Original languageEnglish
Pages (from-to)16460-16469
Number of pages10
JournalJournal of Physical Chemistry C
Volume111
Issue number44
DOIs
Publication statusPublished - Nov 8 2007

Fingerprint

Hydrogen
Vanadates
catalysts
Catalysts
hydrogen
self absorption
reflectance
Vanadium
vanadium oxides
Catalyst supports
Oxides
Raman scattering
Spectroscopy
Raman spectra
augmentation
spectroscopy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Raman spectroscopic study of V/θ-Al 2O 3 catalysts : Quantification of surface vanadia species and their structure reduced by hydrogen. / Wu, Zili; Stair, Peter C; Rugmini, Sreekala; Jackson, S. David.

In: Journal of Physical Chemistry C, Vol. 111, No. 44, 08.11.2007, p. 16460-16469.

Research output: Contribution to journalArticle

@article{b824017f62304af29311591cf0816c07,
title = "Raman spectroscopic study of V/θ-Al 2O 3 catalysts: Quantification of surface vanadia species and their structure reduced by hydrogen",
abstract = "Two interesting topics about supported vanadia catalysts were studied using in situ UV and visible Raman and UV-vis diffuse reflectance spectroscopy (DRS): The quantification of different surface vanadia species and the hydrogen reduction of these vanadia species. Using the diffuse reflectance value as an external standard, we could correct the Raman intensity measurements of V/θ-Al 2O 3 for the self-absorption effect. On the basis of the ability to selectively detect monovanadate (UV-excited), polyvanadate (visible-excited), and V 2O 5 (visible-excited) in the Raman measurements, the distribution of monovanadate, polyvanadate, and V 2O 5 present on dehydrated V/θ-Al 2O 3 samples was successfully quantified as a function of surface VO x density. It is shown that monovanadate species are present at all surface VO x densities studied but are the dominant species at low surface VO x density. Polyvanadate and V 2O 5 are also present and predominate on the surface at intermediate and high surface VO x density. The UV- and visible-excited Raman studies of the V/θ-Al 2O 3 samples reduced in hydrogen show that polyvanadate and V 2O 5 are more easily reduced than monovanadate species. UV Raman is better able to obtain information on reduced vanadia species than visible Raman, mainly because of a decrease in self-absorption and resonance enhancement in the UV region. Comparison of the UV Raman spectra from reduced V/θA1 2O 3 with bulk vanadium oxide compounds suggests that reduced VO x species can assume a V 2O 3-like form. The reduced VO x species redisperse on the support surface upon reoxidation.",
author = "Zili Wu and Stair, {Peter C} and Sreekala Rugmini and Jackson, {S. David}",
year = "2007",
month = "11",
day = "8",
doi = "10.1021/jp074223o",
language = "English",
volume = "111",
pages = "16460--16469",
journal = "Journal of Physical Chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "44",

}

TY - JOUR

T1 - Raman spectroscopic study of V/θ-Al 2O 3 catalysts

T2 - Quantification of surface vanadia species and their structure reduced by hydrogen

AU - Wu, Zili

AU - Stair, Peter C

AU - Rugmini, Sreekala

AU - Jackson, S. David

PY - 2007/11/8

Y1 - 2007/11/8

N2 - Two interesting topics about supported vanadia catalysts were studied using in situ UV and visible Raman and UV-vis diffuse reflectance spectroscopy (DRS): The quantification of different surface vanadia species and the hydrogen reduction of these vanadia species. Using the diffuse reflectance value as an external standard, we could correct the Raman intensity measurements of V/θ-Al 2O 3 for the self-absorption effect. On the basis of the ability to selectively detect monovanadate (UV-excited), polyvanadate (visible-excited), and V 2O 5 (visible-excited) in the Raman measurements, the distribution of monovanadate, polyvanadate, and V 2O 5 present on dehydrated V/θ-Al 2O 3 samples was successfully quantified as a function of surface VO x density. It is shown that monovanadate species are present at all surface VO x densities studied but are the dominant species at low surface VO x density. Polyvanadate and V 2O 5 are also present and predominate on the surface at intermediate and high surface VO x density. The UV- and visible-excited Raman studies of the V/θ-Al 2O 3 samples reduced in hydrogen show that polyvanadate and V 2O 5 are more easily reduced than monovanadate species. UV Raman is better able to obtain information on reduced vanadia species than visible Raman, mainly because of a decrease in self-absorption and resonance enhancement in the UV region. Comparison of the UV Raman spectra from reduced V/θA1 2O 3 with bulk vanadium oxide compounds suggests that reduced VO x species can assume a V 2O 3-like form. The reduced VO x species redisperse on the support surface upon reoxidation.

AB - Two interesting topics about supported vanadia catalysts were studied using in situ UV and visible Raman and UV-vis diffuse reflectance spectroscopy (DRS): The quantification of different surface vanadia species and the hydrogen reduction of these vanadia species. Using the diffuse reflectance value as an external standard, we could correct the Raman intensity measurements of V/θ-Al 2O 3 for the self-absorption effect. On the basis of the ability to selectively detect monovanadate (UV-excited), polyvanadate (visible-excited), and V 2O 5 (visible-excited) in the Raman measurements, the distribution of monovanadate, polyvanadate, and V 2O 5 present on dehydrated V/θ-Al 2O 3 samples was successfully quantified as a function of surface VO x density. It is shown that monovanadate species are present at all surface VO x densities studied but are the dominant species at low surface VO x density. Polyvanadate and V 2O 5 are also present and predominate on the surface at intermediate and high surface VO x density. The UV- and visible-excited Raman studies of the V/θ-Al 2O 3 samples reduced in hydrogen show that polyvanadate and V 2O 5 are more easily reduced than monovanadate species. UV Raman is better able to obtain information on reduced vanadia species than visible Raman, mainly because of a decrease in self-absorption and resonance enhancement in the UV region. Comparison of the UV Raman spectra from reduced V/θA1 2O 3 with bulk vanadium oxide compounds suggests that reduced VO x species can assume a V 2O 3-like form. The reduced VO x species redisperse on the support surface upon reoxidation.

UR - http://www.scopus.com/inward/record.url?scp=36348936602&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=36348936602&partnerID=8YFLogxK

U2 - 10.1021/jp074223o

DO - 10.1021/jp074223o

M3 - Article

AN - SCOPUS:36348936602

VL - 111

SP - 16460

EP - 16469

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 44

ER -