Journal
JOURNAL OF CATALYSIS
Volume 270, Issue 1, Pages 163-171Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2009.12.017
Keywords
Vanadia; Silica; Titania; Methanol oxidation; Kinetics; Theoretical analysis
Categories
Funding
- Office of Energy Research, Office of Basic Energy Sciences, Chemical Science Division, of the US Department of Energy [DE-AC02-05CH11231]
- BP
- National Institutes of Health, National Center for Research Resources, Biomedical Technology Program
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [840505] Funding Source: National Science Foundation
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This study reports the results of a combined experimental and theoretical investigation of a bilayered VOx/TiOx/SiO2 catalyst consisting of vanadia deposited onto silica containing a submonolayer of titania. Raman spectroscopy indicates that Ti atoms are bonded to the silica support via Ti-O-Si bonds, and Raman and EXAFS data indicate that the vandia is present as isolated vanadate groups bonded to the support through V-O-Si and V-O-Ti bonds. For a fixed vanadia surface density (0.7 V/nm(2)), the turnover frequency for methanol oxidation to formaldehyde increases with increasing Ti surface density (0.2-2.8 Ti/nm(2)) and the apparent activation energy decreases. These trends are well represented by a model of the active site and its association with Si and Ti atoms of the support. This model takes into account the distribution of Ti on the silica support, the fraction of active sites with 0, 2, and 3 V-O-Ti support bonds, and the rate parameters determined for each of these active sites determined from quantum chemical calculations and absolute rate theory. (C) 2009 Elsevier Inc. All rights reserved.
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