Mechanistic Studies of Methanol Oxidation to Formaldehyde on Isolated Vanadate Sites Supported on High Surface Area Anatase

Journal Article · Mon Jun 01 04:00:00 EDT 2009 · J. Phys. Chem. C111:14530,2007

OSTI ID:954013

Bronkema, J L; Leo, D C; Bell, A T

The mechanism for methanol oxidation on both TiO{sub 2} and V/TiO{sub 2} was investigated using temperature-programmed experiments with in-situ infrared spectroscopy. Infrared and Raman spectroscopy, along with XANES, show that the V/TiO{sub 2} sample consists predominantly of isolated VO{sub 4} units after calcination. Methanol was found to adsorb on the catalyst in three ways at 323 K: (1) molecularly, (2) across Ti-O-Ti bonds to form Ti-OCH{sub 3}/Ti-OH pairs, and (3) across V-O-Ti bonds to form V-OCH{sub 3}/Ti-OH pairs. Upon heating, two desorption peaks for CH{sub 3}OH and H{sub 2}O were observed on all samples below 500 K. Although TiO{sub 2} produced small amounts of CH{sub 2}O, the addition of vanadium greatly enhanced the rate of formaldehyde formation. Also, on the V/TiO{sub 2} samples, it was noticed that the Ti-OCH{sub 3} groups disappear much more rapidly than on TiO{sub 2} alone. This is likely due to the reverse spillover of methoxide species from Ti to V, with the reaction occurring at lower temperatures at the vanadium center. Formate species were also detected during the experiments, and they are assumed to be intermediates in the decomposition of formaldehyde to CO, CO{sub 2}, and H{sub 2}O. The apparent activation energy of V/TiO{sub 2} for the formation of CH{sub 2}O is 16 kcal/mol.

• Research Organization: Stanford Linear Accelerator Center (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 954013
• Report Number(s): SLAC-REPRINT-2009-379
• Journal Information: J. Phys. Chem. C111:14530,2007, Journal Name: J. Phys. Chem. C111:14530,2007 Journal Issue: 39 Vol. 111; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
ACTIVATION ENERGY
CALCINATION
CATALYSTS
DECOMPOSITION
DESORPTION
FORMALDEHYDE
FORMATES
HEATING
METHANOL
OXIDATION
Other
CHEM
PHYS
RAMAN SPECTROSCOPY
SPECTROSCOPY
SURFACE AREA
VANADATES
VANADIUM