Structure of a Rh/TiO/sub 2/ catalyst in the strong metal-support interaction state as determined by EXAFS

Journal Article · Thu Jul 03 04:00:00 EDT 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100405a001· OSTI ID:5659201

Koningsberger, D C; Martens, J H.A.; Prins, R; Short, D R; Sayers, D E

Reduction of a highly dispersed 2.85 wt% Rh/TiO/sub 2/ catalyst at 473 K after previous calcination at 623 K resulted in EXAFS whose primary contributions are due to nearest rhodium (average coordination number of 3.1 and distance of 2.67 A) and oxygen neighbors (coordination 2.5 and distance 2.71 A). These oxygen neighbors originated at the metal-support interface. The average rhodium-rhodium coordination number did not change in the SMSI state produced by reducing the catalyst at 673 K. However, the average coordination distance contracted by 0.04 A with an accompanying decrease of the Debye-Waller factor of the Rh-Rh bond of 0.0012 A/sup 2/. This is due to the fact that in the SMSI state the surface of the metal particles is not covered with chemisorbed hydrogen. The SMSI state leads to a structural reorganization of the support in the vicinity of the rhodium metal particles. This can be concluded from the appearance of a Rh-Ti bond at 3.42 A in the SMSI state coupled with the fact that the average coordination number of the rhodium-support oxygen bonds does not increase. Other types of rhodium-oxygen bonds could not be detected with EXAFS in this state. Thus, these results provide no evidence for coverage of the metal particle by a suboxide of TiO/sub 2/ in the SMSI state.

• Research Organization: Eindhoven Univ. of Technology, Netherlands
• OSTI ID: 5659201
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:14; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CALCINATION
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
ELEMENTS
EMISSION SPECTROSCOPY
EXPERIMENTAL DATA
FLUORESCENCE SPECTROSCOPY
HIGH TEMPERATURE
INFORMATION
MEDIUM TEMPERATURE
METALS
NONDESTRUCTIVE ANALYSIS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
PYROLYSIS
REDUCTION
RHODIUM
SPECTROSCOPY
THERMOCHEMICAL PROCESSES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY EMISSION ANALYSIS
X-RAY FLUORESCENCE ANALYSIS