Strong metal-support interaction: the role of electronic and geometric factors in real Me/TiO/sub 2/ catalysts

Journal Article · Fri Apr 01 04:00:00 EST 1988 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(88)90318-1· OSTI ID:5218143

Shpiro, E S; Dysenbina, B B; Tkachenko, O P; Antoshin, G V; Minachev, K M

XPS, X-ray-induced AES (XAES), AES, SIMS, and ISS studies of metals (Pt, Rh) supported on TiO/sub 2/ powder catalysts combine to give new evidence in favor of electronic nature of SMSI. When reduced at high temperatures (HTR), the XPS spectra, of MeTiO/sub 2/, corrected for extra-atomic relaxation, exhibit negative chemical shifts of core levels along with a gain in intensity of the density of states near the Fermi edge, indicating an increase of electron density on metal clusters. Tauster's model of SMSI is further confirmed by the appearance of mixed RhTi/sup +/ and RhTiO/sup +/ clusters in SIMS spectra of RhTiO/sub 2/ (HTR), which reflect direct interaction between metal atoms and Ti/sup 3 +/ cations. The latter were detected by Ti L/sub 3/M/sup 23/V Auger peaks. The Rh/sup +/Ti/sup +/ depth profile and the ISS RhTi ratio reveal some migration of TiO/sub x/ entities onto metal surface, but not strong encapsulation of metallic particles is observed in real TiO/sub 2/-supported catalysts reduced at temperatures as high as 500/sup 0/C. Thus, the observed decrease in the activities of MeTiO/sub 2/ in the C/sub 2/H/sub 6/ hydrogenolysis and C/sub 6/H/sub 6/ hydrogenation reactions seems to be accounted for by both geometric and electronic factors. The kinetics of /sup 16/O-/sup 18/O homomolecular isotopic exchange measured for the first time on these catalysts is in accordance with the proposed SMSI model and explains its degradation during catalyst exposure to O/sub 2/ at low or elevated temperatures

• Research Organization: N.D. Zelinskii Institute of Organic Chemistry, Moscow (USSR)
• OSTI ID: 5218143
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 110:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

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02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
AROMATICS
BENZENE
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CATALYTIC REFORMING
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
ELEMENTS
EMISSION SPECTROSCOPY
ETHANE
EVEN-EVEN NUCLEI
HYDROCARBONS
HYDROGENATION
ION MICROPROBE ANALYSIS
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
MASS SPECTROSCOPY
MATHEMATICAL MODELS
METALS
MICROANALYSIS
MOLECULAR MODELS
NONDESTRUCTIVE ANALYSIS
NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN 16
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PHOTOELECTRON SPECTROSCOPY
PLATINUM
PLATINUM METALS
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REFORMER PROCESSES
RHODIUM
SPECTROSCOPY
STABLE ISOTOPES
TEMPERATURE EFFECTS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY