Ethane hydrogenolysis and hydrogen chemisorption over niobia-promoted rhodium catalysts: A new phase by a strong rhodium-niobia interaction

Journal Article · Mon Aug 01 00:00:00 EDT 1988 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(88)90163-7· OSTI ID:6556686

Hu, Z; Nakamura, H; Kunimori, K; Asano, H; Uchijima, T ^[1]

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1. Univ. of Tsukuba (Japan)

Niobia-promoted Rh/SiO{sub 2} catalysts, containing niobia (Nb{sub 2}O{sub 5}) deposited onto Rh/SiO{sub 2} catalysts, exhibited chemical behavior characteristic of strong metal-support interaction, the Rh-Nb{sub 2}O{sub 5} interaction being as strong as that in the Rh/Nb{sub 2}O{sub 5} system. In a typical case, after the high-temperature reduction at 773 K, the H{sub 2} chemisorption ability diminished almost to zero and the catalytic activity for ethane hydrogenolysis decreased by about seven orders of magnitude, compared with the low-temperature reduction (LTR) at 373 K. The phenomenon is reversed after the oxidation in O{sub 2} at 673 K followed by LTR. The extent of Rh-Nb{sub 2}O{sub 5} interaction was sensitive to preparation variables such as the amount of Nb{sub 2}O{sub 5} deposited and preparation method. In particular, the extent of interaction was increased significantly by calcining Nb{sub 2}O{sub 5}-promoted Rh catalysts in air at high temperatures (973 K). An X-ray diffraction study suggested formation of a new phase (RbNbO{sub 4}) by the calcination treatment at 973 K. Temperature-programmed reduction results showed that the reduction peaks shifted to the higher temperature side as the degree of the Rh-Nb{sub 2}O{sub 5} interaction increased. A model for the metal-oxide interaction in the present catalyst system is discussed in terms of the formation of a surface RhNbO{sub 4} compound and the decoration of the Rh surface with a niobia species (NbO{sub x}).

• OSTI ID: 6556686
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 112:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
AIR
ALKANES
CALCINATION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
CONTROL
DECOMPOSITION
DEHYDROGENATION
DIFFRACTION
ELEMENTS
ETHANE
FLUIDS
GASES
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGENATION
MATHEMATICAL MODELS
METALS
MINERALS
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
PROMOTERS
PYROLYSIS
REDUCTION
REFRACTORY METAL COMPOUNDS
RHODIUM
SCATTERING
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY DIFFRACTION