Structural transformation in Nb sub 2 O sub 5 -promoted Rh catalysts during calcination and reduction treatments

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90132-2· OSTI ID:7128430

Hu, Z; Nakamura, H; Kunimori, K; Yokoyama, Y; Asano, H; Uchijima, T ^[1]; Soma, A M ^[2]

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1. Univ. of Tsukuba, Ibaraki (Japan)
2. National Institute for Environmental Studies, Tsukuba (Japan)

The extent of Rh-Nb{sub 2}O{sub 5} interaction in the niobia-promoted Rh/SiO{sub 2} catalyst depends on parameters such as calcination temperature. For the Nb{sub 2}O{sub 5}-promoted Rh/SiO{sub 2} catalyst with the Nb/Rh atomic ratio of unity, no significant SMSI effects were observed after air calcination at 773 K. However, this catalyst exhibits significant SMSI behaviors after calcination at higher temperatures (973 and 1173 K). After high-temperature reduction at 773 K, the capacity of H{sub 2} chemisorption typically diminished almost to zero and the catalytic activity for ethane hydrogenolysis was suppressed by ca. 3.5 orders of magnitude compared with that after low-temperature reduction at 373 K. X-ray diffraction showed that the RhNbO{sub 4} compound was formed, with the amount increasing with increasing calcination temperature. After air calcination at 1173 K, the RhNbO{sub 4} compound was formed almost exclusively on the SiO{sub 2} surface. The RhNbO{sub 4} compound was reduced to Rh and NbO{sub 2} during HTR treatment at 773 K, accompanied by splitting of the large RhNbO{sub 4} particle into a number of smaller Rh particles. The mechanism of Rh-Nb{sub 2}O{sub 5} interaction is discussed. It is proposed that the NbO{sub 2} species formed during the HTR treatment block surface Rh atoms to induce strong Rh-Nb{sub 2}O{sub 5} interaction (SMSI).

• OSTI ID: 7128430
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 119:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400* -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALKANES
CALCINATION
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
DECOMPOSITION
DEHYDROGENATION
DIFFRACTION
ELEMENTS
ETHANE
HYDROCARBONS
HYDROGEN
KINETICS
METALS
MINERALS
MORPHOLOGICAL CHANGES
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
PYROLYSIS
REACTION KINETICS
REDUCTION
REFRACTORY METAL COMPOUNDS
RHODIUM
SCATTERING
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SYNTHESIS
TEMPERATURE DEPENDENCE
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY DIFFRACTION