Catalysis with palladium deposited on rare earth oxides: Influence of the support on reforming and syngas activity and selectivity

Journal Article · Wed Jan 09 23:00:00 EST 1991 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100154a050· OSTI ID:5795006

Le Normand, F; Hilaire, L ^[1]; Barrault, J ^[2]; Breault, R; Kiennemann, A ^[3]

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1. Universite Louis Pasteur, Strasbourg (France)
2. Universite de Poitiers (France)
3. CNRS, EEHEICS, Strasbourg (France)

The influence of the support has been tested on the reactivity of Pd/rare earth oxides catalysts (La{sub 2}O{sub 3}, CeO{sub 2}, Pr{sub 6}O{sub 11}, Nd{sub 2}O{sub 3}, Tb{sub 4}O{sub 7}). According to BET surface area, chemisorption, temperature-programmed reduction (TPR) and oxidation (TPO), x-ray diffraction (XRD) and x-ray photoemission (XPS) characterizations, these catalysts have been classified into three classes according to their ability to create anion vacancies: (i) oxides of the type Re{sub 2}O{sub 3} which are unreducible, (ii) CeO{sub 2} where anion vacancies can be created extrinsically by the reduction process, and (iii) Pr{sub 6}O{sub 11} and Tb{sub 4}O{sub 7} where anion vacancies exist due to the nonstoichiometric nature of these oxides. The authors emphasize also the role of chlorine, coming from the palladium precursor salt, which reacts with the support to form a stable oxychloride phase surrounding the metallic particle and interacting with it. Concerning the catalytic activity, (i) the active site is purely metallic in methylcyclopentane hydrogenolysis, with small selectivity changes on fluorite oxides as compared to Pd/Al{sub 2}O{sub 3} catalysts due to some electronic interaction with the support, but (ii) the mechanism is found to be partly bifunctional in 3-methylhexane aromatization with a large increase in aromatization on Pr{sub 6}O{sub 11} and Tb{sub 4}O{sub 7} supports, and (iii) in syngas conversion, production of high alcohols occurs at the metal-support interface and is favored by the presence of intrinsic anion vacancies on Pr{sub 6}O{sub 11} and Tb{sub 4}O{sub 7} supports.

• OSTI ID: 5795006
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 95:1; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

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CATALYST SUPPORTS
CATALYTIC EFFECTS
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COMPLEXES
DATA
DIFFRACTION
EMISSION
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NUMERICAL DATA
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PHOTOEMISSION
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SCATTERING
SECONDARY EMISSION
SYNTHESIS GAS
TERBIUM COMPOUNDS
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TRANSITION ELEMENT COMPLEXES
X-RAY DIFFRACTION