Characterization of supported palladium catalysts II. Pd/SiO sub 2

Journal Article · Thu Jun 01 04:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90361-8· OSTI ID:6352000

Juszczyk, W; Karpinski, Z ^[1]

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1. Institute of Physical Chemistry of the Polish Academy of Sciences, Warszawa (Poland)

The isomerization of neopentane has been investigated over the 0.76 wt% Pd/SiO{sub 2} catalyst. It is found that after high temperature reduction (HTR, at 873 K) the selectivity for isomerization is much higher than that after low temperature reduction (LTR, at 573 K). A variety of experiments, including kinetic, chemisorption (O{sub 2}, H{sub 2}, and CO), temperature-programmed desorption of H{sub 2}, and X-ray diffraction, showed that this selectivity enhancement cannot be interpreted in terms of H{sub 2} retention by catalyst. Instead, the formation of Pd-Si compound(s) (most probably Pd{sub 3}Si) during HTR seems immediately responsible for the catalytic behavior of HTR Pd/SiO{sub 2} catalysts. A mechanism is proposed for the Pd-SiO{sub 2} interaction in which Pd atoms (or ions) are incorporated into the silica support (via oxygen vacancies) and a new phase of palladium silicide is formed. Regeneration by an oxygen treatment of the HTR sample does not fully restore the low isomerization selectivity typical of LTR samples. The additional selectivity is attributed to an overlayer of oxidized silicon species (after oxidation of the HTR sample) which partially cover the metal.

• OSTI ID: 6352000
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 117:2; 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
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYTIC CRACKING
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
CRACKING
DECOMPOSITION
DESORPTION
DIFFRACTION
ELEMENTS
HYDROCARBONS
HYDROGEN
HYDROGENATION
ISOMERIZATION
KINETICS
METALS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PALLADIUM
PALLADIUM COMPOUNDS
PALLADIUM SILICIDES
PETROLEUM PRODUCTS
PLATINUM METALS
PYROLYSIS
REACTION KINETICS
REDUCTION
REGENERATION
SCATTERING
SEPARATION PROCESSES
SILICA
SILICIDES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY DIFFRACTION