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

Journal Article · Thu Jun 01 00:00:00 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), Vol. 117:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKANES
ISOMERIZATION
PALLADIUM
CATALYTIC EFFECTS
CARBON MONOXIDE
CATALYSIS
CATALYST SUPPORTS
CATALYTIC CRACKING
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMISORPTION
DESORPTION
HYDROGEN
HYDROGENATION
OXIDATION
OXYGEN
PALLADIUM SILICIDES
PETROLEUM PRODUCTS
REDUCTION
REGENERATION
SILICA
X-RAY DIFFRACTION
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRACKING
DECOMPOSITION
DIFFRACTION
ELEMENTS
HYDROCARBONS
KINETICS
METALS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM COMPOUNDS
PLATINUM METALS
PYROLYSIS
REACTION KINETICS
SCATTERING
SEPARATION PROCESSES
SILICIDES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
020400* - Petroleum- Processing
400201 - Chemical & Physicochemical Properties