Elementary steps in the formation of highly dispersed palladium in NaY I. Pd ion coordination and migration

Journal Article · Mon May 01 00:00:00 EDT 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90223-6· OSTI ID:6439078

Homeyer, S T; Sachtler, W M.H. ^[1]

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1. Northwestern Univ., Evanston (USA)

TPR, TPD, TPO, and TPMS have been used to determine the location and chemical state of Pd supported on NaY. Oxidation of the ammine ligands of Pd(NH{sub 3}){sub 4}{sup 2+} is found to be a stepwise process, producing Pd(NH{sub 3}){sub 2}{sup 2+} ions in supercages and Pd(NH{sub 3}){sup 2+} and Pd{sup 2+} ions in sodalite cages. The relative abundance and location of these ions can be controlled by the calcination program. The size of Pd particles after reduction depends on the location and coordination of Pd ions after calcination. Calcination below 250{degree}C leaves Pd ions in the supercages, where their coordination to ammine ligands decreases with increasing calcination temperature. The H/Pd ratio after reduction shows a strong positive correlation with the calcination temperature. It is concluded that the Pd particle size in the kinetic regime is controlled by the relative rates of nucleation and crystal growth, which is in this case are determined by the relative abundances of the Pd tetraammine and diammine ions. At a calcination temperature of 300{degree}C Pd ions lose the third ammine ligand allowing the monoammine Pd ions to migrate into sodalite cages, where the remaining ligand is destroyed at 400{degree}C. 25 refs.

• OSTI ID: 6439078
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 117:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METALS
AMMINES
BIMETALS
CALCINATION
CATALYST SUPPORTS
CATALYSTS
CHEMICAL REACTIONS
COMPLEXES
CONTROL
CRYSTAL STRUCTURE
DECOMPOSITION
DESORPTION
ELEMENTS
METALS
OXIDATION
PALLADIUM
PARTICLE SIZE
PLATINUM METALS
PYROLYSIS
REDUCTION
SIZE
SODIUM
SURFACE PROPERTIES
TEMPERATURE CONTROL
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS
YTTRIUM