Potassium dispersion on silica-supported ruthenium catalysts

Journal Article · Mon Jul 01 04:00:00 EDT 1991 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(91)90110-P· OSTI ID:5641475

Hoost, T E; Goodwin, J G ^[1]

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1. Univ. of Pittsburgh, PA (USA)

Alkali modifiers are known to be quite effective at improving catalyst activity or selectivity for several metal-catalyzed reactions of industrial importance. Yet it is still difficult to address the location and distribution of alkali species in most catalysts. This paper reports on an investigation of the potassium dispersion in a series of 3 wt% Ru/SiO{sub 2} catalysts sequentially doped with potassium nitrate up to (K/Ru){sub atom} = 0.2 followed by rereduction. This series was evaluated extensively using gas volumetric hydrogen chemisorption and the structure-sensitive ethane hydrogenolysis reaction. Hydrogen chemisorption results indicate that the alkali was apparently atomically dispersed on the ruthenium surface. The added potassium species interfered with hydrogen chemisorption on a one-to-one atomic basis. Potassium addition resulted in a decrease in the apparent activation energy and an increase in the apparent hydrogen reaction order for ethane hydrogenolysis. Using the statistical poisoning model of Martin which assumes that the metal surface is uniform for adatom adsorption, the apparent ensemble required for the reaction was estimated to be made up of 12 {plus minus} 3 adjacent exposed surface ruthenium atoms. Using an extension of Martin's model, this structure-sensitive reaction also revealed that at the higher potassium levels the alkali dispersion became nonuniform. This nonuniform dispersion is suggested to be due to a preference of the dopant for certain metal sites. Because of this nonuniform dispersion, the true reaction ensemble size is suggested to be less than 12.

• OSTI ID: 5641475
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 130:1; 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
ACTIVATION ENERGY
ALKALI METALS
ALKANES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
CRYSTAL STRUCTURE
DEHYDROGENATION
DISTRIBUTION
DOPED MATERIALS
ELEMENTS
ENERGY
ETHANE
HYDROCARBONS
HYDROGEN
KINETICS
MATERIALS
MATHEMATICAL MODELS
METALS
MICROSTRUCTURE
MINERALS
NONMETALS
OPTIMIZATION
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POISONING
POTASSIUM
PROMOTERS
REACTION KINETICS
REDUCTION
RUTHENIUM
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENTS