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Crystalllite size effects on activity and selectivity patterns in cyclohexane dehydrogenation-hydrogenolysis over nickel catalysts

Book ·
OSTI ID:6223340

Determinations of crystallite size distributions of a series of silica-supported nickel catalysts by a magnetic granulometry method and the assumption of a perfect cubooctahedron nickel crystallite shape resulted in the identification of five types of site densities: (111) hexagonal face, (100) square face, (111)-(111) edge, (111)-(100) edge, and corners. An intergral microreactor was used to measure product distributions as a function of residence time at different temperatures. The calculated rate constants and activation energies were typical of those reported in the literature. Measurements of metal surface areas for all samples by hydrogen chemisorption gave evidence of surface loss due to pore-trapping and support interactions. Positive correlations of intrinsic rate constants with site densities were obtained for cyclohexane dehydrogenation, benzene hydrogenation, and benzene hydrogenolysis with the (111) hexagonal face sites. Cyclohexane hydrogenolysis showed a positive correlation with the (111)-(111) and (111)-(100) edge sites. Thus, a positive intrinsic factor for cyclohexane hydrogenolysis and negative intrinsic factors for the other three reactions are evident.

OSTI ID:
6223340
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ACTIVATION ENERGY
ALKANES
AROMATICS
BENZENE
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
CORRELATIONS
CRYSTAL STRUCTURE
CYCLOALKANES
CYCLOHEXANE
DATA
DEHYDROGENATION
DISTRIBUTION
ELEMENTS
ENERGY
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN
HYDROGENATION
INFORMATION
KINETICS
METALS
MINERALS
NICKEL
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SORPTION
SURFACE AREA
SURFACE PROPERTIES
TRANSITION ELEMENTS