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Crystallite size effects in nickel catalysts: cyclohexane dehydrogenation and hydrogenolysis

Journal Article · · J. Catal.; (United States)
Crystallite size dependence of cyclohexane dehydrogenation and hydrogenolysis has been studied over silica-supported nickel catalysts. The samples were freshly prepared and sintered catalysts, produced by homogeneous precipitation-deposition and ranging from 25 to 40 wt% Ni on SiO/sub 2/. Crystallite size distributions were determined from magnetization data. Other experimental measurements, such as hydrogen chemisorption and catalytic kinetics, were made in the same cell in order to provide in situ precision. Average crystallite sizes varied from 2 to 4 nm and critical differences were found in this region. Areal rates for dehydrogenation more than doubled, whereas cyclohexane hydrogenolysis decreased by a factor of 5. These findings were shown to be consistent with a model wherein dehydrogenation occurs on crystal face sites and hydrogenolysis on edge positions. Benzene hydrogenolysis followed the same pattern as dehydrogenation, suggesting that common intermediates are involved.
Research Organization:
Univ. of Houston, University Park, TX (USA)
OSTI ID:
5327215
Journal Information:
J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 98:2; ISSN JCTLA
Country of Publication:
United States
Language:
English