Chemisorption of methane on Ni/SiO/sub 2/ catalysts and reactivity of the chemisorption products toward hydrogen

Journal Article · Wed Jun 01 00:00:00 EDT 1983 · J. Catal.; (United States)

OSTI ID:5705756

Kuijpers, E G.M. ^[1]; Breedijk, A K; van der Wal, W J.J.; Geus, J W

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1. VEG-Gasinstituut n.v., Apeldoorn, Netherlands

The chemisorption of hydrogen both on bare and carburized nickel/silica (Ni/SiO/sub 2/) catalysts was studied using a low-field magnetic method, infrared ir spectroscopy, and mass spectrometry. With a freshly reduced and evacuated sample of one of the catalysts. H/sub 2/ chemisorption was investigated as a function of the temperature (30 < T < 100/sup 0/C). It was found that the slope of the magnetization-volume isotherm decreased with increasing temperature, which does not agree with the theory of superparamagnetism. The smaller slope at more elevated temperatures was ascribed to a more extensive coverage of the smaller nickel particles after admission of the initial H/sub 2/ doses. Carburization of the catalysts was established by the decomposition of methane (CH/sub 4/) at temperatures from 30 to 300/sup 0/C. At low surface coverages the carbon was deposited as Ni/sub 3/C strongly affecting the magnetization. At higher surface coverages CH/sub x/-complexes without any effect on the magnetization were chemisorbed. After the decomposition of CH/sub 4/, the catalysts were evacuated at 250/sup 0/C, which was found to result in the conversion of a part of the carbonaceous deposit into methane. Also with the subsequent chemisorption of hydrogen on the carburized catalysts (T = 30/sup 0/C) the reaction between chemisorbed H-atoms and deposited carbon was apparent from the production of CH/sub 4/. From a comparison of the magnetization-volume isotherms for H/sub 2/ chemisorption before and after the deposition of small amounts of carbon it was derived that the decomposition of methane preferentially proceeds on small nickel crystallites. Finally it was found that hydrogen was adsorbed not only on bare nickel (with magnetic effect) but also on nickel carbide (without magnetic effect). 7 figures, 2 tables.

• OSTI ID: 5705756
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 81:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

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10 SYNTHETIC FUELS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical &amp; Physicochemical Properties-- (-1987)
ADSORPTION ISOTHERMS
ALKANES
CARBURIZATION
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
DATA
DECOMPOSITION
ELEMENTS
EXPERIMENTAL DATA
HARDENING
HYDROCARBONS
HYDROGEN
IMPURITIES
INFORMATION
INFRARED SPECTRA
ISOTHERM
MAGNETIZATION
MASS SPECTRA
METALS
METHANE
MINERALS
NICKEL
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
SURFACE HARDENING
SURFACE TREATMENTS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS