Volumetric and calorimetric study of the adsorption of hydrogen, at 296 K, on silica-supported nickel and nickel–copper catalysts

Prinsloo, Jeremia J.; Gravelle, Pierre C.

doi:10.1039/f19807602221

Cited by 22 publications

(5 citation statements)

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“…6. The initial heats were similar for the adsorption of H 2 on the Ni/MgO and Ni/MgO-B catalysts (about 80 kJ/mol), in consistent with the results [22,[38][39][40]. However, the uptake of H 2 on the Ni/MgO-B (540 lmol/g) was significantly higher than that on the Ni/MgO (425 lmol/g).…”

Section: Microcalorimetric Adsorption Of H 2 and Cosupporting

confidence: 92%

Surface Properties of Ni/MgO Catalysts for the Hydrogenation of Lauronitrile

2010

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60%Ni/MgO (wt%) catalysts were prepared by the co-precipitation method and the influence of n-butanol treatment was investigated. The results showed that the treatment with n-butanol improved the dispersion and reducibility of supported nickel, resulted in an increase of H 2 uptake from 410 to 582 lmol/g, corresponding to an increase of active Ni surface area from 32 to 46 m 2 /g (increased by 42%). Accordingly, the catalytic activity for the hydrogenation of toluene to methyl cyclohexane was significantly increased. Microcalorimetric adsorption of H 2 and CO indicated that the treatment with n-butanol increased the amount of active metal sites on the surface, without the change of electron densities of supported nickel surface. Microcalorimetric adsorption of CO 2 and NH 3 revealed the strong surface basicity and weak surface acidity for the Ni/MgO catalysts, especially for the reduced ones. The initial heat for the adsorption of acetonitrile was measured to be about 130 kJ/mol on the Ni/MgO catalysts, indicating the strong interaction between acetonitrile and the supported nickel, which might be an important factor determining the activity of nickel for the hydrogenation of aliphatic nitriles. The surface basicity of the Ni/MgO catalysts might play a role in inhibiting the formation of secondary and tertiary amines and therefore improved the selectivity to primary amine during the hydrogenation of lauronitrile to laurylamine. In addition, the Ni/MgO-B catalyst prepared with n-butanol treatment seemed more active for the hydrogenation of lauronitrile.

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Section: Microcalorimetric Adsorption Of H 2 and Cosupporting

confidence: 92%

Surface Properties of Ni/MgO Catalysts for the Hydrogenation of Lauronitrile

2010

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“…Indeed, calorimetric and TPD studies of hydrogen adsorption on nickel have yielded enthalpies in the overall range of -40 to -120 kJ mol -1 . 52,53 It is now recognized that different forms of hydrogen, with different degrees of interaction, are present on the surface of nickel catalysts 17,54 with reported adsorption enthalpies ranging from -110 to in excess of -400 kJ mol -1 . 54 The data generated in this study suggest that weakly interacting hydrogen is the reactive surface species and the inferred energetics agree with the value of -30 kJ mol -1 quoted by Mirodatos et al 11 in their steady-state study of benzene hydrogenation on unsupported nickel and Ni/SiO 2 catalysts.…”

Section: Rate Expression Common To the Five Aromatic Reactants Resultsmentioning

confidence: 99%

The Role of Hydrogen Partial Pressure in the Gas-Phase Hydrogenation of Aromatics over Supported Nickel

Keane

Patterson

1999

Ind. Eng. Chem. Res.

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The effect of varying the hydrogen partial pressure (from 0.19 to 0.96 atm) on turnover frequencies (TOFs) in the gas-phase hydrogenation of benzene, toluene, and o-, m-, and p-xylene over a Ni/SiO 2 catalyst has been studied. Each system is characterized by well-defined reversible temperature related activity maxima (T max ) where T max was shifted in the conversion of benzene and toluene to lower values as the hydrogen partial pressure was reduced but remained unaffected in reactions involving the isomers of xylene. The range of TOFs reported for each aromatic system and the occurrence of T max are explained on the basis of interplay between the supply and reactivity of active surface species. The observed relationships between reaction temperature and TOF are represented by means of a common extended power rate model. The nature of true and apparent reaction kinetics is discussed, and a compensation effect is established wherein the only reaction variable is the hydrogen partial pressure. The experimentally determined activation energies do not represent the true catalytically relevant energetics because of the existence of preequilibria to the rate-determining step. The measured Arrhenius parameters are shown to be composite terms and are pressure dependent. Catalytically significant heats of adsorption have been extracted from the reaction data, and the TOFs have been found to be inversely proportional to the magnitude of the heat of adsorption of hydrogen.

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“…Heat evolution thermograms. Characteristic thermopile output curves are shown for the three adsorption regions: (1) region I (88 meal released); (2) region II (80 meal released); (3) region III (3 meal released). differences in rate between these two types of processes resulted from differences in the pressure driving force for the gas expansion from the dosing volume into the sample volume (again, the normalizing AP).…”

Section: Resultsmentioning

confidence: 99%

Microcalorimetric study of the progressive oxidation of the surface of graphite-supported iron microcrystals

Gatte¹,

Phillips²

1989

Langmuir

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The adsorption of oxygen at 303 K on iron microcrystals supported on high surface area graphite was studied by using a novel Calvet-type differential microcalorimeter. Both the rate and the heat of adsorption were determined for incremental oxygen doses. Chemisorption was found to proceed through two distinct stages. Initially, the adsorption was rapid and accompanied by the evolution of large amounts of heat. This stage is attributed to the formation of a nonequilibrium film of precursory oxide with an FeO stoichiometry. In the eecond stage, chemical adsorption occurred with progressively lower heats and at progreasively slower rates, apparently until the formation of a passivating oxide f i l m with Fe304 stoichiometry was achieved. In total, two atomic layers of iron in the original particles were fully oxidized. All of these results agree with previous stttdiea of the oxidation of iron single crystals and polycrystalline films. Mossbauer spectroscopy, transmission electron microscopy, and X-ray diffraction were used to determine the particle morphology and the particle size distribution.

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Volumetric and calorimetric study of the adsorption of hydrogen, at 296 K, on silica-supported nickel and nickel–copper catalysts

Cited by 22 publications

References 0 publications

Surface Properties of Ni/MgO Catalysts for the Hydrogenation of Lauronitrile

Surface Properties of Ni/MgO Catalysts for the Hydrogenation of Lauronitrile

The Role of Hydrogen Partial Pressure in the Gas-Phase Hydrogenation of Aromatics over Supported Nickel

Microcalorimetric study of the progressive oxidation of the surface of graphite-supported iron microcrystals

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