Thermomagnetic Analysis of Supported Nickel Catalysts<sup>1</sup>

Selwood, P. W.; Adler, Stephen F.; Phillips, T. R.

doi:10.1021/ja01611a018

Cited by 44 publications

(13 citation statements)

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“…The influence of structural parameters on catalytic performance of heterogeneous precious metal catalysts has been known in principle for nearly 50 years. 1 These correlations are widely based on the particle size on a support and its statistical distribution, which determine dispersion and active surface area of the catalyst material. 2 Depending on the particle size, particular types of atomic configurations (for example edges) 3,4 and crystal planes 5,6 appear at the surface, which can influence the catalytic activity of a particulate catalyst.…”

Section: Introductionmentioning

confidence: 99%

“…Pt(hfa) 2 was used by Hierso et al for the synthesis of Pt/SiO 2 catalysts by a fluidized bed reactor, but the resulting Pt particles were characterized by an unwanted increased amount of carbon residues. 37 Within this study we present the usage of commercially available MeCpPtMe 3 (1) and novel PtMe 2 (iBu-COD) (2) as precursors for the preparation of Pt/TiO 2 nanoparticles. MeCpPtMe 3 (trimethyl(methylcyclopentadienyl)platinum) is an easy to handle, well-characterized precursor which was used for the generation of Pt films and nanoparticles within a number of studies.…”

Section: Introductionmentioning

confidence: 99%

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Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts

Faust

Dinkel

Bruns

et al. 2017

Ind. Eng. Chem. Res.

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In contrast to most wet chemical synthesis routes, chemical vapor deposition (CVD) offers many degrees of freedom for the structuring of Pt nanoparticle catalyst systems, which is a prerequisite for the examination of structure−function correlations in heterogeneous catalysis. Two different suitable metal−organic Pt precursors [MeCpPtMe 3 and novel PtMe 2 (iBu-COD)] were employed to generate highly defined, very narrowly distributed Pt nanoparticles with high active surface areas on well-specified TiO 2 supports of differing surface properties. The TiO 2 supports and the Pt nanoparticles were thoroughly characterized and tested in the water gas shift reaction. The influence of the support particle size and its surface chemistry (hydroxyl groups) as well as the nature of the metal−organic precursors used on the water gas shift (WGS) activity were investigated by nanotechnological methods within this study. A further modification of the support material was done by Na deposition. This catalyst was found to be a highly efficient WGS catalyst with an increase of the catalytic activity by a factor of 3 compared to the nonmodified system.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts

Faust

Dinkel

Bruns

et al. 2017

Ind. Eng. Chem. Res.

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“…The parameter determining the energy of adsorption is then the distance r between the adsorbed particle and the surface mirror plane. For hydrogen atoms on metals, the following equation has been derived --(w~* --w,) = e~/4Kor) (1 q-qao~/2r ~) [9] where ao is the Bohr radius. The distance r will vary with lattice parameter and electron concentration.…”

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confidence: 99%

Overvoltage and Catalysis

Rüetschi

1959

J. Electrochem. Soc.

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Analogies between heterogeneous catalysis on solid-gas interfaces and electrochemical kinetics on solid-liquid interfaces are discussed. The surface potential of a solid-gas interface corresponds to the Galvani potential difference of a solid-liquid interface. These potentials depend to a first approximation linearly on the number of adsorbed potential-determining particles. A corresponding linear variation adsorption energy is explained on the basis of electrostatic or induced interaction between adsorbed particles. This behavior is coherent with a logarithmic dependence of the number of adsorbed particles on the bulk concentration or pressure in the liquid or gaseous phase (Temkin isotherm) and a linear dependence of the activation energy of adsorption on the number of adsorbed particles (Becker-Zeldovich equation). It is shown that the Temkin isotherm corresponds to Nernst's formula for electrode potentials and the Becker-Zeldovich equation to Volmer's equation for the rate of electrochemical reactions, and that these equations follow immediately from the theory of charge-transfer adsorption or electrostatic interaction between (activated) potential-determining species or complexes. This treatment leads to a new interpretation of the charge-transfer coefficient and of the influence of the electronic properties of the electrode material and of specifically adsorbed foreign species on hydrogen overvoltage, oxygen overvoltage, and metal deposition overvoltage.The kinetics and thermodynamics of electrochemical phenomena at solid-liquid interfaces and of catalytic phenomena at solid-gas interfaces are closely related. It is the object of this paper to point out correspondences between the two fields and to derive the fundamental laws of electrochemical thermodynamics and kinetics, in particular the Nernst equation and the Volmer-Tafel equation, from these considerations. Adsorption and InteractionThe relation between the number of adsorbed species on a solid-gas or solid-liquid interface and bulk concentration (or pressure) of the adsorbable species is described by isotherms. The Langmuir isotherm is derived on the assumption that adsorption occurs at fixed sites and that the energy of adsorption is independent of the number of particles adsorbed. Fixed site adsorption is, however, unlikely for many reactions proceeding on electrodes and catalysts. The energy of adsorption usually decreases with increasing number of adsorbed particles. The Freundlich isotherm is therefore more likely to be obeyed since it allows for the latter effect. However, very few experimental results suggest a logarithmic decrease of the energy of adsorption with increasing number of adsorbed species, as derived from the Freundlich isotherm. Very often the energy of adsorption decreases nearly linearly with the number of adsorbed particles. Such a behavior is accounted for by the Temkin isotherm. The latter can be derived for intermediate ranges of coverage from a fixed site Langmuir-type isotherm by allowing for a linear variation in adsorpt...

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“…From this it appears clear that crystallite size does not, in substantial manner, control the catalytic activity of sup- Both these conclusions seem provisional at best. A study of the literature of hydrogenation makes clear that net (nonselective) activity should be a function of crystallite size (17,18) and despite evidence to the contrary (11), it is expected the conditions of reduction would have a strong modifying effect on crystallite size and reactivity.…”

Section: Hydrogenation-activitymentioning

confidence: 99%

Nickel crystallite size and net activity of hydrogenation catalysts

Dafler¹

1977

J Americ Oil Chem Soc

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AND SUMMARYAmong supported nickel-based hydrogenation catalysts, the Ni crystallite size apparently plays a secondary role in net hydrogenation activity for undistilled tallow fatty acids and nonselective hydrogenation of oxidized soybean oil. The nickel crystallite size measured by the x-ray diffraction profile broadening technique of Scherrer varied between 55 A and 150 A. The commercial catalyst with the smallest nickel crystatlite size, in the samples studied, was not the most active for hardening soybean oil, while fatty acid hydrogenation showed a large crystallite catalyst to have the highest activity. Since the percent reduced nickel used in catalytic hydrogenation is not well known if the Ni/NiO ratio is poorly defined, relative activities were then correlated with qualitative x-ray diffraction measurements of the Ni/NiO values. Again, there was no trend in activity as a function of Ni/NiO. This apparent puzzle is probably due to real differences in the micro structure of the catalyst support. A series of experimental reductions using a common green catalyst led to very good correlations between net activity for fatty acid hydrogenation and the crystallite size and Ni/NiO ratio. On a given support, the crystallite dimension can be modified by the reduction treatment and is not sharply fixed by the selection of nickel salt and support. If the stoichiometric ratio of hydrogen is lowered, the crystallite dimension is reduced, but so is the qualitative efficiency of reduction (Ni/NiO), with the result that an exceptionally small crystallite size catalyst may be less active than one with larger crystals, but with more reduced Ni/unit weight.

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Thermomagnetic Analysis of Supported Nickel Catalysts¹

Cited by 44 publications

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Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts

Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts

Overvoltage and Catalysis

Nickel crystallite size and net activity of hydrogenation catalysts

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Thermomagnetic Analysis of Supported Nickel Catalysts1

Cited by 44 publications

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Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO2 Catalysts

Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO2 Catalysts

Overvoltage and Catalysis

Nickel crystallite size and net activity of hydrogenation catalysts

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Thermomagnetic Analysis of Supported Nickel Catalysts¹

Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts

Support Effect on the Water Gas Shift Activity of Chemical Vapor Deposition-Tailored-Pt/TiO₂ Catalysts