The determination of the free-metal surface area of palladium catalysts

Scholten, J

doi:10.1016/0021-9517(62)90012-x

Cited by 61 publications

(4 citation statements)

References 7 publications

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“…In order to calculate the dispersion D (that is, the atomic ratio between the number of surface Pd atoms (Pd s ) and the number of total Pd atoms) from CO chemisorption measurements, the stoichiometric ratio CO/Pd s has to be known. It has been shown that CO chemisorption on Pd can occur in two ways (17,18): a carbon monoxide molecule can be bonded through the carbon to one Pd atom (linear CO) or to two Pd atoms (bridged CO). The ratio of linearly held CO to bridged-bonded CO decreases as the dispersion decreases (19,20) and the result of this is an increase in the global ratio CO/Pd s with dispersion.…”

Section: Synthesismentioning

confidence: 99%

Pd/SiO2-Cogelled Aerogel Catalysts and Impregnated Aerogel and Xerogel Catalysts: Synthesis and Characterization

Heinrichs

Noville

Pirard

1997

Journal of Catalysis

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Section: Synthesismentioning

confidence: 99%

Pd/SiO2-Cogelled Aerogel Catalysts and Impregnated Aerogel and Xerogel Catalysts: Synthesis and Characterization

Heinrichs

Noville

Pirard

1997

Journal of Catalysis

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“…A review on surface area measurements by Farrauto (1974) gives details on the chemisorption method, and the article by Pulvermacher and Ruckenstein (1974) provides details on the other methods including magnetic measurements. Of these methods, gas chemisorption is perhaps the most accurate and certainly the easiest to implement, e.g., Hz on Pt (Spenadel and Boudart, 1960;Adler and Kearney, 1960) and on Ni (Taylor, Yates and Sinfelt, 1964), CO on Pd (Scholten and Montfoort, 1962), and NO on oxides of Cu, N, and Fe (Gandhi and Shelef, 1973). While the chemisorption method is a powerful tool for catalytic research, it has its limitations for the determination of active surface area.…”

Section: Introductionmentioning

confidence: 99%

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Miller

Lee

1984

AIChE J.

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A new experimental method for the measurement of catalyst surface area of supported catalysts has been developed using selective physisorption. The desorption characteristics of a gas are studied separately on the catalyst, the support, and the supported catalyst by carrying out thermal desorption experiments in a continuous flow sorptometer. Differences in the coverage vs. temperature curves, obtained from the thermal desorption experiments, are a measure of the selectivity of the physisorbing gas, and allow calculation of the fraction of total surface area occupied by the catalyst.Two systems have been studied utilizing the thermal desorption with carbon dioxide as adsorbate: potassium carbonate/carbon black and silver/alumina. Supported catalyst surface area was determined for each system; the results were confirmed using physical mixtures of the two components (where the actual area of each component is known) and oxygen chemisorption for the silver/alumina system. The experimental technique allows for straightforward calculation of the catalyst area. D. J. MILLER and H. H. LEE Department of Chemical EngineeringUniversity of Florida Gainesville, FL 3261 1The exposed surface area of a catalyst on a support is an important parameter in the characterization of catalytic behavior, particularly in sintering and dispersion studies. Several experimental methods of determining catalyst area have been developed, including chemisorption, electron microscopy, and X-ray techniques. The difficulties involved in applying electron microscopy to actual catalysts and the sophistication of small angle X-ray scattering prevent their practical application in many cases. Chemisorption techniques have met with success in several catalyst systems, but the chemisorption techniques are limited to well-defined metal catalysts and are not in general applicable to nonmetallic catalysts. This paper presents a new method for determining catalyst area using physical adsorption. The method examines the adsorption characteristics of a gas separately on the catalyst (in powder or gauze form), the support, and the supported catalyst using a thermal desorption technique for the determination of the total exposed catalyst area as a fraction of the total catalyst and support area. This method has several advantages over other methods used in catalyst area measurements:1) The physisorption experiments are easy to carry out and the equipment needed is low cost. The physisorption experiments show good reproducibility, and sample preparation is the same as in conventional physisorption.2) The method can be applied to any catalyst system with the appropriate choice of adsorbing gas, since gases physisorb on all surfaces at low temperatures. This is in contrast to chemisorption, where the specific gas-solid interactions limit application to a few systems.3) The total catalyst area is determined directly from the experiments. Unlike chemisorption, there is no need to know the adsorption stoichiometry to determine the total area. CONCLUSIONS AND SIGNIFIC...

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“…In this manuscript, the host will be referred to as Pt(1.12)Si (IE) . The hydrogen adsorption isotherm was measured by a static volumetric apparatus at 25 °C. , By assuming a stoichiometry of 2 H/surface Pt, the number of Pt surface atoms (Pt s ) was 48.32 μmol. The resulting metal dispersion was ca.…”

Section: Experimental Sectionmentioning

confidence: 99%

Precise Control of Pt Particle Size for Surface Structure–Reaction Activity Relationship

et al. 2018

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The use of surface organometallic chemistry on metal (SOMC/M) allows the controlled and stepwise variation of the platinum particle size in Pt/SiO 2 catalysts. This SOMC/M method is possible thanks to the better affinity of most organometallic compounds with the surface of zerovalent metal particles covered with hydrogen than their support. In this paper, Pt(acac) 2 was used as the organometallic precursor, silica as a support, and then hydrogen to reduce the adsorbed organometallic layer on top of the starting Pt nanoparticle. We partially succeeded in adding one Pt layer with a stepwise particle size increase of around 0.6 nm when going from the first (1G) to the second (2G) refilling run, as obtained from TEM and H 2 chemisorption analysis and then confirmed by DFT calculations. The metal loading could be kept at a very low level (<1−2 wt %), which is relevant for catalytic applications. The particle size distribution remained relatively narrow even after two refilling runs, allowing more precise relationships between particle size and catalytic properties to be established. The TOR H (for hydrogenolysis) dramatically decreased, while TOR I (for skeletal isomerization) slightly increased with increasing the particles size. It is therefore suggested that hydrogenolysis might preferentially occur on low coordination surface platinum atoms (corners and edges), while isomerization occurs mostly on the facets.

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The determination of the free-metal surface area of palladium catalysts

Cited by 61 publications

References 7 publications

Pd/SiO2-Cogelled Aerogel Catalysts and Impregnated Aerogel and Xerogel Catalysts: Synthesis and Characterization

Pd/SiO2-Cogelled Aerogel Catalysts and Impregnated Aerogel and Xerogel Catalysts: Synthesis and Characterization

Determination of catalyst surface area from desorption characteristics of physisorbed gases

Precise Control of Pt Particle Size for Surface Structure–Reaction Activity Relationship

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