The stoichiometry of hydrogen and CO chemisorption on Ir/$gamma;-Al2O3

Krishnamurthy, S.; Landolt, G.R.; Schoennagel, H.J.

doi:10.1016/0021-9517(82)90316-5

Cited by 19 publications

(4 citation statements)

References 9 publications

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“…Firstly, the metal particle size of the different catalysts was investigated by microscopy. Figure 3 [19]. Semi-spherical particles are assumed in all cases with its associated experimental error [20].…”

Section: Characterization Resultsmentioning

confidence: 99%

Low temperature total oxidation of toluene by bimetallic Au–Ir catalysts

Torrente‐Murciano

Solsona

Agouram

et al. 2017

Catal. Sci. Technol.

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Section: Characterization Resultsmentioning

confidence: 99%

Low temperature total oxidation of toluene by bimetallic Au–Ir catalysts

Torrente‐Murciano

Solsona

Agouram

et al. 2017

Catal. Sci. Technol.

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“…McVicker et al reported a H/ Ir ratio close to 2 for small particle sizes (<0.6 nm) over highly dispersed Ir catalysts on Al 2 O 3 [ 18 ]. Krishnamurthy et al have shown that 0.48 wt% Ir/Al 2 O 3 catalyst adsorbed up to 2.72 hydrogen atoms per iridium atom [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Palladium, Iridium, and Rhodium Supported Catalysts: Predictive H2 Chemisorption by Statistical Cuboctahedron Clusters Model

et al. 2018

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Chemisorption of hydrogen on metallic particles is often used to estimate the metal dispersion (D), the metal particle size (d), and the metallic specific surface area (SM), currently assuming a stoichiometry of one hydrogen atom H adsorbed per surface metal atom M. This assumption leads to a large error when estimating D, d, and SM, and a rigorous method is needed to tackle this problem. A model describing the statistics of the metal surface atom and site distribution on perfect cuboctahedron clusters, already developed for Pt, is applied to Pd, Ir, and Rh, using the density functional theory (DFT) calculation of the literature to determine the most favorable adsorption sites for each metal. The model predicts the H/M values for each metal, in the range 0–1.08 for Pd, 0–2.77 for Ir, and 0–2.31 for Rh, depending on the particle size, clearly showing that the hypothesis of H/M = 1 is not always confirmed. A set of equations is then given for precisely calculating D, d, and SM for each metal directly from the H chemisorption results determined experimentally, without any assumption about the H/M stoichiometry. This methodology provides a powerful tool for accurate determination of metal dispersion, metal particle size, and metallic specific surface area from chemisorption experiments.

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“…CO chemisorption experiments were undertaken in order to measure the Ir dispersion and the number of active surface iridium sites [42]. It was assumed that the particles had spherical shapes and the CO-Ir interaction took place with a CO:Ir stoichiometric factor 100 nm 100 nm of 2 [43,44]. The results obtained (see Table 3) corroborated the information suggested by microscopy, as iridium dispersion on silica catalysts was the lowest, and alumina the highest, the order was: silica < ZSM-5 < titania < alumina It was also observed that the increase of the calcination temperature decreased the iridium dispersion.…”

Section: Characterization Resultsmentioning

confidence: 99%