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Title: Nanostructural features of Pd/C catalysts investigated by physical methods: A reference for chemisorption analysis

Abstract

In this work the authors have determined, on a series of 0.5% Pd/C catalysts, the palladium particle sizes by the following physical techniques: (i) X-ray diffraction (XRD) line broadening (LB) method, associated with the Rietveld method, (ii) small-angle X-ray scattering, and (iii) transmission electron microscopy. The catalysts, suitably aged at different temperatures (673, 773, 873, and 973 K), had significantly different metal dispersions. Since the XRD-LB technique is not able to measure directly very small metal particles or clusters (roughly {le}25 {angstrom} in size), because they give diffuse X-ray scattering spreading out into the background, the authors have tackled this problem by means of a suitably tailored Rietveld quantitative analysis. This analysis allowed determination of the Pd fraction visible in the Voigtian XRD peaks and its average crystallite size using the LB method. As to the nanoparticle size of the undetectable fraction, an average value of 20 {angstrom} was assumed, corresponding to the size of a cubooctahedral perfect cluster of the fourth order. Combining all these data, real effective Pd average particle sizes could be calculated and compared with the corresponding values found by CO chemisorption. It was found that a surface Pd/CO stoichiometry of 2 must be assumed, irrespectivemore » of Pd dispersion, to get correct values of the average Pd particle size.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Univ. di Venezia (IT)
OSTI Identifier:
20080275
Resource Type:
Journal Article
Journal Name:
Langmuir
Additional Journal Information:
Journal Volume: 16; Journal Issue: 10; Other Information: PBD: 16 May 2000; Journal ID: ISSN 0743-7463
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; PALLADIUM CARBIDES; CATALYST SUPPORTS; MOLECULAR STRUCTURE; TEREPHTHALIC ACID

Citation Formats

Fagherazzi, G., Canton, P., Riello, P., Pernicone, N., Pinna, F., and Battagliarin, M. Nanostructural features of Pd/C catalysts investigated by physical methods: A reference for chemisorption analysis. United States: N. p., 2000. Web. doi:10.1021/la991463p.
Fagherazzi, G., Canton, P., Riello, P., Pernicone, N., Pinna, F., & Battagliarin, M. Nanostructural features of Pd/C catalysts investigated by physical methods: A reference for chemisorption analysis. United States. doi:10.1021/la991463p.
Fagherazzi, G., Canton, P., Riello, P., Pernicone, N., Pinna, F., and Battagliarin, M. Tue . "Nanostructural features of Pd/C catalysts investigated by physical methods: A reference for chemisorption analysis". United States. doi:10.1021/la991463p.
@article{osti_20080275,
title = {Nanostructural features of Pd/C catalysts investigated by physical methods: A reference for chemisorption analysis},
author = {Fagherazzi, G. and Canton, P. and Riello, P. and Pernicone, N. and Pinna, F. and Battagliarin, M.},
abstractNote = {In this work the authors have determined, on a series of 0.5% Pd/C catalysts, the palladium particle sizes by the following physical techniques: (i) X-ray diffraction (XRD) line broadening (LB) method, associated with the Rietveld method, (ii) small-angle X-ray scattering, and (iii) transmission electron microscopy. The catalysts, suitably aged at different temperatures (673, 773, 873, and 973 K), had significantly different metal dispersions. Since the XRD-LB technique is not able to measure directly very small metal particles or clusters (roughly {le}25 {angstrom} in size), because they give diffuse X-ray scattering spreading out into the background, the authors have tackled this problem by means of a suitably tailored Rietveld quantitative analysis. This analysis allowed determination of the Pd fraction visible in the Voigtian XRD peaks and its average crystallite size using the LB method. As to the nanoparticle size of the undetectable fraction, an average value of 20 {angstrom} was assumed, corresponding to the size of a cubooctahedral perfect cluster of the fourth order. Combining all these data, real effective Pd average particle sizes could be calculated and compared with the corresponding values found by CO chemisorption. It was found that a surface Pd/CO stoichiometry of 2 must be assumed, irrespective of Pd dispersion, to get correct values of the average Pd particle size.},
doi = {10.1021/la991463p},
journal = {Langmuir},
issn = {0743-7463},
number = 10,
volume = 16,
place = {United States},
year = {2000},
month = {5}
}