Structural characterization of Rh/pumice SMAD catalysts

A. Balerna; S. Coluccia; G. Deganello; A. Longo; A. Martorana; G. Martra; C. Meneghini; P. Pertici; G. Pipitone; E. Pitzalis; A. M. Venezia; A. Verrazzani; G. Vitulli

doi:10.1007/s100530050384

2022 Impact factor 1.8

Atomic, Molecular, Optical and Plasma Physics

Eur. Phys. J. D 7, 577-586 (1999)
https://doi.org/10.1007/s100530050384

Structural characterization of Rh/pumice SMAD catalysts

A. Balerna¹, S. Coluccia², G. Deganello³^,4, A. Longo³^,4, A. Martorana³^,4, G. Martra², C. Meneghini¹, P. Pertici⁵, G. Pipitone³^,4, E. Pitzalis⁵, A. M. Venezia³, A. Verrazzani⁵ and G. Vitulli⁵

¹ Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati, Italy
² Dipartimento di Chimica Inorganica, Fisica e dei Materiali, Università di Torino, via P. Giuria 7, 10125 Torino, Italy
³ Istituto di Chimica e Tecnologia dei Prodotti Naturali del CNR, via Ugo La Malfa 153, 90146 Palermo, Italy
⁴ Dipartimento di Chimica Inorganica, Università di Palermo, viale delle Scienze, 90128 Palermo, Italy
⁵ Centro CNR Macromolecole Stereordinate ed Otticamente Attive, Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56100 Pisa, Italy

Received: 2 February 1999
Published online: 15 December 1999

Abstract

The structure of Rh/pumice catalysts prepared by the SMAD (Solvated Metal Atoms Dispersion) technique at different metal loadings has been investigated by EXAFS (Extended X-ray Absorption Fine Structure Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), SAXS (Small-Angle X-ray Scattering), WAXS (Wide-Angle X-ray Scattering) and TEM (Transmission Electron Microscopy). According to EXAFS and XPS, a fraction of the Rh atoms is oxidised, but a noticeable part is also present as . The Rh oxidation is attributed to the interaction of the Rh atoms with the hydroxyls of the support; after the formation of the oxide, the nucleation of metallic rhodium becomes possible. The WAXS data do not show evidence of rhodium fcc crystallites; the metal-bearing particles are probably amorphous and/or very small, as results from the SAXS and TEM data analysis. The disagreement between the latter two techniques, resulting in a small-angle determination of the average size of the particles that is about half that of TEM in the catalyst with the higher Rh loading, is acknowledged and discussed. Preliminary catalytic tests are described, demonstrating the suitability of using a low surface area support for the preparation of SMAD catalysts.

PACS: 61.10.Eq – X-ray scattering (including small-angle scattering) / 61.10.Ht – X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. / 61.16.Bg – Transmission, reflection and scanning electron microscopy (including EBIC)

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999