IFISUR   23398
INSTITUTO DE FISICA DEL SUR
Unidad Ejecutora - UE
artículos
Título:
Palladium nanoparticles´s surface structure and morphology effect on the catalytic activity for dry reforming of methane.
Autor/es:
IGNACIO O. COSTILLA; MIGUEL D. SÁNCHEZ; CARLOS E. GIGOLA
Revista:
APPLIED CATALYSIS A-GENERAL
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2014 vol. 478 p. 38 - 44
ISSN:
0926-860X
Resumen:
Low loaded Pd/a-Al2O3 catalysts (< 0.5% Pd) were characterized and tested for CH4 reforming with CO2 at 650oC. The catalysts were prepared by a recharging   procedure, using an organometallic precursor, followed by intermediate washing and calcinations steps. FTIR spectra of adsorbed CO showed that the Pd surface structure and the particle size were dependent on the number of post-impregnation washing steps. A catalyst sample with a metal dispersion of 33% showing well defined low-index planes and nearly spherical particles was obtained using two-washing steps. It exhibited a high initial activity for CH4 reforming with CO2, followed by a pronounced deactivation due to carbon nanofibers formation and sintering. TEM analysis of the used catalyst revealed the presence of spherical Pd particles at the end of the fibers not attached to the support surface.  On the other hand a high dispersion sample (78%) possessing a large fraction of Pd atoms of low coordination was obtained applying three-washing steps after impregnation. High-resolution transmission electron microscopy (HRTEM) revealed the presence of small hemispherical particles and larger nearly flat ones attached to the support. In this case the catalyst showed a very low initially activity that increased slowly with time up to a steady value. Although sintering also occur and the surface structure of the used catalyst resembled that of low dispersion sample the amount of carbon formed was quite low The observed activation under reaction conditions was associated with the slow development of a surface structure that exhibits mainly the (100) plane favoring the dissociation of methane. However, the initial strong interaction of the particles with the support suggested by HRTEM micrographs seems to remain unaltered despite the particle size increase and consequently the process of nanofibers formation was inhibited.