Premium
X‐ray photoelectron spectroscopic and thermogravimetric studies of rhenium oxides supported on silica
Author(s) -
Cimino A.,
Gazzoli D.,
Inversi M.,
Valigi M.
Publication year - 1987
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740100404
Subject(s) - rhenium , perrhenate , x ray photoelectron spectroscopy , thermogravimetry , thermogravimetric analysis , thermal decomposition , volatilisation , decomposition , oxide , chemistry , inorganic chemistry , materials science , chemical engineering , organic chemistry , engineering
Silica supported rhenium catalysts, containing up to 14% Re (metal) by weight obtained by impregnation with an ammonium perrhenate solution and dried at 110°C, were studied as prepared and then subjected to heat treatments in air, 3 h, in the temperature range 200–750°C. X‐ray photoelectron spectroscopy (XPS) and thermogravimetry (TG), paralleled by chemical analysis and x‐ray diffraction, were applied to identify the occurrence of an interaction between rhenium species formed by thermal decomposition of NH 4 ReO 4 and silica. The results indicate that a weak interaction exists between the products of decomposition of NH 4 ReO 4 and silica, influencing the morphology of the rhenium oxide formed and the temperature of volatilization. The starting material consists of large NH 4 ReO 4 crystals dispersed in the small Cabosil spheres, in agreement with the XPS results (low I(Re)/I (Si) intensity ratio). By heating in air the Re(VII) oxide, produced by the decomposition of the perrhenate, spreads over the silica, as shown by the rise of I(Re)/I (Si) intensity ratio, and its volatilization is slowed down markedly. The volatilization eventually leads to complete loss of Re at about 750°C. The Re(VII) species formed is not in homogeneous situation as indicated by the broadening of the Re 4f peak. A possible scheme for the interaction with the support is suggested.