L. Schlegel et al., SOLID-STATE ION-EXCHANGE OF RHODIUM CHLORIDE WITH HIGHLY DEALUMINATEDY-TYPE ZEOLITE DAY BY THERMAL-TREATMENT AND IN THE PRESENCE OF CARBON-MONOXIDE, Catalysis letters, 23(3-4), 1994, pp. 215-226
The solid-state ion exchange of Rh chloride with highly dealuminated Y
zeolite has been studied by in situ FTIR spectroscopy. Thermal treatm
ent in vacuum and calcination in oxygen up to 600-degrees-C results in
an exchange limited to ca. 25% at temperatures higher than 400-degree
s-C. The ion exchange can be performed much more effectively (over 50%
) and at lower temperatures (100-150-degrees-C) in the presence of CO
in the gas phase. A linear correlation has been found between the form
ation of well-defined Rh(CO)2+ species and the simultaneous loss of ac
id hydroxyl groups for samples treated at different conditions. From t
hese results a model is proposed with the formation of Rh subcarbonyls
, the migration of these species to the cation positions of the zeolit
e and, finally, the formation of the stable well-defined Rh(CO)2+ spec
ies at these positions as essential steps of the ion exchange in the p
resence of CO.