THERMAL-DECOMPOSITION AND FTIR STUDY OF PYRIDINE ADSORPTION ON PT SIO2 SONOGEL CATALYSTS/

Platinum/SiO2 sonogel has been compared with the corresponding xerogel and an impregnated catalyst. The thermal behavior, the FTIR spectra a nd the pyridine adsorption show that Lewis acidity is present in the i mpregnated sample. In the sonogel, Lewis acidity turns to be very low and insensitive to desorption temperature. In the xerogel, both Lewis and Bronsted acidity was observed. In each sample, reduction in situ ( without hydrogen flow) of the metal phase is determined by the OH cont ent. Platinum is highly reduced in the sonogel, partially reduced in t he xerogel and very slightly reduced in the impregnated sample.