A STUDY OF SILICA-SUPPORTED PLATINUM CATALYSTS BY TEMPERATURE-PROGRAMMED REDUCTION

Temperature programmed reduction (TPR) has been used to study the reduction pattern of silica-supported platinum catalysts. It is observed that Aerosil impregnated with H2PtCl6 gives one reduction peak with T-max equal to 436 degrees C, whereas Aerosil impregnated with [Pt(NH3)(4)](OH)(2) gives two distinct peaks in the regions of 207 and 399 degrees C; the integrated peak area is not affected by variation in the heating rate. TPR profiles show that in each case, the reduction peak was immediately followed by a small but clear hydrogen desorption trough with a minimum always around 580 degrees C. This indicates that there is evidently an overlap between the process of reduction (including hydrogen chemisorption) and hydrogen desorption. After correction for the overlap between hydrogen uptake and desorption, the hydrogen consumed in the reduction was calculated and interpreted.