PROPENE HYDROGENATION ON LOW-TEMPERATURE REDUCED PT/TIO2 - EFFECTS OF TIO2 PHASES AND H-2 TREATMENT ON SPECIFIC CATALYTIC ACTIVITY

TiO2 gel obtained by hydrolysis of titanium tetra-n-butoxide was heated at various temperatures, providing poorly crystallized TiO2, disordered anatase and a well crystallized anatase-rutile mixture. Platinum dispersion was obtained on these TiO2 supports by the reduction of platinum-allyl species with H-2 at 278 K. These catalysts and a Pt/SiO2-gel sample were used for propene hydrogenation at various temperatures and H-2/propene molecular ratios. Fresh and run catalysts were subjected to X-ray diffraction analysis for the study of extant phases and determination of average size of platinum particles. In all cases, results obtained for catalysts as prepared or after H-2 treatment at 493 K indicated that the ordinary hydrogenation mechanism was maintained but that important changes of specific catalytic activity were observed, depending on H-2 treatment and nature of the support. TiO2 morphology was assumed to be responsible for the specific activity decrease in Pt on the rutile-anatase mixture and for the opposite effect found for platinum on anatase.