PROPENE HYDROGENATION ON LOW-TEMPERATURE REDUCED PT TIO2 - EFFECTS OFTIO2 PHASES AND H-2 TREATMENT ON SPECIFIC CATALYTIC ACTIVITY/

TiO2 gel obtained by hydrolysis of titanium tetra-n-butoxide was heate d at various temperatures, providing poorly crystallized TiO2, disorde red anatase and a well crystallized anatase-rutile mixture. Platinum d ispersion was obtained on these TiO2 supports by the reduction of plat inum-allyl species with H-2 at 278 K. These catalysts and a Pt/SiO2-ge l sample were used for propene hydrogenation at various temperatures a nd H-2/propene molecular ratios. Fresh and run catalysts were subjecte d to X-ray diffraction analysis for the study of extant phases and det ermination of average size of platinum particles. In all cases, result s obtained for catalysts as prepared or after H-2 treatment at 493 K i ndicated that the ordinary hydrogenation mechanism was maintained but that important changes of specific catalytic activity were observed, d epending on H-2 treatment and nature of the support. TiO2 morphology w as assumed to be responsible for the specific activity decrease in Pt on the rutile-anatase mixture and for the opposite effect found for pl atinum on anatase.