EFFECT OF THE PHASE OF TITANIUM-OXIDE ON METAL-SUPPORT INTERACTION

The metal-support interaction in the system of platinum supported on t itanium oxides of different crystalline structures was investigated. T itanium oxide powders used as supports were prepared by neutralization of TiOCl2-analogue solution with either NaOH or NH3 base at varied pH . Pt was introduced onto the supports by impregnation. The phenomenon of strong metal-support interaction (SMSI) was determined by the suppr ession of chemisorption of H-2 over samples reduced at 773 K, in compa rison with the behavior of samples reduced at 473 K. The loss of adsor ption capacity was proved not due to metal sintering by examining the recovery of adsorption capacity after reduction, reoxidation and reduc tion cycle, accompanied with examination of the size of Pt particle wi th an x-ray diffractiometer and a transmission-electron microscope. Th e results showed that SMSI phenomenon was common to Pt supported on ti tanium oxides of all the varied crystalline structures. However, the c hemisorption capacity of Pt reduced at 473 K varied greatly with the s odium content in the supports, which in turns affects the crystalline structure of titanium oxide. These results are attributed mainly to el ectronic effect endowed by the support.