CO2 REFORMING OF CH4 OVER SUPPORTED PT CATALYSTS

The kinetics of CO2 reforming of CH4 were studied over Pt supported on TiO2, ZrO2, Cr2O3, and SiO2, and the catalysts were characterized usi ng chemisorption, X-ray diffraction, diffuse reflectance infrared Four ier transform spectroscopy (DRIFTS), temperature-programmed hydrogenat ion (TPH), and temperature-programmed surface reaction. Although the P t/SiO2 and Pt/Cr2O3 catalysts deactivated significantly within 5 and 1 5 h onstream, respectively, the Pt/ZrO2 and Pt/TiO2 catalysts exhibite d much higher stability even after 80 to 100 h onstream. TPH results w ith used catalysts showed that both Pt/ZrO2 and Pt/TiO2 have suppresse d carbon deposition under reaction conditions. H-2 and CO chemisorptio n as well as DRIFTS provided evidence of metal-support interactions in the Pt/TiO2 catalyst and indicated that large ensembles of Pt atoms, active for carbon deposition, are deactivated or destroyed by the pres ence of mobile TiOx species. Activities for CO formation and CH4 consu mption on a turnover frequency basis were five times greater on Pt/TiO 2 compared with the other catalysts, suggesting that active sites for reforming are created in the Pt-TiOx interfacial region. The kinetic b ehavior was explained well by a kinetic model recently proposed for su pported Ni. (C) 1998 Academic Press.