Propane Dehydrogenation over Pt/TiO₂–Al₂O₃ Catalysts

This paper describes an investigation on understanding catalytic consequences of Pt nanoparticles supported on a TiO₂–Al₂O₃ binary oxide for propane dehydrogenation (PDH). The TiO₂–Al₂O₃ supports were synthesized by a sol–gel method, and the Pt/TiO₂–Al₂O₃ catalysts were prepared by an incipient wetness impregnation method. Both as-prepared and post-experiment catalysts were characterized employing N₂ adsorption–desorption, X-ray diffraction, Raman spectra, H₂–O₂ titration, temperature-programmed desorption, thermogravimetric analysis, temperature-programmed oxidation, transmission electron microscopy, and Fourier-transform infrared spectra of chemisorbed CO. We have shown that TiO₂ is highly dispersed on Al₂O₃, and the addition of appropriate amount of TiO₂ improves propylene selectivity and catalytic stability, which is ascribed to the electron transfer from partially reduced TiO_<i>x</i> (<i>x</i> < 2) to Pt atoms. The increased electron density of Pt could reduce the adsorption of propylene and facilitate the migration of coke precursors from the metal surface to the support. The addition of TiO₂, however, also increases the amount of strong acid centers on the supports and the excessive TiO₂ addition might lead to a significant amount of coke formation. The electron transfer effect and the acid sites effect of TiO₂ addition exert an opposite influence on catalytic performance. The trade-off between the electron transfer effect and the acid sites effect is studied by varying the amount of TiO₂ loading. An optimal loading content of TiO₂ is 10 wt %, which results in a higher propylene selectivity and a better stability