Propane Dehydrogenation over Pt/TiO2–Al2O3 Catalysts

Abstract

This paper describes an investigation on understanding catalytic consequences of Pt nanoparticles supported on a TiO 2 –Al 2 O 3 binary oxide for propane dehydrogenation (PDH). The TiO 2 –Al 2 O 3 supports were synthesized by a sol–gel method, and the Pt/TiO 2 –Al 2 O 3 catalysts were prepared by an incipient wetness impregnation method. Both as-prepared and post-experiment catalysts were characterized employing N 2 adsorption–desorption, X-ray diffraction, Raman spectra, H 2 –O 2 titration, temperature-programmed desorption, thermogravimetric analysis, temperature-programmed oxidation, transmission electron microscopy, and Fourier-transform infrared spectra of chemisorbed CO. We have shown that TiO 2 is highly dispersed on Al 2 O 3, and the addition of appropriate amount of TiO 2 improves propylene selectivity and catalytic stability, which is ascribed to the electron transfer from partially reduced TiO x ( x < 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 TiO 2, however, also increases the amount of strong acid centers on the supports and the excessive TiO 2 addition might lead to a significant amount of coke formation. The electron transfer effect and the acid sites effect of TiO 2 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 TiO 2 loading. An optimal loading content of TiO 2 is 10 wt %, which results in a higher propylene selectivity and a better stability.