(44k) Effect of Phosphorus Modification over Pt/Al2O3 catalyst for Non-Oxidative Propane Dehydrogenation

Catalytic dehydrogenation of propane to propene is important for the production of high-value chemical intermediates such as polypropylene, propylene oxide, and acrylic acid. Pt-based catalysts are considered to be promising catalysts due to their high catalytic activity for C-H bond cleavage. Here, we report the catalytic properties of phosphorus (P) modified Pt/Al₂O₃ for propane dehydrogenation.

To elucidate the promotion effect of P and its role during the reaction, 1Pt-xP/Al₂O₃ (x=1~5, wt %) catalysts were prepared by sequential wet impregnation. The physicochemical properties of the catalysts were investigated by CO chemisorption, x-ray diffraction, in-situ x-ray absorption spectroscopy, propane temperature programmed surface reaction spectroscopy, and CO diffuse reflectance infrared fourier transformation spectroscopy.

The addition of phosphorus to Pt catalysts leads to the formation of Pt-P alloy during 600 °C reduction pretreatment. The formation of Pt-P alloy results in the co-presence of metallic Pt and Pt-P alloy in the Pt nanoparticles of the P-modified catalysts. For the propane dehydrogenation at 600 °C, the unmodified 1Pt-0P/Al₂O₃ catalyst showed 38% propane conversion and 83% propylene selectivity. However, P-modified 1Pt-1P/Al₂O₃ catalyst showed dramatically increased selectivity of 95% at similar conversion, indicating a synergistic effect of metallic Pt and Pt-P alloy species on catalytic performance for PDH. The addition of more P content leads to a further increase in propylene selectivity, but excess Pt-P alloy species lowered the activity of 1Pt-xP/Al₂O₃ catalysts. We found that the metallic Pt is the main active species, but Pt-P alloy species promote the selective formation of propylene by suppressing cracking activation.