Catalytic Properties of PtSn/Al₂O₃/MCM-41 Catalysts for Propane Dehydrogenation

The catalytic properties of PtSn/γ-Al2O3, PtSn/MCM-41 and PtSn/Al2O3/MCM-41 catalysts for propane dehydrogenation were studied using microreactor tests combined with X-ray diffraction (XRD), BET surface area and pore structure measurements, temperature-programmed reduction (TPR), H2-chemisorption and thermogravimetric (TG) analysis. It was shown that the PtSn catalysts supported on Al2O3-modified MCM-41 (Al2O3/MCM-41) exhibited higher activity than the PtSn/MCM-41 catalyst, and higher catalytic stability than the conventional PtSn/γ-Al2O3 catalyst for propane dehydrogenation. The characterization results of the catalysts revealed that on the surface of pure MCM-41, the dispersed Sn species were easier to be reduced to metallic state due to weak interaction of Sn with MCM-41 support, resulting in lower Pt dispersity and thus lower catalytic activity. In contrast, modifying the surface of MCM-41 by alumina could enhance the interaction between Sn and Al2O3/MCM-41 support, and increase Pt dispersity and catalytic activity for propane dehydrogenation. Moreover, the PtSn/Al2O3/MCM-41 catalysts had larger bare fraction of Pt surface after coke deposition, leading to their higher catalytic stability than the PtSn/γ-Al2O3 catalyst. It is suggested that the unique catalytic properties of PtSn/Al2O3/MCM-41 catalysts are correlated not only to the strong interaction of Sn with Al2O3/MCM-41support but also to the mesoporous structure of the Al2O3/MCM-41 support.