Oxidative Dehydrogenation of Propane over Pt-Sn/Si-Beta Catalysts: Key Role of Pt-Sn Interaction

The selective oxidative dehydrogenation of propane (ODHP) represents an attracting route for propylene production. Despite of significant achievements made so far, eligible ODHP catalysts with high propylene selectivity at acceptable propane conversions are still being explored.

Herein, we report the construction of bimetallic Pt-Sn catalysts supported on dealuminated Si-beta zeolite, which exhibit remarkable performance in ODHP reaction (75% propylene selectivity at 37% propane conversion, and 1.22 g_C3H6/(g*h)propylene productivity at 773 K). With silanols created from zeolite dealumination as anchoring sites, the homogeneous distribution of Pt and Sn species is guaranteed and their close contact is clearly demonstrated by electron microscopy analyses. The key role of Pt-Sn interaction in ODHP is therefore established.

Characterization results from temperature-programmed reduction by hydrogen (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) indicated the interaction between Pt and Sn species, and the electron transfer from SnO₂ to Pt species was clearly demonstrated by XPSand FTIR spectra of CO adsorption. Temperature-programmed desorption experiments revealed that the propane adsorption was significantly strengthened while the propylene adsorption weakened on bimetallic Pt-Sn/Si-beta catalyst, which accordingly resulted in its remarkable performance in ODHP reaction. The TEM analyses on the catalyst before and after reaction are very impressive. The spatial separation of Pt and Sn species was observed on used Pt-Sn/Si-beta catalyst and it was responsible for the catalytic deactivation.