Elucidating strong metal-support interactions in Pt–Sn/SiO2 catalyst and its consequences for dehydrogenation of lower alkanes.

The addition of tin (Sn) is commonly used as a design strategy for catalyst optimization of platinum-based catalysts. The mechanistic understanding of this class of systems is, however, obscured by the structural complexity. Herein, a series of catalyst characterization techniques including X-ray absorption fine structure (XAFS) and in-situ CO diffuse reflectance infrared fourier transform spectroscopy (CO-DRIFTS) were utilized to study the catalyst structure. It was found that the structure and catalytic properties are closely related with the interaction between Pt and SnO 2 (specifically the Pt-SnO 2 strong metal-support interaction (SMSI)), which can be continuously tuned by thermal treating the Pt-Sn/SiO 2 precursor at different atmospheres and temperatures. The treatment in an oxidative atmosphere (O 2 ) also can generate Pt-SnO 2 SMSI, which became weak at higher temperatures and led to the growth of Pt nanoparticles (NPs). Pt-SnO 2 SMSI became stronger when the oxygen atmosphere was changed to an inert (N 2 ) atmosphere. Small metallic Pt NPs were formed and their dispersion was increased with increasing treatment temperature with inert gas. The catalyst presented a moderate activity in the dehydrogenation of lower alkanes. The treatment in a reductive atmosphere (H 2 ) produced the strongest Pt-SnO 2 SMSI and most active catalyst. Highly dispersed Sn surface-enriched Pt–Sn alloy NPs were formed on SiO 2 , in which Pt was most electron rich. The apparent activation energy in n -butane dehydrogenation is higher on Pt–Sn/SiO 2 _1073 K H 2 than the corresponding one on Pt–Sn/SiO 2 _1073 K N 2 . The kinetic studies revealed that the extreme isolation of Pt on Pt–Sn/SiO 2 _1073 K H 2 (geometrical effects) dominantly contributed to its superior catalytic performance. The present work highlights the effects of thermal treatment-induced Pt-SnO 2 SMSI, providing a new insight into the structure of Pt–Sn bimetallic catalysts and the promotional role of Sn in the dehydrogenation of lower alkanes to olefins on Pt surfaces. [ABSTRACT FROM AUTHOR]