Elucidating the underlying surface chemistry of Sn/Al2O3 catalysts during the propane dehydrogenation in the presence of H2S co-feed

Incipient wetness impregnation was used to deposit dispersed tin (Sn) atoms on gamma-Al2O3. The morphology and structure of the catalysts were characterized using Raman, X-ray Photoelectron Spectroscopy (XPS), and low energy ion scattering (LEIS) combined with N-2-physisorption and in situ infrared diffuse reflectance spectroscopy (DRIFTS) using NH3 and CO2 as probe molecules, H-2- temperature-programmed reduction (H-2-TPR), and steady-state reaction kinetics measurements. The effects of H2S on the surface chemical composition and structure of the resulting catalysts were systematically studied. The results showed isolated and well-dispersed Sn oxide sites of the deposited catalyst with nanoparticles observed only at relatively high coverages of 10% Sn at a coverage ranging from 0.48 to 2.8 Sn atoms nm(-2). DRIFT spectroscopy evidenced a decrease in the number of Lewis acid sites on H2S treated Sn/Al2O3 suggesting surface tin species re-dispersing and blocking the active sites of gamma-Al2O3. Overall, the surface analysis results presented here suggest that the active catalytic sites in the presence of H2S involve Al2O3 rather than bulk sulfide and Sn atoms dispersed over alumina towards propane dehydrogenation.

Automated summary

Initiated by incipient wetness impregnation, dispersed tin atoms were deposited on gamma-Al2O3. Various characterization techniques were used to analyze the morphology and structure of the catalysts, revealing isolated and well-dispersed Sn oxide sites at relatively high coverages. The study suggests that active catalytic sites during propane dehydrogenation involve Al2O3 rather than bulk sulfide and Sn atoms dispersed over alumina.