Modification of Zeolites with Tin to Synthesize Pt–Sn/MFI Catalysts for Propane Dehydrogenation

Modification of MFI-type zeolites with tin involves impregnating the zeolite with an SnCl2 solution in excess NaCl, calcination (to fix the tin oxide), and water washing (to remove excess NaCl). Loading platinum on the tin-modified support results in a highly active (5–10 mol of C3H6 per mol of Pt per second), selective (96–98% towards propylene), and stable catalyst for dehydrogenation of propane. Due to the high dispersion of tin, which serves as an anchor for platinum, the average Pt particle size is 1.2 nm. The dispersion of tin is facilitated not only by the molecular dilution of its precursor with sodium chloride but also by the redispersion of tin across the surface due to the formation of volatile SnCl4 during calcination.