Silica- and L-zeolite-supported Pt, Pt/Sn and Pt/Sn/K catalysts for isobutane dehydrogenation Original Research Article

Reaction kinetics measurements, temperature programmed oxidation (TPO), transmission electron microscopy, and chemisorption measurements were used to study silica- and L-zeolite-supported Pt catalysts for isobutane dehydrogenation at 798 K in pure isobutane and at 873 K with a 2 : 1 hydrogen : isobutane feed. Highly selective dehydrogenation catalysts were prepared by depositing Pt and Sn on K-L-zeolite, as well as by depositing Pt, Sn, and K on silica. At 873 K and in the presence of hydrogen, the Pt/Sn/K-L catalysts exhibited significantly higher rates of isobutene production compared to the Pt/Sn/K/silica catalyst. Addition of Sn and K to Pt decreased the extent of carbon deposition on the catalysts by reducing the size of the Pt surface ensembles, thereby inhibiting the formation of highly dehydrogenated surface species that lead to coke and other undesirable products (e.g. hydrogenolysis). The presence of Sn may also facilitate the transport of the carbon deposits from the active sites to the support. In the absence of hydrogen, the pores of Pt/K-L-zeolite become blocked by carbonaceous deposits during isobutane dehydrogenation at 798 K. At 873 K and in the presence of hydrogen, the Pt/Sn/K-L catalysts exhibit deactivation due to coking, enrichment of the surface with tin, and/or sintering of the metal particles.