Pt-Sn clusters anchored at Al3+penta sites as a sinter-resistant and regenerable catalyst for propane dehydrogenation

Abstract

Pt-based catalysts are widely used in propane dehydrogenation reaction for the production of propylene. Suppressing irreversible deactivation caused by the sintering of Pt particles under harsh conditions and regeneration process is a significant challenge in this catalyst. Herein, a series of highly ordered mesoporous Al2O3 supports with different levels of Al3+penta sites, are fabricated and used as the support to disperse Pt-Sn2 clusters. Characterizations of Pt-Sn2/meso-Al2O3 with XRD, NMR, CO-IR, STEM, TG, and Raman techniques along with propane dehydrogenation-regeneration cycles test reveal the structure-stability-regenerability relationship. The coordinatively unsaturated pentacoordinate Al3+ (Al3+penta) can strongly anchor Pt atoms via a formation of Al-O-Pt bond, and thus stabilize the Pt-based particles at the surface of Al2O3. The stability and regenerability of Pt-Sn2/meso-Al2O3 are strongly dependent on the content of Al3+penta sites in the Al2O3 structure, and a high level of Al3+penta sites can effectively prevent the agglomeration of Pt-Sn2 clusters into large Pt nanoparticles in the consecutive dehydrogenation-regeneration cycles. The Pt-Sn2/meso-Al2O3-600 with the highest level of Al3+penta (50.8%) delivers the best performance in propane dehydrogenation, which exhibits propane conversion of 40% and propylene selectivity above 98% at 570 °C with 10 vol% C3H8 and 10 vol% H2 feed. A slow deactivation in this catalyst is ascribed to the formation of coke, and the catalytic performance can be fully restored in the consecutive dehydrogenation-regeneration cycles via a simple calcination treatment.