Bimetallic clusters confined inside silicalite-1 for stable propane dehydrogenation

The noble metal-based bimetallic clusters with high atom utilization and surface energy have been widely applied in heterogeneous catalysis, but the stabilization of these metastable clusters in harsh reaction conditions is quite challenging. Herein, we synthesize a series of Pt-, Pd-, and Ru-based clusters promoted by a second non-noble metal (Zn, Cu, Sn, and Fe), which are confined inside silicalite-1 (pure silica, S-1) crystals by a ligand-protected method. The second metal could well stabilize and disperse the noble atoms inside the rigid S-1 zeolites via Si-O-M bonds, thus enabling to lower the usage of expensive noble metals in catalysts. The as-synthesized bimetallic catalysts exhibited excellent performance in non-oxidative propane dehydrogenation (PDH) reaction, which is typically operated above 500 °C. The PtZn@S-1, PtCu@S-1, and PtSn@S-1 with only a ∼ 0.17 wt.% Pt loading offer a significant enhancement in PDH performance compared with the conventional PtSn/Al2O3 catalyst with a 0.5 wt.% Pt loading prepared by impregnation method. Notably, the PtSn@S-1 provides a propane conversion of 45% with a 99% propylene selectivity at 550 °C, close to the thermodynamic equilibrium. Furthermore, the PtSn@S-1 exhibits excellent stability during 300 h on stream and high tolerance to regeneration by a simple calcination step.