Metal confinement and silanol chemistry for durable PtSn catalysts in CO2-assisted propane dehydrogenation

CO 2 -assisted oxidative dehydrogenation of propane (CO 2 –ODHP) is a promising route to overcome the thermodynamic limitations of conventional propane dehydrogenation while enabling CO 2 utilization. However, PtSn/SiO 2 catalysts still suffer from rapid deactivation under CO 2 –ODHP conditions, the origin of which remains poorly understood. Herein, we systematically elucidate the deactivation mechanism of PtSn/SiO 2 catalysts and propose a silica encapsulation strategy to simultaneously suppress metal sintering and refractory coke formation. Although the introduction of CO 2 significantly reduces overall coke deposition, the PtSn/SiO 2 catalyst exhibits accelerated deactivation due to severe nanoparticle sintering and the accumulation of highly graphitized carbon species. By applying a controlled SiO 2 overcoating via a modified Stöber method, PtSn nanoparticles are effectively stabilized through the formation of robust Sn–O–Si anchoring linkages. An optimal silica loading of 5 wt% affords the Si(5)@PtSn/SiO 2 catalyst with a dramatically reduced deactivation rate constant (0.007 h⁻¹), while maintaining high propylene selectivity. Comprehensive TGA, Raman, and GC–MS analyses reveal that long-chain organosilane species (C 29 H 62 O 2 Si) constitute the key precursor for soluble coke species associated with silanol sites under CO 2 –ODHP conditions. The formation of these species is strongly correlated with the density of isolated surface silanol groups, which promote Si–O–C bond formation and permanently anchor coke precursors on the catalyst surface. The silica overcoating effectively modulates isolated silanol environment via enhanced hydroxyl condensation, thereby suppressing the generation of organosilane-derived coke nuclei. This work provides molecular-level insight into coke evolution on silica-supported Pt catalysts and demonstrates that balancing metal confinement with surface hydroxyl chemistry is critical for designing durable Pt-based catalysts for CO 2 -assisted propane dehydrogenation.