Alumina-supported non-noble metal high-entropy catalysts with stabilized active tetrahedral Co2+ species for propane dehydrogenation
Abstract
Co-based catalysts are promising non-noble metal candidates for propane dehydrogenation (PDH) owing to the high activity and cost-effectiveness, while their stability is limited by the rapid sintering and coking deactivation during reaction. Herein, an alumina-supported non-noble metal high-entropy catalyst (CoGaZnCeCaOx/Al2O3) with stabilized active tetrahedral Co2+ species was designed based on the high electronegativity of Co species, exhibiting the propane conversion of 18.5% with propylene selectivity of 80.0% at 600 °C over 50 h with a deactivation rate constant as low as 0.0035 h-1. Due to the sluggish diffusion effect of high-entropy structure, the migration of surface metal species was hindered. This prevented the aggregation of crystalline particles, allowing the metals to remain highly and uniformly dispersed while remaining stable even under a strongly reducing atmosphere. The high configurational entropy suppressed the precipitation of metallic Co during reduction and ensured stability of the tetrahedral Co2+ species. Meanwhile, the higher electronegativity rendered Co2+ species electron-rich, promoting propylene desorption and inhibiting deep dehydrogenation, which thereby significantly boosted anti-coking performance of CoGaZnCeCaOx/Al2O3, as coke deposited was nearly four times lower than on CoOx/Al2O3. Additionally, such high-entropy catalyst showed superior regenerability, featuring uniform element distribution and no detectable Co sintering after regeneration. This work provides a new strategy for developing stable non-noble metal PDH catalysts.
