Highly Dispersed Cobalt Species Stabilized by Silanol Groups on Alkali-Treated Silicalite-1 for Propane Dehydrogenation

Cobalt-based catalysts are promising for propane dehydrogenation (PDH), but their practical application is hindered by limited propylene yields, rapid deactivation, and an incomplete understanding of the catalytically relevant Co species. Here, alkaline treatment was used to increase the density of silanol defects on Silicalite-1, thereby creating abundant anchoring sites for highly dispersed Co species. The resulting Co/Silicalite-1 catalyst achieved 45% propane conversion, 96% propylene selectivity, and stable operation over 60 h on stream (kd = 0.005 h−1). Combined characterization indicates that silanol defects stabilize highly dispersed, defect-anchored Co species that are responsible for the superior PDH performance. By contrast, supports with lower silanol defect densities favor aggregated CoOx/Co3O4-like species, which are less selective for PDH, more susceptible to reduction to metallic Co under reducing conditions, and more prone to cracking and coke formation. These findings reveal a strong correlation between silanol defect density, Co speciation, and catalytic performance, offering mechanistic insights and design principles for the development of efficient PDH catalysts.