Surface hydroxyl-modulation for constructing isolated vanadium active species for propane dehydrogenation

Vanadium-based catalysts have been regarded as a promising candidate for Pt- and Cr-based materials in propane dehydrogenation (PDH) application. However, regulating the coordination environment and polymeric degree of vanadium oxides (VO_X) at nanoscale level remains great challenges. Herein, an efficient VO_X catalyst with the adjustable polymeric degree is achieved by a surface hydroxyl-modulation. Specially, the physicochemical properties of VO_X species are precisely regulated by controlling the density and dispersion of hydroxyl (OH) on silicalite-1 (S-1). The properly introduced OH could effectively tailor the polymeric degree of VO_X species. Characterization results reveal the VO_X sites preferentially tend to migrate and anchor on the OH groups, thereby contributing to the high dispersion of VO_X sites with tetrahedrally coordinated VO₄ sites. Besides, the OH regulation is also favorable for moderating the surface V density, electron-rich V³⁺, and the isolated VO_X active species. Benefiting from the active sites with suitable polymeric degree, the optimal 5VO_X/S-1_550 catalyst exhibits outstanding catalytic activity (initial propane conversion of 24.5 %, initial propylene selectivity of 96.7 %) and stability under industrial conditions, which is comparable to the previously reported vanadium-based catalysts. This work not only affords an alternative methodology for the rational design of VO_X-based catalysts, but also paves a way to improving PDH performance at the nanoscale.