CoO_x Nano-clusters anchored onto 10-membered ring of Silicate-1 boost propane dehydrogenation.

Abstract

Cobalt-zeolites catalysts for propane dehydrogenation (PDH) suffer from low activities on the confined Co sites in zeolites or poor stabilities on the CoO_x species in presence of hydrogen. In this work, we synthesize a unique Co structure with (≡Si-O)₂Co(≡Si-O)₂…CoO clusters (smaller than 2 nm) onto desilicated Silicate-1 via impregnation-dry gel transformation approach. This structure leads to a high C₃H₆ formation rate of 34 mmol g_cat^-1 h^-1 as well as a low deactivation rate of 0.0116 h^-1 at specific conditions (100% propane, 550 °C, 5.0 h^-1, 72 h), outperforming currently reported Co-based catalysts in terms of maximum activity and stability. The integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM) and extended X-ray absorption fine structure (EXAFS) measurements confirm that CoO clusters bond with the O atoms adjacent to the tetrahedrally coordinated Co single sites anchored on the 10-membered ring of Silicate-1. The electron-negativity property of ((≡Si-O)₂Co(≡Si-O)₂…CoO) species facilitates the adsorption of H^* from C₃H₈ and the following dehydrogenation steps, and thus enhancing the overall activity, while its lower formation energy ensures the higher catalyst stability even in presence of hydrogen atmosphere. The designed Co-based catalyst offers great potential for taking the combined advantages of Co singles atoms as well as CoO_x clusters for high-performance PDH.