The development of low-cost and toxicity-free cobalt oxide-based catalysts for propane dehydrogenation to propylene (PDH) has gained momentum. Titanosilicate-1 (TS-1) supported CoO_x catalysts doped with different alkali and alkaline earth metal ions (M = Na, K, Mg, Ca and Ba) were prepared by adjusting the acidity, reducibility and oxidation state to increase the activity and stability during the PDH reaction. It was found that the decrease in the number of Lewis acid sites and lack of Co²⁺O_x species with the addition of K ions led to an almost complete loss of the activity of the Co-K catalyst. However, Co-Ca catalyst exhibited moderate acidity, more Lewis acid sites, a larger amount of the in-situ formed highly-dispersed metallic Co⁰ nanoparticles (~5 nm) and Co²⁺O_x species strongly interacting with the support, all of which were responsible for its highest space-time yield (STY) of propylene formation. Though Co₃O₄ particles were more active for the side reactions, they could be readily reduced to metallic Co⁰ nanoparticles during the PDH process, and increased the selectivity to propylene with time on stream. Specifically, it was demonstrated that the highly dispersed metallic Co⁰ nanoparticles were also active for the PDH activity, but was lower than Co²⁺O_x species that were strongly interacted with TS-1 support.

The article links: https://doi.org/10.1016/j.fuel.2024.132259