Ultra-small Metallic Nickel Nanoparticles on Dealuminated Zeolite for Active and Durable Catalytic Dehydrogenation

Each step in the catalyst synthesis process plays an important role in tuning the catalyst structures. For zeolite-supported nickel catalysts, we found the conventional calcination-reduction method typically leads to the formation of large nickel particles, but a pre-aging in hydrogen or nitrogen at a low temperature prior to final reduction can result in ultra-small nickel nanoparticles in a metallic state. This pre-aging treatment facilitates the interaction between Ni²⁺ cations and silanol nests on zeolite before the decomposition of the metal salt, leading to the formation of nanoparticles with an average diameter of ~1.2 nm. In contrast, the pre-calcination in oxygen caused the Ni²⁺ aggregation before the decomposition of the metal salt precursor, yielding nickel nanoparticles larger than 5 nm. Given the structure sensitivity of nickel in cyclohexane dehydrogenation for hydrogen production, the ultra-small nickel nanoparticles exhibited significantly enhanced activity and durability compared to previous nickel catalysts.