Catalyst deactivation and regeneration during methane catalytic cracking over supported nickel catalysts

Abstract

Catalytic deactivation through carbon deposition, or coking, is a critical challenge in methane catalytic cracking, especially when utilizing nickel-based catalysts. Nickel catalysts are renowned for their high activity and selectivity; however, they are highly susceptible to deactivation due to carbonaceous deposits. These deposits obstruct active sites, encapsulate catalyst particles, and reduce pore accessibility, compromising overall performance. This study investigates the mechanisms of coking of carbon deposits while forming the desired carbon filament, focusing on carbon filament nucleation and growth and the impact of these processes on catalyst performance.

Carbon diffusion and precipitation through nickel catalysts are essential for carbon filament (CF) growth during methane catalytic cracking. This process, driven by a concentration gradient across the nickel particle, leads to carbon deposition at the metal/carbon filament interface. Key mechanisms include hydrocarbon adsorption, carbon dissolution, and diffusion through nickel particles. While filament formation enhances catalyst activity, encapsulation by amorphous carbon ultimately causes deactivation. This research integrates insights into adsorption kinetics and carbon diffusion to develop strategies for reducing catalyst deactivation and optimizing carbon nanotube production. The findings emphasize the importance of controlling carbon filament formation to extend catalyst lifespan and improve regeneration strategies, offering valuable insights for optimizing methane cracking for hydrogen production.