Spent Iron-Char Catalysts Are Not Waste: A Viewpoint on Integrating Methane Pyrolysis with Steelmaking

Abstract

Methane pyrolysis offers a CO2-free pathway to hydrogen production; however, its commercial deployment remains hindered by a stoichiometric constraint: each kilogram of H2 co-produces three kilograms of solid carbon, which rapidly deactivates the catalyst. Conventional strategies aiming to extend catalyst lifetime are therefore fundamentally incompatible with this inherent stoichiometric constraint. This perspective advocates a paradigm shift: rather than mitigating carbon deposition, we strategically harness it. By designing iron-loaded char catalysts whose spent form is an intimately mixed Fe/C composite suitable for potential use as metallurgical feedstock in steelmaking, we recast catalyst deactivation from an operational failure into a value-capturing endpoint. Experimental results demonstrate that the spent ASC/Fe@C composite exhibits CO2 gasification reactivity markedly superior to that of commercial metallurgical coke. Onset occurs at a temperature approximately 150 °C lower, and conversion reaches 70.7% at 900 °C compared to just 6.5% for coke. This integration of catalytic function with end-of-life value provides a pathway to couple clean hydrogen production with the steel industry. The steel industry, which consumes billions of tons of carbonaceous feedstocks annually, represents a suitable large-scale destination for methane pyrolysis’s million-ton-scale solid carbon output, providing a potential sink for this carbon stream pending quantitative techno-economic validation. Consequently, this approach establishes a cross-sectoral circular carbon economy, potentially eliminating the need for energy-intensive catalyst regeneration while simultaneously advancing steel decarbonization.