Coproduction of Hydrogen and Steelmaking Feedstock via Catalytic Methane Pyrolysis over Apricot Shell Char-Supported Iron Catalysts

This study delves into the technical strategy of coproducing hydrogen and steelmaking feedstock through catalytic methane pyrolysis, with the aim of converting the the carbon byproduct from a disposal challenge into a value-added resource. A bifunctional catalyst, namely, apricot shell char-supported iron (ASC/Fe), is devised to combine catalytic function with the product value, allowing the spent catalyst−carbon mixture to be directly utilized as a ferrocarbon feedstock for the steel industry. The structure−activity relationship and catalytic performance are comprehensively investigated. The results indicate that the catalyst attains a high specific surface area of 211.6 m 2 /g subsequent to iron loading, offering abundant active sites and favorable mass transfer channels. At 900 °C and a CH 4 flow rate of 10 mL/min, the ASC/Fe-40 catalyst demonstrates excellent stability over an 11 h period, sustaining a methane conversion above 86%, with a cumulative hydrogen yield of 12,042.1 mL and a carbon yield of 3.11 g. Mechanistic analysis unveils a two-tier “carbon buffering” deactivation mechanism. Initially, metallic iron absorbs active carbon atoms through bulk carburization, thereby delaying surface graphitic encapsulation. Subsequently, iron carbide (C 0.12 Fe 1.88 ) forms as an active intermediate phase that maintains catalytic activity, leading to a gradual rather than an abrupt deactivation. The spent solid product (ASC/Fe@C) is characterized as a composite comprising apricot shell char, metallic iron, iron carbide, and graphitic carbon. Its gasification reactivity in CO 2 is evaluated with respect to its potential as a steelmaking feedstock. Notably, the ASC/Fe@C demonstrates a gasification onset temperature of approximately 850 °C, which is 150 °C lower than that of commercial metallurgical coke. At 900 °C, it achieves a conversion rate of 70.7%, in contrast to only 6.5% for coke. This superior performance is attributed to the intrinsic high reactivity of the apricot shell char matrix and the catalytic activation of CO 2 molecules by the dispersed iron/iron carbide species. In general, this study verifies the feasibility of the “coproduction” concept, providing a new material foundation and technical pathway for coupling clean hydrogen production with low-carbon steelmaking.