Converter Dust as a Low-Cost, Efficient Catalyst for Ammonia Cracking to Decarbonize Ironmaking

Abstract

Catalyst-assisted ammonia cracking offers an efficient route for on-site hydrogen production to support low-carbon ironmaking, while developing low-cost and eco-friendly catalysts is critical for industrial sustainability. This work proposes a circular strategy to upcycle converter dust, a typical Fe-rich steelmaking waste, into a high-efficiency catalyst for ammonia conversion, aiming to decarbonize the ironmaking process. The converter dust was systematically characterized regarding oxide composition, mineralogy, morphology, and nanostructure. Ammonia conversion behavior was evaluated at 450–800 °C with a gas hourly space velocity (GHSV) of 30,000 mLNH3·h–1·gcat–1. Results show that the converter dust is dominated by iron oxides (77.24 wt % TFe, mainly Fe3O4) and exhibits a natural nanoparticle structure with uniform dispersion of Zn, Ca, and Mg impurities. The ammonia reaction over converter dust exhibits three temperature-dependent stages: physical adsorption at 450–500 °C, coexistence of reduction and catalytic cracking at 550–650 °C, and dominant high-efficiency catalytic cracking at 700–800 °C. Nearly complete ammonia conversion is achieved at 800 °C. Phase characterization reveals a temperature-driven evolution pathway of Fe3O4 → Fe4N → α-Fe, where metallic α-Fe serves as the primary active phase at high temperatures. Moreover, the converter dust shows excellent stability, maintaining stable ammonia conversion over 36 h at 700 °C. Further tests on simulated samples confirm that the inherent metal impurities enhance surface alkalinity and reducibility, synergistically boosting catalytic performance. This study not only realizes high-value utilization of steelmaking solid waste but also provides a low-cost, self-compatible catalytic technology for ammonia cracking in hydrogen-based low-carbon ironmaking.