Influence of Ni:Fe Ratio on Steam Reforming of Sewage Sludge Pyrolysis Volatiles over Redox-Prepared Ni–Fe/Al ₂ O ₃ Catalysts for Hydrogen/Syngas Production

Pyrolysis offers a promising valorization route for sewage sludge, yet still urgently demands reforming catalysts with high activity. This work systematically investigates the catalytic performance of Ni–Fe/Al2O3 bimetallic catalysts in steam reforming sewage sludge pyrolysis volatiles across different Ni:Fe ratios. The experimental results indicated that bimetallic catalysts performed better than monometallic catalysts, and the most hydrogen-rich syngas was produced over the 1.5% Ni–3% Fe/Al2O3 catalyst. The characterization test results showed that a 1.5% Ni–3% Fe/Al2O3 catalyst facilitates the increased hydrodeoxygenation of oxygenated compounds and promotes the cleavage of hydrocarbons for hydrogen generation. Simultaneously, the best redox cycle and interaction between Ni and Fe were also observed on this catalyst. All of these conditions favor this catalyst’s capacity to generate maximum hydrogen. This study establishes a theoretical basis for the catalytic pyrolysis of sewage sludge, aiming to produce hydrogen-enriched syngas efficiently.