Enhanced hydrogen production from sewage sludge via steam gasification using Ni catalysts supported on red mud-derived perovskite oxides

This study, by developing the steam gasification process to convert sewage sludge (SES) into H₂-rich gas, aimed to provide sustainable energy solutions and mitigate SES-derived environmental risks. Notably, by utilizing red mud, a hazardous industrial byproduct, as a sustainable precursor for perovskite oxides, this study developed Ni-based catalysts using a novel sol–gel combustion method, further enhancing the eco-friendliness and cost-effectiveness. To prepare the catalysts, Al(OH)₃ was first extracted from red mud and subsequently used, along with various metals (Ce, La, and Y), to synthesize perovskite oxides. These perovskite oxides were wash-coated onto a monolith reactor, after which 10 % Ni was introduced to form the Ni/MAlO₃ (M = Ce, La, and Y) catalysts. With a feedstock-to-catalyst ratio of 10/1 at 800 °C, the Ni/MAlO₃ catalysts demonstrated a considerably higher gas yield and H₂ generation compared with that of conventional Ni/Al₂O₃. In particular, Ni/YAlO₃ achieved the highest gas yield (56.0 wt%) and H₂ selectivity (62.2 vol%) because of the combined influence of well-dispersed metallic Ni active sites and redox properties of Y cations within the perovskite oxide structure, which enhanced tar cracking, water–gas shift, and both steam and dry reforming reactions. Notably, coke formation was effectively suppressed over the Ni/MAlO₃ catalysts (<0.54 wt%). Reducing the catalyst-to-feedstock ratio slightly decreased the gas yield and H₂ selectivity, whereas increasing the reaction temperature enhanced both gas yield and H₂ selectivity, reaching maximum values of 56. 1 wt% and 66.3 vol%, respectively, at 850 °C.