Bi-reforming and tri-reforming of methane: a comprehensive review of catalyst development, processes, and industrial perspectives.

Bi-reforming (BRM) and tri-reforming (TRM) of methane have emerged as advanced, hybrid reforming methods that simultaneously utilize CH4, CO2, H2O, and, for TRM, O2 to produce cleaner, more flexible syngas for next-generation chemical and energy systems. This review compiles findings from 220 studies, primarily published between 2015 and 2025 that investigate the basics of reactions, catalyst development, thermodynamic behavior, and the transition to industrial deployment. BRM combines steam and dry reforming, achieving CH4 conversions of 85-95% and CO2 conversions of 50-80% at 750-900 °C. Syngas with H2/CO ratio of ∼2 is acceptable for methanol and dimethyl ether (DME) synthesis. TRM combines partial oxidation, enabling autothermal operation and potentially minimizing external heat requirement by up to 25%. It also achieves CH4 and CO2 conversions of 75-100% at 750-850 °C, generating hydrogen-rich syngas with H2/CO ratios of 2 or greater, which is ideal for Fischer-Tropsch fuel and hydrogen production. While promoters, dopants, and mixed-oxide supports significantly enhance redox stability and coke resistance under coupled reforming conditions, nickel-based catalysts remain the most popular due to their affordability and strong C-H activation capabilities. Noble-metal-modified systems exhibit higher stability, frequently retaining more than 90% conversion over 100-300 hours. Problems persist, despite the progress made, including sintering, redox cycling, impurity poisoning, and limitations in reactor-level heat management. Synthesizing multifunctional catalysts with stability exceeding 500 hours and utilizing artificial intelligence to optimize reaction conditions are future directions for research. BRM and TRM have high potential for industrial decarbonization and sustainable syngas generation.