Intensified Biogas-to-Fuels/Chemicals: Optimizing Tandem Bireforming and Fischer–Tropsch Synthesis in a Single Reactor

Gas-to-liquid (GTL) technologies offer promising pathways for converting biogas into sustainable fuels and chemicals, yet conventional approaches require multireactor systems operating under significantly different conditions. This study investigates an intensified, integrated approach that combines bireforming and Fischer–Tropsch synthesis (FTS) into a single-reactor system with distinct temperature zones under uniform pressure. In the reforming zone (700–850 °C), a Ni3Zn/SiO2 catalyst converted methane and carbon dioxide into syngas, achieving single-pass CH4 and CO2 conversions of 82 and 23%, respectively. The syngas produced was subsequently converted to hydrocarbons in the FTS zone (350–400 °C) in the same reactor by using a potassium-promoted iron catalyst, yielding 16% total C2+ mass, which included 9.8% C2–C4 (6.5% olefins) and 3.8% C5+ hydrocarbons in the gas phase, along with liquid diesel-range products (C9–C19). Catalyst stability was demonstrated over 15 h of continuous operation using landfill-derived biogas. Parametric sensitivity study of the reaction conditions revealed that the hydrocarbon yield and product distribution could be effectively tuned by adjusting the FTS temperature and pressure to balance reaction kinetics and thermodynamic constraints. These results highlight the potential for this integrated approach to significantly enhance the economic feasibility and sustainability of small-scale, distributed GTL processes utilizing renewable biogas and stranded gas resources.