Tri-reforming of surrogate biogas over Ni/Mg/ceria–zirconia/alumina pellet catalysts

Abstract

ABSTRACTThe performance of catalytic tri-reforming under industrially relevant situations (e.g., pellet catalysts, pressurized reactor) was investigated using surrogate biogas as the feedstock. Tri-reforming using Ni/Mg/Ce0.6Zr0.4O2/Al2O3 pellet catalysts was studied in a bench scale fixed-bed reactor. The feed molar ratio for CH4:CO2:air was fixed as 1.0:0.70:0.95. The effects of temperature (800–860°C), pressure (1–6 bar), and H2O/CH4 molar feed ratio (0.23–0.65) were examined. Pressure has substantial impact on the reaction and transport rates and equilibrium conversions, making it a key variable. At 860°C, CO2 conversion increased from 4 to 61% and H2/CO molar ratio decreased from 2.0 to 1.1 as the pressure changed from 1 to 6 bar. CO2 conversion and H2/CO molar ratio were also influenced by the temperature and H2O/CH4 molar ratio. At 3 bar, CO2 conversion varied between 4 and 43% and the H2/CO molar ratio varied between 1.2 and 1.9 as the temperature changed from 800 to 860°C. At 3 bar and 860°C, CO2 conversion decreased from 35 to 8% and H2/CO molar ratio increased from 1.7 to 2.4 when the H2O/CH4 molar ratio was increased from 0.23 to 0.65. This work demonstrates that the tri-reforming technology is feasible for converting biogas under scaled-up conditions in a fixed-bed reactor.