Catalytic Carbon Dioxide Reforming of Methane to Synthesis Gas over Activated Carbon Catalyst

The catalytic activity and kinetic behavior of catalytic reforming of methane with carbon dioxide over activated carbon were investigated as a function of reaction temperature, gas hourly space velocity (GHSV), and partial pressures of CH4 and CO2. The CH4 and CO2 conversions were greatly influenced by the reaction temperature in the range of 850−1050 °C. The apparent activation energies for CH4 and CO2 consumption and CO and H2 production were 32.63 ± 1.06, 25.54 ± 1.79, 24.81 ± 3.06, and 32.99 ± 2.58 kcal/mol, respectively. The curves of reaction rates versus GHSV showed various trends at different temperatures and indicated 7500 mL/h·g-cat was sufficient for operation in the kinetic regime. The reaction rate of methane and carbon dioxide over activated carbon was affected significantly by the partial pressures. Under a higher CO2 pressure, the excess CO2 reacted with H2 through the reverse water−gas shift (RWGS) reaction. The predictions of the CH4 and CO2 reaction rates based on a semiexperimental formula fitted satisfactorily with the experiments data. The results of mass balance, BET, XRD, and SEM studies in the deactivation test indicated that the catalyst deactivation was mainly attributed to the carbon deposition and might be alleviated at high temperatures. On the basis of the experimental results and Langmuir−Hinshelwood mechanism in the literature, a reaction mechanism was proposed. The overall reaction pathway involves the adsorption and cracking of methane and CO2 adsorption and gasification with carbon cracked. The RWGS reaction occurs simultaneously. Overall, a derived semitheoretical kinetic equation satisfactorily predicted the experimental results.