Design of a Sabatier Reactor for CO2 Conversion into Synthetic Methane

Design of a Sabatier reactor for CO₂ conversion into synthetic methane

Duo Sun and David Simakov

Department of Chemical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Converting CO₂-reach streams (e.g., biogas, fermentation off-gas, flue gas) into synthetic natural gas (SNG) via Sabatier reaction (CO₂ hydrogenation into CH₄) is an attractive route for CO₂ utilization [1-3]. There is a potential to decrease CO₂ emissions significantly and, at the same time, to reduce the consumption of fossil natural gas. To make the process sustainable, H₂ which is required for this reaction should have zero or very low carbon footprint. This requirement is achievable if H₂ is produced via water electrolysis using renewable electricity (hydro, wind, solar) or surplus (e.g., nuclear) electricity. Electrolysis can be done in a highly efficient way using polymer electrolyte membrane (PEM) electrolyzes [4]. However, a number of technological issues remain to be resolved, including catalyst deactivation and thermal management (Sabatier reaction is highly exothermic) [5]. The study presented herein focuses on the design of a highly efficient and compact Sabatier reactor for CO₂ hydrogenation into synthetic natural gas.

The general concept is a heat-exchanger type packed bed with active cooling for efficient heat removal. Compressed air, steam, or molten salt can be used as a coolant; molten salts are excellent heat transfer fluids due to their high heat capacity and thermal conductivity [6-9]. To identify the optimal configuration, we performed numerical simulations, using a transient pseudo-homogeneous model [10]. We searched for optimal operating conditions to maximize methane yield and to prevent at the same time reactor overheating and catalyst deactivation. We have identified several configurations that allow highly efficient CO₂ hydrogenation, providing CO₂ conversions and CH4 yields higher than 90%. A preliminary techno-economic evaluation demonstrates the potential of this approach for commercialization.

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