Methanation of CO2: Structural response of a Ni-based catalyst under fluctuating reaction conditions unraveled by operando spectroscopy

• Maximum CO2 conversion of 81% at 400 °C obtaining 80% CH4.
• Operando XAS study during methanation of CO2 under changing reaction conditions.
• Significant changes in the structure of the Ni particles under reaction conditions.
• Deactivation of the catalyst in the second methanation cycle after H2 dropout.
• Partial oxidation of Ni particles leads to lower catalytic methanation performance.

The methanation of CO2 as a relevant strategy for energy storage has been studied by operando X-ray absorption spectroscopy under dynamic H2/CO2 and CO2 reaction atmospheres. A typical CO2 conversion of 81% was reached at 400 °C with a 23 wt.-% Ni/CaO–Al2O3 catalyst, yielding 80% of CH4. The operando XAS experiment under working conditions revealed pronounced structural changes, e.g., a fast bulk oxidation of the Ni particles after removal of H2 from the H2/CO2 (4:1) gas stream. A lower performance of the catalyst was observed in the subsequent methanation cycle due to the presence of a residual oxidized fraction of Ni.

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