Plasma-catalytic CO₂ methanation over Ni supported on MCM-41 catalysts: Effect of metal dispersion and process optimization

Catalytic carbon dioxide (CO₂) conversion technologies can be important components in carbon capture, storage and utilization for CO₂ mitigation and possible future economic activity and have gained significant attention globally in past decades. Electrified non-thermal plasma (NTP) catalysis enables CO₂ hydrogenation into value-added chemicals under mild conditions. If the hybrid process is coupled with renewable energy and green hydrogen, it can be the promising solution to address the energy and carbon emission challenges. To enhance the energy efficiency of NTP-catalytic systems, bespoke catalyst design and process optimization are necessary. Here, using Ni catalysts supported on mesoporous MCM-41 and NTP-catalytic CO₂ methanation as the model systems, the effects of Ni metal dispersion, argon (Ar) addition and residence time on the NTP catalysis were also studied. The findings show that (i) increased metal dispersion alone did not lead to significant enhancement in the performance of NTP catalysis (e.g., CH₄ production rate: 31.4 × 10⁻⁵ mol/(s·g_Ni) for 42.6 % Ni dispersion vs. 26.8 × 10⁻⁵ mol/(s·g_Ni) for 25.1 % dispersion), (ii) Ar addition to the system led to the decreased methane production rate (e.g., CH₄ selectivity decreased by ∼19 % due to the increase in Ar addition to the system from 5 to 50 mL/min), and (iii) optimization of the residence time could improve the performance of NTP-catalytic CO₂ methanation (i.e., an extension of the residence time to 0.69 s resulted in the higher CO₂ conversion of 72.7 % and CH₄ selectivity of 95.9 % at 9.6 kV than that at 0.49 s and 11 kV).