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CO₂ conversion to synthesis gas via DRM on the durable Al₂O₃/Ni/Al₂O₃ sandwich catalyst with high activity and stability

Zhao, Yu, Kang, Yunqing, Li, Hui, Li, Hexing
Green chemistry 2018 v.20 no.12 pp. 2781-2787
active sites, aluminum oxide, carbon, carbon dioxide, carbon monoxide, catalysts, coatings, durability, green chemistry, hydrogen, methane, nanoparticles, nickel, synthesis gas, temperature
CO₂ conversion to synthesis gas with a CO/H₂ molar ratio around 1 was realized by using the dry reforming of methane reaction (DRM) at 800 °C. The key problem was to design catalysts with both high activity and strong durability at such a high reaction temperature. This work developed a novel Al₂O₃/Ni/Al₂O₃ sandwiched catalyst prepared by coating Al₂O₃-supported Ni nanoparticles with a porous Al₂O₃ thin film by atomic layer deposition (ALD). The catalyst with 80 layers of Al₂O₃ thin films exhibited the highest activity. Both CO₂ and CH₄ conversions reached nearly 100% with absolute selectivities towards CO and H₂. More importantly, this catalyst displayed excellent stability and could be used for more than 400 h in the DRM reaction at 800 °C without significant deactivation. Mechanism analysis revealed that the deactivation mainly resulted from the gathering of Ni nanoparticles at high temperature, corresponding to the decrease of Ni active sites. Moreover, a large-sized Ni active site could easily cause carbon deposition, which could further accelerate the catalyst deactivation. The Al₂O₃/Ni/Al₂O₃ sandwiched catalyst could effectively protect Ni nanoparticles from gathering owing to the double strong interactions between the Ni active sites and Al₂O₃ support.