DBD plasma-assisted CO ₂ methanation using zeolite-based catalysts: Structure composition-reactivity approach and effect of Ce as promoter

In the present work the effects of the structure composition in terms of Si/Al ratio and Ce addition in the performances of Ni-based zeolites for CO ₂ methanation under DBD plasma-assisted catalysis were evaluated. Results were compared with the obtained for a commercial Ni/γ-Al ₂ O ₃ catalyst and all samples were tested both under thermal and non-thermal DBD plasma conditions. It was found that a higher Si/Al ratio led to better performances not only under thermal but, especially, under plasma conditions, which was attributed to the lower affinity of this sample to water and, thus, to a decrease in the inhibitory role of this compound in Sabatier reaction. Furthermore, the addition of Ce as promoter favoured the dielectric properties of the materials and gave additional sites for CO ₂ activation leading to much better results than the obtained for a commercial Ni/γ-Al ₂ O ₃ sample and for the Ni/zeolite, especially under plasma conditions. Indeed, the best zeolite of this work (NiCe/Zeolite) reported a CH ₄ yield of 75% with a power supply of 25 W while, under the same conditions, the commercial sample and the un-promoted Ni/Zeolite presented just 23% and 15%, CH ₄ yield, respectively. To our knowledge, this is the first time that a structure-reactivity relationship is attempted with zeolite catalysts under DBD plasma-assisted methanation conditions at atmospheric pressure. These facts also indicate that an important route is being opened, allowing answering to the essential question "what are the important characteristics a catalyst must have to show a better performance under plasma-assisted catalysis?".