Non-thermal plasma assisted synthesis and physicochemical characterizations of Co and Cu doped Ni/Al2O3 nanocatalysts used for dry reforming of methane

•Synthesis of Co and Cu doped Ni/Al2O3 nanocatalysts by non-thermal plasma.•Smaller particle size and uniform morphology for plasma treated Ni–Co/Al2O3.•More reactivity for plasma treated Ni–Co/Al2O3 in dry reforming of methane.•Getting H2/CO very close to 1 at high temperatures over plasma treated Ni–Co/Al2O3.•High stability of Ni–Co/Al2O3 in comparison to Ni–Cu/Al2O3 in dry reforming of methane.

Ni/Al2O3 nanocatalysts doped with Co and Cu were prepared by co-impregnation and modified by non-thermal plasma. The nanocatalysts were characterized by XRD, FESEM, TEM, EDX dot-mapping, BET, FTIR, TGA-DTG, and XPS analysis. According to XRD and XPS results, good interaction between active phase and support can be observed in both Ni–Co/Al2O3 and Ni–Cu/Al2O3 nanocatalysts. A uniform morphology, high surface area, and well dispersed particles of active sites in Ni–Co/Al2O3 nanocatalyst were observed that shows the effect of cobalt in controlling Ni ensemble size. In contrast Ni–Cu/Al2O3 nanocatalyst had no homogenous dispersion of active phase due to sintering of copper particles. The activity measurements illustrated better Ni–Co/Al2O3 nanocatalyst activity in comparison to Ni/Al2O3 and Ni–Cu/Al2O3 in terms of CH4 and CO2 conversion. H2 and CO yield were higher for Ni–Co/Al2O3 and higher H2/Co ratio was obtained as well. Whereas Ni/Al2O3 and Ni–Co/Al2O3 did not experience deactivation, Ni–Cu/Al2O3 suffered from activity loss by ca. 22% and 16% for CH4 and CO2 conversion, respectively. Sintering most likely happened in Ni–Cu/Al2O3 nanocatalyst due to high temperature of calcination while cobalt by controlling the size of Ni particles, alternated the size of active sites to a size range in which carbon formation was suppressed. Ni/Al ratio from XPS analysis which signifies Ni dispersion on alumina support was 5.15, 9.16, and 6.35 for Ni/Al2O3, Ni–Co/Al2O3, and Ni–Cu/Al2O3 nanocatalysts respectively. The highest ratio of Ni/Al was for Ni–Co/Al2O3 nanocatalyst that shows the best coverage of support by Ni active phase in this nanocatalyst.

Graphical abstractAccording to XRD and XPS results, good interaction between active phase and support can be observed in both Ni–Co/Al2O3 and Ni–Cu/Al2O3 nanocatalysts. A uniform morphology, high surface area, and well dispersed particles of active sites was observed in Ni–Co/Al2O3 nanocatalyst that reveals effect of cobalt in controlling the Ni ensemble size. In contrast Ni–Cu/Al2O3 nanocatalyst due to sintering of copper particles did not have a homogenous dispersion of active phase. The Ni/Al ratio was the highest for Ni–Co/Al2O3 nanocatalyst that shows the best coverage of support by Ni active phase in this catalyst. The activity measurements illustrated better activity and stabillity of Ni–Co/Al2O3 catalyst compared to Ni–Cu/Al2O3 nanaocatalyst. The H2 and CO yield was higher for Ni–Co/Al2O3 and higher H2/Co ratio was obtained as well.Figure optionsDownload full-size imageDownload as PowerPoint slide