xNiyCo/SBA-15-CD (x+y=5%, x/y=5/0~0/5, mass ratio) catalysts, prepared by β-cyclodextrin (CD) modified impregnation method, were characterized by N2-physisorption, XRD, ICP-OES, XAFS (XANES&EXAFS), XPS, H2-TPR, TPR-TPD, TEM-EDS and TGA-DSC. Their catalytic performance was also tested in carbon dioxide reforming of methane in a quartz tube microreactor with a CH4/CO2 feed ratio of 1/1 at 800oC. XANES, EXAFS and XPS results of fresh catalysts indicate that the Ni and Co interact strongly with each other, and Co species dissolve into the NiO lattice during the preparation process. TPR results suggest that the new H2 consumption peak should be due to the reduction of NixCoyO, which is the precursor of Ni-Co alloy. Lattice parameters of metal particles on spend catalysts follow the Vegard’s law, which confirm the formation of alloy, though the homogeneity of Ni-Co alloy is not uniform. The initial conversions are close for the catalysts with Ni/Co higher than 2.5/2.5, but the stabilities of bimetallic catalysts with Ni/Co=2.5/2.5~4.5/0.5 are better than the mono-metal 5Ni and 5Co catalysts, due to the synergistic effect. Confined effect of mesoporous structure and the synergistic effect contribute to the better performance. Among the bimetallic catalysts, 4.5Ni0.5Co and 3Ni2Co show the best performance. The better stability of 4.5Ni0.5Co should attribute to a novel Co-rich shell/Ni-rich core structure, whereas the highest proportion of Ni-Co homogenous alloy in 3Ni2Co should be the primary reason to the better performance.

Synergetic effect of Ni and Co in Ni-Co/SBA-15-CD catalysts and their catalytic performance in carbon dioxide reforming of methane

251st National Meeting (2016)

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