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

Abstract

xNiyCo/SBA-15-CD (x + y = 5%, x/y = 0/5–5/0, mass ratio) catalysts, prepared by a β-cyclodextrin (CD) modified impregnation method, were characterized and employed in the carbon dioxide reforming of methane. Ni and Co interacted strongly with each other, and the Co species dissolved into the NiO lattice during the preparation process. The new H2 consumption peaks in the H2-temperature programmed reduction (TPR) should be attributed to the reduction of NixCoyO, which was the precursor of the Ni–Co alloy. The lattice parameters of the metal particles on reduced and spent catalysts followed Vegard's law, which confirmed the formation of the alloy. The TOFs of the bimetallic catalysts were greater than the monometallic catalysts and the stabilities of the bimetallic catalysts with Ni/Co = 2.5/2.5–4.5/0.5 were better than the monometallic catalysts. The synergistic effect of Ni and Co, the addition of β-CD, the sequence of impregnation and the confinement effect of the ordered mesoporous structure contributed to the better catalytic performance. Among the bimetallic catalysts, 4.5Ni0.5Co and 3Ni2Co showed the best stability. The better stability of 4.5Ni0.5Co can be attributed to a Co-enriched surface segregation structure, whereas the highest proportion of the Ni–Co alloy (precursor) in 3Ni2Co should be the primary reason to its better performance.