Stabilizing Ni-Co Alloy on Bimodal Mesoporous Alumina to Enhance Carbon Resistance for Dry Reforming of Methane

Alloying nickel with a transition metal and further stabilizing an active metal on bimodal support are regarded as a promising strategy to improve carbon resistance for dry reforming of methane (DRM) reaction. In this work, a bimodal mesoporous alumina-supported Ni-Co alloy catalyst (NiCo/MMAl) was prepared via the evaporation-induced self-assembly method and employed to catalyze DRM reaction. The promotive effect of Ni-Co alloy with a bimodal porous structure on the carbon resistance was investigated. The presence of Ni-Co alloy was confirmed on porous alumina. The NiCo/MMAl catalyst possessed two porous structures, a small-sized mesopore at 10 nm and a large-sized one at 40 nm. NiCo/MMAl exhibited enhanced carbon resistance, in which only 2.3% carbon formed on the catalyst surface, lower than a unimodal mesoporous alumina-supported NiCo catalyst (NiCo/MAl, 12%) and Ni catalyst (Ni/MAl, 24%). The kinetic study suggested that on the unimodal mesoporous alumina, alloying Ni with Co increased the activation energy of CH4 dissociation (∼66 kJ/mol) compared to Ni/MAl (51.7 kJ/mol), thus showing high activity for suppressing CH4 dissociation. In addition, the large-sized mesoporous structure on NiCo/MMAl favored mass transport. As a result, the enhanced carbon resistance for NiCo/MMAl was not only attributed to the suppression of CH4 dissociation by Ni-Co alloy but also to the promotive effect of the large-sized mesopore structure on enhancing mass transport.