Influence of active metal loading and oxygen mobility on coke-free dry reforming of Ni–Co bimetallic catalysts

Two different techniques (precipitation with ammonia and hydrothermal synthesis with ethylene glycol, both followed by autoclave aging) were employed for the synthesis of CeO2–ZrO2 mixed oxides on a 80–20 wt.% basis. Aging parameters, such as time and temperature, were systematically investigated in order to determine the optimal conditions to maintain high surface area and oxygen mobility of the prepared solids. Different loadings of nickel and cobalt (3, 6, 12 and 18 wt.%) were subsequently deposited via homogeneous deposition precipitation method. Calcined bimetallic catalysts were characterized by N2 adsorption–desorption, XRD, H2-TPR, TPO-TGA and FE-SEM methods, and tested for activity, selectivity and stability in the reforming of equimolar CH4–CO2 gas streams. During temperature programmed methane reforming tests, syngas with a H2/CO ratio between 0.3 and 0.79 was produced. Growth of carbon nanofilaments over the catalyst does not lead to deactivation, but can cause reactor plugging. Two conditions are vital and must be fulfilled simultaneously to avoid excessive carbon deposition: strong interaction between the NiCo bimetallic particles and CeZr support, which exists only at NiCo loadings up to 6 wt.%, as well as high oxygen mobility within the highly defective CeO2–ZrO2 crystalline lattice for timely carbon oxidation.

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► Carbon accumulation in the form of nanofilaments does not affect catalyst deactivation.
► Active NiCo bimetallic particles can be finely dispersed at loadings below 6 wt.%.
► High oxygen mobility within the CeZr support is promoted by small crystallite size and highly defective structure.
► High oxygen mobility and finely dispersed active metal phase support long term coke-free operation.