Combination of dry reforming and partial oxidation of methane on NiO–MgO–ZrO2 catalyst: Effect of nickel content

The effect of nickel content on NiO–MgO–ZrO2 catalysts was investigated. They were characterized by XRD, in-situ XRD, TPR and BET and tested in POM and DRM coupled reactions (1.5CH4:1CO2:0.25O2), to produce syngas (H2/CO), at 750 °C for 7 h. Among these catalysts the NiO-MgO–ZrO2 catalyst with 20 wt.% nickel content showed the best activity and selectivity in the catalytic processes. The MgO–ZrO2 (MZ) solid solution and the interactions between Ni and MZ increased the rate of conversion of reactants (CH4 and CO2) into syngas on the catalysts. Although the Ni° active sites are required for high activity and selectivity, high nickel content favored the formation of large Ni° particles during the reforming reaction, thus lowering the catalytic performance. The combination of DRM and POM exhibited high conversion rates and selectivity on the NiMZ catalyst with 20 wt.% Ni and 20 mol% MgO, demonstrating that this coupled reaction can be performed efficiently and that problems arising from hot spots on the catalyst, due to POM, can be solved.

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► Excess of NiO lead to large Ni particles lowering the catalytic performance.
► High NiO load promoted large Niº particles and large amounts of coke.
► Zirconium nickel oxide was formed under reducing and reacting condition.
► NiO particles added in the MgO-ZrO2 system retarded the NiO reduction.