Transient studies of low-temperature dry reforming of methane over Ni-CaO/ZrO2-La2O3

The low temperature reforming of methane by carbon dioxide is studied over a calcium oxide promoted Ni catalyst supported on a tetragonal zirconia stabilized by lanthana, which presents an improved stability compared to the non-promoted catalyst. Steady-state catalytic activity measurements, diffuse reflectance infrared Fourier transform spectroscopic analysis and isotopic temporal analysis of products experiments reveal the occurrence of a bifunctional mechanism on the promoted catalyst: methane is activated on the Ni particles, carbon dioxide interacts with the calcium oxide to form carbonates which scavenge carbon from nickel at the Ni-O-Ca interphase, thus restoring Ni particles to the original state. This is assumed to hinder the formation of deactivating coke, which explains the improved catalytic stability of the promoted catalyst. The main route for the carbon deposit formation is found to be the methane cracking in spite of the low temperature reaction.

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► TAP investigation of the low temperature methane dry reforming reaction mechanism.
► Deactivating carbon deposits arise from methane cracking on nickel metal.
► Boudouard reaction does not occur in spite of the low temperature reaction.
► On Ni-ZrLa the reactants (CH4 and CO2) are activated on the metallic phase.
► On Ni-Ca-ZrLa the CO2 is activated on the promoter enabling a bifunctional mechanism.