Dry reforming of methane over Ni/Ce0.8Ti0.2O2-δ: The effect of Ni particle size on the carbon pathways studied by transient and isotopic techniques

• Ni/Ce 0.8 Ti 0.2 O 2-δ with d Ni of 22 nm is efficient and coke-resistant for DRM at 750 °C. • Carbon accumulation during DRM at 750 °C is derived by the CH 4 activation route. • Oxidation of carbon by lattice oxygen of support is faster than by oxygen of CO 2 . • Carbon formed after 12 h DRM at 750 °C is 300 times less on Ni of 22 than 45 nm in size. • Initial TOF(s −1 ) of CH 4 decomposition depends on Ni particle size (22–45 nm). The effects of Ni particle size (d Ni ∼ 22–45 nm) of Ni/Ce 0.8 Ti 0.2 O 2-δ on the carbon paths in the dry reforming of methane at 750 °C have been investigated by various transient and isotopic experiments. The aim was to provide new insights for improving catalyst’s coke-resistance. Various correlations have been derived between d Ni and (i) the initial kinetic rates (per Ni particle) of CH 4 dissociation and CO disproportionation reactions along with their respective amounts of carbon accumulation, (ii) the integral rates of CH 4 conversion and CO formation and the amount of carbon deposition in the DRM, and (iii) the rate of carbon removal by lattice oxygen of support compared to that by oxygen formed via the CO 2 activation route during DRM. The former rate was found larger than the latter one independent of d Ni (nm). CH 4 dissociation is the exclusive route of inactive carbon formation during DRM independent of d Ni .