NixAl1O2-δ mesoporous catalysts for dry reforming of methane: The special role of NiAl2O4 spinel phase and its reaction mechanism

The structure evolution of surface NiAl2O4 spinel phase in NixAl1O2-delta mesoporous catalysts, synthesized by the citric acid sol-gel method, was systematically investigated. Small-size Ni nanoparticles, obtained by partial reduction from NiAl2O4 spinel in NixAl1O2-delta catalysts with low Ni contents at high temperature, can effectively inhibit the carbon formation from kinetics, while the irreducible NiAl2O4 counterpart can participate in elimination of carbon deposition. The constructed structure of Ni-0-NiAl2O4 interfaces, produced by exsolution of Ni from NiAl2O4 spinel, is responsible for its high long-term stability and excellent resistance to coking and sintering for dry reforming of methane (DRM) reaction. The structure sensitivity and kinetic compensation effect of CH4 dissociation on Ni-0 active sites are observed. DRM reaction proceeds via a Langmuir-Hinshelwood mechanism accompanied by an additional redox mechanism. It is noteworthy that the active oxygen species generated by filling the oxygen vacancies of NiAl2O4 spinel by CO2 provide another rapid redox route to eliminate carbon species.

Automated summary

The evolution of the surface NiAl2O4 spinel phase in NixAl1O2-delta mesoporous catalysts synthesized by the citric acid sol-gel method was systematically studied. The constructed Ni-0-NiAl2O4 interfaces and active oxygen species generated by filling oxygen vacancies of NiAl2O4 spinel play important roles in enhancing the stability and resistance to coking and sintering in dry reforming of methane reaction.