Dry reforming of methane over Ni/Al2O3 catalyst derived from partially reduced dendritic layered NiAl2O4

Abstract

The Ni/Al₂O₃ catalysts derived from dendritic layered NiAl₂O₄ at different reduction temperatures are systematically investigated to understand their dry reforming of methane (DRM) performance and the occurrence of coking and sintering. The characterization results including SEM/TEM/BET show that the dendritic layered morphology can effectively stabilize Ni nanoparticles and catalyst structure, thus ensuring the anti-sintering performance of the catalyst. Meanwhile, the partially reduced NiAl₂O₄ on the 10Ni-Al₂O₃-700 (reduction temperature of 700 °C) can form small Ni nanoparticles and defective spinel phase. The imperfect NiAl₂O₄ spinel has abundant surface oxygen vacancies that can adsorb and activate CO₂, supported by the CO₂ partial pressure experiment and CO₂-TPD result, and this provides a CO₂-assisted dissociation pathway with CH_xO* as a key intermediate for CH₄ conversion. And it will compete with the direct dissociation of CH₄ as the main source of coking, thereby reducing the coking on the catalyst. 10Ni-Al₂O₃-700 has similar DRM performance to 10Ni-Al₂O₃-800, with CO₂ and CH₄ conversion of 83.6 % and 71.1 %, at 650 °C, but with much less carbon deposition (25.6 % vs 57.3 %). Meanwhile, the initial DRM activity can be restored by regeneration treatment.