Ni/LaBO3 (B = Al, Cr, Fe) Catalysts for Steam Reforming of Methane (SRM): On the Interaction Between Ni and LaBO3 Perovskites with Differed Fine Structures

Abstract

With the target to fabricate more feasible catalysts for SRM to produce hydrogen, the interaction between Ni and LaBO₃ (B = Al, Cr and Fe) perovskite supports with different B-sites has been explored. To avoid the formation of big Ni grains, the Ni loading is intentionally set as low as 2 wt%. XRD and Raman results revealed that the three LaBO₃ supports are composed of pure perovskite phase, but have differed fine crystal structures. While LaFeO₃ and LaCrO₃ can be indexed to the orthorhombic perovskite phase, LaAlO₃ can be indexed to the hexagonal phase. H₂-TPR and XPS results have validated that NiO has varied interfacial interactions with the LaBO₃ supports through partial electron transfer from the supports to Ni. As a consequence, the active metallic Ni surface areas are in the order of 2%Ni/LaAlO₃ > 2%Ni/LaCrO₃ > 2%Ni/LaFeO₃, well consistent with the reaction performance. Furthermore, by varying the B-site element, the abundance of the active surface oxygen species (mainly O₂²⁻) is varied, obeying the sequence of 2%Ni/LaCrO₃ > 2%Ni/LaAlO₃ > 2%Ni/LaFeO₃, well consistent with the anti-coking ability of the catalysts. It is discovered that the change of the fine crystal structure of LaBO₃ supports can influence the SRM performance of the 2%Ni/LaBO₃ catalysts evidently. The reaction performance of the catalysts is mainly determined by the active Ni surface area, but the anti-coking ability is majorly decided by the amount of active oxygen species.