Influence of LaNiO₃ Shape on Its Solid-Phase Crystallization into Coke-Free Reforming Catalysts

Abstract

Shape-controlled LaNiO3 nanoparticles were prepared by modified hydrothermal and precipitation routes resulting in cubes, spheres, and rods. The solid-phase crystallization of LaNiO3 into its active catalyst form, Ni/La2O3, was found to be highly dependent on the shape and structure of the parent nanoparticle. Factors such as the crystallization pathway and Ni2+-ion depletion are considered as key factors influencing the final material. Catalysts derived from LaNiO3 spheres and rods were found to be free of carbon accumulation after 100 h of reforming, while those derived from cubes showed excessive carbon accumulation and signs of sintering. All three catalysts are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and thermogravimetric analyses (TGA). The presence of defects, particularly stacking faults within the perovskite, may impact the reduction pathway and subsequent catalytic properties. Stable and active catalysts can therefore be designed and tuned by controlling the shape and structure of perovskite precursors.

Oxidative Steam Reforming of Raw Bio-Oil over Supported and Bulk Ni Catalysts for Hydrogen Production

“…The Ni commercial catalyst, G90, has the lower specific surface area and pore volume among the studied supported catalysts. The low values of BET surface area observed in Table 2 for the Ni-La perovskites are characteristic for these materials with low porosity [32,33]. Nevertheless, there are differences between the two types of perovskites due to the meso-macroporosity of LaNiO 3 catalyst, so that the meso-macropore volume of this catalyst (0.068 cm 3 g −1 , calculated as the difference between total pore volume and that of micropore) is significantly higher than that of La 2 NiO 4 catalyst (0.012 cm 3 g −1 ).…”

Recent Scientific Progress on Developing Supported Ni Catalysts for Dry (CO2) Reforming of Methane

“…The Ni particles that were exsoluted from LaNiO 3 spheres and rods were highly dispersed on the supports and exhibited high catalytic activity and stability towards DRM reaction [72]. Recently, the fabrication Ni particles alloyed with Re and Fe by exsolution method has been also demonstrated [73]. The exsoluted Ni-alloy particles were firmly 'socketed' into a La 2 O 3 /LF supports and they exhibited high catalytic activity towards DRM reaction without showing carbon accumulation and particles sintering over 70 h of operation [73].…”

“…Recently, the fabrication Ni particles alloyed with Re and Fe by exsolution method has been also demonstrated [73]. The exsoluted Ni-alloy particles were firmly 'socketed' into a La 2 O 3 /LF supports and they exhibited high catalytic activity towards DRM reaction without showing carbon accumulation and particles sintering over 70 h of operation [73].…”

“…Ni particles that were exsoluted from LaNiO3 spheres and rods were highly dispersed on the supports and exhibited high catalytic activity and stability towards DRM reaction [72] [73]. Kaydouh et al demonstrated that the "two solvent" method resulted in much selective dispersion of Ni nanoparticles at interior of the mesoporous structure of SBA-15 silica [81].…”

Role of 2D and 3D defects on the reduction of LaNiO3 nanoparticles for catalysis

“…The ability of Ni/La 2 O 3 to show stable catalytic performance is related to the dispersion of Ni on the La 2 O 3 support and the strength of the metal bond with the oxide support. These parameters have been previously reported to depend on the LaNiO 3 synthesis method, but there is no clear understanding about how to predict which pathway will be taken and why one route may be preferable from a catalytic performance perspective 12, 13 . The two most reported reaction pathways are: a 3-step pathway where LaNiO 3 is reduced through A n+1 B n O 3n+1 Ruddlesden-Popper (RP) phases (Reactions 1–3); and a 2-step pathway where LaNiO 3 is reduced through a A n B n O 2n+1 Brownmillerite phase (Reactions 4–5)…”