Morphological, Structural, and Chemical Properties of Thermally Stable Ni-Nb₂O₅ for Catalytic Applications

Abstract

Structural stability is a pivotal property required for Nb2O5 to be applied as a solid-acid catalyst in heterogeneous catalytic reactions. When combined with Ni, Nb2O5 produces cheap and active hydrogenation catalysts. Ni-Nb2O5 operates as a bifunctional catalyst and is being widely explored for various catalytic applications without, however, exploring its structural stability and its effects on catalytic activity and durability. Herein we studied two forms of niobia, one with nonuniform morphology and another comprising a nanorod morphology. Various selected Ni loadings were dispersed on the two supports via a deposition–precipitation method. Physical and chemical characterization revealed that morphological control in combination with a highly efficient Ni deposition method is key in producing a structurally stable Ni-Nb2O5 catalyst. High surface area and porosity as exhibited by the Nb2O5 nanorods, in the pseudohexagonal phase, combined with small, well-dispersed Ni particles, provide a structurally stable material up to 500 °C, with high acidity (Lewis and Brønsted acid sites). Moreover, the local and long-range order, characterized in situ (XANES and XRD), determined the temperature limits for the optimization of metallic Ni particles in relation to the Nb2O5 structure.

Design of Nickel Supported on Water-Tolerant Nb2O5 Catalysts for the Hydrotreating of Lignin Streams Obtained from Lignin-First Biorefining

“…To verify whether the synthesis rendered Nb 2 O 5 nanorods, the Nb 2 O 5 material was examined by using high-angle annular dark-field (HAADF)-STEM (Figure 2). The HAADF-STEM images show that the hydrothermal synthesis produced Nb 2 O 5 nanorods with approximately 8–25 nm length and 3–4 nm width (Leal et al., 2019). The nanorod dimensions are in line with those of previous studies showing that the crystal growth in the hydrothermal method follows an oriented attachment mechanism (Leite et al., 2006), producing nanorods smaller than those synthesized in the presence of a surfactant as a shape-directing agent.…”

“…Hydrothermal synthesis of TT-Nb 2 O 5 nanorods in the presence of H 2 O 2 represents a route receiving far less attention, but with the most promising results regarding the textural and acidic properties of niobia (Leal et al., 2019). Despite the improved chemical and physical properties, such Nb 2 O 5 nanorods have not yet been explored in the chemistry of lignin hydrotreating.…”

“…CUB constitutes a class of methods for deconstruction of lignocellulose that renders high-quality pulps together with depolymerized and passivated lignin streams (Ferrini and Rinaldi, 2014, Galkin and Samec, 2016, Graça et al., 2018, Renders et al., 2017, Rinaldi, 2017, Schutyser et al., 2018, Sultan et al., 2019, Rinaldi et al, 2019). TT-Nb 2 O 5 nanorods were prepared via hydrothermal synthesis by employing ammonium niobium oxalate and H 2 O 2 as the structure-directing agent (Leal et al., 2019, Leite et al., 2006, Pavia et al., 2010). TT-Nb 2 O 5 nanorods were then loaded with several Ni contents.…”

Uso da rubrica na avaliação da aprendizagem em curso de Engenharia

“…Para a amostra calcinada foi observada a presença de dois picos referentes ao óxido de níquel (NiO) em aproximadamente 43° e 79° (JCPDS 78-0643). Na amostra reduzida observa-se a presença de dois picos em 44° e 51°, indexado ao níquel metálico (JCPDS 87-0712) (LEAL et al, 2019). Na redução com NaBH 4 , observou-se que o pico de 44° apresentou baixa intensidade e a ausência do pico de 51°.…”

Interplay of Solid–Liquid Interactions and Anisotropic Aggregation in Solution: The Case Study of γ-AlOOH Crystallites

“…This is often due to the nonisotropic character of the reliance of an involved physical property (electronic conductivity, light absorption, plasmon resonance...). , For surface-related applications, the overexpression of selected facets due the morphology control may enhance the chemical reactivity, which is useful for photocatalysis or ion insertion in the structure . Another application of anisotropic nanoparticles is the preparation of liquid crystals, and few examples of inorganic liquid crystals can be found in the literature. − A less studied application of anisotropic objects is their use as a building unit for the design of original porous materials for catalytic applications. , Indeed, the stacking of elongated objects may offer a more opened porosity to ease reactant uptake and product release …”