Open Access
Facile synthesis of an Ni/LaAlO3 - perovskite via an MOF gel precursor for the dry reforming of methane
(Elsevier, 2024) Muñoz Alvear, Helir Joseph; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
A simple strategy to prepare the pure perovskite phase of lanthanum aluminate (LaAlO3) by calcination of a highly porous, dry MOF precursor gel has been developed. This study demonstrates that the structural and textural properties, such as specific surface area, pore volumes and pore sizes, of precursor-like metal-organic gels (MOG) (MOG-Al-La) based on metal-organic framework (MOF) structures can be modulated by optimizing the solvothermal treatment time. The perovskite obtained after solvothermal treatment at 120º C for 12 h and calcination at 750º C maintained the mesoporous characteristics of the MOF precursor, with a small particle size due to the decrease in crystallization temperature. These properties in the support allowed a good dispersion of the active Ni sites, low reducibility, and a strong interaction between them and the support, thus suppressing sintering under the severe catalytic reaction conditions evaluated (GHSV = 120,000 cm3/g-h) for the dry reforming of methane. The resulting MOX-(12 h)-LaAlO3-750-Ni catalyst gave a CH4 average conversion of 75% and CO2 average conversion of 80% after 20 h of reaction. The improved stability of the catalyst was attributed to suppression of the formation of the dense network of carbon filaments that can stress and subsequently fracture the support, cause attrition of the catalyst granules and hinder diffusion of the reactants both through the pores of the support and the interparticle spaces.
Open Access
Progress and recent strategies in the synthesis and catalytic applications of perovskites based on lanthanum and aluminum
(MDPI, 2022) Muñoz Alvear, Helir Joseph; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Lanthanum aluminate-based perovskite (LaAlO3) has excellent stability at high temperatures, low toxicity, and high chemical resistance and also offers wide versatility to the substitution of La3+ and Al3+, thus, allowing it to be applied as a catalyst, nano- dsorbent, sensor, and microwave dielectric resonator, amongst other equally important uses. As such, LaAlO3 perovskites have gained importance in recent years. This review considers the extensive literature of the past 10 years on the synthesis and catalytic applications of perovskites based on lanthanum and aluminum (LaAlO3). The aim is, first, to provide an overview of the structure, properties, and classification of perovskites. Secondly, the most recent advances in synthetic methods, such as solid-state methods, solutionmediated methods (co-precipitation, sol–gel, and Pechini synthesis), thermal treatments (combustion, microwave, and freeze drying), and hydrothermal and solvothermal methods, are also discussed. The most recent energetic catalytic applications (the dry and steam reforming of methane; steam reforming of toluene, glycerol, and ethanol; and oxidative coupling of methane, amongst others) using these functional materials are also addressed. Finally, the synthetic challenges, advantages, and limitations associated with the preparation methods and catalytic applications are discussed.
Open Access
Recent advances in the application of Ni-perovskite-based catalysts for the dry reforming of methane
(Taylor & Francis, 2024-09-17) Muñoz Alvear, Helir Joseph; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Ni-based catalysts have been reported to be very efficient in methane reforming processes, surpassing some noble metals. In the particular case of methane reforming in the presence of carbon dioxide (dry reforming of methane, DRM), modifying and controlling the initial properties of the catalyst becomes crucial to resist carbon deposition and Ni metal sintering. This is because the DRM process is carried out at high temperatures. In this sense, perovskite-based catalysts are of special interest given that they are synthesized at high temperatures and, therefore, can conserve their properties during the reaction. Perovskites are represented by the general formula ABO3 or A2BO4. The properties of these oxides depend on the nature of metals A and B and their possible partial substitution, which allows control of their redox and acid/basic properties. This review delves into the thermodynamic and kinetic aspects of the DRM, highlighting that the properties of A and B can affect catalytic performance. Following this, the focus shifts to B-cation substitution, which can increase the catalytic performance of the catalyst via synergistic effects due to the formation of Ni metal alloys. Next, in an analogous manner, the analysis will examine A-cation substitution, which allows control over the acid/basic properties and, therefore, coke formation and deposition. Given the inherently low textural properties of perovskites, methods for enhancing these properties are also summarized. These methods encompass both direct improvements and deposition of the perovskites on a support. Finally, new lines of research focused on softening DRM reaction conditions and promoting the process at lower temperatures are also highlighted.

Muñoz Alvear, Helir Joseph

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