Al2O3 nanofibers prepared from aluminum Di(sec-butoxide)acetoacetic ester chelate exhibits high surface area and acidity

• Published in: Journal of catalysis Vol. 405; pp. 520 - 533
• Main Authors: Rodriguez-Olguin, M.A., Atia, H., Bosco, M., Aguirre, A., Eckelt, R., Asuquo, E.D., Vandichel, M., Gardeniers, J.G.E., Susarrey-Arce, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2022
• Subjects: Acidity; DFT; Electrospinning; Nanofibers; NH3-TPD; Porous Alumina; Electrospinning; Acidity; NH3-TPD; DFT; Nanofibers; Porous Alumina
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2021.11.019

[Display omitted] •Electrospun alumina nanofibers exhibit high acidity.•The nature of the acid sites in alumina nanofibers is assessed with IR-Pyridine.•Total acidity and acid sites distribution is assessed with NH3-TPD.•Desorption kinetics of adsorbed ammonia (NH3) using density-functional theory (DFT) is provided.•A mathematical model using a regression procedure is used to estimate NH3 desorption energy on alumina nanofibers. Alumina (Al2O3) is a widely used material for catalysis in the chemical industry. Besides a high specific surface area, acid sites on Al2O3 play a crucial role in the chemical transformation of adsorbed molecules, which ultimately react and desorb from the catalyst. This study introduces a synthetic method based on electrospinning to produce Al2O3 nanofibers (ANFs) with acidity and porosity tuned using different aluminum precursor formulations. After electrospinning and heat treatment, the nanofibers form a non-woven network with macropores (∼4 μm). Nanofibers produced from aluminum di(sec-butoxide)acetoacetic ester chelate (ASB) show the highest total acidity of ca. 0.70 µmol/m2 determined with temperature-programmed desorption of ammonia (NH3-TPD) and BET. The nature of the acid site in ASB ANFs is studied in detail with infrared (IR) spectroscopy. Pyridine is used as a molecular probe for the identification of acid sites in ASB. Pyridine showed the presence of Lewis acid sites prominently. Density-functional theory (DFT) is conducted to understand the desorption kinetics of the adsorbed chemical species, such as ammonia (NH3) on crystalline γ-Al2O3. For our analysis, we focused on a mobile approach for chemisorbed and physisorbed NH3. The computational results are compared with NH3-TPD experiments, ultimately utilized to estimate the desorption energy and kinetic desorption parameters. The experiments are found to pair up with our simulation results. We predict that these non-woven structures will find application as a dispersion medium of metallic particles in catalysis.