Enhanced Hydrothermal Stability of gamma-Al2O3 Catalyst Supports with Alkyl Phosphonate Coatings

Autor(es)

Van Cleve, Tim ^[1] ; Underhill, Devon ^[1] ; Rodrigues, Mariana Veiga ^{[2, 3]} ; Sievers, Carsten ^[2] ; Will Medlin, J. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Colorado Boulder, Dept Chem & Biol Engn, JSCBB D125, 3415 Colorado Ave, Boulder, CO 80303 - USA

^[2] Georgia Inst Technol, Sch Chem & Biomol Engn, Atlanta, GA 30332 - USA

^[3] UNESP, Inst Quim Araraquara, Rua Prof Francisco Degni 55, BR-14800900 Araraquara, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Langmuir; v. 34, n. 12, p. 3619-3625, MAR 27 2018.
• Citações Web of Science: 5

Resumo

In this study, monolayers formed from organophosphonic acids were employed to stabilize porous gamma-Al2O3, both as a single component and as a support for Pt nanoparticle catalysts, during exposure to hydrothermal conditions. To provide a baseline, structural changes of uncoated gamma-Al2O3 catalysts under model aqueous phase reforming conditions (liquid water at 200 degrees C and autogenic pressure) were examined over the course of 20 h. These changes were characterized by X-ray diffraction, NMR spectroscopy, N-2 physisorption, and IR spectroscopy. It was demonstrated that gamma-alumina was rapidly converted into a hydrated boehmite (AlOOH) phase with significantly decreased surface area. Deposition of alkyl phosphonate groups on gamma-alumina drastically inhibited the formation of boehmite, thereby maintaining its high specific surface area over 20 h of treatment. Al-27 MAS NMR spectra demonstrated that hydrothermal stability increased with alkyl tail length despite lower P coverages. Although the inhibition of boehmite formation by the phosphonic acids was attributed primarily to the formation of Al2O3-POx bonds, it was found that use of longer-chain octadecylphosphonic acids led to the most pronounced effect. Phosphonate coatings on Pt/gamma-Al2O3 improved stability without adversely affecting the rate of a model reaction, catalytic hydrogenation of 1-hexene. (AU)

• Processo FAPESP: 16/01590-4 - Combinação de química supramolecular e emulsões na síntese de catalisadores lamelares esfoliados
• Beneficiário: Mariana Veiga Rodrigues
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado