Chemical Weathering of Alumina in Aqueous ...
Document type :
Article dans une revue scientifique
DOI :
Permalink :
Title :
Chemical Weathering of Alumina in Aqueous Suspension at Ambient Pressure: A Mechanistic Study
Author(s) :
Abi Aad, Jane [Auteur]
Casale, Sandra [Auteur]
Michau, Mathieu [Auteur]
Courty, Philippe [Auteur]
Diehl, Fabrice [Auteur]
Marceau, Eric [Auteur]
Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181
Unité de Catalyse et Chimie du Solide - UMR 8181 [UCCS]
Carrier, Xavier [Auteur]
Casale, Sandra [Auteur]
Michau, Mathieu [Auteur]
Courty, Philippe [Auteur]
Diehl, Fabrice [Auteur]
Marceau, Eric [Auteur]
Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181
Unité de Catalyse et Chimie du Solide - UMR 8181 [UCCS]
Carrier, Xavier [Auteur]
Journal title :
ChemCatChem
Volume number :
9
Pages :
2186-2194
Publication date :
2017-02-27
HAL domain(s) :
Chimie/Catalyse
English abstract : [en]
Transition aluminas rank among the main supports used for heterogeneous catalysis. Their stability in the aqueous phase is a key issue for catalytic processes, as their hydration can be strongly detrimental to their ...
Show more >Transition aluminas rank among the main supports used for heterogeneous catalysis. Their stability in the aqueous phase is a key issue for catalytic processes, as their hydration can be strongly detrimental to their physicochemical and mechanical properties. As a consequence, the design of more stable alumina-based supports relies on a better understanding of the mechanisms leading to their chemical and physical degradation. It is shown here that if suspended in water at atmospheric pressure and at temperatures up to 70 °C, all transition aluminas (from γ to θ-Al2O3) transform into Al(OH)3 polymorphs (bayerite, gibbsite, and nordstrandite), although to different extents. A quantitative study of the aluminum concentration in solution and of the amount of hydroxides demonstrates that Al2O3 hydration occurs through a two-step dissolution/heterogeneous precipitation process, with nucleation of Al(OH)3 on the surface of the alumina grains followed by particle growth. The grains become more fragile because of chemical weathering; the ensuing mechanical degradation by attrition, in turn, brings the weathering process to completion. The nature of the main hydroxide polymorph is a function of aluminum concentration and ageing time: first the kinetic product, bayerite, then nordstrandite and eventually gibbsite, the most thermodynamically stable hydroxide. Increasing crystallinity and decreasing specific surface area of alumina leads to a reduced amount in hydroxide formation.Show less >
Show more >Transition aluminas rank among the main supports used for heterogeneous catalysis. Their stability in the aqueous phase is a key issue for catalytic processes, as their hydration can be strongly detrimental to their physicochemical and mechanical properties. As a consequence, the design of more stable alumina-based supports relies on a better understanding of the mechanisms leading to their chemical and physical degradation. It is shown here that if suspended in water at atmospheric pressure and at temperatures up to 70 °C, all transition aluminas (from γ to θ-Al2O3) transform into Al(OH)3 polymorphs (bayerite, gibbsite, and nordstrandite), although to different extents. A quantitative study of the aluminum concentration in solution and of the amount of hydroxides demonstrates that Al2O3 hydration occurs through a two-step dissolution/heterogeneous precipitation process, with nucleation of Al(OH)3 on the surface of the alumina grains followed by particle growth. The grains become more fragile because of chemical weathering; the ensuing mechanical degradation by attrition, in turn, brings the weathering process to completion. The nature of the main hydroxide polymorph is a function of aluminum concentration and ageing time: first the kinetic product, bayerite, then nordstrandite and eventually gibbsite, the most thermodynamically stable hydroxide. Increasing crystallinity and decreasing specific surface area of alumina leads to a reduced amount in hydroxide formation.Show less >
Language :
Anglais
Audience :
Internationale
Popular science :
Non
Administrative institution(s) :
ENSCL
CNRS
Centrale Lille
Univ. Artois
Université de Lille
CNRS
Centrale Lille
Univ. Artois
Université de Lille
Collections :
Research team(s) :
Matériaux pour la catalyse (MATCAT)
Submission date :
2019-09-25T14:06:31Z