Stabilization of self-assembled alumina mesophases

Lidia López Pérez, Sébastien Perdriau, Gert ten Brink, Bart J. Kooi, Hero Jan Heeres, Ignacio Melián-Cabrera

Research output: Contribution to journalArticle

Abstract

An efficient route to stabilize alumina mesophases derived from evaporation-induced self-assembly is reported after investigating various aspects in-depth: influence of the solvent (EtOH, s-BuOH, and t-BuOH) on the textural and structural properties of the mesophases based on aluminum tri-sec-butoxide (ATSB), synthesis reproducibility, role of nonvolatile acids, and the crystallization and thermal stability of the crystalline counterparts. Mesophase specific surface area and pore uniformity depend notably on the solvent; s-BuOH yields the highest surface area and pore uniformity. The optimal mesophase synthesis is reproducible with standard deviations in the textural parameters below 5%. The most pore-uniform mesophases from the three solvents were thermally activated at 1023 K to crystallize them into γ-alumina. The s-BuOH mesophase is remarkably thermally stable, retaining the mesoscopic wormhole order with 300 m2/g (0.45 cm3/g) and an increased acidic site density. These features are not obtained with EtOH or t-BuOH, where agglomerated γ-Al2O3 crystallites are formed with lower surface areas and broader pore size distributions. This was rationalized by the increase of the hydrolysis rate using EtOH and t-BuOH. t-BuOH dehydrates under the synthesis conditions or reacts with HCl, situations that increase the water concentration and rate of hydrolysis. It was found that EtOH exchanges rapidly, producing a highly reactive Al-ethoxide, thus enhancing the hydrolysis rate as well. Particle heterogeneity with random packing of fibrous and wormhole morphologies, attributed to the high hydrolysis rate, was observed for mesophases derived from both solvents. Such a low particle coordination favors coarsening with enlargement of the pore size distribution upon thermal treatment, explaining the lower thermal stability. Controlled hydrolysis and formation of low-polymerized Al species in s-BuOH are possibly responsible for the adequate assembly onto the surfactant. This was verified by the formation of a regular distribution of relatively size-uniform nanoparticles in the mesophase; high particle coordination prevents coarsening, favors densification, and maintains a relatively uniform pore size distribution upon thermal treatment. The acid removal in the evaporation is another key factor to promote network condensation in this route.

Original languageEnglish
Pages (from-to)848-855
Number of pages8
JournalChemistry of Materials
Volume25
Issue number6
Early online date8 Mar 2013
DOIs
Publication statusPublished - 26 Mar 2013

Fingerprint

Aluminum Oxide
Hydrolysis
Alumina
Stabilization
Pore size
Coarsening
Evaporation
Thermodynamic stability
Heat treatment
Acids
Crystallization
Aluminum
Densification
Crystallites
Surface-Active Agents
Specific surface area
Self assembly
Structural properties
Condensation
Surface active agents

Keywords

  • γ-alumina
  • alkoxide chemistry
  • coarsening
  • evaporation-induced self-assembly
  • mesoporosity
  • sol-gel
  • solvent effects
  • thermal stability

Cite this

López Pérez, L., Perdriau, S., ten Brink, G., Kooi, B. J., Heeres, H. J., & Melián-Cabrera, I. (2013). Stabilization of self-assembled alumina mesophases. Chemistry of Materials, 25(6), 848-855. https://doi.org/10.1021/cm303174r
López Pérez, Lidia ; Perdriau, Sébastien ; ten Brink, Gert ; Kooi, Bart J. ; Heeres, Hero Jan ; Melián-Cabrera, Ignacio. / Stabilization of self-assembled alumina mesophases. In: Chemistry of Materials. 2013 ; Vol. 25, No. 6. pp. 848-855.
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López Pérez, L, Perdriau, S, ten Brink, G, Kooi, BJ, Heeres, HJ & Melián-Cabrera, I 2013, 'Stabilization of self-assembled alumina mesophases', Chemistry of Materials, vol. 25, no. 6, pp. 848-855. https://doi.org/10.1021/cm303174r

Stabilization of self-assembled alumina mesophases. / López Pérez, Lidia; Perdriau, Sébastien; ten Brink, Gert; Kooi, Bart J.; Heeres, Hero Jan; Melián-Cabrera, Ignacio.

In: Chemistry of Materials, Vol. 25, No. 6, 26.03.2013, p. 848-855.

Research output: Contribution to journalArticle

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T1 - Stabilization of self-assembled alumina mesophases

AU - López Pérez, Lidia

AU - Perdriau, Sébastien

AU - ten Brink, Gert

AU - Kooi, Bart J.

AU - Heeres, Hero Jan

AU - Melián-Cabrera, Ignacio

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Y1 - 2013/3/26

N2 - An efficient route to stabilize alumina mesophases derived from evaporation-induced self-assembly is reported after investigating various aspects in-depth: influence of the solvent (EtOH, s-BuOH, and t-BuOH) on the textural and structural properties of the mesophases based on aluminum tri-sec-butoxide (ATSB), synthesis reproducibility, role of nonvolatile acids, and the crystallization and thermal stability of the crystalline counterparts. Mesophase specific surface area and pore uniformity depend notably on the solvent; s-BuOH yields the highest surface area and pore uniformity. The optimal mesophase synthesis is reproducible with standard deviations in the textural parameters below 5%. The most pore-uniform mesophases from the three solvents were thermally activated at 1023 K to crystallize them into γ-alumina. The s-BuOH mesophase is remarkably thermally stable, retaining the mesoscopic wormhole order with 300 m2/g (0.45 cm3/g) and an increased acidic site density. These features are not obtained with EtOH or t-BuOH, where agglomerated γ-Al2O3 crystallites are formed with lower surface areas and broader pore size distributions. This was rationalized by the increase of the hydrolysis rate using EtOH and t-BuOH. t-BuOH dehydrates under the synthesis conditions or reacts with HCl, situations that increase the water concentration and rate of hydrolysis. It was found that EtOH exchanges rapidly, producing a highly reactive Al-ethoxide, thus enhancing the hydrolysis rate as well. Particle heterogeneity with random packing of fibrous and wormhole morphologies, attributed to the high hydrolysis rate, was observed for mesophases derived from both solvents. Such a low particle coordination favors coarsening with enlargement of the pore size distribution upon thermal treatment, explaining the lower thermal stability. Controlled hydrolysis and formation of low-polymerized Al species in s-BuOH are possibly responsible for the adequate assembly onto the surfactant. This was verified by the formation of a regular distribution of relatively size-uniform nanoparticles in the mesophase; high particle coordination prevents coarsening, favors densification, and maintains a relatively uniform pore size distribution upon thermal treatment. The acid removal in the evaporation is another key factor to promote network condensation in this route.

AB - An efficient route to stabilize alumina mesophases derived from evaporation-induced self-assembly is reported after investigating various aspects in-depth: influence of the solvent (EtOH, s-BuOH, and t-BuOH) on the textural and structural properties of the mesophases based on aluminum tri-sec-butoxide (ATSB), synthesis reproducibility, role of nonvolatile acids, and the crystallization and thermal stability of the crystalline counterparts. Mesophase specific surface area and pore uniformity depend notably on the solvent; s-BuOH yields the highest surface area and pore uniformity. The optimal mesophase synthesis is reproducible with standard deviations in the textural parameters below 5%. The most pore-uniform mesophases from the three solvents were thermally activated at 1023 K to crystallize them into γ-alumina. The s-BuOH mesophase is remarkably thermally stable, retaining the mesoscopic wormhole order with 300 m2/g (0.45 cm3/g) and an increased acidic site density. These features are not obtained with EtOH or t-BuOH, where agglomerated γ-Al2O3 crystallites are formed with lower surface areas and broader pore size distributions. This was rationalized by the increase of the hydrolysis rate using EtOH and t-BuOH. t-BuOH dehydrates under the synthesis conditions or reacts with HCl, situations that increase the water concentration and rate of hydrolysis. It was found that EtOH exchanges rapidly, producing a highly reactive Al-ethoxide, thus enhancing the hydrolysis rate as well. Particle heterogeneity with random packing of fibrous and wormhole morphologies, attributed to the high hydrolysis rate, was observed for mesophases derived from both solvents. Such a low particle coordination favors coarsening with enlargement of the pore size distribution upon thermal treatment, explaining the lower thermal stability. Controlled hydrolysis and formation of low-polymerized Al species in s-BuOH are possibly responsible for the adequate assembly onto the surfactant. This was verified by the formation of a regular distribution of relatively size-uniform nanoparticles in the mesophase; high particle coordination prevents coarsening, favors densification, and maintains a relatively uniform pore size distribution upon thermal treatment. The acid removal in the evaporation is another key factor to promote network condensation in this route.

KW - γ-alumina

KW - alkoxide chemistry

KW - coarsening

KW - evaporation-induced self-assembly

KW - mesoporosity

KW - sol-gel

KW - solvent effects

KW - thermal stability

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López Pérez L, Perdriau S, ten Brink G, Kooi BJ, Heeres HJ, Melián-Cabrera I. Stabilization of self-assembled alumina mesophases. Chemistry of Materials. 2013 Mar 26;25(6):848-855. https://doi.org/10.1021/cm303174r