Structural analysis of highly porous γ-Al2O3

Louise Samain, Aleksander Jaworski, Mattias Edén, Danielle M. Ladd, Dong Kyun Seo, F. Javier Garcia-Garcia, Ulrich Häussermann

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

Two highly porous γ-aluminas, a commercial catalyst obtained from the calcination of boehmite and a highly mesoporous product obtained from amorphous aluminum (oxy)hydroxide via a sol-gel-based process were investigated by 27Al nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), and atomic pair distribution function (PDF) analysis of synchrotron powder diffraction data. NMR data showed for both materials a distribution of tetrahedrally and octahedrally coordinated Al at a 0.30:0.70 ratio, which is typical for γ-aluminas. TEM studies revealed that rod-shaped particles with about 5 nm in thickness are the building blocks of the porous structure in both materials. These particles often extend to a length of 50 nm in the commercial catalyst and are considerably shorter in the sol-gel-based material, which has a higher surface area. Refinement of PDFs revealed the presence of a ~1 nm scale local structure and the validity of a tetragonal average structure for both materials. This tetragonal average structure contains a substantial fraction of non-spinel octahedral Al atoms. It is argued that the presence of local structure is a general feature of γ-alumina, independent of precursor and synthesis conditions. The concentration of "non-spinel" Al atoms seems to correlate with surface properties, and increases with increasing pore size/surface area. This should have implications to the catalytic properties of porous γ-alumina.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalJournal of Solid State Chemistry
Volume217
DOIs
Publication statusPublished - Sep 2014

Keywords

  • Crystal structure
  • Gamma alumina
  • PDF analysis
  • Porous materials

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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    Samain, L., Jaworski, A., Edén, M., Ladd, D. M., Seo, D. K., Javier Garcia-Garcia, F., & Häussermann, U. (2014). Structural analysis of highly porous γ-Al2O3. Journal of Solid State Chemistry, 217, 1-8. https://doi.org/10.1016/j.jssc.2014.05.004