Control of surface acidity and catalytic activity of γ-Al 2O3 by adjusting the nanocrystalline contact interface

Roxana Vidruk, Miron V. Landau, Moti Herskowitz, Vladimir Ezersky, Amir Goldbourt

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

Densification of 2-2.5 nm nanocrystals assemblies in the three-level hierarchical structure of γ-Al2O3 aerogel significantly increases the surface acidity, as determined using indicator titration, NH3-TPD, and FTIR of adsorbed pyridine. Thermal treatment at 1073 K and insertion of additional alumina inside the aerogel pores eliminated the slit micropores with shrinkage of nanocrystals assemblies (N 2-adsorption, HRTEM, SEM) increasing the contact interface by a factor of 2. It caused a fivefold increase in alumina surface acidity and the strength of Lewis acid sites with no measurable dehydration (weight loss, TGA). This was attributed to the formation of additional low-coordinated aluminum ions with higher charge in the areas with atomic disorder of high-angle grain boundaries, detected by 27Al MAS NMR, HRTEM, XPS, and XRD. Densification of nanocrystalline alumina aerogel yielded a higher catalytic activity in dehydration of isopropanol; it was 10-fold more active compared with commercial γ-alumina on the catalyst weight basis.

Original languageEnglish
Pages (from-to)215-227
Number of pages13
JournalJournal of Catalysis
Volume282
Issue number1
DOIs
StatePublished - 15 Aug 2011

Keywords

  • Acidity
  • Aluminum oxide
  • Densification
  • Isopropanol dehydration
  • Nanoparticles contact interface

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