(100) facets of γ-Al2O3: The active surfaces for alcohol dehydration reactions

Ja Hun Kwak, Donghai Mei, Charles H.F. Peden, Roger Rousseau, János Szanyi

Research output: Contribution to journalArticlepeer-review

78 Citations (Scopus)

Abstract

Temperature programmed desorption (TPD) of ethanol, as well as ethanol and methanol dehydration reactions were studied on γ-Al2O 3 in order to identify the active catalytic sites for alcohol dehydration reactions. Two high temperature (>473 K) desorption features were observed following ethanol adsorption. Samples calcined at T ≤ 473 K displayed a desorption feature in the 523-533 K temperature range, while those calcined at T ≥ 673 K showed a single desorption feature at 498 K. These two high temperature desorption features correspond to the exclusive formation of ethylene on the Lewis (498 K) and Brønsted acidic (~525 K) sites. The amount of ethylene formed under conditions where the competition between water and ethanol for adsorption sites is minimized is identical over the two surfaces. Furthermore, a nearly 1-to-1 correlation between the number of under-coordinated Al3+ ions on the (100) facets of γ-Al 2O3 and the number of ethylene molecules formed in the ethanol TPD experiments on samples calcined at T ≥ 673 K was found. Titration of the penta-coordinate Al3+ sites on the (100) facets of γ-Al2O3 by BaO completely eliminated the methanol dehydration reaction activity. These results demonstrate that in alcohol dehydration reactions on γ-Al2O3, the (100) facets are the active catalytic surfaces. The observed activities can be linked to the same Al3+ ions on both hydrated and dehydrated surfaces: penta-coordinate Al3+ ions (Lewis acid sites), and their corresponding -OH groups (Brønsted acid sites), depending on the calcination temperature.

Original languageEnglish
Pages (from-to)649-655
Number of pages7
JournalCatalysis Letters
Volume141
Issue number5
DOIs
Publication statusPublished - May 1 2011

Keywords

  • (100) facets
  • Alcohol
  • Dehydration reactions
  • Penta-coordinate Al ions

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Fingerprint Dive into the research topics of '(100) facets of γ-Al<sub>2</sub>O<sub>3</sub>: The active surfaces for alcohol dehydration reactions'. Together they form a unique fingerprint.

Cite this