Lewis and Bronsted acid catalysis with AlMCM-41 and AlMMS: dependence on exchange cation

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Abstract

Mesoporous solid acid catalysts based on AlMCM-41 and AlMMS have been prepared. The two catalysts exhibit similar unidimensional pore structures with hexagonal symmetries. AlMMS shows less long-range order than AlMCM-41 but is considerably easier to synthesise. The catalytic activities have been measured and compared in the Lewis-acid-catalysed alkylation of toluene with benzyl chloride, and the Bronsted-acid-catalysed alkylation of toluene with benzyl alcohol. Activities have been measured for catalysts ion-exchanged with H+, Fe3+, Al3+ and Na+, and following thermal activation at temperatures of 150-350 degrees C. They have also been compared with K10, a mesoporous acid-treated clay catalyst. Results show that the acid-treated clay is the most active of the three catalysts in both reactions. For all catalysts, the Fe3+ forms exhibit the highest Lewis acid catalytic activities, and the Al3+ and H+ forms show higher Bronsted acid activities. Infrared spectra of adsorbed pyridine show relative concentrations of Lewis and Bronsted acid sites consistent with this. Differences in the dependence of catalytic activities on thermal activation temperature are interpreted in terms of the hydration properties of the catalysts.

Original languageEnglish
Pages (from-to)57-64
Number of pages8
JournalCatalysis Letters
Volume56
Issue number1
DOIs
Publication statusPublished - 1 Nov 1998

Keywords

  • MCM-41
  • MMS
  • mesoporous molecular sieve
  • solid acid
  • acid-treated clay
  • acid-activated clay
  • montmorillonite
  • acid catalysis
  • Lewis acidity
  • Bronsted acidity
  • alkylation
  • MESOPOROUS MOLECULAR-SIEVES
  • ALKYLATION
  • PYRIDINE
  • CLAYS

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