Application of sulfonic acid functionalized MCM-41 materials-Selectivity changes in various probe reactions

B. Rác, Mariann Nagy, I. Pálinkó, Árpád Molnár

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

MCM-41 mesoporous ordered silica materials with covalently anchored propanesulfonic acid groups with varying pore diameters (1.6-3.5 nm) were synthesized. Two samples were prepared in the presence of appropriate templating agents (hexadecyltrimethylammonium chloride, decyltrimethylammonium bromide). After template removal they were reacted with 3-mercaptopropyltrimethoxysilane followed by transforming the thiol groups by oxidation to sulfonic acid functions. Two other catalyst samples were also prepared by treatment with phenyltriethoxysilane before template removal and functionalization. Sample characterization was performed by physical (low-angle X-ray powder diffraction, nitrogen adsorption, and desorption) and chemical (acid-base titration) methods. Three catalytic transformations were studied. Highly selective formation of para-tert-butylphenol through the isomerization of the ortho isomer was found in the alkylation of phenol with 2-methylpropan-2-ol over three of the catalysts. In the pinacol rearrangement of meso-hydrobenzoine, the rates of formation of diphenylacetaldehyde produced through phenyl migration with much higher steric requirement, parallel the changes in pore sizes. The reactivity of three aromatic ketones (acetophenone, 2-acetylnaphtalene, and 3-acetylphenantrene) in the formation of cyclic ketals over three of the catalysts depends significantly on the steric bulk of the reacting molecules. Furthermore, reactivity of the molecules with larger ring size in competitive reactions decreased and even stopped almost completely after the first hour and only the smaller molecule reacted further. Molecular modeling indicated that steric requirements might have significant effects on the reactivity over MCM-41-based catalysts. The results are interpreted as resulting from the combined effect of structural features of catalyst samples, catalyst ageing, and diffusion limitations.

Original languageEnglish
Pages (from-to)152-159
Number of pages8
JournalApplied Catalysis A: General
Volume316
Issue number2
DOIs
Publication statusPublished - Jan 10 2007

Fingerprint

Sulfonic Acids
Multicarrier modulation
Catalysts
Acids
Molecules
Molecular modeling
Alkylation
Isomerization
Phenol
Ketones
Titration
Sulfhydryl Compounds
Silicon Dioxide
Isomers
X ray powder diffraction
Phenols
Pore size
MCM-41
Desorption
Nitrogen

Keywords

  • Alkylation of phenol
  • Catalyst ageing
  • Cyclic ketals
  • Diffusion limitation
  • Grafting
  • Mesoporous silicas
  • Pinacol rearrangement
  • Propanesulfonic acid

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

Application of sulfonic acid functionalized MCM-41 materials-Selectivity changes in various probe reactions. / Rác, B.; Nagy, Mariann; Pálinkó, I.; Molnár, Árpád.

In: Applied Catalysis A: General, Vol. 316, No. 2, 10.01.2007, p. 152-159.

Research output: Contribution to journalArticle

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