Hydronium-Ion-Catalyzed Elimination Pathways of Substituted Cyclohexanols in Zeolite H-ZSM5

Peter H. Hintermeier, Sebastian Eckstein, Donghai Mei, Mariefel V. Olarte, Donald M. Camaioni, Eszter Baráth, Johannes A. Lercher

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Hydronium ions in the pores of zeolite H-ZSM5 show high catalytic activity in the elimination of water from cyclohexanol in aqueous phase. Substitution induces subtle changes in rates and reaction pathways, which are concluded to be related to steric effects. Exploring the reaction pathways of 2-, 3-, and 4-methylcyclohexanol (2-McyOH, 3-McyOH, and 4-McyOH), 2- and 4-ethylcyclohexanol (2-EcyOH and 4-EcyOH), 2-n-propylcyclohexanol (2-PcyOH), and cyclohexanol (CyOH) it is shown that the E2 character increases with closer positioning of the alkyl and hydroxyl groups. Thus, 4-McyOH dehydration proceeds via an E1-type elimination, while cis-2-McyOH preferentially reacts via an E2 pathway. The entropy of activation decreased with increasing alkyl chain length (ca. 20 J mol-1 K-1 per CH2 unit) for 2-substituted alcohols, which is concluded to result from constraints influencing the configurational entropy of the transition states.

Original languageEnglish
Pages (from-to)7822-7829
Number of pages8
JournalACS Catalysis
Volume7
Issue number11
DOIs
StatePublished - 3 Nov 2017

Keywords

  • Dehydration
  • Elimination reactions
  • Heterogeneous catalysis
  • Homogeneous catalysis
  • Zeolite

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