Methanol-to-hydrocarbons conversion: The alkene methylation pathway

Rasmus Y. Brogaard*, Reynald Henry, Yves Schuurman, Andrew J. Medford, Poul Georg Moses, Pablo Beato, Stian Svelle, Jens K. Nørskov, Unni Olsbye

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Research on zeolite-catalyzed methanol-to-hydrocarbons (MTH) conversion has long been concerned with the mechanism of the reaction between methanol and alkenes. Two pathways have been debated: (1) the stepwise, proceeding through a surface-methoxy intermediate and (2) the concerted, in which the alkenes react directly with methanol. This work addresses the debate through micro-kinetic modeling based on density functional theory calculations of both pathways, as well as experiments employing temporal analysis of products to investigate the kinetics of the stepwise pathway for a series of alkenes in H-ZSM-22 zeolite. The model predicts the stepwise pathway to prevail at typical MTH reaction temperatures, due to a higher entropy loss in the concerted as compared to the stepwise pathway. The entropy difference results from intermediate release of water in the stepwise pathway. These findings lead us to suggest that the stepwise pathway should also be considered when modeling MTH conversion in other zeolites.

Original languageEnglish
JournalJournal of Catalysis
Volume314
Pages (from-to)159-169
Number of pages11
ISSN0021-9517
DOIs
Publication statusPublished - 2014
Externally publishedYes

Keywords

  • Alkene methylation
  • Density functional theory
  • Methanol-to-hydrocarbons conversion
  • Micro-kinetic modeling
  • Reaction pathway
  • Temporal analysis of products
  • Zeolite catalysis
  • ZSM-22

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