Structure-Activity Relationships in Alkane Dehydrogenation on γ-Al2O3: Site-Dependent Reactions

Mudit Dixit, Pavlo Kostetskyy, Giannis Mpourmpakis

Research output: Contribution to journalArticlepeer-review

80 Scopus citations

Abstract

A promising route to produce olefins, the building blocks for plastics and chemicals, is the nonoxidative dehydrogenation of alkanes on metal oxides, taking advantage of the Lewis acid-base surface functionalities of the oxides. However, how alkane dehydrogenation activity depends on the strength of surface acid-base site pairs is still elusive. In this work, we provide fundamental insights into the reaction mechanisms of propane dehydrogenation on different facets of γ-Al2O3 and develop structure-activity relationships, using density functional theory calculations and first-principles molecular dynamics simulations. We identified the binding energy of dissociated H2 as an activity descriptor for alkane dehydrogenation. Interestingly, a volcano relationship between catalytic activity and dissociative H2 binding energy was discovered for propane dehydrogenation, unraveling a site-dependent catalytic behavior on γ-Al2O3, with a concerted surface mechanism being energetically preferred to a sequential one on the most active sites. We demonstrated that although surface hydration, in general, blocks strong Lewis acid-base pairs on the (110) γ-Al2O3 surface, the presence of hydroxyl groups (on neighboring to strong Lewis sites) can enhance the propane dehydrogenation activity of a "defect site pair" (AlIII-OIII) of the metastable surface. Moreover, we performed ab initio metadynamics simulations of the most active site on γ-Al2O3 to examine the hydrogen formation and surface dynamics under dehydrogenation reaction conditions. Metadynamics simulations demonstrated that the poisoning of active sites by hydrogen adsorption is unlikely under experimental conditions. The developed relationships can be utilized to screen metal oxide surfaces and accelerate the discovery of active catalysts for alkane conversion to olefins.

Original languageEnglish
Pages (from-to)11570-11578
Number of pages9
JournalACS Catalysis
Volume8
Issue number12
DOIs
StatePublished - 7 Dec 2018
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

Keywords

  • catalyst activity
  • density functional theory
  • metadynamics
  • oxides
  • propane dehydrogenation
  • surface hydration
  • volcano plot

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