A computational investigation of ring-shift isomerization of sym-octahydrophenanthrene to sym-octahydroanthracene catalyzed by acidic zeolites

Xiaowa Nie, Michael J. Janik, Xinwen Guo, Chunshan Song

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

The ring-shift isomerization of sym-octahydrophenanthrene (sym-OHP) to sym-octahydroanthracene (sym-OHA) catalyzed by acidic zeolites (Mordenite (MOR) and Faujasite (FAU)) was investigated by the ONIOM(DFT:UFF) and DFT approaches. A "five-membered ring" mechanism through carbocation rearrangement via 1-2 migration was proved to be kinetically favored over a "six-membered ring" mechanism through Friedel-Crafts reactions. Computational studies based on the "five-membered ring" mechanism demonstrate that a decreasing Bronsted acid site strength from Al-H-MOR to Ga-H-MOR to B-H-MOR reduces the catalytic activity. The catalyst acid site strength would thereby impact the yield of sym-OHA. The isomerization barrier increases when using an Al-H-FAU catalyst that has a similar Bronsted acid site strength as Al-H-MOR but considerably bigger cages, indicating that apart from the desired density and strength of acid sites, optimal zeolite catalysts should have a pore size that better fits the intermediates and transition states. DFT calculations on Gibbs free energy were performed to evaluate the equilibrium ratios of sym-OHA to sym-OHP at specific reaction temperatures from 175 to 325 °C. The results indicate that reaction temperature has a moderate impact on the equilibrium yield of sym-OHA, whose formation is relatively favorable at a lower temperature under experimental conditions.

Original languageEnglish (US)
Pages (from-to)16644-16653
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume14
Issue number48
DOIs
StatePublished - Dec 28 2012

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Fingerprint Dive into the research topics of 'A computational investigation of ring-shift isomerization of sym-octahydrophenanthrene to sym-octahydroanthracene catalyzed by acidic zeolites'. Together they form a unique fingerprint.

  • Cite this