论文名称：A computational investigation of ring-shift isomerization of sym-octahydrophenanthrene to sym-octahydroanthracene catalyzed by acidic zeolites
论文类型：期刊论文
发表刊物：PHYSICAL CHEMISTRY CHEMICAL PHYSICS
收录刊物：PubMed、SCIE、Scopus
卷号：14
期号：48
页面范围：16644-16653
ISSN号：1463-9076
摘要：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 degrees 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.
发表时间：2012-12-28