(324f) Theoretical Studies of Alkene Isomerization and Dimerization in Zeolites

Light olefin feedstocks produced by the Fischer-Tropsch process can be upgraded to either linear or branched higher hydrocarbons through oligomerization in acidic, medium-pore zeolites. A fundamental understanding of the many possible reaction pathways can provide insight into the performance and product distribution of these catalysts. Density functional theory is used to analyze the acid-catalyzed pathways of butene isomerization and propene dimerization reactions in cluster models of the zeolite H-MFI. Systematic evaluation of the effects of cluster model size and level of theory on interaction and activation energies is presented. Carbenium ion transition states are observed in all cases, and it is shown how these transition states are stabilized by the inclusion of zeolite framework atoms and by treating these systems with dispersion-corrected density functionals. The convergence of interaction and activation energies with respect to cluster size is discussed.