Catalytic Isomerization of 2-pentene in H-ZSM-22

First-principles calculations using VASP reveal the lowest energy reaction pathway for the catalyzed skeletal isomerization of 2-pentene by the acidic zeolite H-ZSM. Three potential mechanisms were evaluated: an ethyl-shift pathway, a dimethylcyclopropane (DMCP) intermediate pathway and a pathway involving an edge-protonated DMCP species. The results indicate that the DMCP intermediate pathway is the kinetically preferred pathway with a classical barrier height of 98 kJ/mol. Evident in the calculations is the influence of the transient intermediate stability along the reaction path; with secondary carbenium ions leading to energetically favored mechanisms.