Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene to its exo isomer over zeolite catalysts Original Research Article

Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD over zeolite catalysts (HY, H-USY, Hβ, HZSM-5 and HMOR) was studied as a green synthesis route for exo-THDCPD. The HY and H-USY catalysts showed catalytic activity while the Hβ, HZSM-5 and HMOR catalysts did not. Higher yield of exo-THDCPD was obtained over the H-USY catalyst than that over the HY catalyst, attributing to the presence of strong acid sites and mesopores in the H-USY catalyst. The yield of exo-THDCPD obtained via vapor-phase isomerization was better than that reported via liquid-phase isomerization. In addition to the properties of the catalyst itself, the vapor-phase isomerization process of endo-THDCPD was also affected by the reaction temperature, the concentration of endo-THDCPD, the contact time and the time on stream. Under the optimized conditions, high purity (>98 wt%) exo-THDCPD was directly obtained without any separation processes. Although deactivation of the catalyst with the time on stream was observed, the activity could be recovered easily via regeneration in air.