Isomerization of endo-dicyclopentadiene using Al-grafted MCM-41

The isomerization of endo-dicyclopentadiene (endo-DCPD) using Al-grafted MCM-41 was studied as an industrial practical synthesis route for exo-DCPD. The catalyst was prepared with post-synthesis grafting method, characterized by XRD, N2 adsorption/desorption, 27Al and 29Si MAS NMR, in-situ pyridine adsorption IR and NH3-TPD. The materials retain ordered mesoporous structure and high surface area. Al atoms are preferentially anchored in tetra-coordination, but these in octa-coordination increase significantly in case of high Al content. The amount of Brønsted acid is closely related to the amount of tetra-coordinated Al species whereas that of Lewis acid corresponding to the total Al content. The prepared material shows higher activity than microporous zeolites because its mesoporous structure gives free diffusion and excellent coke tolerance capability. A good correlation between the conversion of endo-DCPD and the amount of Lewis acid was observed. Specifically, the weak Lewis acid sites catalyze the endo- to exo-isomerization, meanwhile the moderate ones account for the [2 + 2] cycloaddition of two DCDP molecules. Catalyst with Si/Al of 8 is most active due to its highest concentration of weak Lewis acid. Addition of inert solvent, relatively low reaction temperature and high catalyst dosage can improve the isomerization. The deactivated catalyst can be easily regenerated by calcination.

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► Al-grafted MCM-41 shows higher activity than Hβ.
► Weak Lewis acid sites are the active site.
► Sample with Si/Al ratio of 8 shows highest selectivity of 85%, with conversion of 70%.
► The deactivated catalyst is easily regenerated by calcination.