The endo- to exo-isomerization of dicyclopentadiene was performed in liquid phase using acidic zeolites. Among the zeolites tested, the activity order is H beta > HY > HUSY > HZSM-5 approximate to H-mordenite. Beta and Y-type zeolites exhibit higher activity because of their large three-dimensional channels. Surface passivation of H beta confirms that the reaction proceeds in the inner channels. TG measurements verify that HY is deactivated very quickly because the strong acidity induces serious coke formation, but this phenomenon is much less over beta zeolites. Evaluation on H beta with different SiO2/Al2O3 ratios indicates that both the weak Lewis acid concentration and isomerization activity of zeolites monotonically decrease with the SiO2/Al2O3 ratio. Thus a weak acid, especially a weak Lewis acid, of H beta is responsible for the isomerization reaction. Calcination at 500 degrees C provides the highest activity due to complete removal of template residues, generation of large amounts of weak Lewis acid, and good crystal structure. The H beta concentration was also studied: the optimal value is 15 wt%. Zeolites deactivated due to coke deposition can be regenerated by calcination in air flow at 500 degrees C, and there was no obvious activity loss after four times' regeneration. (C) 2009 Elsevier B.V. All rights reserved.