A novel reactivation technique using non-oxygen gas was developed to regenerate the acid sites on the coked mordenite in the disproportionation of toluene (TDP). Hydrogen reactivation procedure is particularly effective. It was found that the novel technique is applicable as long as the H/C atomic ratio of the coke on mordenite is greater than around 1.0. The H/C ratio of deposited coke was correlated with the structures of polyaromatics. These results indicate that application of the reactivation technique is limited to those coke precursors lighter than alkyl-pyrene structure. (c) 2006 Elsevier B.V. All rights reserved.