Abstract: Over Mo/HZSM-5 catalysts, various carbonaceous depositions occurred during the course of methane dehydroaromatization(MDA). These species of surface carbon formed on HZSM-5 zeolite or Mo/HZSM-5 catalysts with different Mo loadings were investigated by means of TPH, TPCO₂ and TPOin combination with thermal gravimetric analysis(TG). The results of TGrevealed that, the total amount of coke formed on 6Mo/MCM 22 during TPSRis larger than those formed on HZSM-5 zeolite, 2Mo/HZSM-5 and 10Mo/HZSM-5 catalysts. The TPOprofiles recorded during the procedure of coke burning off show two different temperature peaks. The results of TPOand TGafter TPHsuggested that, the TPHexperiments only had an effect on the coke burnt off at a high temperature, but didn′t result in the diminishing of the coke burnt off at low temperature peak. On the other hand, the result of the coked catalyst after succeeding TPCO₂ experiments exhibited an obvious reduction in the areas of both the high and low temperature peaks, particularly in the area of the low temperature peak. The study on the catalysts with different Mo loadings suggested that, the percentage of the coke burnt off at a low temperature turned larger with the increase of Mo loading, respectively. And the change trend of the coke burnt off at a high temperature was opposite exactly. By using the experiments of TPSR, TPH, TPCO₂ and TG, quantitative analysis of the coke and the kinetics of its burning off process have been done. The results show that, either TPHor TPCO₂ can diminish the starting temperature and decrease the activation energy, and there are some differences among the catalysts with various Mo loadings.

Key words: Methane dehydro aromatization, HZSM₅ zeolite, TG, TPR, Coke