The Study Of Catalyst For Non-oxidative Aromatization Of Methane With Propane

Conversion of Methane to aromatics by low-temperature activation in the presence of higher hydrocarbon is of great scientific and practical importance. This method also provides a new way of utilization of methane and natural gas. In this paper, the non-oxidative activation and aromatization of methane with propane as co-reactant over metal-loaded HZSM-5 catalysts were studied. The activity, surface acidity, CH₄ adsorption, reducibility, and carbon deposition of the catalysts were investigated by using micro-reaction, ¹³C isotope labeled pulse reaction, NH₃-TPD, CH₄-TPD-MS, H₂-TPR and TG. The results were as follows:Methane non-oxidative aromatization using propane as co-reactant was achieved over Zn/HZSM-5. The conversion of Methane and propane were 30.8% and 75.5%, respectively, and the selectivity of aromatics was as high as 86.4% at 600℃ and GHSV (C1+C3+N₂)=3000cm³g^-1h^-1 with C1/C3 molar ratio =1.0.The effects of time on stream, space velocity, reaction temperature, and feed gas composition (C1/C3) on activity over 6%Zn/HZSM-5 were investigated. It was found that the activation of methane was promoted efficiently by co-added propane. This method could provide a new process for methane activation at low temperature.The influence of preparation method was investigated over Zn-Cu/HZSM-5 and Zn-Mo/HZSM-5. It was found that the activity and stability of step-impregnated catalyst were higher than that of co-impregnated catalyst.CH₄ incorporation has been conclusively conformed by mass spectral analysis of aromatics produced in a broadened pulse of ¹³CH₄ and C₃H₈ under identical condition, which show significant ¹³C enrichment in the aromatics fragments.The CH₄-TPD-MS experiments gave rich information about adsorption, desorption, and decompose of CH₄. We hope that the method can provide a new way for the study of the activation and reaction mechanisms of methane.NH₃-TPD results indicated that the intensity and amount of strong acid site decreased, and the amount of weak acid site increased after the addition of Mo, Cr, Cu and Fe to Zn/HZSM-5. These changes of acidic sites might be the reason of...