The Study Of Zn/HZSM-5 And Pt-Zn/HZSM-5 Catalysts For Non-oxidative Aromatization Of Methane With Propane

Conversion of methane to aromatics by low-temperature activation in the presence of higher hydrocarbon is 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 Zn/HZSM-5 and Pt-Zn/HZSM-5 were studied.The properties and behavious of the catalysts in the non-oxidative activation and aromatization of methane in the presence of propane were investigated by means of TPD,TPSR,TPO,TPH,UV-Raman,¹³CH₄ istope tracing etc.The main results are presented as follows.Methane non-oxidative aromatization using propane as co-reactant was achieved over Zn/HZSM-5 and Pt-Zn/HZSM-5.The conversion of methane and propane were 18.1%and 92.37%,respectively,and the selectivity of aromatics was as high as 55.49%over Mo loaded HZSM-5 and the above values were 21.49%,92.91%and 79.44%over Pd-Ga/HZSM-5 at 823 K and GHSV(C₁+C₃+N₂)=750 cm³g^-1h^-1with C₁/C₃/N₂ molar ratio=10:2:1.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.And propane dehydroaromatization was also affected by the presence of methane.The non-oxidative activation and aromatization of methane and propane over Zn/HZSM-5 and Pt-Zn/HZSM-5 were studied by TPSR,TG,UV-Raman,TPO and TPH.It was found that the hydrogen-rich carbonaceous or active carbon deposits process over catalysts are required for methane aromatization.The activation of methane is promoted with the addition of propane for C₃H₈ was much easier than CH₄ to form active carbon deposits needed for aromatization. The Pt-Zn/HZSM-5 catalyst exhibits better catalytic performance compared to Zn/HZSM-5 catalyst.It is found that the proper addition of Pt to Zn/HZSM-5 markedly improve the conversion of methane and greatly enhances the yield of aromatics along with effective reduction of coke formation.This is probably because of the great increase in the amount of the weak acid sites after addition of Pt and high dehydrogenation ability of Pt.