Tandem dual bed Mo/HZSM-5 and Mo/HMCM-22 catalysts with enhanced catalytic performance for natural gas conversion to aromatics

摘要

Natural gas / methane conversion to aromatics and hydrogen through non-oxidative dehydroaromatization reaction is an attractive way for C1 utilization. In this contribution, the thermal stability of high (12 wt%) and low (5 wt%) Mo loading catalysts on HZSM-5 and HMCM-22 zeolites was studied under different pretreatment conditions. It was found that using reductive pretreatment, especially pretreated with CH4 + H-2 mixtures, Mo catalysts exhibited high thermal stability with well-kept zeolite structure, resulting in enhanced catalytic performance for methane non-oxidative dehydroaromatization to aromatics. About 7% benzene yield obtained on 12 wt% Mo/HMCM-22 catalyst at 700 degrees C. On the contrary, the zeolite structure was collapsed as the catalysts pretreated with inert gas or air due to the formation of Al-2(MoO4)(3), as confirmed by XRD and Al-27 solid NMR. When the catalysts were applied to natural gas conversion, the tandem dual bed 12 wt% Mo/HMCM-22 and 12 wt% Mo/HZSM-5 catalysts exhibited excellent catalytic performance using CH4 + H-2 pretreatment. At 650 degrees C, 9% stable benzene yield was achieved over 120 h reaction time for a single run, taking advantages of high benzene yield from Mo/HMCM-22, and good stability from Mo/HZSM-5 catalysts, with great potential for commercial applications.