Ammonia-basified 10 wt% Mo/HZSM-5 material with enhanced dispersion of Mo and performance for catalytic aromatization of methane

Mo/HZSM-5 is an excellent catalyst for nonoxidative aromatization of methane, but it tends to deactivate rapidly due to severe coking. To date much effort has been devoted to enhancing activity and stability of Mo-impregnated HZSM-5 zeolite with Mo loading of 6 wt% or lower in methane aromatization. For this aromatization reaction, this work first reports a significant improvement in the catalytic performance of 10 wt% Mo/HZSM-5 material after preparation via impregnating HZSM-5 zeolite with ammonia-basified molybdate aqueous solution and pretreatment with a CH4/Ar/He (9:1:10, v/v) mixture. After 38 h of continuous reaction at 700 degrees C and 1500 mL g(-1) h(-1) (90 vol% CH4 /Ar), this 10 wt% Mo-impregnated catalyst is still able to give an aromatic yield of 7% and a CH4 conversion of 9.1%. This enhanced catalytic performance of this 10 wt% Mo sample is attributed to the ammonia basification of impregnating solution in catalyst preparation, which leads to a larger amount of highly dispersed Mo species in the zeolitic channels and a less amount of Bronsted acid sites remained on the Mo/HZSM-5 catalyst.