A Remarkable Enhancement of the Catalytic Activity and Stability of Methane Dehydro-aromatization on Mo-based, Alkali-treated HZSM-5 Catalysts

摘要

During the past ten years, great progress has been made in the field of methane dehydro-aromatization (MDA) under non-oxidative conditions. Until recently, the best catalyst was Mo/HZSM-5. The significant problem of MDA under non-oxidative conditions involves facilitating the activation of methane molecules while increasing the reaction stability. These two points often directly conflict one another. The activation of methane molecules needs a high temperature, while this condition inevitably leads to coke formation on the catalyst contributing to the catalyst deactivation. In order to increase the catalyst stability the alkali pretreatment of NH_4ZSM-5 before Mo loading was carried out in this paper. The catalyst stability can be enhanced obviously on 6Mo/HZSM-5 catalyst pretreated by alkali before Mo loading. The alkali treatment conditions (content of the alkali solution/M, temperature/°C, time/h) were (0.05, 50, 1) and (0.2, 80, 5) and denoted as AT1 and AT2 respectively. After filtering and drying, the zeolite was ion-exchanged to obtain the NH_4~+ form zeolite. Mo-containing catalysts (Mo wt% = 6%) were prepared by impregnation method.