Methane dehydro-aromatization over Mo/MCM-22 catalysts: a highly selectivecatalyst for the formation of benzene

A molybdenum-modified MCM-22 catalyst has been used for methane dehydro-aro matization. The catalytic performance on this Mo/MCM-22 catalyst is feature d by a higher yield of benzene and a lesser yield of naphthalene in compari son with that on a Mo/HZSM-5 catalyst under the same experimental condition s. Methane conversion of 10.0% and benzene selectivity of 80% over a 6Mo/MC M-22 catalyst at 973 K was obtained. Based on the effect of contact time, i t is suggested that the reaction is severely inhibited by the products, pro bably due to their strong adsorption and slow desorption. The Mo/MCM-22 cat alysts were characterized by XRD, NH3-TPD and TPSR techniques. XRD patterns of the Mo/MCM-22 catalysts confirmed that Mo species are highly dispersed on/in the MCM-22 zeolite if the Mo loading is less than 10%. NH3-TPD experi ment shows that the MCM-22 zeolite contains strong and exchangeable Bronste d acid sites. TPSR of methane revealed that there is an induction period du ring which the Mo species are reduced by methane and transformed probably i nto Mo2C or Mo2OxCy. It is concluded that the nature of the methane dehydro -aromatization reaction over the Mo/MCM-22 catalysts is similar to that on the Mo/HZSM-5 catalysts. The unique pore systems, the proper acid strength of the MCM-22 zeolite and the Mo species are factors important for methane dehydro-aromatization over Mo/MCM-22 catalysts.