Significant interests have been laid on non-oxidative methane aromatization reaction by various famous research groups in the world in recent years, because this reaction is of scientific importance towards the understanding the nature of scission of C-H bond of CH4 , which is a most stable molecular in alkane family. In the present work, we focus on some interesting aspects of this topic, leading to fruitful results. A novel catalyst, by which the product distribution is regulated, i.e. Mo/HMCM-22, is prepared.

Compared with Mo/HZSM-5 catalyst and other current catalysts system, it gives much higher benzene yield (973 K, 1 atm,Yben >7.5%), lower heavy aromatics yields and a longer lifetime for methane aromatization reaction. These characteristics are attributed to the shape-selectivity of the special channel systems of MCM-22 zeolite (12-ring supercages connected by 10-ring windows). On the base of ESR experiments under working condition, ¹H MAS NMR, 2D ²⁷Al Multiple-quantum MAS NMR technique, Monte Carlo simulation method and ab initio DFT method, it is concluded that the migrated Mo will anchor on the framework aluminum of the zeolite through oxygen bridges, forming a Mo species with C2v symmetry. This species is just the precursor of the active center, which is responsible for the initial rupture of C-H bond of methane aromatization reaction. During the induction period of the reaction, this species will be transformed to lattice molybdenum carbide, being in charge of further activation of methane. If this transformation process is done before the reaction, the temperature needed for methane activation and benzene formation will be greatly lowered (760 and 847 K, respectively).
    By different temperature programming methods, it is verified that there are different carbonaceous depositions on the catalyst surface: carbidic carbon, carbonaceous deposition associated with molybdenum carbide, and two aromatic-type cokes. The latter two coke depositions are believed to be the reason for the deactivation of the catalysts. With the removal of

part of framework aluminum of HZSM-5 by steaming-treatment, the yield of benzene increased while the formation of aromatic-type coke was suppressed, which enables the improvement of the durability of this reaction.     An apparatus, enabling the investigation of high-temperature catalytic reaction by in-situ NMR technique, is developed in present work, which is highly acclaimed by our peers (C&EN, Vol. 78, No. 34, page 39).