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Methane dehydroaromatization over Mo/HZSM-5 catalysts: The reactivity of MoCx species formed from MoOx associated and non-associated with Brönsted acid sites

“…80%. On the other hand, regardless of the loading of a 6 wt.% Mo species on the HZSM-5 zeolite, no peaks characteristic of the MoO 3 crystallites were observed in the XRD pattern of each 6Mo/ HZSM-5(t) catalyst, indicating that the crystallite size of the MoO 3 species on the zeolite surface was smaller than 5 nm, as reported previously [20,28].…”

“…Our early 13 C NMR experiments also showed that carbon species did form on Mo and Brönsted acid sites, respectively [28]. Ichikawa and coworkers attributed the low-temperature peak to a reactive coke associated with Mo 2 C and the high-temperature one to irreversible or inert coke [60].…”

“…Therefore, during the early research stage of this topic, the Mo species were physically divided into two types, i.e., Mo species located on the external surface and the ones residing in the zeolite channels. Some of the researchers believed that the Mo species located on the external surface were active species for the MDA reaction [20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Recent progress in methane dehydroaromatization: From laboratory curiosities to promising technology

“…Ethylene would then undergo subsequent oligomerization on the acidic sites of the zeolite to produce the final aromatic products. Jiang et al [100] investigated the induction period by combining a pulse reaction method with TPSR, UV laser Raman spectroscopy, and 13 C NMR techniques. They showed that Mo 6+ interacts with methane to produce H 2 O and CO 2 /CO, becoming partially reduced in the process.…”

Study of the carbonaceous deposits formed on a Mo/HZSM-5 catalyst in methane dehydro-aromatization by using TG and temperature-programmed techniques

“…Since the Mo/HZSM-5 is a bi-functional catalyst, having both the function of dehydrogenation and the function of acid catalysis, carbonaceous deposits can be formed on both Mo species and acid sites. Jiang et al characterized the coke by 13 C MAS NMR technique and reported that the carbonaceous deposits can be formed either on the acid sites of the zeolite or on the Mo species of the Mo/HZSM-5 catalyst [19]. Weckhuysen et al reported their characterization of the surface carbon formed during the conversion of methane to benzene over Mo/HZSM-5 catalyst [12].…”