Carbonaceous Deposition on Mo/HMCM-22 Catalysts for Methane Aromatization: A TP Technique Investigation

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

“…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]. In our continuing studies on the carbonaceous deposits from the TPO profiles of the 6Mo/TiO 2 and the 6Mo/MCM-22 after MDA reaction at 973 K for 3 h [61,62], we found that the 6Mo/MCM-22 gave a doubled peak located at 742 and 830 K, respectively. Meanwhile, only one peak corresponding to the carbonaceous deposits The calculation is based on the assumption that the activation and dehydrogenation of methane on Mo carbide species is the rate-determining step in the MDA reaction.…”

Direct conversion of methane under nonoxidative conditions

“…The chemical nature of the carbonaceous deposits was characterized on Mo/HZSM-5 and Mo/MCM-22 catalysts by temperature-programmed surface reaction (TPSR) of CH 4 , temperature-programmed hydrogenation (TPH), temperature-programmed reaction of CO 2 (TPCO 2 ), temperature-programmed oxidation (TPO), and thermal-gravimetric analysis (TGA) [51][52][53]. There are at least three different kinds of cokes: carbidic carbon in molybdenum carbide, molybdenum-associated coke, and aromatic-type coke on acid sites.…”

On the Reactivity of Mo Species for Methane Partial Oxidation on Mo/HMCM-22 Catalysts

“…However, it is easy to see that with these methods not only the polymolybdate species but also the isolated tetrahedral Mo species would be lowered, so that the intention in clarifying the specificity of isolated Mo species for HCHO forming would be difficult to achieve. In this study, by employing Mo/HMCM-22 as the catalyst samples, which have been extensively and systematically studied in our lab [18][19][20], we tried to study the reactivity of Mo species for methane partial oxidation into formaldehyde from a new point of view. Instead of changing the amount of polymolybdate species in the catalyst preparation step, we characterized the Mo species in the fresh and used catalysts.…”