The chemical nature of carbonaceous deposits and their role in methane dehydro-aromatization on Mo/MCM-22 catalysts

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.…”

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

“…During the temperature ramp, the evolved species were monitored at m/e = 28 (CO), 32 (O 2 ) and 44 (CO 2 ), respectively. The data from TGA and TPO were calculated and analyzed by the methods described in our previous paper [46,47]. Briefly, the data at m/e = 28 recorded originally was corrected by subtracting the contribution from the CO 2 signal to get the data of CO. Then, the data of CO was multiplied by its response parameter, and was added to the data of CO 2 to get the data of total carbon oxides.…”

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.…”