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

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.…”

“…The results suggest that H 2 might only react with the coke, which is burned off at high temperatures in the TPO experiment, while CO 2 can eliminate the carbonaceous deposits, which are burned off at both low and high temperatures. Either the procedure of TPH followed by TPCO 2 or the procedure of TPCO 2 followed by TPH, could only partially reduce the amount of coke on a coked 6% Mo/HZSM-5 catalyst [51].…”

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.…”

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

“…Studies on the carbonaceous deposits have been undertaken on Mo/ HZSM-5 catalysts by several researchers [10,[28][29][30][31][32][33][34]. Lunsford and co-workers [10] investigated the nature of surface carbon species by XPS.…”