Methane aromatization over 2 wt% Mo/HZSM-5 in the presence of O2 and NO

In the non-oxidative aromatization reaction (temperature = 770degreesC, flow rate = 34 ml min(-1)), 2 wt% Mo/HZSM-5 deactivated after 4 h due to severe coking. We observed that with a suitable amount of O-2 (less than or equal to5.3 vol%) in the methane feed, the catalyst could last for more than 6 h with a ca. 4% yield of aromatics at 770degreesC. Depending on the concentration of O-2 or the reaction temperature, there are three reaction zones in the catalyst bed: (i) methane oxidation; (ii) methane reforming; and (iii) methane aromatization. CO and H-2 produced in the first two zones are accountable for stability amelioration of the catalyst. The addition of NO exhibited similar effects on the reaction. Further increase in O-2 (greater than or equal to8.4 vol%) or NO (greater than or equal to14.2 vol%) concentration would result in CO and CO2 being the predominant carbon-containing products; C2H4 and C2H6 were generated in small amounts and no aromatics were detected.