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

In the non-oxidative aromatization reaction (temperature = 770 C, 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 O2 (≤5.3 vol%) in the methane feed, the catalyst could last for more than 6 h with a ca. 4% yield of aromatics at 770 °C. Depending on the concentration of O2 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 H2 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 O2 (≥8.4 vol%) or NO (≥14.2 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.