Efficient regeneration of Mo/HZSM-5 catalyst by using air with NO in methane dehydro-aromatization reaction

To regenerate the Mo/HZSM-5 catalyst used for methane aromatization at 1023 K, one can remove all the deposited hydrocarbon at 823 K by using pure air. With a small amount of NO addition to air (1/50 vol/vol), the coke removing ability was strongly promoted. The deposited hydrocarbon on the used catalyst started to be removed above 603 K, and the total coke removing temperature was 723 K. Much lower regeneration temperature suppressed the migration and sublimation of Mo species during the regeneration, preventing any structure change of the Mo active sites, which resulted in the very stable methane dehydro-aromatization performance on the regenerated Mo catalyst. As a result, the benzene formation rates of the catalyst started to decrease after the eighth regeneration cycle with NO addition to air, while the benzene formation rates of the catalyst regenerated with pure air started to decrease only after the fourth regeneration cycle. (C) 2004 Elsevier B.V. All rights reserved.