Methane dehydroaromatization with periodic CH4-H2 switch: A promising process for aromatics and hydrogen

Abstract

Long-term stability test of Mo/HZSM-5-N catalysts (HZSM-5-N stands for nano-sized HZSM-5) in methane dehydroaromatization (MDA) reaction has been performed with periodic CH4-H2 switch at 1033–1073 K for more than 1000 h. During this test, methane conversion ranges from 13% to 16%, and mean yield to aromatics (i.e. benzene and naphthalene) exceeds 10%. N2-physisorption, XRD, NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition, and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke, thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition. The effect of zeolite particle size on the catalytic activity was also explored, and the results showed that the nano-sized zeolite with low diffusion resistance performed better. It is recognized that the size effect was enhanced by reaction time, and it became more remarkable in a long-term MDA reaction even at a low space velocity.