Effect of Bed Height on the Performance of a Fixed Mo/HZSM-5 Bed in Direct Aromatization of Methane

The catalyst-overloading strategy is often employed to extend the catalytic lifetime of fixed catalyst bed reactors in chemical processes. The applicability of this strategy to the Mo/HZSM-5 catalyst for non-oxidative methane dehydroaromatization was confirmed for the first time by examining the influence of bed height on the catalytic stability and lifetime aromatic productivity of an integral fixed Mo/HZSM-5 bed at a defined temperature and different CH₄ superficial velocities. Increasing the bed height proved to have a very limited effect on extending either the stable period of aromatics production of the bed or its lifetime aromatics productivity. Simultaneous coke formation over all layers of the bed was also confirmed to be responsible for rapid deactivation of the whole bed, and pyrolysis of the intermediate C₂H₄ was found to be the dominant route to coke formation.