Methane dehydro-aromatization on Mo/ZSM-5: About the hidden role of Brønsted acid sites

Whereas the hegemony of the Fischer–Tropsch synthesis is well established for the valorization of methane in the case of important gas fields, the methane dehydro-aromatization reaction remains an interesting solution to convert methane obtained as by-product of oil extraction and thus fight against flaring and global warming. Until now, it was generally accepted that the molybdenum is anchored on the Brønsted acid sites of the zeolite as (Mo2O5)2+ species. The molybdenum performs the dehydrogenation and coupling of CH4 to ethylene which is consecutively oligomerized to benzene over the Brønsted acid sites. In the present work, we bring evidence that this picture is actually more complicated than it seems. The Si/Al ratio of the zeolite, and consequently the density of available Brønsted acid sites, plays a dramatic role on the anchoring mode of the molybdenum and on its catalytic activity.

Methane dehydro-aromatization reaction remains an interesting solution to convert methane obtained as by-product of oil extraction and thus fight against flaring and global warming. Until now, it was generally accepted that the molybdenum is anchored on the Brønsted acid sites of the zeolite as (Mo2O5)2+ species. The molybdenum performs the dehydrogenation and coupling of CH4 to ethylene which is consecutively oligomerized to benzene over the Brønsted acid sites. We bring evidence that this picture is actually more complicated than it seems. The Si/Al ratio of the zeolite, and consequently the density of available Brønsted acid sites, plays a dramatic role on the anchoring mode of the molybdenum and on its catalytic activity. Figure optionsDownload as PowerPoint slide