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Abstract
Oxygen-free methane conversion into benzene was carried out in a catalytic membrane reactor over 0.5%Ru-3%Mo/HZSM-5 in the temperature range 873-973 K following three reaction protocols: (i) straight-run catalytic reactor without hydrogen permeation (OFF), (ii) cycled OFF/ON hydrogen permeation sequences, and (iii) cycled OFF/ON hydrogen permeation sequences intertwined with CH4/H2 regenerative steps. X-ray photoelectron spectroscopy analysis of fresh and spent catalysts identified, in all cases, three types of carbon species that formed during aromatization, including carbide formation. The presence of a permeating membrane did not give rise to different chemical states of carbon and molybdenum on the catalyst from those known to form in straight runs under no hydrogen permeation. The ON mode, i.e., during permeation, led to the accumulation of graphite-like and aromatic-aliphatic (coke) species on the catalyst. However, both types of carbon were reduced during the OFF step either by autogenous hydrogen or via an external source of hydrogen under CH4/H2 regenerative steps.
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1 Department of Chemical Engineering, Laval University, Québec, Canada; Research Center for the Properties of Interfaces and Catalysis CERPIC, Laval University, Québec, Canada
2 Department of Chemistry, Laval University, Québec, Canada; Research Center for the Properties of Interfaces and Catalysis CERPIC, Laval University, Québec, Canada