Silica-encapsulated Fe2O3 oxygen carriers for selective chemical looping combustion of hydrogen

[Display omitted] •Dehydroaromatization with chemical looping overcome the thermodynamic barriers.•Silica-encapsulated iron oxides selectively oxidize hydrogen.•A high iron–silica interaction provides facile looping reaction by iron silicate.•Methane conversion of 49% and aromatics yield of 36% is achieved in 4 h. Methane dehydroaromatization (MDA) combined with chemical looping (CL) combustion of hydrogen can overcome the MDA thermodynamic constraints conventionally limiting conversion. Development of selective hydrogen-oxidation oxygen carriers in the presence of aromatics in the CL is key to improve MDA performance in the coupled reaction system. Here we show that a novel oxygen carrier (silica-encapsulated Fe2O3 with Fe/Si mole ratio of 1.2) yields high overall methane conversion (49%) and aromatics yield (up to 36%) during 4 h of recirculating a stream in the developed system. A silica layer encapsulating Fe2O3 favors hydrogen transport and oxidation, preventing aromatics diffusing to the Fe2O3 surface. A close physical contact between iron oxide particles and silica, and near complete encapsulation of the particles by the silica layer can facilitate hydrogen conversion without full depletion of iron oxides by forming iron silicates. The silica-encapsulated iron oxide particles can be reoxidized in air after depletion of its oxidative capacity.