Self-structured monolithic TiO₂-Mn₂O₃-Na₂WO₄-foam catalyst towards efficient oxidative coupling of methane

A monolithic TiO₂-Mn₂O₃-Na₂WO₄-foam catalyst is developed via a self-structuring method for the oxidative coupling of methane reaction. The TiO₂-Mn₂O₃-Na₂WO₄ slurry is injected into a hard template of polyurethane activated carbon sponge (PACS); and polyvinyl alcohol (PVA) is introduced into the slurry to increase its macroscopic viscosity. The calcination at 800 °C in air removes PACS and PVA to form the foam structure, and simultaneously, the interpenetrating nanorods of TiO₂-Mn₂O₃-Na₂WO₄ are generated, which grants this foam monolith strong mechanical strength. Such catalyst effectively couples advanced catalysis of TiO₂-Mn₂O₃-Na₂WO₄ with enhanced heat/mass transfer stemmed from the foam structure. At 740 °C, CH₄/O₂ molar ratio of 5/1, 0.1 MPa, and gas hourly space velocity of 6000 h⁻¹, 25.3% CH₄ conversion and 71.6% C_2-3 selectivity can be achieved over the preferred catalyst. The self-structuring strategy is efficient to fabricate the more-advanced monolithic OCM catalyst.