Binder-free dip-coating of Mn₂O₃-Na₂WO₄-TiO₂ catalyst onto monolithic SiC-foam towards efficient oxidative coupling of methane

Monolithic SiC-foam-structured Mn₂O₃-Na₂WO₄-TiO₂ catalysts are developed via a binder-free dip-coating method for the oxidative coupling of methane reaction. MnTiO₃-assisted growth of coating from nanoparticles to nanorods proceeds spontaneously to form interpenetrating nano-structure in the presence of alkali (such as Na₂WO₄) during the high-temperature calcination treatment, which grants the coating strong robustness. This catalyst involves the effective and efficient coupling of advanced catalysis of Mn₂O₃-Na₂WO₄-TiO₂ coating with enhanced heat/mass transfer stemmed from SiC-foam substrate. The preferred catalyst is the one with 40 wt% coating at Mn₂O₃/Na₂WO₄/TiO₂ weight ratio of 2.2%/5.1%/32.7%, giving 26% CH₄ conversion and 69% C_2-3 selectivity at 800 °C and 0.1 MPa for a feed gas of CH₄/O₂ of molar ratio of 5/1 at gas hourly space velocity of 4000 h⁻¹. The SiC-foam-structured Mn₂O₃-Na₂WO₄-TiO₂ catalyst can also be used for this reaction in the form of bead string reactor, and the highest C_2-3 yield of 13% is obtained with 18% CH₄ conversion and 72% C_2-3 selectivity at 0.35 MPa, 20,000 h⁻¹, CH₄/O₂ molar ratio of 6.5/1, and 800 °C.