Synthesis of Na2WO4-MnxOy supported on SiO2 or La2O3 as fiber catalysts by electrospinning for oxidative coupling of methane

Abstract

The oxidative coupling of methane (OCM) is an attractive route to convert natural gas directly into value-added chemical products (C2+). This work comparatively investigated SiO2- or La2O3-supported Na2WO4-MnxOy (denoted as NWM) catalysts in powder and fiber forms. The powder catalysts were prepared using a co-impregnation method and the fiber catalysts were prepared successfully using an electrospinning technique. The NWM/La2O3 fiber catalysts were activated at low temperature (500 °C) and had a 4.7% C2+ yield, with the maximum C2+ yield of 9.6% at 650 °C, while the NWM/SiO2 fiber catalyst was activated at 650 °C and had a maximum C2+ yield of 20.4% at 700 °C. The XPS results in the O 1s region indicated that NWM/La2O3 had a lower binding energy than NWM/SiO2, suggesting that the lattice oxygen species is easily released from the catalyst surface and creates vacancy sites that enhance performance. The stability test of the catalysts indicated that the La2O3-containing catalysts had excellent activity and high thermal stability, while the SiO2-containing catalysts had a higher C2+ yield when the prepared catalysts were compared at 700 °C. Considering the same component catalysts, the fiber catalysts achieved higher performance because their heat and mass transfer properties were enhanced.