A single-stage partial oxidation of methane to methanol: a step forward in the synthesis of oxygenates†
An NTP hybrid system was designed in combination with metal oxide (MOX)-coated glass beads (GB) to synthesize value-added fuels and chemicals directly from methane. The combined plasma-packed mode was found to be a promising alternative to thermal catalysis, as it successfully enabled the single-step partial oxidation of methane to produce liquid oxygenates at atmospheric pressure and room temperature. When comparing plasma without packing (58%) and MOX/GB coupled plasma mode, the later method enhances the liquid selectivity to 74% with the introduction of C2 oxygenates in addition to C1 chemicals. Among the coated materials applied, NiO-coated GBs showed the highest liquid yield of ∼10%, including the maximum methanol yield of ∼5%, while coupled with NTP-DBD mode. Gas discharge-promoted methane conversion was observed in the presence of GB and MOX/GB, which can be attributed to the enhanced electric field generated as a result of the improved plasma strength created by the beads. Also, the oxide layer of metal oxide nanoparticles provides a catalytic base for adsorption/desorption of methane and other gas phase active species, which can facilitate the partial oxidation process of methane either by the gas-phase active oxygen species or through the interaction of surface hydroxyl groups.