Methane Bubbled Through Seawater Can be Converted to Methanol With High Efficiency

Abstract Partial oxidation of methane (POM) is achieved by forming air‐methane microbubbles in saltwater to which an alternating electric field is applied using a copper oxide foam electrode. The solubility of methane is increased by putting it in contact with water containing dissolved KCl or NaCl (3%). Being fully dispersed as microbubbles (20–40 µm in diameter), methane reacts more fully with hydroxyl radicals (OH·) at the gas‐water interface. The alternating voltage (100 mV) generates two synergistic POM processes dominated by Cl − → Cl· + e − and O 2 + e − → O 2 −• under positive and negative potentials, respectively. By tuning the frequency and amplitude, the extent and path of the POM process can be precisely controlled so that more than 90% methanol is selectively formed compared to the two byproducts, dichloromethane, and acetic acid. The methane to methanol conversion yield is estimated to be 57% at a rate of approximately 887 µM h −1 . This method appears to have potential for removing methane from air using seawater or for converting higher‐concentration methane sources into value‐added methanol.