The selective methane conversion is environmentally and economically important, because it is a cheap resource and its flaring comes with a multi-billion dollar loss of value, while producing carbon dioxide. The ability to perform direct methane to methanol conversion at small to medium scales valorises methane and would enable transport it as a liquid away from remote sites. A survey of catalytic conversion of methane to methanol illustrates the impossibility to achieve high yield, because already below ten percent methane conversion, it is the more reactive methanol that is further oxidized.[1] Methods that stabilize an oxidized intermediate show more potential. One of the more promising heterogeneous routes employs transition-metal exchanged zeolite, of which copper[2] and iron[3] receive the most attention. By chemical looping, the catalyst is first oxygen activated, then methane is reacted and subsequently methanol is desorbed by steam.[4] Avoiding the simultaneous presence of oxygen and methane prevents complete oxidation. Multiple structures are proposed as active site and there is a large impact of zeolite structure on copper-oxo species and thus on methanol production.[5] Besides identification of what is the structure of an active site, optimization of the conditions has shown that isothermal operation is possible, which is a significant simplification of the originally proposed conditions, which included a temperature swing of more than 200 degrees.[6]

The talk will review the progress in catalytic and non-catalytic direct methane to methanol conversion, identify what are the structural requirements to achieve high productivity, and how the treatment conditions influence yield.