An evaluation of direct methane conversion processes

Methane is the primary constituent of both natural gas and the associated gas resulting from crude oil production. These gases have little value unless they can be moved to large-scale consumers through a pipeline or transported as liquefied gases. Because conversion of methane to a transportable liquid hydrocarbon fuel would open new markets, it is a goal being actively pursued by many groups around the world. Currently, two large-scale, viable approaches for converting methane to liquid hydrocarbons are being used: the methanol-to-gasoline (MTG) route, and the Fischer--Tropsch (FT) route. Both of these processes begin with the production of synthesis gas from methane,which is a high-temperature, endothermic, costly operation. Concepts for directly converting methane to a liquid hydrocarbon fuel without reforming methane to synthesis gas conceptually appear attractive. A few have reached the stage where a preliminary evaluation directed at understanding the critical process factor is possible. The authors report on their studies involving the following process schemes: oxidative coupling, partial oxidation, and oxyhydrochlorination.