Progress in the direct catalytic conversion of methane to fuels and chemicals

This paper reviews the state-of-the-art in catalytic processes to convert methane (a major component of natural gas) to more valuable hydrocarbons as fuels or chemicals. The scope is restricted to "direct" conversion, meaning that processes involving synthesis gas as an intermediate are not considered. Oxygenated products (e.g., alcohols) are also not considered. In all cases, the processes are concerned with catalytic dehydrogenation. The two most widely studied processes are oxidative coupling of methane (OCM) and methane dehydroaromatization (MDA). After reviewing the relevant catalysis literature, the paper goes on to review reactor implementations. Hydrogen- and/or oxygen-permeable membranes can potentially play valuable roles in improving methane conversion and product yields. Despite over 30 years of research, there are still no direct-conversion processes that can compete commercially with methane reforming followed by processes such as Fischer-Tropsch synthesis. Thus, the future practical development and deployment of OCM and MDA will rely on the research and development of advanced catalysts and innovative processes. The present review helps to document the foundation on which the needed development can build.