The increasing demands on high value-added chemicals such as olefins and aromatics and the recently discovered large reserves and resources of methane, such as shale gas, coal bed methane and methane hydrate have prompted worldwide research interest on methane conversion.
However, the methane molecule is the most stable organic molecule and its selective activation and direct conversion is long considered as the "Holy Grail" in the field of chemistry. The challenge of methane conversion lies in controlled activation of the highly stable C-H bond and selective C-C coupling to form value-added chemicals while avoiding complete dehydrogenation and overoxidation.
The team led by Prof. BAO Xinhe from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences developed a promising new technology that offers an efficient methane transformation process to ethylene, aromatics (benzene and naphthalene), and hydrogen. It is enabled by a new nano-confined catalyst, i.e., the iron single sites embedded within the lattice of silica.
CH4 is activated over these sites in the absence of oxidants, generating methyl radicals. The methyl radicals then desorb from the surface and undergo a series of gas-phase reactions to form products. With this catalyst, single-pass conversion of methane reached 48%, and the total hydrocarbon selectivity exceeds 99%. This provides a potential new technology for efficient natural gas utilization by avoiding the energy-intensive syngas generation and little-to-no emission of CO2 and coke.
This work was published in Science on May 9, 2014.