A research team has discovered that gamma radiation can transform methane into a diverse array of products at room temperature. These products include hydrocarbons, oxygen-rich molecules, and amino acids, as discussed in the journal Angewandte Chemie. Such reactions are likely significant for the creation of complex organic compounds in the universe and may even play a role in the emergence of life. Additionally, these findings provide new methods for the industrial transformation of methane into valuable products under mild conditions.
Leading this research effort at the University of Science and Technology of China (Hefei) is Weixin Huang, who notes that these findings deepen our fundamental understanding of how molecules develop in the universe. “Gamma rays, which are high-energy photons found in cosmic rays and the decay of unstable isotopes, supply the necessary energy to initiate chemical reactions involving simple molecules within the icy mantles of interstellar dust and ice grains,” explains Huang. “This process can generate more complex organic molecules, likely starting from methane (CH4), which is prevalent across the interstellar medium.”
While Earth and other planets in the so-called habitable zone experience higher pressures and temperatures, most research into cosmic processes is conducted under vacuum and at very low temperatures. In contrast, the Chinese team explored methane reactions at room temperature in both gas and aqueous phases using a cobalt-60 radiation source.
The resulting products vary based on the initial materials used. Pure methane has a very low yield, producing mainly ethane, propane, and hydrogen. However, adding oxygen significantly enhances conversion rates, leading primarily to the production of CO2, CO, ethylene, and water. When water is involved, the reaction produces acetone and tertiary butyl alcohol, while in the gas phase, ethane and propane are formed. The introduction of both water and oxygen greatly speeds up the reactions, resulting in the creation of formaldehyde, acetic acid, and acetone in the aqueous environment. If ammonia is also included, acetic acid can convert to glycine, an amino acid that has been identified in space. “Under gamma radiation, glycine can be synthesized from methane, oxygen, water, and ammonia, all of which are abundantly found in space,” states Huang. The research team developed a reaction pathway that outlines how these individual products are produced, with radicals like oxygen (∙O2−) and ∙OH playing a critical role. The rates of these radical reactions do not depend on temperature, implying that these processes could also occur in space.
Moreover, the research team found that different solid particles making up interstellar dust—such as silicon dioxide, iron oxide, magnesium silicate, and graphene oxide—affect product selection in various ways. This variation in interstellar dust composition may explain the observed differences in molecular distributions throughout space.
Specifically, silicon dioxide facilitates a more selective transformation of methane into acetic acid. Huang expresses, “With gamma radiation being an accessible, safe, and sustainable energy source, this represents a potentially new strategy for utilizing methane as a carbon feedstock, which can be effectively converted into high-value products under mild conditions—a longstanding challenge in industrial synthetic chemistry.”
