Scientists have developed an efficient new way to convert methane into methanol at room temperature. The technique could help reduce greenhouse gas emissions and provide a cleaner way to make key products.
While carbon dioxide gets most of the attention, it’s not the only greenhouse gas changing the Earth’s climate. Methane is emitted in smaller amounts but is 34 times more potent, so reducing its levels remains a priority. Excess methane from industrial processes is often burned off, but that produces CO2.
A commonly sought alternative is to convert methane into methanol, which can be used to make a range of products like fuels, plastics and construction materials. The problem is, the conversion process usually requires high temperatures and pressures, which makes it energy-intensive.
In recent years, scientists have been experimenting with new catalysts that show promise in converting methane into methanol at room temperature and ambient pressure, including a titanium and copper catalyst and ways to improve iron zeolite crystals.
For the new study, researchers at the University of Manchester and Oak Ridge National Laboratory developed a new technique using a metal-organic framework (MOF) as a catalyst. These structures are extremely porous, and in this case those pores contain a variety of components that each play a role in the catalytic process.
First, methane and oxygen are mixed into water, which is then continuously flowed through the MOF granules. Exposing the MOF to sunlight triggers a chemical reaction that converts the gaseous methane into liquid methanol, which can then be easily extracted from the water.
The main thing that makes this particular conversion so tricky is breaking the carbon-hydrogen bond in methane in order to insert an oxygen atom to form a new bond and make methanol. In this case, the components held in the MOF absorb the light and generate electrons, which are then passed on to the oxygen and methane flowing through, causing them to combine to form methanol.
In tests, the solid catalyst was able to work efficiently, and could be washed and reused at least 10 times, for a minimum of 200 hours of reaction time. With further refinement, the technique could help reduce methane emissions, as well as the environmental footprint of methanol production.
"This process has been termed the 'holy grail of catalysis’,” said Martin Schröder, corresponding author of the study. “Instead of burning methane, it may now be possible to convert the gas directly to methanol, a high-value chemical that can be used to produce biofuels, solvents, pesticides and fuel additives for vehicles. This new MOF material may also be capable of facilitating other types of chemical reactions by serving as a sort of test tube in which we can combine different substances to see how they react."
The research was published in the journal Nature Materials.
Source: Oak Ridge National Lab via Phys.org
