Catalyst converts methane into polymers at room temperature

This is the claim of chemical engineers, who believe the new catalyst could be deployed at sites of methane production, including power plants and cattle sheds.

“What to do with methane has been a longstanding problem,” said Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and senior author of the study published in Nature Catalysis. “It’s a source of carbon, and we want to keep it out of the atmosphere but also turn it into something useful.”

Methane is produced by methanogens, a form of bacteria found highly concentrated in landfills, swamps, and other sites of decaying biomass. Agriculture is a major source of methane, and methane gas is also generated as a by-product of transporting, storing, and burning natural gas. Overall, it is estimated to account for about 15 per cent of global temperature increases.

At the molecular level, methane is made of a single carbon atom bound to four hydrogen atoms. In theory, this molecule should be a good building block for making useful products such as polymers. So far, converting methane to other compounds has proven difficult because getting it to react with other molecules requires high temperature and high pressures.

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To achieve methane conversion without that input of energy, the MIT team designed a hybrid catalyst with a zeolite and a naturally occurring enzyme. Zeolites are abundant, inexpensive clay-like minerals, and previous work has found that they can be used to catalyse the conversion of methane to carbon dioxide.

For this study, the researchers iron-modified aluminium silicate paired with an enzyme called alcohol oxidase. Bacteria, fungi, and plants use this enzyme to oxidise alcohols.

This hybrid catalyst performs a two-step reaction in which zeolite converts methane to methanol, and then the enzyme converts methanol to formaldehyde. That reaction also generates hydrogen peroxide, which is fed back into the zeolite to provide a source of oxygen for the conversion of methane to methanol.

The catalyst particles are suspended in water, which can absorb methane from the surrounding air. For future applications, the researchers envision that it could be painted onto surfaces.

“Other systems operate at high temperature and high pressure, and they use hydrogen peroxide, which is an expensive chemical, to drive the methane oxidation. But our enzyme produces hydrogen peroxide from oxygen, so I think our system could be very cost-effective and scalable,” MIT postdoc Jimin Kim, a lead author of the paper, said in a statement.

Once formaldehyde is produced, the researchers showed they could use that molecule to generate polymers by adding urea. This resin-like polymer, urea-formaldehyde, is currently used in chip board, textiles and other products.

The researchers envision that this catalyst could be incorporated into pipes used to transport natural gas. Within those pipes, the catalyst could generate a polymer that could act as a sealant to heal cracks in the pipes, which are a common source of methane leakage. The catalyst could also be applied as a film to coat surfaces that are exposed to methane gas, producing polymers that could be collected for use in manufacturing, according to the researchers.