A new catalyst can turn methane into something useful | MIT News

Although it is less abundant than carbon dioxide, methane gas contributes disproportionately to global warming because its molecular structure means it retains more heat in the atmosphere than carbon dioxide.

MIT chemical engineers have now developed a new catalyst that can convert methane into useful polymers, which could help reduce greenhouse gas emissions.

“What to do with methane has been a long-standing problem,” says Michael Strano, Carbon P. Dubbs Professor of Chemical Engineering at MIT and senior author of the study. “It’s a source of carbon and we want to keep it out of the atmosphere but also convert it into something useful.”

The new catalyst operates at room temperature and atmospheric pressure, which could make it easier and more economical to use at methane production sites such as power plants and livestock farms.

Daniel Lundberg PhD ’24 and MIT postdoc Jimin Kim are the lead authors of the study, which appears today in Natural catalysis. Former postdoc Yu-Ming Tu and postdoc Cody Ritt are also authors of the article.

Capture methane

Methane is produced by bacteria known as methanogens, which are often found in high concentrations in landfills, swamps and other sites of decaying biomass. Agriculture is a major source of methane, and methane gas is also produced as a byproduct of the transportation, storage, and combustion of natural gas. Overall, it is assumed that it is responsible for around 15 percent of the global temperature increase.

At the molecular level, methane is made up of a single carbon atom bonded to four hydrogen atoms. In theory, this molecule should be a good building block for making useful products such as polymers. However, converting methane into other compounds has proven difficult because high temperatures and high pressures are typically required to react with other molecules.

To achieve methane conversion without this energy expenditure, the MIT team developed a hybrid catalyst with two components: a zeolite and a naturally occurring enzyme. Zeolites are abundant, inexpensive clay-like minerals, and previous work has shown that they can be used to catalyze the conversion of methane to carbon dioxide.

In this study, researchers used a zeolite called iron-modified aluminum silicate paired with an enzyme called alcohol oxidase. Bacteria, fungi and plants use this enzyme to oxidize alcohols.

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

This series of reactions can occur at room temperature and does not require high pressure. The catalyst particles are suspended in water, which can absorb methane from the surrounding air. For future applications, the researchers imagine that it could be painted onto surfaces.

“Other systems operate at high temperature and pressure and use hydrogen peroxide, an expensive chemical, to drive methane oxidation. But our enzyme produces hydrogen peroxide from oxygen, so I think our system could be very cost-effective and scalable,” says Kim.

Creating a system that includes both enzymes and artificial catalysts is a “smart strategy,” says Damien Debecker, a professor at the Institute of Condensed Matter and Nanoscience at the University of Leuven, Belgium.

“Combining these two families of catalysts is challenging because they typically operate under quite different operating conditions. By removing this limitation and mastering the art of chemo-enzymatic collaboration, hybrid catalysis becomes key: it opens up new perspectives to allow complex reaction systems to occur in a more intensive way,” says Debecker, who was not involved in the research .

Construction polymers

Once formaldehyde is created, the researchers showed that they could use this molecule to create polymers by adding urea, a nitrogen-containing molecule found in urine. This resinous polymer, known as urea formaldehyde, is now used in particle board, textiles and other products.

The researchers imagine that this catalyst could be installed in pipes used to transport natural gas. In these pipes, the catalyst could create a polymer that could act as a sealant to heal cracks in the pipes, which are a common cause of methane leaks. The catalyst could also be applied as a film to coat surfaces exposed to methane gas, creating polymers that could be collected for use in production, the researchers say.

Strano’s lab is currently working on catalysts that could remove carbon dioxide from the atmosphere and combine it with nitrate to make urea. This urea could then be mixed with the formaldehyde produced by the zeolite enzyme catalyst to produce urea-formaldehyde.

The research was funded by the US Department of Energy.