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Platinum catalyst may be the key to reducing methane emissions

Orphan gas wells are one of the main sources of methane emissions. (Reference image by Hillebrand Steve, U.S. Fish and Wildlife Service, Wikimedia Commons).

Researchers at Iowa State University, Purdue University and Johns Hopkins University have found and tested a catalyst technology that appears to be safe and efficient to keep methane out of the atmosphere and make use of the greenhouse gas.

In a paper published in the journal Nature Catalysis, the group explains that methane produces more warming than other greenhouse gasses but most processes aimed at repurposing it are complicated because breaking its four carbon-hydrogen bonds involves high temperatures and mixing the flammable gas with oxygen to produce syngas to make methanol and hydrogen to make ammonia.

Other conversion reactions aren’t very efficient and also produce carbon dioxide.

Given this state of affairs, the US-based researchers developed a catalyst that consists of one or two layers of platinum, each layer just an atom thick, deposited on two-dimensional metal carbide structures called “MXenes.” In this case, the structures are made from carbon, molybdenum and titanium.

According to the team, the thin layers essentially allow every platinum atom to be used as a catalyst and prevent the formation of residues that cover and deactivate the platinum. That means less platinum is required to make the catalyst.

Although their initial goal was to identify the electrical and thermal properties of various carbides, they ended up making a better-than-expected discovery in the MXene surfaces.

“We had never seen carbide so active,” coauthor Yue Wu from Iowa State University said in a media statement. “It’s usually very inert. It’s used, for example, for high-speed drill bits—the surface is hard and inert.”

Seeing these properties, Wu and his colleagues started using the technology to remove hydrogen from shale gas, a work that evolved to study other reactions involving natural gas.

“Nobody tried to use these carbides for these high-volume reactions before,” the scientist said.

Keys to the methane-to-ethane/ethylene conversion are making the carbides pure enough and making the surfaces clean enough to support the reactions. Get it all right, and those reactions exhibit about 7% methane conversion with about 95% selectivity toward ethane/ethylene in a continuously operating fixed-bed reactor. The products can be turned into plastics and resins, such as the common and ubiquitous polyethylene plastic.

“Remarkably, these novel catalysts run for 72 hours of continuous operation without any signs of deactivation, indicating a promising start toward technologies suitable for exploitation on the industrial scale,” Wu said.

In his view, the new catalyst technology is revolutionary as it opens the door to reducing the emission of methane and its combustion product, CO2, in the future.