New Nanoparticle Converts CO2 Emissions Into Fuel

By Sunny Lewis for Maximpact

LOS ANGELES, California, February 25, 2020 (Maximpact.com News) – Futuristic power plants could function not as destructive sources of planet-warming carbon dioxide, but as a carbon-neutral closed loops. Instead of smokestacks that pump carbon emissions into the atmosphere, power plants of the future could capture all their waste carbon dioxide (CO2), converting it into fuel to power each plant.

Scientists at the University of Southern California’s Viterbi School of Engineering, collaborating with researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), are working to bring this vision closer to reality.

The team has just announced its discovery of a metal carbide nanoparticle, a compound of carbon and metal that can convert CO2 into fuel. These particles can for the first time be produced sustainably at low temperature.

The research team says this means the particles can be produced at an industrial scale at a low cost, and with minimal environmental impact, providing a vital pathway toward reducing the world’s greenhouse emissions.

Burning fossil fuels, such as coal, oil and natural gas, spews almost seven billion metric tonnes of CO2 into the atmosphere every year, the Smithsonian Institution reported in 2018.

Noah Malmstadt, professor in USC Viterbi’s Mork Family Department of Chemical Engineering and Materials Science, is one of the authors of the new research, in collaboration with Frederick Baddour from NREL and Richard Brutchey, professor of chemistry at the University of Southern California. Their work was published in the “Journal of the American Chemical Society” under the title, “An Exceptionally Mild and Scalable Solution-Phase Synthesis of Molybdenum Carbide Nanoparticles for Thermocatalytic CO2 Hydrogenation.”

Malmstadt said that the aim of the project was to capture carbon emissions from an emission source, such as a flue, and then to convert it into usable fuels, with the nanoparticles functioning as a catalyst to enable the reaction.

“Basically what we’re doing is we’re turning the carbon dioxide from carbon oxygen bonds to carbon hydrogen bonds. So, we’re turning carbon dioxide back into hydrocarbons,” Malmstadt said.

“Hydrocarbons are basic fuel stock. You can either turn them into fuel stock chemicals such as methane or propane. Or you can use them as the basis for chemical synthesis so they can be building blocks for making more complex chemicals,” Malmstadt said.

He said that hydrocarbons were also “feedstock” chemicals that could potentially be used to create other carbon-based material, so carbon emissions could be converted into material to make consumer products as well as hydrocarbon fuel.

Applications include converting waste carbon dioxide into carbon monoxide or hydrocarbons for use as fuels or solvents or as raw materials to create plastics, rubber, and pesticides.

“We hope that by continuing to develop more mild and controlled methods of preparing nanostructured carbide catalysts we can help to facilitate the commercialization and deployment of these exciting materials,” says lead author of the study and NREL scientist Frederick Baddour.

Until now, the process for creating the catalyst particles has been very energy intensive, explained Malmstadt, making it an impractical solution for converting carbon emissions.

The carbides have been created using a process where they are heated to temperatures higher than 600 degrees centigrade, a process that makes it difficult to control the size of the particles, which impacts on their effectiveness as catalysts.

Preparing metal carbides for catalysis has typically involved extreme environments, with high concentrations of flammable gases and high temperatures (1,100°F). In search of a milder, more scalable process, the research team developed a solution-phase route to prepare metal carbide nanoparticles using a continuous flow millifluidic reactor at temperatures nearly half of what was typically required.

Malmstadt said the millifluidic reactor process is a very small scale chemical reactor system, which has a minimal environmental footprint. This means the particles can be produced at temperatures as low as 300 degrees centigrade, resulting in smaller, more uniform particles, which make them ideal for converting CO2 to hydrocarbons.

“We are producing the particles sustainably, using green chemistry methods,” Malmstadt said.

“The chemical reactor system operates in channels that are less than a millimeter across, which offers a ton of advantages over traditional reactors, particularly in terms of making materials that are very uniform and very high quality,” he said.

The resulting nanoparticles have a very high surface area to mass ratio. “So for each amount of metal that you have in the catalyst, you get more active surface area that can do chemistry,” said Malmstadt.

He compared the team’s new reaction process to the way that supercomputers have evolved over time. Early supercomputers were housed in large laboratories and required giant memory banks and energy-intensive cooling systems. By contrast, present day distributed or cloud-based supercomputer systems are simply a grid of standard computers that run in parallel and share resources.

“So it would be the same way of thinking for this approach to scaling chemical production,” Malmstadt said. “Instead of using a large chemical reactor, instead you use a bunch of these millifluidic reactors, and you just operate them all in parallel.”

Malmstadt said that this process also offers a significant cost savings over larger scale chemical reactor production of carbide nanoparticles.

“This offers an easy route to scale the chemistry,” he said, “and from the point of view of sustainability in terms of energy use, and the amount of personnel hours that go into producing the materials, it’s much lower for these millifluidic routes than it is for traditional approaches to manufacturing the chemicals.”

Other scientists who contributed to this research were Nicholas Bedford with the School of Chemical Engineering, University of New South Wales, Australia, and Joshua Wright at the Department of Physics, Illinois Institute of Technology.

The new methods developed by the team to prepare these nanoparticles have the potential to enhance our understanding of metal carbides while paving the way toward their cost-effective and efficient production at industrial scales.