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Datye, graduate students search for ways to make catalytic converters more efficient

April 15, 2011 - By Karen Wentworth

UNM Distinguished Professor of Chemical and Nuclear Engineering Abhaya Datye, and his graduate students Eric Peterson and Andrew De La Riva, are focused on finding a way to make catalytic converters on diesel engines as efficient as possible by engineering them to work at lower temperatures. Catalytic converters in vehicles convert harmful pollutants into less harmful emissions.

Catalytic converters can be more efficient if they work at lower temperatures, so they quickly begin converting toxic air pollution to harmless compounds soon after the vehicle is started. When a diesel engine is started on a cold morning, the catalytic converter is cold and does not work efficiently. Until the engine warms sufficiently, the catalytic converter is unable to remove the clouds of partially burned fuel billowing into the air.

See Datye explain the process.

Both the U.S. Department of Energy (DOE) and General Motors are funding research at UNM to find a way to improve the catalytic converters that filter the pollutants. The DOE is interested in one thing - finding a way to make catalytic converters work well at cooler temperatures, specifically 150 degrees Celsius.

For General Motors, the research problem is a little different. Catalytic converters use platinum as a catalyst because it is more efficient than other metals in helping the engine completely burn its fuel. But the metal is only mined in South Africa and it’s extremely expensive, so Datye and his graduate students are looking at how palladium, another metal which is less expensive, can work with platinum to achieve efficient combustion. In a recent paper, they published their results on nanoparticles of palladium and platinum.

They went to use equipment at Argonne National Lab because they needed to “see” what was occurring with the catalysts on a molecular level. The results of that experiment can be found here

Now Datye and his students are pushing to determine precisely what happens on the atomic level as the fuel interacts with the catalysts as it combusts.

De la Riva is the experimentalist. “I work with all the parts and try to get the data right," he said. "This is a different support you are seeing here, but we’re trying to do the same thing. Is it stable? Is it not stable? See these rod shapes? If we go to 150 they may change to an amorphous lump of nothing,." Because they are working on such a small scale, it is very difficult just to correctly measure their work.

Peterson analyzes the x-ray diffraction of the particles. He is able to infer the size of the particles by the width of the peaks. “The catalyst nanoparticle size is actually really a key metric because the larger the particles the less efficient the catalyst is because catalysis happens on the surface and as particles grow they lose surface area," Peterson said. "The precious metal atoms don’t function when they are on the inside of a catalyst. So ideally what you would like to do is have single atoms or clusters of several atoms that all have their surfaces exposed to the gasses that are coming in and reacting."

They expect their manipulation of the platinum and palladium atoms to make the catalytic converters more efficient, but they don’t know yet how much the efficiency can be increased.
The Union of Concerned Scientists says diesel engines, which power most trucks, buses and trains, are responsible for nearly half of all nitrogen oxides and more than two-thirds of all particulate matter emissions from transportation systems in the United States. If the efficiency of the catalytic converters can be increased, it will reduce the amount of toxic pollutants in the air. That’s something that will make the long days in the lab very worthwhile.