Maybe too late for Volkswagen, but this is useful research as diesel will be around for a few decades yet.
Researchers have discovered a new reaction mechanism that could be used to improve catalyst designs for pollution control systems to further reduce emissions of smog-causing nitrogen oxides in diesel exhaust.
The research focuses on a type of catalyst called zeolites, workhorses in petroleum and chemical refineries and in emission-control systems for diesel engines.
New catalyst designs are needed to reduce the emission of nitrogen oxides, or NOx, because current technologies only work well at relatively high temperatures.
“The key challenge in reducing emissions is that they can occur over a very broad range of operating conditions, and especially exhaust temperatures,” said Rajamani Gounder, the Larry and Virginia Faith Assistant Professor of Chemical Engineering in Purdue University’s Davidson School of Chemical Engineering. “Perhaps the biggest challenge is related to reducing NOx at low exhaust temperatures, for example during cold start or in congested urban driving.”
However, in addition to these “transient” conditions, future vehicles will naturally operate at lower temperatures all the time because they will be more efficient.
“So we’re going to need catalysts that perform better not only during transient conditions, but also during sustained lower exhaust temperatures,” Gounder said.
He co-led a team of researchers who have uncovered an essential property of the catalyst for it to be able to convert nitrogen oxides. Findings will be published online in the journal Science on Thursday (Aug. 17) and will appear in a later print issue of the magazine.
“The results here point to a previously unrecognized catalytic mechanism and also point to new directions for discovering better catalysts,” said William Schneider, the H. Clifford and Evelyn A. Brosey Professor of Engineering at the University of Notre Dame. “This is a reaction of major environmental importance used to clean up exhaust.”
The work was performed by researchers at Purdue, Notre Dame and Cummins Inc., a manufacturer of diesel engines.
“Cummins has been supporting Purdue chemical engineering research related to the abatement of engine emissions for the past 14 years,” said Aleksey Yezerets, director of Catalyst Technology at Cummins. “This publication shows one example of the many insights into these complex processes that we have worked on together through the years.”
Zeolites have a crystalline structure containing tiny pores about 1 nanometer in diameter that are filled with copper-atom “active sites” where the chemistry takes place. In the new findings, the researchers discovered that ammonia introduced into the exhaust “solvates” these copper ions so that they can migrate within the pores, find one another, and perform a catalytic step not otherwise possible.