In Indiana, researchers 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.
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.