Researchers at the Georgia Institute of Technology have uncovered important evidence that explains how water, usually an inhibitor of catalytic reactions, can sometimes promote them. The findings could lead to fewer constraints on reaction conditions potentially leading to the development of lower cost techniques for certain industrially important catalytic reactions. The results appear in the September 6, 2005 issue of Physical Review Letters.
A snapshot of the reaction in which a water molecule enhances the transformation of carbon monoxide to carbon dioxide. Illustration of reaction turning carbon monoxide (CO) into carbon dioxide (CO2) using a water molecule (H20) to enhance the catalytic activity of an eight-atom nanocluster of gold. Color key: oxygen atoms = red; hydrogen atoms = white; carbon atoms = aquamarine; gold atoms = gold; and magnesium atoms = green.
“Normally, in most catalytic reactions, water can stop the reaction. It kills the catalyst,” said Uzi Landman, director of the Center for Computational Materials Science, Regents’ and Institute professor and Callaway chair of physics at Georgia Tech.
And that’s a big problem because ensuring that a reaction is water-free can add to production costs. Many catalytic reactions occur at high temperatures, which evaporates the water, said Landman. “However, any time that the reaction temperature is lowered and there’s humidity unfavorable effects may occur. You hope that when you heat the reaction up that the adsorbed water will come off, but sometimes it doesn’t. Sometimes the adsorption of water leads to an irreversible modification, such as oxidation, and deactivation of the catalyst. It’s poison; it poisons the catalyst,” he said.
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