October 26, 2010 — From childhood stories of pirate treasure to fine jewelry, there is a near-universal understanding that gold is scarce, lustrous and valuable. Researchers at the University of Virginia's School of Engineering and Applied Science have expanded the concept of gold's value by showing how it – and other metals – can be used as catalysts for creating more environmentally friendly chemical processes.
The discovery by chemical engineers Robert J. Davis and Matthew Neurock could one day serve as the foundation for creating a wide range of consumer products, including biorenewable carbon feedstocks like ethanol, as opposed to the petroleum-based chemicals currently being used as common building blocks for commodities such as cosmetics, plastics, pharmaceuticals and fuels.
The U.Va researchers' work on the subject, completed with help from graduate students Bhushan N. Zope and David D. Hibbitts, was published in the paper — "Reactivity of the Gold/Water Interface During Selective Oxidation Catalysis" — in the Oct. 1 issue of Science. The journal, founded by Thomas Edison in 1880 and published by the American Association for the Advancement of Science, is one of world's leading publications for scientific news and research.
Traditionally, the chemical industry has used petroleum to create the higher-value chemicals that are then used to manufacture commodities. As one example, petroleum is converted into the commodity chemical benzene, which is then converted into an intermediate chemical and ultimately used to make plastics.
Davis and Neurock are part of a large field of researchers working on the science that will allow the chemical industry to transition from petrochemical processes to one that uses sustainable, biorenewable carbon feedstocks.
The U.Va. researchers have shown that gold – the most inert of all metals – has high catalytic reactivity when placed in alkaline water. They studied the mechanism for oxidizing ethanol and glycerol into acids, such as acetic acid and glyceric acid, which are used in everything from food additives to glues, by using gold and platinum as catalysts.
Although the high price of gold and the additional cost of acid recovery reduce the likelihood that the chemical industry will use the oxidation process for converting biorenewable carbon feedstocks to higher value chemicals, the researchers' discovery offers an important stepping stone for scientists and engineers in the field.
"We've shown that by better understanding the oxidation chemistry on gold and other metal catalysts, we can begin to outline a path for developing a range of different reactions needed to transition from a petroleum-based chemical industry to one that uses biorenewable carbon feedstocks," said Davis, principal investigator on the research paper and professor and chair of the Department of Chemical Engineering.
Using water to help oxidize the alcohols with oxygen in the air, as opposed to using expensive inorganic oxidants and harmful organic solvents, is an important element of the growing field's aim to offer a more sustainable, environmentally safe alternative to traditional petrochemical processes.
Until the completion of the U.Va. group's research, it wasn't fully understood how water can play an important role in the oxidation catalysis of alcohols. In the past, catalysis in water hasn't been a major issue for the chemical industry: Because petroleum and many petroleum products aren't water-soluble, water hasn't generally been considered to be a useful solvent.
The researchers, all from the U.Va. School of Engineering and Applied Science's Department of Chemical Engineering, combined concepts in electrochemistry and catalysis to uncover the critical factors in the oxidation of alcohols to chemical intermediates.
The research also required merging experimental lab work, led by Davis, with Neurock's expertise in the theory of catalytic chemistry.