For release: Sept. 25, 2000
Contacts:
Andreja Bakac, Molecular Processes, (515) 294-3544
Saren Johnston, Ames Lab Public Affairs, (515) 294-3474
AMES, Iowa -- A chemist at the U.S. Department of Energy's Ames Laboratory is carrying out safe and simple chemical reactions that could bring about a big change in how industrial chemicals are produced, making the process more efficient, economical and environmentally friendly.
Andreja Bakac studies the effects of light on chemical reactions. While many photochemical reactions are initiated by ultraviolet light, Bakac uses readily available visible light from a lamp or from the sun for her photo-oxidation experiments with hydrocarbons, a group of extremely abundant and significant chemical compounds.
The relevancy of hydrocarbons to our everyday existence is indisputable. Among other uses, they make possible the gas for our cars and the heat for our homes. Petroleum and natural gas are mixtures of hydrocarbons. In fact, petroleum crude oil is the world's largest source of hydrocarbons.
Plentiful as they are, hydrocarbons -- especially saturated hydrocarbons, ones to which additional elements or compounds cannot be attached -- are basically lifeless and won't react on their own. Bakac said this class of compounds could become an important feedstock for the chemical industry if they could be made more reactive. The standard method of doing this is by using heat to drive the chemical reaction. However, Bakac noted, "Light is typically a lot cheaper than heat, and it's perfectly clean environmentally."
Simple air is the oxidant for Bakac's hydrocarbon oxidation reactions. "Air or oxygen, that's as innocuous as oxidants get," she said. "That's what's so wonderful about this approach and what makes it so attractive."
In addition to light and air, Bakac uses a brilliant-yellow aqueous solution of uranyl ions as a photosensitizer to absorb the light needed to drive the oxidation reactions. Although many people may associate the word "uranium" with radiation pollution, Bakac explained that should her experiment eventually be considered for industrial applications, depleted uranium would be used. In depleted uranium, the amount of the fissile uranium -- the isotope that splits apart -- has been reduced to well below natural levels. "The U.S. has a lot of depleted uranium just waiting to be put to use," she said. "It's there, it's available and it's safe."
Bakac has used her environmentally friendly system to successfully photooxidize various hydrocarbons. She has been able to oxidize benzene to phenol, a process that is industrially significant because phenol is an important starting chemical in the manufacture of such products as resins, paints, adhesives, phenolic plastics, synthetic fibers, herbicides and insecticides.
"Phenol is currently produced in a very cumbersome, multistep reaction," said Bakac. "Yet, we do it very nicely with our uranium and light system. It's a very clean reaction, and we get fantastic yield, which means light is being used very efficiently."
Another notable reaction is the photooxidation of the hydrocarbon toluene to benzaldehyde, an important intermediate in the chemical industry. Although the yield has not been as significant as that for the benzene-to-phenol reaction, Bakac expects this to change with continued development of her system.
As research funding becomes available, Bakac hopes to make her hydrocarbon photooxidation reactions even more efficient by developing a method of immobilizing the uranium so that it can be removed when the reaction is over and used again in other experiments.
"I want to take a solid support and deposit the uranium onto it so that when it's put into solution, the uranium will stick to that support and not wash into the solution," Bakac explained. "The support would have to be thin enough to let light in, and the molecules would have to be able to move in and out and react with one another.
"There are some tremendous advantages to the ability to recover the uranium," she continued. "You have to be able to give assurances to the community you work in that you're not disposing of uranium in the ground water, soil or anywhere else. Also, recovering the uranium would make the whole process more cost-efficient. If you can pull the catalyst out and reuse it, that has to be a better way to go."
Ames Laboratory is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.
Last revision: 9/22/00 sd
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