Designer solvents promise revolutionary pollution solution

SAN DIEGO - New designer liquids that can replace hazardous and polluting organic solvents are poised to revolutionize industrial chemistry and dramatically reduce pollution at its source, according to researchers.

The designer solvents, known as ionic liquids, are the subject of a major five-day symposium, April 1-5, at the 221st national meeting of the American Chemical Society, the world's largest scientific society. More than 80 papers will be presented during the symposium.

"Ionic liquids mean that organic chemistry has entered the 21st century. Things will never be the same again," says leading green chemist Ken Seddon, Ph.D., a professor at Queen's University of Belfast in Northern Ireland and one of the symposium's organizers.

Ionic liquids, which are chemically similar to table salt, are liquid at room temperature. Table salt doesn't turn into a liquid until it's heated to nearly 1500 F (800 C).

Unlike organic solvents, many ionic liquids do not evaporate or escape into the atmosphere easily. Another advantage of the liquids is that they can be recycled and reused as solvents many times. Solvents are widely used in many industries, and by individuals, for cleaning, degreasing, stripping and thinning. Examples of well-known organic solvents include acetone, kerosene and naphtha. Ionic liquids can be tailor-made to dissolve a vast range of substances.

The potential market for ionic liquids is huge. Currently, about $6 billion worth of organic solvents are used worldwide by the petrochemical and pharmaceutical industries. A French company already is using ionic liquids to manufacture plasticizers, chemicals that soften brittle plastics.

Researchers have also designed and synthesized ionic liquids that remove cadmium and mercury from water, which could be used to clean up industrial effluent. When ionic liquids come in contact with contaminated water, they snatch and sequester metal ions, according to James H. Davis, Jr., Ph.D., assistant professor in the department of chemistry at the University of Southern Alabama in Mobile. Davis developed the water purification technique with Robin D. Rogers, Ph.D., director of the Center for Green Manufacturing at the University of Alabama in Tuscaloosa.

The Alabama researchers have also devised a way of using ionic liquids to remove impurities from natural gas. Unrefined natural gas contains many contaminants, particularly carbon dioxide and hydrogen sulfide. They "sour" the gas, lowering its fuel value and contributing to acid rain when the gas is burned. Conventional techniques use organic solvents to remove contaminants. During the purification process, however, the organic solvents can get caught up in the natural gas stream - in effect, exchanging one contaminant for another.

The ionic liquid solvents that Davis designed and synthesized incorporate chemical groups that react with carbon dioxide and hydrogen sulfide, literally binding them into the solvent. Preliminary results indicate that heating contaminant-laden ionic liquids in a vacuum reverses the binding process, permitting the liquids to be reused, he says.

Oxidation of organic compounds is one of the most fundamental reactions in chemistry. Such reactions create epoxides - biologically reactive chemicals that are widely used in making pharmaceuticals. Although these reactions usually require organic solvents, Mahdi M. Abu-Omar, Ph.D., of the University of California, Los Angeles, has created a system that uses an ionic liquid solvent and hydrogen peroxide - an environmentally friendly way to create epoxides without generating waste. Even the metallic catalyst remains in the ionic liquid phase, so it can be recovered and recycled.

The ionic liquid research being presented at the weeklong symposium is just the tip of the iceberg, say the scientists. Compared to the 300 organic solvents widely used in the chemical industry, more than a trillion possible ionic liquids are possible. "We're still in Edison mode," says Rogers.

The research cited in this release is being presented during the symposium "Green (or Greener) Industrial Applications of Ionic Liquids."

Robin D. Rogers, Ph.D., is director of the Center for Green Manufacturing at the University of Alabama in Tuscaloosa, and one of the organizers of the symposium. He also is editor of the American Chemical Society journal, "Crystal Growth and Design." (The papers on his research, IEC 1 and 347, will be presented at 8:00 a.m., Sunday, April 1, and 2:45 p.m., Wednesday, April 4, in the Westin Horton Plaza hotel, California C. He is a co-author of 11 other papers and posters being presented during the symposium.)

Ken Seddon, Ph.D., is a professor at Queen's University of Belfast in Northern Ireland and one of the organizers of the symposium. He also is editor of the American Chemical Society journal, "Crystal Growth and Design."(The paper on his research, IEC 2, will be presented at 8:45 a.m., Sunday, April 1, in the Westin Horton Plaza hotel, California C. He is a co-author of six other papers being presented during the symposium.)

James H. Davis, Jr., Ph.D., is an assistant professor in the department of chemistry at the University of Southern Alabama in Mobile. (The paper on his research, IEC 251, will be presented at 11:00 a.m., Tuesday, April 3, in the Westin Horton Plaza hotel, Plaza A-B. He is a co-author of four other papers and posters being presented during the symposium.)

Mahdi M. Abu-Omar, Ph.D., is an assistant professor in the department of chemistry and biochemistry at the University of California, Los Angeles. (The paper on his research, IEC 312, will be presented at 10:00 a.m., Wednesday, April 4, in the Westin Horton Plaza hotel, California C.)

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