'Switchable' Solvents Make Chemical Manufacturing More Environmentally-friendly

The team, led byQueen’s chemist Dr. Philip Jessop, has developed new solvents (liquidsthat dissolve other substances) that are both cleaner and cheaper whenused in the production of many chemicals. Because each step in achemical process often requires a different solvent, there can be agreat deal of waste which is both costly and damaging to theenvironment.

“We all want the products of the plastics andpharmaceutical industries, but we don’t want the pollution,” says Dr.Jessop, Canada Research Chair in Green Chemistry. “Our research isseeking ways to decrease the amount of solvent waste generated by thesecompanies.” In the ratio of waste-to-product, pharmaceutical and other“fine chemical” industries are far dirtier than the oil industry, henotes.

These new “switchable” solvents discovered by Dr. Jessop’steam change their properties when alternately exposed to carbon doxideand nitrogen, making it possible to re-use the same solvent formultiple steps in a chemical process, rather than discarding andreplacing the solvent after each stage.

Also on the team from theQueen’s Chemistry Department are graduate students David Heldebrandtand Xiaowang Li, and from the Georgia Institute of Technology Drs.Charles Eckert and Charles Liotta, both winners of 2004 PresidentialGreen Chemistry Challenge Awards.

The organic solvents tested bythis research group are known as ionic liquids: a salt that is moltenat room temperature, or near-room temperature. “They have been widelyhailed as environmentally benign because they have no vapor pressure,and they also have some unusual properties,” says Dr. Eckert, aprofessor in the School of Chemical and Biomolecular Engineering atGeorgia Tech.

However, the new ionic liquids are differentbecause exposure to nitrogen gas causes them to change back intoregular (non-ionic) liquids. “It’s a potential tool for benign andeconomical processing in the manufacture of high-value-added specialtychemicals, such as pharmaceuticals,” Dr. Eckert adds.

Greenchemistry refers to the development of chemical products and processesthat reduce or eliminate the use and generation of hazardoussubstances. Rather than focusing on the natural environment andpollutant chemicals in nature, this type of chemistry seeks to reduceand prevent pollution at its source. “We’re concerned with pollutionprevention rather than treatment,” says Dr. Jessop. “That’s a much moreeconomical way to approach the problem.”