Switchable solvents make chemical manufacturing more environmentally-friendly

Researchers from Queen’s University and the Georgia Institute of Technology have discovered a new environmentally-friendly way to make chemicals for pharmaceutical and other industries, such as plastics, pesticides, dyes and fragrances.

The team, led by Queen’s chemist Dr. Philip Jessop, has developed new solvents (liquids that dissolve other substances) that are both cleaner and cheaper when used in the production of many chemicals. Because each step in a chemical process often requires a different solvent, there can be a great deal of waste which is both costly and damaging to the environment.

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

These new “switchable” solvents discovered by Dr. Jessop’s team change their properties when alternately exposed to carbon doxide and nitrogen, making it possible to re-use the same solvent for multiple steps in a chemical process, rather than discarding and replacing the solvent after each stage.

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

The organic solvents tested by this research group are known as ionic liquids: a salt that is molten at room temperature, or near-room temperature. “They have been widely hailed as environmentally benign because they have no vapor pressure, and they also have some unusual properties,” says Dr. Eckert, a professor in the School of Chemical and Biomolecular Engineering at Georgia Tech.

However, the new ionic liquids are different because exposure to nitrogen gas causes them to change back into regular (non-ionic) liquids. “It’s a potential tool for benign and economical processing in the manufacture of high-value-added specialty chemicals, such as pharmaceuticals,” Dr. Eckert adds.

Green chemistry refers to the development of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Rather than focusing on the natural environment and pollutant chemicals in nature, this type of chemistry seeks to reduce and prevent pollution at its source. “We’re concerned with pollution prevention rather than treatment,” says Dr. Jessop. “That’s a much more economical way to approach the problem.”