Chemical switch

Chemical switch

By manipulating chemical reactions, a Queen's chemist has set his sights on greening an industry
May 26, 2010

Queen's University chemist Philip Jessop tries to 'green' the way industries operate.
Greg Black, Queen's University

As a “green chemist,” Philip Jessop spends his days trying to help the chemical industry create products in a less expensive and more environmentally friendly way. That’s why the Queen’s University professor of inorganic chemistry has high hopes for an innovative solvent he’s developed that may yield benefits for manufacturers of everything from pharmaceuticals to paint removers and cooking oils.

The solvent addresses several problems associated with the production of, for instance, soybean-based cooking oil. Typically, to extract the oil, dried and flaked soybeans are immersed in hexane, a volatile organic compound commonly used as an industrial solvent. Hexane dissolves the oil from the soybeans, giving a liquid mixture of hexane and soybean oil, and the two are separated using distillation. Essentially, the solvent is boiled off until all that’s left is the oil.

But using volatile solvents and industrial-scale distillation requires massive amounts of energy. As well, volatile solvents are dangerous. Hexane, for example, is highly flammable and is a known neurotoxin; it also contributes to smog. Similar issues exist with other industrial solvents, such as ether, chloroform and toluene, which are widely used in chemical manufacturing and, after they’re used, often end up as waste.

Federal statistics suggest Canadian companies released 5,676 tonnes of hexane into the air in 2008, which Jessop says is a conservative estimate, since some releases go undetected or unreported. 

An illustration of the switchable solvents that

An illustration of the switchable solvents that can dissolve and release substances on command.
Philip Jessop, Queen's University

Jessop’s “switchable” solvents — he’s developed several over the years — sidestep these issues by offering a clean alternative to volatile solvents and distillation. One solvent, for example, is normally hydrophobic, meaning it mixes with oil but repels water. When it reacts with carbon dioxide, however, the solvent becomes hydrophilic — it likes water but repels oil. Thus Jessop can use it to extract the soy oil and then use carbonated water — the basis of fizzy soft drinks — to pull the solvent out of the oil. Bubbling air through the carbonated water flushes out the carbon dioxide, releasing the solvent. In the end, Jessop is left with water and the solvent in its original state. The solvent can be reused, and once it’s recarbonated, so can the water.

Jessop’s switchable solvent is now being tested to determine whether it’s viable for large-scale commercial applications. If it is, it could be a game changer: although the solvent is more expensive than many volatile organics now in use, it could allow chemical companies to economize in other areas and reduce harmful emissions at the same time.  

“Because they wouldn’t be using volatiles, the chemical companies won’t have to spend as much on insurance and fire safety for their workers, and taking distillation out of the picture dramatically reduces their energy costs,” says Jessop, who recently received a Killam Research Fellowship for his work. “The solvent isn’t flammable and can be reused, so they save money that they would otherwise spend on single-use solvents.”