Scientists Develop Potent Acids to Take Down Destructive Fluorocarbons

While their brethren, the dreaded chlorofluorocarbons (CFCs), may be on the wane, fluorocarbons -- a class of equally dangerous industrial gases -- are still wreaking havoc. As the name implies, the main distinguishing characteristic between CFCs and fluorocarbons is that the latter lacks chlorine; that is, unfortunately, one of the few meaningful differences, as both are extremely destructive in their own respects.

Unlike CFCs, which were banned from use because of their harmful impact on the ozone layer, fluorocarbons remain widely in use: found in everything from clothing, blood substitutes and lubricants to refrigerants. The strength and lack of reactivity of their C-F bonds, which renders them water repellent, has made them an ideal chemical for many industries. http://www.sciencemag.org/cgi/content/full/321/5893/1168Fluorocarbons: a double threat
The inertness of their bonds can prove to be too much of a good thing, however. As Robin Perutz of the University of York explains in the latest issue of Science, fluorocarbons are very difficult to get rid of and can't easily be recycled into other useful compounds. And that's a big problem because they are very potent greenhouse gases: roughly 6,500 times more so than carbon dioxide. To make matters worse, they are also toxic in the soil or water.

Using acids to "blow the C-F bonds apart"
Fortunately, two scientists who developed acids capable of breaking the C-F bonds in 2005 -- Oleg Ozerov and Chris Douvris of Brandeis University -- have refined their method, finding a way to sustain the reaction for long periods of time. In their first attempts, Ozerov and Douvris had only been able to sustain the "Lewis acids" for short periods, making them less practical.

In this reaction, one molecule of the acid can neutralize up to 2700 bonds at room temperature, converting the fluorocarbon into a safer form in 24 hours.

NewScientist's Colin Barras explains how the reaction would work:

The process starts when a silylium molecule rips a fluoride ion from its carbon partner. That produces a stable silicon atom bonded to fluorine, and a highly reactive naked carbon ion is left behind.

This is then neutralised when it grabs a hydrogen ion from the silicon in a triethylsilane molecule, producing a safer carbon-hydrogen bond and creating a fresh molecule of silylium to attack more C-F bonds.

The reaction is a "downhill" process, using very little energy, says Ozerov, and the end products have little impact on the atmosphere.

Though it's still too early to tell whether this new reaction could scale up to the level that would be needed to significantly reduce fluorocarbon levels, it's a promising first step that will receive much more scrutiny in the coming years.

Image from Science

Via ::NewScientistTech: 'Unbreakable' greenhouse gas meets its doom at last (news website)

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Tags: Air Quality | Ozone

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