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The end products of the reaction, hydrocarbons and fluorosilanes, do not have greenhouse-gas properties and are easier to dispose of than fluorocarbons.
Ozerov and Douvris tried out their catalytic method on three fluorocarbon test substrates. In each case, they were able to get almost all of the material to react; one substrate took just six hours to break down completely, at only 25 °C.
Robin Perutz, a catalyst expert at the University of York, in the U.K., says that Ozerov and Douvris's method is "an impressive discovery. It's really important to convert problematic fluorocarbons into something fairly harmless, and at the moment this can only be done by extremely high-temperature chemistry. These guys have said we can do an awful lot just at room temperature, and that's a big step towards getting rid of more unwanted fluorocarbons."
There are a few challenges to meet before the catalyst could be used to clean up fluorocarbons on a large scale, however. To begin with, cheaper sources would need to be found for the silicon-based reagents, says Ozerov.
Véronique Garny, director of the Fluorinated Chemicals Groups at the European Chemical Industry Council, says that even then it might be hard for the catalyst technique to beat the established methods. Fluorosilanes, Ozerov acknowledges, have some toxicity--although he says that they "can easily be processed further." But according to Garny, the existing techniques "are simpler, have completely nontoxic end products, and work fine with highly contaminated starting materials, something which Ozerov's process still needs to show."
Garny sees more potential for the catalyst method in attacking solid and liquid fluorocarbons that pollute land and water. Perutz points out, however, that these pollutants are often particularly hard to break down because they are extra rich in strong fluorine-carbon bonds. Ozerov and Douvris have not yet tested their method against such recalcitrant fluorocarbons.
"The technique still has quite a long way to go before it can be used widely," says Perutz. "But it's certainly a very promising step with a lot of potential."
I'd like to know more about the hydrocarbons produced by the reaction. What are they exactly?
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justahick
19 Comments
Ozone Destroying?
Hmm, since CFC's have been banned for so long, you would think that the ozone hole would be well on its way to being mended.
Since it's not, and the hole's geometry seems to match the strength of the earth's magnetic field, which is in the process of reversing and is weakest where the ozone is thinnest, one would reasonably conclude that the science that claimed that CFCs were destroying the ozone were simply wrong.
So, the article would seem to be perpetuating a myth. Is this a sample of what passes for education at MIT these days?
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travism
8 Comments
Re: Ozone Destroying?
CFCs are going to be causing ozone depletion for quite some time. The chemistry of ozone depletion is well known and has nothing to do with the Earth's magnetic field. CFCs break up at high altitudes into chlorine which reacts with ozone, splitting the ozone up into plain oxygen then reverts back into chlorine and attacks more ozone molecules. Quite a nasty example of catalysts in action.
The fact that the chlorine stays up there causing ozone thinning for a long period of time does not mean stopping CFC use was pointless. On the contrary...
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justahick
19 Comments
Re: Ozone Destroying?
You seem to have entirely missed my point about the ozone hole seeming to stay in one place in the world, almost exactly over the area where the earth's magnetic field is weakest.
I'll try to be clearer: I've never seen an atmospheric chemical reaction that stayed over one region of the world for decades. But maybe those CFC's are just amazing catalysts...
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travism
8 Comments
Re: Ozone Destroying?
There are a couple of reasons why the ozone hole stays over the south pole (and southern countries like Australia). One reason is because of the direction of winds and the types of clouds which form over the south pole, which have the effect of concentrating some pollutants like CFCs.
The other is that ozone is formed by the reaction between oxygen and UV light. It doesn't form in darkness and as you know the polar regions are dark during winter.
The CFCs remain though, destroying ozone made the previous summer. Therefore, ozone levels plummet and are not replenished over winter whereas anywhere else in the world you have daily replenishment which at least partially offsets the effects of CFCs.
This means that the ozone hole reforms every winter above Antarctica then as wind directions change etc it gets blown North, stripping the UV protection from countries like Australia in time summer.
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