Destruction of refrigerants

En has a job working at a company that tracks the use of refrigerants. Interestingly, this company is called TrakRef.

This begs the question "why would you track these?"

Well, two reasons really. At first, these were using CFCs, chlorofluorocarbons. These are similar to normal hydrocarbons that we're all familiar with like octane and similar except that some of the hydrogens are replaced with either chlorine or fluorine. These were eventually shown to have a very negative effect on the ozone layer as the chlorine atom catalyzes the destruction of the ozone (O3). The production and use of these chemicals were banned with the implementation of the Montreal Protocol. Going a step back, the reason we were using CFCs in the first place is that they are really benign substances for people to be around They are generally safe to handle and are reasonably tame stuff.

But destroying the ozone later is bad.

So, what to do?

Well, you can replace the chlorine in the molecule with more fluorines and get rid of the destruction, right? Well, yes... but now you have a molecule that is far better at trapping heat than normal CO2 is. Pound for pound it's way over 1500 times worse than CO2.

Ok. So what now? We still need cooling. Alternatives are things like butane and similar flammable liquids which bring their own set of problems. (Though industry is shifting to them anyway). So we're still reliant on these things which are bad.

That's when I got to thinking. Being a big of an amateur scientist I set to figure out how I would destroy these molecules. This isn't really a hard thing in industry and they do this all the time, but I wanted to see if I could come up with a way myself to see if I understood the chemistry of this enough.

The process I came up with, above, is the same thing they use in industry!

😃

The way I was thinking is that the C-F bonds are really strong due to the high electronegativity of the fluorine atom, so they'll wind up being a very strong covalent bond. (The strength of this bond, incidentally, is one of the things that make it desirable for refrigeration: it forms a highly polar molecule that has a higher boiling point than a similar non-polar molecule) You would need to replace that with something that's even stronger.

Enter water, H2O.

Heat the whole thing up really really hot (and I'm guessing adding somet catalysts that I have no idea about at the moment... platinum maybe since it interacts with hydrogen so readily?) and you decompose the CFCs liberating the fluorine, which is then free to grab a hydrogen from the water, to which it binds to even stronger than the original carbon. Which frees up the carbon to grab the oxygen.

Ok, so now you have gaseous HF and CO2. CO2 isn't that bad... it's exactly as bad as CO2 and not 1500x as bad as the source, so you have a big win. But a fluorine gas is nothing to sneeze at either. So just bubble that shit through water which causes the HF to disassociate into hydrofluoric acid!

And once you have an acid, all you have to do is add in a base and blammo! You get a fluorine salt that'll precipitate out of the solution.

And this is exactly what happens in industry... I was just happy that I was able to derive all this myself. I learned all the background to solve this on YouTube courtesy of NurdRage and Nile Red. 😃