What properties of platinum and rhodium/palladium allow these

they catalyse reactions that degrade pollutants into water vapor and carbon dioxide, hence CATALYTIC convertic

>>8897734
OP is asking how they do it that. How do catalysts work

It's probably too complicated for /sci/

>>8897734
So would the nitrogen oxides naturally break down into N2 and O2 eventually, since catalysts don't actually create a reaction, they just speed it up?

Yeah haha, sorry if I wasn't clear

>>8897743
yeah i just have a basic understanding buuuut:
https://en.wikipedia.org/wiki/Catalytic_converter
http://auto.howstuffworks.com/catalytic-converter.htm
https://www.google.ca/search?q=catalytic+converter&oq=catalytic&aqs=chrome.0.0j69i57j0l4.2914j0j7&sourceid=chrome&ie=UTF-8

>>8897750
Those just say "yeah the catalysts separate harmful gasses into less harmful gasses"

They don't say how that happens

>>8897744
nitrogen oxides break down into nitric acid and other stuff in water (very bad for the environment)
catatlyic converters circumvent this somewhat

>>8897752
the wikipedia article is pretty in depth

>>8897753
I know, I'm wondering what property of the catalysts induces the redox reactions though. Like why do platinum and rhodium work the best at reducing nitrogen oxides?

>>8897759
No, it just says which metals are used (platinum, palladium, and rhodium) and says they're effective catalysts. I want to know why those metals are so effective

>>8897761
I'm just guessing but maybe it's a valence thing?

>>8897770
hmm interesting. What specifically?

>>8897761
https://en.wikipedia.org/wiki/Platinum_black
>it can absorb a large amount of oxygen or hydrogen gas to catalyse reactions with hydrocarbons

>>8897774
Oh interesting, thanks! But what property makes platinum so good at absorbing oxygen/hydrogen?

>>8897780
regular platinum doesn't have this property as far as i understand, it needs to be processed into platinum black which is chemically different

idk about the other catalysts

>Platinum, Rhodium, Nickel and so on are all transition metals. Because they have a lot of unpaired electrons (in d-orbitals) they are paramagnetic which helps with further polarizing other molecules and they need only very low transition energies for those electrons which allows them to achieve a lot of different oxidation states with little energy. This enables them to easily create multiple weak covalent bonds with other compounds. Put together these properties allow transition metals to move around electrons with little energy and bond/break up bonds that would otherwise take more energy. One has to remember though that this only speeds up reactions and all those reactions could happen theoretically on their own.

Does that seem reasonable?

A few years back niggers around here were stealing these by cutting them out of people's cars and scrapping the Platinum.

>>8897872
a few years ago whites were stealing airbags

File: 1356292285736.png (107KB, 855x865px) Image search: [Google]

107KB, 855x865px

>>8897752
>https://en.wikipedia.org/wiki/Catalytic_converter

>>8897752
>Those just say "yeah the catalysts separate harmful gasses into less harmful gasses"
>They don't say how that happens

My understanding is that science does not know why exactly it is a catalyst works, just that it does, as can be demonstrated on a bench in a flask.

In my gen chem the prof said because it PROBABLY has something to do with surface area, electromagnetic properties AND geometry

The crystal structure of Pd/Pt substrates are complex, imagine a crumpled piece of paper straightened out and put on a table. Some vertxes are higher and some lower. Now imagine a continuous indeterminate flux of electrons across the surface on these massive atoms which, being far from the nucleus, can be expected to interact somewhat with nearby molecules. This is the electromagnetic interface which NOx molecules and CO and air collide at very high temperatures. You should imagine increasing molecular velocity at/near these surfaces, overcoming typical repulsions which would prevent the sharing of electrons and intermediate reactions.

>>8897723
they dont seperate them, they turn them into something else. catalytic converters arent filters, theyre literally catalytic converters.