[mihir94]

Hey all,
This is my first post at Chemical forums.
A great forum BTW, I really like learning and discussing Chemistry with people.

My Question is that can we use oxygen filtering zeolites in car air intake. It means that pure oxygen would be availiable in the engine block. Wouldn't that mean better efficiency and less CO and unburnt petrol?

Also, Since N₂ isn't going in the engine, we wouldn't have pollutants belonging to the NO_x family?

[fledarmus]

You are right that removing the nitrogen from the oxygen source would remove most of the NO_x compounds from the exhaust. Unfortunately, switching to a pure oxygen feed, regardless of the source of the feed, leads to a lot of additional problems that would need to be engineered out of the engine. The "inert" nitrogen in the air is doing far more than providing undesired side-reactions - it is also diluting the gasoline and oxygen to the point where you get a controlled burn rather than an explosion, and carrying a lot of heat out of the engine so the rest of the cooling system can keep up. Pure oxygen is also an extremely corrosive atmosphere, and you could easily end up igniting the metal in the engine as well as the fuel, especially if it is an aluminum or magnesium containing alloy.

So your first step would need to be designing an engine that could run for ~100,000 miles, whether it was operated 12 hours daily or only 1 hour/week, on a pure oxygen/fuel mixture. Then you can worry about the source of pure oxygen.

[vmelkon]

It would make it more efficient because if you have nitrogen, the nitrogen is a heat sink. You lose energy to it.
The added bonus is that you don't get NO2, N2O4 and other oxides of nitrogen.
The next problem is that if you are going to use pure oxygen, then you will either have an excess of oxygen (now oxygen acts as a heat sink) or you have to add the proper amount of fuel so you'll have too much force.
As fledarmus mentioned, oxygen is corrosive to aluminum. If you don't add enough fuel, the excess oxygen might corrode your engine walls. If you add the exact amount, I don't know if it would still corrode.

[curiouscat]

What's the volumetric air consumption of a typical car? I think your zeolite-unit would have to be absolutely HUGE to match the capacity.

I don't think you'd have any passenger space left at all.   

But I'm speculating; would love to see a calculation.

Also, what's the entropic overhead to separating N2 and O2? The energy has to come from somewhere; possibly the air pump. Would the additional energy provided by the engine be enough to compensate?

Overall, I don't think it will be any more efficient; but you it might be more powerful.  Isn't this similar to hot rod racers using "Nitro"?

[fledarmus]

It would make it more efficient because if you have nitrogen, the nitrogen is a heat sink. You lose energy to it.

That all depends on how you are calculating efficiency. Yes, the nitrogen is a heat sink, but if there was no heat sink you would burn out your engine, which isn't particularly efficient. You would either have to replace the nitrogen with some other inert gas, which involves carrying around an additional tank, or you would have to redesign the engine to shed more heat and to use a much smaller volume displacement.  Then you're into a comparison of apples and oranges. Simply attempting to run the engine with only the oxygen proportion of the atmosphere would not work, and replacing the entire atmosphere with oxygen would corrode the entire system if it didn't ignite the gasoline too early.

The question becomes, could you design an engine running on fuel/oxygen, that was more efficient than a fuel/atmosphere engine. Then you can consider what it would take to supply the pure oxygen feed.

[curiouscat]

Apparently the idea is not as crazy as it initially sounded to me. There seems significant patent activity:

e.g.
http://www.google.com/patents/US6543428?printsec=description#v=onepage&q&f=false

No one's using pure O2 but some form of enriched air.

There's an old patent by one  Martin E. Gerry "Pure oxygen supply to an internal combustion engine"; that one does use pure O2 but it all seems a bit wacky to me.