Image credit: North Arizona Uni
And now ladies and gents, we have PHOTOCHEMICAL SMOG
forgive me, Im a little hazy on this topic…
yes I went there.
SO. Photochemical smog is bad because ozone and nitrogen dioxide causes coughing and wheezing and all that jazz at concentration of 0.15ppm. Not healthy. It also attacks double bonds in polymers (therefore idk your car tyres will just fall to bits as you pass through that yellow coloured cloud) (Don’t quote me). And it causes issues with photosynthesis, which results in decreased health or life of plants.
It is formed because of all the polluntants in the atmosphere, particularly Nitric oxides and unburnt hydrocarbons. Which all happens in the combustion chamber of motor ve-hicklez.
We have primary polluntants which go directly into the atmosphere and contribute the the smog. firstly, there is NITRIC OXIDE:
N2 + O2 ——high temperature —-> 2NO
And then there are hydrocarbons which have escaped combustion, the little shits just float on right out the engine. Secondary pollutants stem from primary ones, but undergo chemcial changes first:
NO2 + hv —> NO + O
O2 + O —> O
This process shown ^ involves nitrogen dioxide and is major reactiveness undergoing photochemical dissociation. The atomic oxygen then reacts with molecular oxygen and results in OZONE. We also have:
Hydrocarbons + molecules or free radicals —> aldehydes or peroxyacl nitrates (PAN)
TO solve this terrible environmental issue we have CATALYTIC CONVERTERS
- honeycomb structure - increased surface area
- catalysts - platinum, palladium, rhodium
Reactions that take place within the converter as follows:
2CO + O2 —> 2CO2
CO + H20 —> CO2 + H2
C8H18 + 8H20 —> 8CO + 17H2
2CO + 2NO —> 2CO2 + N2
2H2 + 2NO —> 2H2O + N2
- the converter works best with a air: fuel ration of 14.6:1.
- the oxygen level is kept at optimum by a oxygen sensor.
- the optimum temperature of the converter is >400oC