Chemistry [[Module Three]] Petroleum: Combustion

[[Combustion of Petroleum Fractions]]

Fractions obtained from petroleum are used as fuels
Hydrocarbons burn easily in air with exothermic reactions
Sulphur containing impurities occur with hydrocarbens and when these burn they produce oxides of sulphur which are toxic and dissolve in water producing acid rain.

[[Combustion of alkanes]]

Alkanes burn easily in air/Oxygen with very exothermic reactions

[Complete Combustion]
-Presence of sufficient oxygen
-CO2 and H2O formed
- As carbon chain increases, more oxygen is needed and more energy released

CH4 +2O2 --> C02 +H2O

C4H10 +61/2O2 ---> 4CO2 +5H2O

[[Incomplete Combustion]]
- presence of insufficient oxygen
- water is formed
- carbon monoxide or carbon is formed
- carbon monoxide = hazard = can lead to accidental death by CO poisening

[[Internal Combustion Engines]]
CO also formed by incomplete combustion of petrol vapour in car engine
Other pollutants formed - nitrous oxides mainly
Nitrous oxides formed when petrol/air mix is sparked and explodes -> provides enough energy for nitrogen to react woth oxygen

N2 +O2 --> 2NO

upon cooling it reacts with oxygen

2NO + O2 ---> 2NO2

and then with water and more oxygen

4NO2 + 2H2O + 02 ---> 4HNO3 = acid rain

[[Catalytic Converters]]
-help to remove pollutants from car wxhausts
- cermatic honeycomb coveredwith metals such as platinum, palladium and rhodiun
- These catalyse reactions between pollutants and remove 90% harmful gases

2CO + 2NO --> 2CO2 +N2

Pollutants become - CO2, N2 and H2O which are harmless