Unrefined petroleum appears as a viscous dark-brown liquid, often called crude oil. It is a complex mixture of alkanes, alkenes, cycloalkanes and aromatic compounds. However, the actual compound of petroleum depends on the location.
Fractionation Distillation Tower.
The hydrocarbon component in petroleum can be classified according to their range of boiling points. These hydrocarbons can be separated by using fractional distillation. Crude oil will be heated up to 400°C and converted to viscous oil into hot vapour and fluid. It enters the fractionating tower and condenses into various components according to their temperature, and some gases are drawn off at the top of the tower. The unvaporized residual oil are collected at the bottom.
Gasoline is the best known petroleum product. The components in gasoline are more suitable to use for fueling an automobile, however rapid burning of gasoline-air mixture causes a hard jerk rather than a smooth push to the piston. So herein lays the problem for further treatment of gasoline.
The octane rating of hydrocarbon can be improved by adding small amount of anti-knocking agents, the most widely used anti-knocking agents are:
2-4g of either these two compound are added into a gallon of gasoline to reduce the hard jerk. However, these compounds are highly toxic and causes serious environment problem. Therefore, unlead gasolines containing methyl tert-butyl ether (MTBE) is used to replace it.
Four Stroke Cycle
The four stages of operation of an internal combustion engine are:
a) Intake- The intake valve opens to let in the gasoline-air mixture.
b) Compression- The two valves are closed during the compression stage.
c) Power- The fuels react and the piston is pushed outward.
d) Exhaust- The exhausted valve open to let gaseous out when the piston travels back up.
Reaction: C8H18 + 25/2 O2 → 8CO2 + 9H2O
Heat is released in the reaction.