Chemistry – Organic chemistry - Fuels | e-Consult
Organic chemistry - Fuels (1 questions)
Fractional distillation is a process used to separate the different hydrocarbons present in petroleum (crude oil) based on their different boiling points. The process involves heating the crude oil in a furnace to a high temperature (around 400°C) to vaporize the hydrocarbons. This hot vapour is then passed into the bottom of a fractionating column, which is cooler at the bottom and gradually gets cooler towards the top.
The apparatus used in fractional distillation consists of a furnace, a fractionating column, and a condenser. The furnace heats the crude oil, converting it into vapour. This vapour enters the fractionating column. The column is designed with a temperature gradient – it’s hotter at the bottom and cooler at the top. As the vapour rises through the column, it gradually cools. Hydrocarbons with higher boiling points condense at the lower, hotter parts of the column and can be collected as liquids. Hydrocarbons with lower boiling points continue to rise further up the column before condensing at the cooler upper sections. Different fractions condense at different temperatures.
The separation is based on the difference in boiling points of the various hydrocarbon components of crude oil. Each fraction has a characteristic boiling point range. Typical fractions and their boiling point ranges are:
Fraction | Approximate Boiling Point Range (°C) | Typical Uses | ||
Gases (methane, ethane, propane, butane) | -161 to 0 | Fuel for cooking and heating, LPG |
| Petrol (gasoline) | 30 to 200 | Fuel for cars |
| Kerosene (paraffin oil) | 200 to 300 | Jet fuel, heating oil |
| Diesel oil | 300 to 350 | Fuel for diesel engines |
| Lubricating oil | 350 to 400 | Reducing friction in engines |
| Bitumen (asphalt) | 350 to 400 | Road surfacing |
Two uses for petrol are as a fuel for cars and as a component in petrol mixtures.