Overview
This lecture explains how crude oil is separated into useful hydrocarbons using fractional distillation and describes the main uses for each fraction.
Hydrocarbons and Crude Oil
- Crude oil is a mixture of molecules called hydrocarbons.
- Hydrocarbons vary in size and have different boiling points.
- Longer-chain hydrocarbons have higher boiling points than shorter chains.
Fractional Distillation Process
- Fractional distillation separates crude oil into fractions with similar numbers of carbon atoms.
- Crude oil is heated to a high temperature, causing it to boil and all hydrocarbons to vaporize.
- The vapor enters a fractional distillation column that is hotter at the bottom and cooler at the top.
- Hydrocarbon vapors rise up the column and condense back to liquids at their specific boiling points.
- Liquid fractions are removed at various heights in the column.
- Long-chain hydrocarbons with high boiling points are removed from the bottom.
- Short-chain hydrocarbons with low boiling points remain as gases and are removed from the top.
Uses of Fractions
- Some fractions serve as fuels: petrol and diesel for cars, kerosene for jets, heavy fuel oil for ships, and liquefied petroleum gas for camping.
- Other fractions act as feedstocks to make chemicals like solvents, lubricants, detergents, and polymers.
Key Terms & Definitions
- Hydrocarbon — molecule made of hydrogen and carbon only.
- Fractional Distillation — process to separate a mixture into parts (fractions) based on boiling points.
- Fraction — group of hydrocarbons with similar numbers of carbon atoms and similar boiling points.
- Feedstock — chemical used to make other chemicals in industry.
Action Items / Next Steps
- Learn and memorize the stages of fractional distillation.
- Study the uses and functions of each fraction.
- Review relevant exam questions on fractional distillation.