Fractional distillation of crude oil
ChemistryOrganic ChemistryAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Organic Chemistry
Crude oil is heated and fed into a fractionating tower: short-chain hydrocarbons with low boiling points rise to the top, while long-chain ones with high boiling points settle near the bottom. Set the furnace temperature and the crude oil composition to see which fraction each tray collects (gas, gasoline, kerosene, diesel, heavy residue) and how the product ratios change. Three more tabs cover fuel quality: blend 2,2,4-trimethylpentane with heptane and test fuels in a model engine that knocks, see how cracking, reforming and isomerisation raise the octane number, and compare complete with incomplete combustion.
Lesson: Crude oil and petroleum refining
What it shows
Crude oil is a mixture of hundreds of hydrocarbons that can be separated because their boiling points differ: longer chains have stronger intermolecular forces and higher boiling points. In a fractionating column each vapour rises until it reaches a tray cool enough to condense. Petrol quality is measured by the octane number, the percentage of 2,2,4-trimethylpentane in a heptane blend that knocks the same way; engines with higher compression ratios need higher numbers. Cracking, reforming and isomerisation make branched and ring molecules that resist knock, and burning with too little air gives carbon monoxide and soot.
How to use
In Distillation, change the Furnace temperature and the Crude oil type and read the tray products. In Octane & knock, choose a Fuel, mix a reference blend with the two sliders, set the Compression ratio and press Run engine test; the knock meter and the table record each test. In Raising octane, choose a Process and press Run the process. In Combustion, move Air supply and press Record result.
Parameters you can change
- Opening tab Distillation, Octane number and knock, Raising the octane number, Complete and incomplete combustion
- Furnace temperature 100–450 °C
- Crude oil type Light crude (more low-boiling fractions), Medium crude, Heavy crude (more residue)
- Compression ratio of the test engine 7–13
- Air supply (% of the air needed) 50–150 %
Questions to explore
- Why is gasoline collected higher up the column than diesel?
- Is each fraction a single compound or a mixture, and how do boiling points explain this?
- What happens to the diesel fraction when the Furnace temperature is lowered to 250 °C?
- Why does petrol RON 90 knock at a compression ratio where RON 98 runs smoothly?
- Which products form when the Air supply is 70% instead of 100%, and why is that dangerous?
