Fractional Distillation of Crude Oil
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff
Categories: Organic Chemistry, Mixtures and Separation
Alternative titles: Distilling Petroleum Mixtures
Summary
A crude oil sample is heated and liquid fractions are collected as temperature rises, modeling how refineries separate petroleum by boiling range.
Procedure
- Gather a distillation setup (heat source, round-bottom flask, fractionating column, thermometer at the vapor takeoff, condenser, receiver), crude oil sample, balance, graduated cylinders or pipets, timers, and data sheets.
- Measure and record the crude oil volume placed in the distillation flask; weigh the crude-filled flask to determine the crude mass and calculate the crude density.
- Assemble the apparatus securely with clamps; ensure the thermometer bulb sits at the level of the side arm so it reads vapor temperature, not liquid temperature.
- Begin gentle heating to produce a steady distillation drip rate; keep the column insulated if available so separation improves.
- Collect the first fraction over a defined temperature window; record start and end temperatures for the cut and label the receiver with the fraction number.
- Increase heat gradually to obtain subsequent fractions, defining each by its boiling range; avoid overheating or bumping and maintain a moderate distillation rate.
- Continue until no more distillate is obtained or the maximum target temperature is reached; allow heavy residue to cool before handling.
Links
The Distillation of Crude Oil - Science Skool:
Crude Oil Distillation: A Billion-Dollar Lab Experiment - Wheeler Scientific:
📄 Oil Distillation - Jim Lokken: https://www.tsfx.edu.au/resources/P_-_Fract_Dist_-_Prince_William_Sound_RCAC_-_Track_2_9-10_-_Oil_distillation.pdf?srsltid=AfmBOopKYZqoGEq-UjJpkMI77di9lPy6B7Ilh9cVpp67fHaucqRjYjgd
Variations
- Add a proper fractionating column and insulation to compare simple vs fractional distillation performance.
- Characterize fractions further using simple flammability tests by a trained instructor with micro-quantities in a fume hood.
Safety Precautions
- Wear splash goggles, lab coat, and nitrile gloves; tie back hair and secure loose clothing.
- Conduct all work in a fume hood or very well ventilated space; crude oil contains volatile, toxic, and odorous compounds including sulfur species.
- Use an electric heating mantle or regulated hot plate; avoid open flames due to flammable vapors.
- Verify all joints are secure; use Keck clips and support stands to prevent collapse or tipping.
- Keep the distillation rate moderate to prevent flooding of the column and bumping; use boiling chips unless using a spinning band or similar system that prohibits them.
- Ensure cooling water flows before heating; check that the condenser outlet is directed into a secured receiver.
- Do not distill to complete dryness; leave residue to avoid overheating heavy ends that can decompose.
- Label and cap all collected fractions promptly; keep away from ignition sources.
- Dispose of crude residues and fractions as hazardous waste according to local regulations; never pour hydrocarbons down the drain.
Questions to Consider
- What condition must be met for two substances to be separated by fractional distillation? (They must have different boiling points under the same pressure.)
- How does molecular size generally relate to volatility in petroleum fractions? (Lower molecular weight fractions are more volatile and boil at lower temperatures.)
- How can heavy gas oils be converted into gasoline-range products industrially? (By cracking and reforming, often with catalysts and sometimes with hydrogen, to make smaller, higher-octane molecules.)
- What observations might indicate sulfur compounds in a crude or fraction? (Pungent or rotten-egg odors, darker color, heavier character; analytical tests would confirm.)
