Oil Refinery Notes

Crude oil formation occurred over millions of years.
Tiny sea plants and animals died and were buried on the ocean floor.
Over time, they were covered by layers of silt and sand.
The remains were buried deeper and deeper.
The enormous heat and pressure turned them into oil and gas.
Today, drilling occurs through layers of sand, silt, and rock to reach the rock formations containing oil and gas deposits.

Many useful materials can be produced from crude oil.
Crude oil can be separated because it is a mixture.
The different components of a mixture have different properties which we can use to help separate them from each other.
It can be separated into different fractions using fractional distillation, and some of these can be used as fuels.

Fractional distillation separates crude oil into different fractions based on boiling points.
Process:
- Oil is heated to about $370°C$ and pumped into the bottom of a fractionating column, where it vaporizes.
- The column is very hot at the bottom but much cooler at the top. As the vaporized oil rises, it cools and condenses.
- Heavy fractions (containing large molecules) have high boiling points and condense near the bottom of the column.
- Lighter fractions (containing small molecules) have lower boiling points and condense further up the column.
Fractions and their uses/properties:
- Gases (1 to 4 Carbon atoms): Less than $40°C$ , Liquified petroleum gas, Carbon black, Petrochemicals.
- Gasoline (5 to 12 Carbon atoms): $40°C$ - $200°C$ , Natural gasoline useful as a motor fuel, industrial solvents, Petrochemicals, Aviation gasoline, Motor gasoline, Naphthas, Solvents.
- Light distillates (12 to 16 Carbon atoms): $200°C$ - $300°C$ , Petrochemicals, Kerosene.
- Intermediate distillates (15 to 18 Carbon atoms): $250°C$ - $350°C$ , Refined oils, Gas oil, Petrochemicals, Heavy furnace oil, Diesel fuel oil.
- Heavy distillates (16 to 20 Carbon atoms): $300°C$ - $370°C$ , Lubricating oil, Grease, Heavy oils, Wax, Cracking stick, Petrochemicals, Lubricating oil, Fuel oil.
- Residues (More than 20 Carbon atoms): Greater than $370°C$ , Petroleum jelly, Road oils, Asphalt, Petroleum coke, Heating and cooking fuel, Starting material for plastics, gasoline additives.

Higher demand for smaller fractions exists.
A process called cracking is used to break the molecules in the larger fractions into smaller molecules.
Around 75% is converted into petrol and diesel.

Heated to $500°C$ .
Uses Aluminium oxide as a catalyst.
Produces a mixture of alkanes and alkenes (C=C bonds).
Effectiveness can be improved by adding hydrogen in a process called hydrocracking.
Compromise between the cost of the process and the price of the product.

A series of processes to remove corrosive or polluting contaminants.
Can also be used to improve how the product works – increasing octane rating of car fuels.

There is a legal requirement to limit the amount of sulfur in car fuels – to limit damage to air quality.
The removal of sulfur improves the effectiveness of catalytic converters.
The sulfur can be taken and used to create sulfuric acid.

Used to turn straight chain alkanes into cyclical rings.
Catalytic reforming to make benzene: $CH2-CH2-CH2-CH2-CH2-CH3 \rightarrow C6H6 + 4H_2$

Is a measure of a fuels resistance to detonation.
Scale of 0-100 – higher is better.
Low octane fuels cause “knocking” where the fuel will detonate without input from the sparkplug causing damage to the engine.
Small chains have a lower octane rating.
Chains that have rings or branches have a higher rating.

Catalytic reforming to increase the amount of carbon rings.
Alkylation – used to create high octane fuels without carbon rings by creating alkanes with branched chains.

P4. Describe the three main steps of refining oil.
- Separation – fractional distillation
- Conversion - cracking
- Treating – desulfurization and reforming
M4. Explain how cracking and reforming help to balance the supply and demand of different products of crude oil.
D1. Define what is meant by “Octane Rating” and describe the advantages of using fuels with a high octane rating. Describe how the octane rating of fuels can be increased.