Crude oil
Petroleum has formed from prehistoric marine organisms.
Crude oil, also known as petroleum, is formed from the remains of ancient marine organisms that lived in the Earth’s oceans millions of years ago. Here’s a simplified explanation of how crude oil is formed:
Over millions of years, dead marine organisms, such as plankton and algae, sank to the ocean floor. These organisms contained carbon-rich organic matter.
As these organic materials settled on the ocean floor, they were covered with layers of sediment, such as mud and silt. The pressure from the overlying sediment began to compress the organic matter.
Heat and Pressure: The burial of the organic material under sediment layers subjected it to increasing heat and pressure from the Earth’s crust.
Under high temperatures and pressures, the organic matter underwent a series of chemical reactions, forming hydrocarbons that make up most of the crude oil.
Crude oil can be separated into different fractions.
Each fraction collected from the fractionating column represents a range of hydrocarbons with similar boiling points.
Crude Oil Input: Crude oil, a complex mixture of hydrocarbons, is fed into a distillation column.
Heating: The crude oil is heated in a furnace to about 400°C,
turning it mostly into vapour.Distillation Column: This tall column has many trays or plates stacked vertically. It’s cooler at the top and hotter at the bottom.
Separation: As the vapour rises, compounds with higher boiling points condense on the lower trays, while those with lower boiling points continue to rise and condense on higher trays.
Collection: Different hydrocarbons are drawn off at different heights:
Further Processing: Some fractions are further processed or ‘cracked’ to break down larger molecules into more useful smaller ones (e.g., turning heavy residues into gasoline).
Fractionating column.
How the different fractions are used.
Refinery Gases (Top of the Column)
- Components: Methane, ethane, propane, butane.
- Uses:
- Domestic heating and cooking (LPG – liquefied petroleum gas).
- Feedstock for making chemicals and plastics.
Gasoline (or Petrol)
- Components: Mixture of hydrocarbons.
- Uses:
- Fuel for internal combustion engines in cars and some smaller planes
Kerosene (or Paraffin Oil)
- Components: Hydrocarbons with about 10 to 16 carbon atoms.
- Uses:
- Jet fuel for airplanes.
- Domestic heating and lighting.
Diesel Oil (or Gas Oil)
- Components: Hydrocarbons with approximately 12 to 20 carbon atoms.
- Uses:
- Fuel for diesel engines in vehicles, trains, and some boats.
- Industrial heating.
Lubricating Oils
- Components: Larger hydrocarbons.
- Uses:
- Making lubricants for engines and machinery.
- Greases and waxes.
Fuel Oils
- Components: Even larger hydrocarbons.
- Uses:
- Fuel for ships and industrial heating.
- Power generation.
Bitumen (Bottom of the Column)
- Components: Largest hydrocarbon chains.
- Uses:
- Road surfacing.
- Roofing materials.
- Waterproofing.
As you move from the top to the bottom of the distillation column, the hydrocarbon chains get longer, and the boiling points get higher. These fractions cover a broad spectrum of uses in transportation, domestic applications, industry, and construction.
The industry also employs processes like “cracking” to break down heavier fractions into lighter, more valuable products.
CATALYTIC CRACKING.
- Temperature: Around 500°C.
- Pressure: Mild pressures.
- Catalyst: Zeolites, which are comprised mainly of alumina (Al2O3) and silica (SiO2).
What’s obtained?
- Gasoline: Used to fuel cars.
- Diesel: Fuelling cars and larger vehicles.
- Liquefied Petroleum Gas (LPG): Used for cooking and heating.
- Alkenes (like ethene and propene).
These are the building blocks for many chemicals and plastics.
Example using decane: C10H22 → C2H4 + C5H12 + C3H6
⇓
