Overview
This lecture explains how crude oil, a non-renewable fossil fuel composed mainly of hydrocarbons, is separated into useful components through fractional distillation.
Crude Oil: Formation and Properties
- Crude oil is a fossil fuel formed from ancient biomass, mainly plankton, buried under mud millions of years ago.
- High heat and pressure over time converted this organic matter into crude oil, which accumulates in rock layers underground.
- Crude oil is a finite (non-renewable) resource that will eventually run out if used unsustainably.
- The main compounds in crude oil are hydrocarbons, mostly alkanes (chains of carbon and hydrogen).
Fractional Distillation of Crude Oil
- Fractional distillation separates crude oil into different components based on their boiling points.
- The process starts by heating crude oil until most of it vaporizes.
- The vaporized mixture enters a fractionating column, which is hottest at the bottom and cooler towards the top.
- Hydrocarbons condense back into liquids when they reach a region cooler than their boiling point.
Fractions and Their Uses
- Long-chain hydrocarbons (high boiling points) condense first at the bottom (e.g., bitumen for roads, heavy fuel oils, lubricants).
- Shorter-chain hydrocarbons (lower boiling points) rise higher and condense further up the column (e.g., diesel, petrol, kerosene for fuels).
- Very short-chain hydrocarbons remain gases throughout (e.g., LPG—liquefied petroleum gas, mainly propane and butane).
- Shorter-chain fractions are more flammable and make better fuels, while longer chains are less useful as fuels.
Additional Uses and Petrochemicals
- Substances obtained from crude oil are called petrochemicals and can be used as raw materials (feedstock) in industry.
- Petrochemicals help make solvents, polymers, detergents, and lubricants.
Key Terms & Definitions
- Crude oil — A natural, finite mixture of hydrocarbons formed from ancient organic matter.
- Alkanes — Saturated hydrocarbons containing only single bonds between carbon atoms.
- Fractional distillation — A separation process based on differences in boiling points.
- Fraction — A group of hydrocarbons collected at a certain level in the distillation column.
- Bitumen — A long-chain hydrocarbon used for surfacing roads.
- LPG (Liquefied Petroleum Gas) — A fuel containing mostly short-chain alkanes like propane and butane.
- Petrochemicals — Substances derived from crude oil used as industrial feedstock.
Action Items / Next Steps
- Review the process of cracking to understand how long-chain hydrocarbons are converted into shorter ones.
- Study uses and properties of different fractions obtained from crude oil.
- Read more on the environmental impact and sustainability of using fossil fuels.