Hydrocarbon Cracking & Why It Is Done | Organic Chemistry | Chemistry | FuseSchool

Summary

This video explains the process of cracking, which breaks down long-chain hydrocarbons into smaller, more useful molecules. The demand for small-chain hydrocarbons as fuels is high, but fractional distillation often leaves an excess of large hydrocarbons. Cracking helps address this by creating smaller alkanes and alkenes, useful in fuels and plastics. The process can be done via thermal cracking (high temperature and pressure) or catalytic cracking (lower temperature, using a catalyst). The video highlights that catalytic cracking is more commonly used in industry due to its efficiency.

Takeaways

• 😀 Cracking is the process of breaking down large hydrocarbons into smaller alkane and alkene molecules.
• 😀 Smaller hydrocarbons are in high demand as they make better fuels, used in cars, airplanes, lorries, and home heating.
• 😀 Crude oil contains hydrocarbons with different carbon chain lengths, with smaller ones being more volatile and useful as fuels.
• 😀 After fractional distillation, the supply of long-chain hydrocarbons exceeds the demand, which is where cracking comes in.
• 😀 Cracking can produce alkenes, which are valuable for manufacturing plastics.
• 😀 Cracking occurs through thermal cracking or catalytic cracking.
• 😀 Thermal cracking uses high temperatures (up to 750°C) and high pressure (70 atmospheres) to break the bonds in large hydrocarbons.
• 😀 Catalytic cracking is the preferred industrial method, using lower temperatures (around 500°C) and a zeolite catalyst.
• 😀 The random nature of cracking means large hydrocarbons can break down into various combinations of smaller molecules (e.g., C12H26 into octane and butene or decane and ethane).
• 😀 Catalytic cracking produces molecules with 5-10 carbon atoms, which are particularly useful in petrol production.

Q & A

What is the purpose of the cracking process?

The cracking process breaks down large hydrocarbons into smaller alkanes and alkenes, which are more useful as fuels and in the manufacture of plastics.

Why are smaller hydrocarbons more useful than larger ones?

Smaller hydrocarbons have lower boiling points, are more volatile, and are easier to ignite, making them more useful as fuels compared to larger hydrocarbons.

What is the main challenge with the supply of hydrocarbons after fractional distillation?

After fractional distillation, the supply consists mainly of large chain hydrocarbons, whereas there is a high demand for smaller chain hydrocarbons, which are better suited for use as fuels.

What are the two types of cracking methods mentioned?

The two types of cracking are thermal cracking and catalytic cracking.

What happens during thermal cracking?

During thermal cracking, large hydrocarbons are heated to temperatures up to 750°C and exposed to high pressure (70 atmospheres), which causes the bonds between carbon atoms to break and form smaller molecules.

How does catalytic cracking differ from thermal cracking?

Catalytic cracking involves heating large hydrocarbons to around 500°C and passing them over a zeolite catalyst. This method requires lower temperature and pressure and is more efficient for producing molecules useful in petrol.

What type of molecules are typically produced by catalytic cracking?

Catalytic cracking typically produces molecules with chain lengths between 5 to 10 carbon atoms, which are very useful in petrol.

Why is catalytic cracking the preferred method in the industry?

Catalytic cracking is preferred because it uses lower temperatures and pressures and produces more molecules that are useful in petrol.

What is an example equation showing a cracking reaction?

An example equation is the breakdown of C12H26 into octane (C8H18) and butene (C4H8). Other possible products could include decane and ethane, or butane, pentane, and propene.

What is the significance of the alkenes produced during cracking?

The alkenes produced during cracking, such as butene and ethene, are important because they can be used in the manufacture of plastics.