Fractional distillation

What is crude oil?

A mixture consisting mainly of alkane hydrocarbons which can be separated into different fractions. It is made from the breakdown of organic matter over millions of years.

Why is crude oil described as non-renewable?

-takes millions of years to form
-being depleted faster than it can be replenished

What are the environmental impacts of burning crude oil?

• greenhouse gases are released (e.g., CO2)

• impurities in crude oil like sulphur react with oxygen to form sulphur dioxide (acid rain)

What is the purpose of fractional distillation?

To separate hydrocarbons in crude oil into different, useful 'fractions' based on boiling point.

How does fractional distillation work?

• crude oil is vapourised before entering the fractionating column

• fractionating column is hot at the top and cool at the bottom

• oil vapours will condense at different points along the column according to boiling point

What type of hydrocarbons condense at the top of the fractionating column?

\-small hydrocarbons with a short chain length and low b.p

\-low viscosity

\-high flammability

\-e.g. gasoline and naphtha

What type of hydrocarbons condense at the bottom of the fractionating column?

-large hydrocarbons with a long chain length and high b.p
-high viscosity
-low flammability
-e.g., fuel oil and diesel

What are the fractions of crude oil in order of highest to lowest b.p (up the column)?

fuel oil, diesel oil, kerosene, naphtha, gasoline (petrol)
bitumen residue is found at the very bottom