Petroleum

Question 1

What are the four stages of fractional distillation?

Answer 1

1) crude oil is vaporised at 350 degrees c
2) vaporised crude oil goes into the fractioning column and rises up through the trays. The largest hydrocarbons don’t vaporise at all because their boiling points are too high, they run to the bottom and form residue.
3) each fraction condenses at a different temperature, and fractions are drawn off at different levels in the column.
4) the hydrocarbons with the lowest boiling points don’t condense. They are drawn off as gases.

Question 2

What is cracking and why do we need it?

Answer 2

People want lots of the light fractions and not so many of the heavier ones, so they ‘crack’ the heavier long chain alkanes into smaller hydrocarbons. It involves breaking C-C bonds. The main way of doing this is catalytic cracking.

Question 3

What is catalytic cracking?

Answer 3

The heavier fractions are passed over a catalyst at a high temperature and a moderate pressure. This then breaks them into smaller molecules. The catalyst cuts costs so that it can be done at a Lower temperature and pressure.

Question 4

What is catalytic cracking useful for?

Answer 4

Making petrol because there is a high percentage of branched hydrocarbons and aromatic hydrocarbons.

Question 5

What kind of octane rating runs more smoothly

Answer 5

High octane rating

Question 6

Is it better to have long alkanes or short branched alkanes in petroleum?

Answer 6

Short branched alkanes.

Question 7

What is crude oil?

Answer 7

A mixture of hydrocarbons. It can be separated into useful ‘fractions’ by fractional distillation