Crude oil

1. Physical Processes in Oil Refining
Fractionation (or fractional
distillation) is the process of
physically separating the
components of a mixture of
compounds based on the
differences in their boiling points.
The compounds with the lowest
boiling points are made up of the
smallest molecules.
They have fewer electrons and
weaker London forces compared
with larger molecules.

2. To get to the next level, the
vapours are forced through
condensed liquid in each tray.
When the temperature of the
liquids in a tray is below the
boiling point of a particular
compound, that compound
condenses and is collected.

3. Another common physical process is solvent extraction – the addition
of a solvent to selectively dissolve and remove a specific compound.

4. Chemical Processes in Oil Refining
Fractionation alone does not produce enough of the hydrocarbons that
are in market demand, so further chemical refining is needed.
Here, the gasoline
fraction is cracked, then
fractionated again.

5. Cracking
Cracking is a chemical process where large molecules are broken down
into smaller molecules.
• thermal cracking – using high temperatures and pressures
• catalytic cracking – catalyst reduces the need for extreme temperatures
and pressures
larger molecules → smaller molecules + carbon
Hydrocracking combines catalytic cracking and hydrogenation.
larger molecules + hydrogen → smaller molecules
Remember the Cracker Cats?

6. Catalytic Reforming and Alkylation
aliphatic molecule → aromatic molecule + hydrogen
Catalytic reforming is the chemical process that converts aliphatic
molecules in a gasoline fraction to aromatic gasoline molecules.
Alkylation (or isomerization) is the process of converting an aliphatic
molecule into a branched isomer.
aliphatic molecule → more branched molecule

7. Complete Combustion
A hydrocarbon (fuel) reacts with oxygen to produce carbon dioxide and
water vapour as the only chemical products.
Incomplete Combustion
A hydrocarbon (fuel) reacts with oxygen to produce products
other than carbon dioxide and water vapour, such as carbon
monoxide and carbon (soot).
hydrocarbon + (excess) O2(g) → CO2(g) + H2O(g)
hydrocarbon + (insufficient) O2(g) →
x C(s) + y CO(g) + z CO2(g) + H2O(g)

8. The larger the excess of oxygen available, the smaller the amount of
carbon monoxide and soot that is produced.
When any hydrocarbon burns, complete and incomplete combustion
reactions happen simultaneously.