A tall fractionating column is fitted above the mixture, with several condensers located at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.
Crude oil is a mixture of hydrocarbons, or compounds that only contain carbon and hydrogen. Crude oil is a non-renewable resource that provides fuel for cars. To refine petroleum means to separate it into groups with molecules of the same size, which can be carried out by fractional distillation. When petroleum evaporates, its vapours condense at different temperatures in the fractionating column. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms and a similar range of boiling points.
Refinery gas is a non-condensable gas that consists mainly of hydrogen, methane, ethane and olefins. It has the smallest molecules and the lowest boiling point among the fractions obtained by distillation. They are very volatile, have low viscosity, and ignite easily.
Gasoline is used as fuel for cars. Naphtha is used as the starting point or feedstock for chemicals. It is mainly used to make plastics or as a solvent for paints, rubber, and industrial extraction industries. Kerosene is used as jet fuel or fuel for oil stoves and lamps. Diesel is used as fuel for diesel engines. Fuel oil is used as fuel for ships and home heating systems. Lubricating oil is used as lubricating oils, waxes, and polishes. Bitumen, also known as asphalt, is a dense and viscous residue that is used for making roads.
Down the fractionating column, the size of the molecules, the boiling point, and the viscosity increases. The lowest fraction is the least volatile and least flammable.
Refining petroleum in the lab
Heat the petroleum. Compounds with smaller, lighter molecules evaporate first, since the weaker molecular forces require less energy to free. The thermometer reading rises, and vapours condense in the cool test tube. Once the thermometer reaches 100 degrees celsius, replace the first test tube with an empty test tube. The liquid in the first test tube is the first fraction. Collect further fractions, replacing the test tube at 150, 200, 300 degrees celsius.