In our other videos we have learnt how fractional distillation is used to separate hydrocarbons into fractions with a similar boiling point. In this video you will learn the names of some of the most important fractions and their uses. As you are now aware, large hydrocarbons have higher boiling points and so are removed at the bottom of the fractionating column. Smaller molecules condense higher up the column. We will now take a look at the fractionating column.
at some of the common fractions as we move down from the top of the fractionating column. Some of the smallest molecules are between one and four carbons in length. This fraction has such a low boiling point that it is still a gas when it is removed from the very top of the fractionating column.
This fraction is known as refinery gas or bottled gas. Bottled gas because it can be stored in bottles under high pressure. You could well have seen bottles of propane or butane running barbecues or heaters in your home and these are examples of the refinery gas fraction. Petrol is between 5 to 7 carbons in length. It is still a fraction of small chain hydrocarbons and therefore these vaporise at a low temperature and are easily ignited.
This makes it useful as a fuel in the internal combustion engine of a car or other vehicles. Naphtha is not such a useful fuel but it is a valuable source of organic molecules which can be cracked to make more fuels or form alkenes. Alkenes can be turned into polymers and polymers can make plastics which are used in our everyday lives.
Kerosene has an important use as a fuel for jet engines, in aircraft and even in some rockets. Kerosene is also called paraffin in some parts of the world. and is a common fuel burnt in paraffin or kerosene lamps used for lighting Diesel is the next fraction it is a common fuel in cars, vans and lorries it is not as volatile as petrol and instead of spark ignition it ignites under compression below diesel are the residue fractions Fuel oil is a fuel used in power stations and ships lubricating oil which sticks to surfaces and reduces friction and protects from rust. And finally waxes which along with the oils can be used for polishing surfaces. The very bottom fraction is bitumen.
This is a thick black adhesive used on roads either as the surface finish or combined with stone chippings to create a solid resistant material. It can also be used to cover roofs, due to its waterproofing properties. All these fractions are separated from the crude oil mixture.
To try and explain the importance of crude oil consider these facts. There are estimated to be over 1 billion cars in the world of which many will be using petroleum as their fuel. There are many million flights each year each burning kerosene fuel. Not forgetting the mass of plastic that is made and used each day for products and their packaging. Even the bitumen used to surface and resurface roads around the world.
As you can see, crude oil contains many useful products that just need to be separated from the crude oil mixture. Now, at the end of this lesson, you should have a better understanding of why crude oil is such a valuable resource and the use. of each of the main fractions.