The means of transport that we use today are powered very differently to those that we have discussed in the previous section. The road vehicles that we all use everyday are all powered thanks to an internal-combustion engine in which fuel is burnt inside the engine rather than in a separate furnace, such as in the steam engine model. The first internal combustion engine was patented by Nikolaus Otto in 1876 and used gas as the combustion fuel. Advances in the oil industry in the late 19th Century meant that the Otto engine begun to use liquid fuel, Petroleum (or Rock oil), as its main source of power. The modern petrol engine is a revised version of the Otto engine.
Good question! - The Rock oil is a naturally found mineral oil that can be pumped from underground oil reservoirs where it had gathered over millions of years. The oil is actually thought to be the remains of living organisms that have undergone long periods of high heat and pressure due to many layers of sediment building up over time. The resulting oil seeped through porous rocks to an area of impermiablity where the oil is often held under pressure beneath a layer of natural gas until it is mined. Below is a pie chart illustrating worlds main crude oil producers as of 1996. These figures have changed over the past few years (for example Russia is now the worlds leading producer) but the data was the only official source available.
Petroleum has no value to us in its crude form and so must be refined by fractional distillation which is the separating of the components of the oil by their different boiling points. The oil pumped from the ground is mainly made up of straight chain and branched hydrocarbons, called aliphatic hydrocarbons, which contain of a lot of energy and so can be used in combustion reactions (which we are interested in in this case). The main hydrocarbon chains which are contained in the crude oil are:
These hydrocarbons are separated in a fractional distillation column into which the crude oil is pumped in through the bottom, where the heat is the greatest. The very longest carbon chains settle as liquids at the bottom of the column and are pumped off as bitumen which is then used for tarring roads and roofs. Bitumen usually has Hydrocarbon chains in excess of 80 carbons long and is a very viscous liquid.
As the size of the Hydrocarbon chains decrease so does the boiling point of the fraction so the smaller fractions are gaseous to a higher point in the column, until they reach a point where it is possible for them to condense back to liquid form where they are pumped out. Below is a diagram of the fractional distillation column showing the different levels at which the fractions are recovered.
As you can see from the diagram the fraction that we are mainly interested in is the gasoline fraction which contains between 5 and 10 carbon chains and has a boiling point of around 70°C. This fraction is contains the fuel that we need to power our road vehicles. However the fractions beneath the gasoline in the column, ie. the heavy gas fraction, can sometimes be modified so that the Hydrocarbon chains are broken into smaller ones around the same size of the Gasoline fraction. This process is called catalytic cracking as it is done using a catalyst such as zeolite, bauxite and aluminum hydrosilicate.
There are two main types of catalytic cracking - Fluid catalytic cracking and Hydrocracking.
After the hydrocarbons have been cracked then the products undergo further fractional distillation to remove any impuities from the oils.
Now we can go for a spin!!!
Move on.Adam Parks.