Diagram of the formation of crude oil and natural gas
Crude oil reservoirs are generally found in areas where there is or was a saline lake of ocean.
Fossil fuels are often referred to as stores of the sun’s energy. This is true in some respects. Energy as we know it can never be destroyed just transferred into different types The plants and animals did get their energy from the sun. The sun also contributed to the heating of the surface, transforming the organic material to oil. The oil we use is a result of the energy given to the animals that have died, from the sun. The sun also helped in the disintegration of the animal after is dead; but what people mean when they say that fossil fuels are stores of the sun’s energy is reinforcing the point of saying that the plants and animals that make the oil got their energy from the sun.
Heat and power will be produced as the chemical potential energy stored in the fossil fuel when Crude oil or any of the fossil fuels are burned. This comes from the energy that was originally sun energy stored in the living species (that under pressure and temperature became the fossil fuels) gets transferred into heat energy, light energy and power.
Useful products from crude oil
Crude oil is the raw material that is then refined to get several beneficial substances. We find this resource so valuable to the compounds that it contains.
To understand how other products are taken from crude oil, one must examine the composition of the oil. Crude oil is a mixture of hydrocarbons (molecules that contain hydrogen and carbon in various structures)
The compounds in crude oil are separated by fractional distillation. It uses the physical property of boiling points of the hydrocarbons to separate them. Smaller hydrocarbons have lower boiling points than big hydrocarbons and so they move further up the column, where constant vaporization and condensation occur as hydrocarbons rise. The constant condensation and vaporization purify the liquid. A temperature gradient is uses and the different heights in the column correspond to the different temperatures. . The fractions are used for different purposes and this depends at which temperature they are collected. The fractions are so important because they contain different hydrocarbons of different molecular mass.
Many useful products come out of distillation such as:
Fractional distillation is started by putting crude in a fractional column and a furnace is placed at the bottom and it heats up the crude oil. Compounds with lower boiling points evaporate and rise to the top of the column and are collected there. In this image we see different parts of a refinery that are used to further convert fractions to gasoline, ethane and hydrogen. The fractional column is present with a reformer, alkylation unit, cracking units and a Coker.
Once the crude oil has been fractionally distilled, the fractions (stated above in the table) can be converted into more useful chemicals by the processes known as cracking, using the reformer, the alkylation unit and a Coker. Cracking is used to break down large hydrocarbon molecules into smaller ones so that they change their state and become more useful. Cracking is generally used to break down oils into motor oil, jet fuel or diesel fuel as illustrated by the diagram.
There are two main forms of cracking, thermal decomposition: where the long chains of hydrocarbons are heated till vaporized. Or there is catalytic cracking, where a catalyst is used to break the hydrocarbon as well. Pollution emitting factories, use catalysts to break down the sulphur dioxide into sulphur and oxygen an example of cracking
In gasoline (a result of cracking crude oil) they must be having machines to take out impurities. In these machines, compounds are changed into other compounds. E.G
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C2H4+H2 C2H6
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C5H10+(catalyst) C4H10+C
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C5H10+(catalyst) C3H6+C2H4
These equations show the breakdown of hydrocarbons into smaller safer hydrocarbons. It can be seen in the second equation how Pentene gets broken down (with the help of a catalyst) into butane and carbon.
Gasoline is a product of crude oil that is used every day by cars. In order to make it better, experts investigated how to make the gasoline smoother so that the car would run better. They realized that the answer was in the Octane number. Gasoline needs a certain amount of octane molecules and a certain amount of heptane molecules. They realized that under compression heptane spontaneously ignited and octane didn't, so in altering the composition of gasoline and setting the ratio of octane to heptane as 8 to 1 they were able to increase the quality and quantity of petrol.
Future developments:
As it was mentioned before, our world runs on fossil fuels, and it is this dependency that is causing many problems, such as polluting our atmosphere and due to it being a non-renewable energy source, it is quite costly and causes economic problems.
Pollutants such as Nitrogen Oxides, Carbon Monoxide, Sulphur Dioxide and lead compounds, lead to the hole in our ozone layer as well as affecting millions, by polluting the air we breathe and giving people lung cancer and other problems.
This concept was laughable a few years ago, but now people are standing up and acknowledging that this is a big problem. This is another problem with the combustion of fossil fuels. Yet demand keeps on increasing and the refineries are finding it hard to keep up with demand. The slower and less available oil becomes, the higher the prices are, a problem that we are faced with now.
Fossil fuels are known to be non-renewable because they took millions of years to form, and at the rate that they are getting used up there will not be left to sustain us till more is formed, this being said, there are other alternatives that have been looked into.
Alternatives such as biodiesels, natural gas, vegetable oils, hydrogen fuel cells, bioalcohols and nuclear power have been talked about.
The problems with using natural gas, is that it too is finite just as fossil fuels are, though the concept of compressing natural gas (CNG) is a clean energy efficient fuel.
Compressed air can also be used and is compressed at around 1/10 of the price of any fossil fuels.
Hydrogen fuel cells are the new way forward; a fuel cell is an electrochemical energy conversion device. It converts the chemicals in it to hydrogen oxygen and water and produces electricity; in this way it causes no pollution, as there is a constant flow of chemicals the cell never dies.
Alternatives to polluting fossil fuels are being looked into, and are an upcoming field as researchers are only beginning to see how pollution is truly effecting our environment.
Conclusion
Crude oil, amongst other things is something we, as teens, take for granted. We do not think about how it is affecting the planet we only care that it helps to take us where we need to go. In writing this paper, I have realized how much money is put into producing this finite resource, and I am more aware of the processes used to refine crude oil and why hydrocarbons are so important in today’s world. I have also drawn from this product how dependant the world is on crude oil and fossil fuels in general. The science behind this topic has made this an interesting theme to cover.
WEBSITES
www.bbc.co.uk-( fractional distillation image)
www.wikipedia.com-search: oil refinery, petroleum
www.google.com-images-crude oil, fractional distillation
http://www.elmhurst.edu/~chm/onlcourse/chm110/outlines/distill.html
http://www.dit.ie/DIT/science/chemistry/rsccomp/competition00/distillation/topframe.html-( BP data table)
www.howstuffworks.com-crude oil
FOTOS
Books:
How things work – national geographic: john Langone
Explaining chemical processes 4th edition: Kenneth A. Solen
I had help from Naveen das (my brother, University Cambridge, UK, reading 2nd year Chemical engineering) and Carmen Marin from the year above as well, as they both help with organization and explaining difficult concepts such as cracking.
