Crude oil is one of the three main fossil fuels (along with natural gas and coal) – it is also known as petroleum. It is formed from millions of microscopic plants and animals that have been buried in sediment and subjected to high temperatures and pressure for a long time. It consists of a mixture of hydrocarbons with a range of sizes and boiling points.
It is the raw material for a host of everyday products from fuels such as petrol and diesel, lubricating oils, tar (bitumen), wax and grease. About 90 million barrels of it are used worldwide each day. A barrel is 159 litres (42 US gallons). It is estimated that there are about 35 years of crude oil reserves remaining. However, this has been the figure for well over 35 years! Our ability to reach reserves of oil improve with time meaning that the estimate has stayed constant despite our increasing demand. New technologies such as fracking also increase our ability to find and extract fossil fuel reserves.
The environmental impacts of using crude oil include oil slicks, acid rain and global warming. Alternatives to fossil fuels include wind turbines, hydroelectric dams and solar panels.
Petrol and other parts of crude oil are extracted by fractional distillation. I wrote about the fractional distillation of liquid air here. The crude oil is heated and pumped into the base of a fractionating tower under pressure. The bottom of the tower is about 360 °C and the top of the tower closer to room temperature. Most of the components of the oil rise up the column as vapour. The longest chain hydrocarbons, with the highest boiling points, remain a liquid and can be removed from the base of the column. As the vapour rises up through the fractionating tower different hydrocarbons condense at different levels. Shorter chain molecules have lower boiling points than longer chain ones.
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I have written about hydrocarbons quite often on the blog. You should probably read Hydrocarbon Explosions and Chimneys Swept for good measure. For a little mathematical challenge, read Breaking The Bonds.
Questions…
- Under what circumstances would you use simple distillation? (I assume you have read this.)
- I put out some empty 75 cl champagne bottles to be recycled this morning. How many would I need to completely hold one barrel of crude oil?
- The distillation of air produces several products. Name one and an industrial use it has.
- Methane is the simplest alkane with only one carbon atom. Name another alkane and state how many carbon atoms it has.
- Name a substance produced when a hydrocarbon burns in an inadequate air supply.
- What is naphtha?
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