• Paraffins

  • There are two kinds of paraffins: N (normal) paraffins and Isoparaffins. N-paraffins have carbon atoms that will form chain-like molecules. Isoparaffins are similar to N-paraffins except they have offshoots or branches of carbons from the chain. It was first commercially produced in 1867, paraffin wax is known for its colorless, or white appearance when solid; however when it is a liquid it turns mostly translucent. It’s melting point ranges from 120 to 150° F. However, there isn’t just one type of paraffin wax, common types of paraffins in diesel fuel are: decane, n-pentadecane, methyltetradecane, eicosane, and methylnonadecane. Because paraffins have a straight molecular structure, paraffins are the main reason why diesel fuel will eventually begin to turn into a solid state, a process known as gelling, a big problem for diesel engines. At 32 ° F the paraffin in the fuel will begin to cloud the fuel, and at 15 to 10° F it will begin to “gel” and make a diesel engine unable to run. Kerosene can be added to the fuel beforehand, reducing the fuel’s viscosity and making it much less prone to gelling.

Chemistry’s Role

None of the components in diesel fuel are individually made. Diesel fuel could be seen as something that naturally occurs as it is extracted from the earth (oil), but the final product, diesel fuel, is a man made product. The crude oil that is extracted from the earth is put in a distillation tower, the oil is then heated up to over 400°C. This begins a process, known as separation, that separates different components that have different boiling temperatures. As you go up the distillation tower the boiling temperature is cooler and the refining process is more tedious. Diesel fuel is created at the lower end of the tower, then comes kerosene, gasoline, butane, and propane. These compounds are then collected by a distillation plate, which takes that compound away and stores it in a storage tank. Chemistry plays a big role in this process, as scientists need to know the chemical composition of each mixture (ex. how many hydrogen and carbon atoms are in each compound) that is being separated at each boiling point. They need to know where to put the distillation plates in the tower to collect each compound effectively and efficiently.
Background Research

Diesel’s most obvious differences are its physical properties. Diesel fuel is sometimes called “diesel oil”, because of how oily it is, it smells different, it’s heavier and more much more oily, it evaporates much slower than gasoline, and has a higher melting point, ranging from 200 – 380°C. Chemically, diesel fuel contains more carbon atoms than gasoline does. Gasoline usually being C9H20 and Diesel usually being C12H23.

• How is it Made?

  • Crude oil is placed into a distillation tower and the liquid is then heated to over 400°C.

  • Once the liquid begins to heat up, different chains of hydrogen and carbon atoms (hydrocarbons) begin to separate.

  • Diesel fuel begins to emerge between temperatures of 200°C and 380°C. Which is collected on distillation plates and siphoned off to a diesel holding tank.