What is distillation?
Distillation is a way to separate mixed liquids by utilizing the different boiling points of the liquids. We can distill a mixture by heating it to a temperature which lies between the boiling points of the two liquids. The liquid with the lower boiling point here evaporates; while the other liquid remains in liquid form in the flask. When the first liquid is in gaseous form, it is transferred to another container where it cools down and condenses. Thus it goes from gas phase back to the liquid phase. The result is two containers -with the two liquids that are now separated from each other.
Distillation of alcohol
We are now looking at a concrete example where we want to distill a mixture of water and ethanol. Ethanol is an alcohol with a boiling point of 78.4 ° C and water boils at 100 ° C. It is therefore necessary to heat this mixture to a minimum of 78.4 ° C, but the temperature must not exceed 100 ° C. Basically, it is a good idea to choose a temperature that is just above the boiling point of ethanol – for example 80 ° C.
When the mixture is heated to about 80 ° C (either using a hotplate or a bunsen burner), the ethanol will begin to evaporate and this gas will move through the distillation head and into the cooler. The cooler is equipped with water that transforms the gas back to the liquid phase. The liquid then condenses on the glass in the cooler and then drops into a beaker that collects the distillate which is the ethanol. As the temperature of the mixture is not higher 100 ° C, the water remains in liquid form. However, it should be remembered that water at 80 ° C-90 ° C can also evaporate to a lesser extent, thus diluting the distilled ethanol. One can get a cleaner product by distilling the distillate of the first distillation.
Distillation of crude oil
Distillation is mainly used in refining crude oil on the so-called oil refineries. Here, however, the principle is typically extended to fractional distillation. In this type of distillation, crude oil is first distilled at about 400 ° C, and that which does not evaporate, is sorted off and used for, for example, asphalt. After that, a new distillation is made on the rest of the crude oil, and in that way it is possible to separate the different ingredients of the crude one by one by repeated distillations, lowering the temperature for each distillation. This gives the pure products such as diesel, petroleum, butane and propane. In practice, after the fractional distillation, a large number of refining processes of the individual products will take place before the finished products are obtained.