Crude Oil Distillation

Today I did the Crude Oil Distillation experiment. In this experiment, crude oil is placed in a beaker and a Bunsen burner placed underneath it.  The crude oil is then heated until white smoke is seen filling the container. This smoke  exits the container via a condenser and is captured in a test tube.

One of the things that I found interesting about this lab was the fact that there were distinct temperatures at which the white gas clouds form. I would apply heat to the container for a while and then suddenly the white cloud would appear and the temperature increase would level off until the gas cloud had dissipated. The reason for this is when the white gas cloud appeared it meant the boiling point of one of the molecules in the crude oil had been reached and it was starting to boil off.  When something is boiling the energy being applied to it, in this case the heat, is going into the phase change and therefore is not changing the temperature of the solution or gas.

I found it interesting how the colour of the liquids that boiled off changed as the heat required to boil them increased. If the liquid boiled at a low temperature its colour was almost perfectly clear, however if its boiling point was high the colour of the liquid was very dark. This can be seen in the visual representation of colour vs. boiling point in Figure 1.

Figure 1. This is a visual representation of how the colour changed as the boiling point of the substances increased. The higher the boiling point the darker the colour of the substance.

After I distilled the crude oil into eight different test tubes each marked with its boiling point I attempted to light a small amount of each liquid on fire. I did this using a burn tray and a propane torch. I found the lower the boiling point of the substances the faster and more forcibly it would burn.  The substances with high boiling points I could not even light, despite holding an open flame on them for some time. The results from this experiment are illustrated in Figure 2.

Figure 2. This is a visual representation of my results when I tried to light the different substances I boiled off the crude oil. This graph shows boiling point vs. flammability.

I was amazed at the amount of different compounds I could boil out of crude oil and was surplussed at how easy it was to tell the substances apart by their boiling points.  Out of curiosity, I looked up the boiling point of diesel and found it to be 154°C. It would have been cool to know this while doing the experiment and being able to know when diesel was being produced.

-Kyle