Propane, Butane, Pentane: A Refinery Operator's Quick Reference

If you work in a refinery, I recommend memorizing a few saturation temperatures of light hydrocarbons.

If you look around a typical refinery, you'll see that a lot of energy is used to separate hydrocarbons with three, four, and five carbon atoms.

Propane, Butane, and Pentane

The straight-chain versions of these molecules are called propane, butane, and pentane.

Sometimes, you'll see the type of molecule abbreviated as "CX" where "X" represents the number of carbon atoms.

For example, "C4" is referring to hydrocarbons with four carbon atoms such as butane and isobutane.

A Note on Looking Things Up

Instead of memorizing, you could always just look up the saturation point, but I just think it's helpful to have points of reference already in your head.

If you do choose to ask your preferred AI, I recommend asking for a calculation using an equation of state (such as Peng-Robinson) instead of asking for a saturation temperature at a certain pressure.

A Quick Example

If it's 60 degrees F outside, what is the lightest hydrocarbon of propane, butane, and pentane that will stay as a liquid?

The answer is pentane (C5). The boiling point of butane is right around the freezing point of water, which is how I remember it. Pentane will not boil until about 97 degrees F.

Rules of Thumb

Also, as a reminder, work is not school. Calculations accurate to the hundredths place are rarely required for practical troubleshooting. Quick estimates and rules of thumbs are not only acceptable, but highly encouraged!