The Science of Propane

I've always been fascinated by HOW things are made. So when I heard that there are so many petroleum products in use today that are BYPRODUCTS of the refining process, or even NATURALLY OCCURRING, my curiosity was sparked. So I'd like to take this opportunity to share what I've learned by doing a segment every couple of weeks called


This week's segment: PROPANE

Propane is a molecule made of 3 carbon atoms and 8 hydrogen atoms. The fact that it is made of hydrogen and carbon is why you hear petroleum products referred to as "hydrocarbons". Propane kind of looks like this:

So how is it made? Well, propane is naturally occurring. It was created along with several other types of hydrocarbons (such as crude oil, butane, and gasoline) over LONG periods of time, when bacteria, plants, animals, etc. decomposed. That's why they're called "Fossil Fuels" (not because they came from dinosaurs).

Once the fossil fuels have been pumped from the ground, the propane is separated from the other chemicals and refined. Propane belongs to a class of fossil fuels known as liquefied petroleum gases (LPGs) what are known for their ability to be converted to a liquid under relatively low pressures.

In its liquid state, propane is 270 times smaller than it is as a gas, and that allows it to be more easily transported and stored.


Approximately 15 billion gallons of propane are consumed by The United States per year! The largest users are the chemical and manufacturing industries, which use propane to pressurize aerosol cans!


According to,

"Propane manufacture involves separation and collection of the gas from its petroleum sources. Propane and other LPGs are isolated from petrochemical mixtures in one of two ways—by separation from the natural gas phase of petroleum and by refinement of crude oil.

1. Both processes begin when underground oil fields are tapped by drilling oil wells. The gas/oil hydrocarbon mixture is piped out of the well and into a gas trap, which separates the stream into crude oil and "wet" gas, which contains natural gasoline, liquefied petroleum gases, and natural gas.

2. Crude oil is heavier and sinks to the bottom of the trap; it is then pumped into an oil storage tank for later refinement. (Although propane is most easily isolated from the "wet gas" mixture, it can be produced from crude oil. Crude oil undergoes a variety of complex chemical processes, including catalytic cracking, crude distillation, and others. While the amount of propane produced by refinery processing is small compared to the amount separated from natural gas, it is still important because propane produced in this manner is commonly used as a fuel for refineries or to make LPG or ethylene.)

3. The "wet" gas comes off the top of the trap and is piped to a gasoline absorption plant, where it is cooled and pumped through an absorption oil to remove the natural gasoline and liquefied petroleum gases. The remaining dry gas, about 90% methane, comes off the top of the trap and is piped to towns and cities for distribution by gas utility companies.

4. The absorbing oil, saturated with hydrocarbons, is piped to a still where the hydrocarbons are boiled off. This petroleum mixture is known as "wild gasoline." The clean absorbing oil is then returned to the absorber, where it repeats the process.

5. The "wild gasoline" is pumped to stabilizer towers, where the natural liquid gasoline is removed from the bottom and a mixture of liquefied petroleum gases is drawn off the top.

6. This mixture of LP gases, which is about 10% of total gas mixture, can be used as a mixture or further separated into its three parts—butane, isobutane, and propane (about 5% of the total gas mixture).

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