Propane
Overview
Propane (PRO-pane) is a colorless gas with an odor of natural gas. It occurs naturally in petroleum and natural gas. It belongs to the alkane family of organic compounds, compounds consisting of only carbon and hydrogen, all joined by single bonds. Propane is commonly sold as fuel, often available in a liquefied form known as liquid propane gas, or LPG.
Key Facts
Formula:
C3H8
Elements:
Carbon, hydrogen
Compound Type:
Alkane; saturated hydrocarbon; organic
State:
Gas
Molecular Weight:
44.10 g/mol
Melting Point:
−187.63°C (−323.73°F)
Boiling Point:
−42.1°C (−43.8°F)
Solubility:
Slightly soluble in water; soluble in ethyl alcohol, ether, benzene
How It Is Made
Propane is most widely available as a component of petroleum and natural gas, fossil fuels that formed many millions of years ago when marine organisms died, sank to the bottom of seas, and were eventually buried under massive layers of debris. The decay of those organisms without access to oxygen resulted in the formation of so-called fossil fuels: natural gas, petroleum, and coal. All fossil fuels are complex mixture of some free carbon and a very large variety of hydrocarbons. Natural gas, for example, consists primarily of methane, ethane, and propane.
Roughly half of all the propane produced in the United States comes from petroleum gases produced during the refining of crude oil and half from natural gas. The mixture of gases from either refined petroleum or natural gas is liquefied and then allowed to boil off, changing back to the original gases. Each gas boils off at its characteristic boiling point and can be captured and removed as it escapes from the liquid mixture. Often, propane is allowed to remain in its liquid state and is then made available as liquid propane gas (LPG). LPG is easier to store and transport than is gaseous propane.
Interesting Facts
Propane's natural odor is so faint that it can often not be detected when leaks occur. To avoid the problem of unexpected fires and explosions, manufacturers usually add a compound with a strong odor, such as ethanediol, to make leaks more noticeable.
Common Uses and Potential Hazards
About 100 billion liters (27 billion gallons) of propane were produced in the United States in 2004. The largest portion of that output (45 percent) was used for space heating, water heating, the operation of appliances, and other purposes in commercial and residential buildings. Propane has many advantages as a fuel:
- It produces less pollution than gasoline or coal.
- Propane water heaters are less expensive to purchase and operate than are electric water heaters, and they can heat more water than electric heaters.
- Propane fireplaces are less expensive and less polluting than wood-burning fireplaces, and they can be turned on and off with a switch.
- Many professional cooks prefer propane stoves to electric stoves because they heat instantly and are easier to control.
- Propane dryers take three-quarters of the time of electric dryers to dry the same amount of clothes.
- Propane appliances continue to operate during power outages, unlike electric appliances.
The second most important application of propane is in the petrochemical industry where the compound is used for the production of a host of organic chemicals, primarily ethylene and propylene. Ethylene and propylene are two important compounds used in the production of plastics and other kinds of polymers. They ranked third and sixth on the list of the largest volume chemicals produced in the United States in 2004.
Farm use and industrial use follow next in importance, each accounting for about 7 percent of the propane used in the United States each year. On farms, propane is used to operate farm equipment and irrigation systems, to dry crops, and to help control weeds. In industries, the compound is used for space heating, for soldering, for cutting and treating metals, and as a fuel for fork lifts. Finally, a relatively small amount of propane is used as a fuel for cars, trucks, and other vehicles. Many people argue that more vehicles should be built to operate on propane because the gas produces fewer pollutants, reduces wear and tear on engines, and burns more efficiently than gasoline. So far, however, propane-powered vehicles have not become very popular in the United States. In the early 2000s, there were about 350,000 propane-powered vehicles in the United States and about 4 million in the world.
In moderate amounts, propane presents no health hazards to humans. In larger quantities, it may have a narcotic effect, producing drowsiness, disorientation, headaches, and confusion. The gas is both flammable and explosive and requires special care when being used.
Words to Know
One of a family of organic compounds consisting of only carbon and hydrogen, all joined by single bonds. A compound consisting of very large molecules made of one or two small repeated units called monomers.For Further Information
"Facts about Propane." National Propane Gas Association. http://www.npga.org/files/public/Facts_About_Propane.pdf (accessed on November 3, 2005).
"Propane." Air Liquide. http://www.airliquide.com/en/business/products/gases/gasdata/index.asp?GasID=53 (accessed on November 3, 2005).
"Propane Education and Research Council." http://www.propanecouncil.org/ (accessed on November 3, 2005).
"Propane: Exceptional Energy." http://www.usepropane.com (accessed on November 3, 2005).
"/Propane: What is Propane?" Vehicle Buyer's Guide for Consumers. http://www.eere.energy.gov/cleancities/vbg/consumers/lpg.shtml (accessed on November 3, 2005).
Sherman, Josepha, and Steve Brick. Fossil Fuel Power. Mankato, Minn.: Capstone Press, 2003.
See Also
Ethylene; Methane; Propylene
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