Propane
Propane is a colorless, odorless, and nontoxic gas, classified as a hydrocarbon with the chemical formula C3H8. It is primarily found in natural gas and crude oil, making up to 6% of these sources. Commercially, propane is produced by separating it from natural gas or during the refinement of crude oil. Known for being a clean-burning fuel, propane generates carbon dioxide and water when combusted, producing a higher heat of combustion compared to many other fuels.
Due to its efficiency and relatively low environmental impact, propane is widely used for heating, cooking, and as fuel for engines, particularly in agricultural settings. It is also a key component of liquefied petroleum gas (LPG), which is commonly transported in tanks or cylinders. However, caution is advised when using propane indoors, as incomplete combustion can lead to the production of carbon monoxide, a toxic gas. Propane has been a significant energy source since its discovery in the early 20th century and continues to play a crucial role in various applications today.
Propane
Where Found
Propane occurs in natural gas, to the extent of up to 6 percent, as well as with crude oil. It is commercially available after its separation from or the gases formed when heavy oil is broken down (cracked) to produce gasoline. The principal gas deposits are in the United States, Canada, the former Soviet bloc, and the Middle East.
Primary Uses
Propane has been extensively used as a fuel since its isolation in the early twentieth century. It is a “clean” fuel that produces carbon dioxide and water as well as a quantity of heat.
Technical Definition
Propane’s condensed chemical formula is C3H8 or CH3CH2CH3, and it is a colorless, odorless, and nontoxic gas. It has a of 0.58 gram per cubic meter at -450° Celsius, a melting point of -187° Celsius, and a boiling point of -42.2° Celsius. Its heat of combustion (the energy released when a hydrocarbon is burned in the presence of oxygen to produce carbon dioxide and water) is relatively high and is equal to 531 kilocalories per mole, or 2,220 kilojoules per mole.
Description, Distribution, and Forms
Propane is the third-lightest alkane of the hydrocarbon family after methane and ethane. Propane is almost insoluble in water, moderately soluble in alcohol, and very soluble in ether.
According to the US Energy Information Administration, the proven world reserves of natural gas (most of which is methane) were 7,299 trillion cubic feet in 2021. This figure suggests that there are ample supplies of propane gas for the near future. Such sources include ultradeep gas, which is in the form of deposits as deep as 15,000 meters, the hydrated gas that exists in the Arctic regions, and the reserves beneath the oceans.
Unlike coal and products, such as diesel fuel, which create environmental problems when burned, propane and natural gas are clean fuels. Pollution-control equipment is generally unnecessary. Incomplete combustion of propane, however, yields carbon monoxide (instead of carbon dioxide) and water. Carbon monoxide is particularly toxic to humans, since it has an excellent binding ability to the iron of hemoglobin and displaces oxygen during the breathing process. As a result, the tissues die from oxygen starvation. Incomplete propane combustion takes place in areas that do not have sufficient oxygen, such as closed garages and relatively airtight rooms. Because of this danger, the use of camping stoves indoors to heat water is highly discouraged. Another area of great concern is the deliberate inhaling of propane by teenagers. “Huffing” propane as an intoxicant for about five minutes may easily lead to death.
Propane and butane have largely replaced the freons as propellants in aerosol cans. Freons, which are chlorinated, brominated, and/or fluorinated hydrocarbons, are easily broken down by light into stable radicals, which are prime suspects in causing damage to the earth’s protective ozone layer.
History
In 1910 Walter O. Snelling discovered propane while working for the US Bureau of Mines. Snelling and others started the American Gasol Company to sell propane. The product reached its peak in the post–World War II era, when many houses were equipped with propane stoves. In the 1960s, Chevrolet built and marketed propane trucks. In 1990, propane was designated a clean fuel.
Obtaining Propane
Propane is not a common starting reagent in industrial synthetic processes. Nevertheless, more than 20 percent of the propane obtained from natural gas sources is converted to its unsaturated derivative, propylene. This process involves its decomposition in hot tubes. Propane is also used in the synthesis of the colorless, flammable gas ethylene, which serves as the monomer of the useful polymerpolyethylene. Polyethylene is the essential ingredient of many household plastics (such as plastic wraps for food items). Ethylene is formed via cracking, a process that involves high temperatures of about 500° Celsius and several atmospheres of pressure. Isopropyl alcohol, also known as rubbing alcohol, was the first petrochemical synthesized via propane in the 1920s. The high-temperature of propane to acetaldehyde is also of commercial importance.
Uses of Propane
Propane and the next higher alkane, butane, are the main components of liquefied petroleum gas (LPG), which may be carried in tanks or cylinders and used as camping gas and in portable cooking stoves. In certain areas, LPG is transported via pipelines, and it may also be used for internal combustion engines. In many agricultural areas, propane and butane are more cost-effective tractor fuels than gasoline and diesel fuel. Commercially, the clean-burning fuel is maintained in the liquid state, which is obtained under conditions of elevated pressures, in a steel container. It converts spontaneously to the gas state upon exposure to the normal atmospheric pressure. Unlike propane, butane condenses to a liquid at 0° Celsius and thus cannot be used for camping under cold conditions. As a result, butane tends to be used in the southern United States, while propane (which condenses at -42° Celsius under normal pressure conditions) is used in the North.
As noted previously, propane has a high heat of combustion, which, combined with its ease of transport, makes it a convenient fuel. Another way of measuring the fuel capacity of propane is its “heating value,” which measures the amount of heat evolved when a gram of propane is burned. Propane’s value is about 6,098 kilocalories per liter. Overall, the fuel capacity of propane is about 2.5 times that of natural gas.
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