Propane
The propane (from the Greek pro, «first order»; pion, «fat» and the chemical suffix -ane , since all its bonds are single) is a colorless and odorless gas. It belongs to the aliphatic hydrocarbons with single carbon bonds, known as alkanes. Its chemical formula is C3H8.
Features
Mixtures of propane with air can be explosive with concentrations of 1.8 to 9.3% Vol propane. The propane flame, like that of other fuel gases, it must be completely blue; any yellowish, orange or reddish part of the flame indicates poor combustion. At room temperature it is inert towards most reagents, although it reacts with bromine, for example, in the presence of light. In high concentrations, butane has narcotic properties.
This gas is highly flammable, so care must be taken to avoid having sparks or flames nearby that could ignite and cause a fire.
History
Propane, a 3-carbon molecule, was identified as a volatile component in gasoline by Dr. Walter O. Snelling of the US Bureau of Mines in 1910. Due to the volatility of these light hydrocarbons, they were known as "savages" ("wild" in English) due to the high vapor pressure in unrefined gasoline. On March 31, the New York Times reported on Dr. Snelling's work with liquefied gas and that "...a steel bottle of this gas will be enough to light an ordinary home for three weeks."
It was during this time that Snelling, in collaboration with Frank P. Peterson, Kerr Chester, and Kerr Arthur, created ways to liquefy LP gases during refining of natural gasoline. Together they founded the American Gasol Co., the first commercial propane seller. Snelling had produced relatively pure propane in 1911, and on March 25, 1913, his method of processing and producing LP gases received a patent. A separate method of producing LP gas through compression was created by Frank Peterson and patented in 1912.
The 1920s saw increased LP-Gas production, with the first year of production recording a total of 223,000 gallons (840 m³) in 1922. In 1927, annual marketed LP-Gas production reached 1 million gallons (3,800 m³), and by 1935, annual sales had reached 56 million US gallons (210,000 m³). Major industry developments in the 1930s included the introduction of the transportation tank car, odorization of gas, and the construction of local bottle-filling plants. The year 1945 marked the first in which annual sales reached one billion gallons. By 1947, 62% of homes in the United States had been equipped with natural gas or propane for cooking.
In 1950, the Chicago Transit Authority ordered 1,000 propane buses, and by 1958, US sales had reached 7 billion US gallons (26 million m³) annually. An increase from 8 billion to 10 billion was reported in 2004, with some 15 billion US gallons (57 million m³) of propane used annually in the US.
The root "prop-" in its name and those of other compounds with three-carbon chains are derived from "propionic acid".
Vapor pressure
The following table shows the vapor pressure of propane as a function of temperature:
| Temperature (°C) | Pressure (Pa) |
|---|---|
| 80 | 1 765 197 |
| 40 | 1 287 123 |
| 30 | 1 103 248 |
| 15 | 735 499 |
| 0 | 490 333 |
| -10 | 372 653 |
| - 20 | 269 683 |
| - 30 | 184 365 |
| - 40 | 122 583 |
Summary
Propane is usually obtained from natural gas or gases from "cracking" produced in petrochemical facilities. In the laboratory it can be prepared by Clemmensen reduction of acetone.
Uses
The main use of propane is for energy use as fuel. Based on the lower boiling point than butane and the higher energy value per gram, it is sometimes mixed with it or propane is used instead of butane. In the chemical industry it is one of the starting products in the synthesis of propene via the dehydrogenation reaction. Considerable research is being done to develop economically viable processes for the oxidative conversion of propane to propylene and acrylic acid.. It is also used as a refrigerant gas (R290) or as a propellant gas in aerosols.
Energy content
The enthalpy of combustion of propane gas where all products return to the standard state, for example, where water returns to its liquid state at standard temperature (known as the higher heating value), is (2219.2 ± 0.5) kJ / mol, or (50.33 ± 0.01) MJ/kg. [14] The enthalpy of combustion of propane gas where the products do not return to the standard state, for example where hot gases, including water vapor escaping from a chimney (known as the lower heating value) is -2043.455 kJ / mole. [15] The lower heat value is the amount of heat available from the burning of the substance where the products of combustion are vented to the atmosphere. For example, the heat from a fireplace when the fireplace is open.
Density
The density of liquid propane at 77 °F (25 °C) is 0.493 g/cm³, which is equivalent to 4.11 pounds per US liquid gallon, or 493 g/L. Propane expands at 1.5% per 10°F. Therefore, liquid propane has a density of approximately 4.2 pounds per gallon.