PROPANE

Propane is a three-carbon chain alkane with the molecular formula C3H8. 
Propane is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. 
A by-product of natural gas processing and petroleum refining, Propane is often a constituent of liquefied petroleum gas (LPG), which is commonly used as a fuel in domestic and industrial applications and in low-emissions public transportation; other constituents of LPG may include propylene, butane, butylene, butadiene, and isobutylene. 

CAS:    74-98-6
MF:    C3H8
MW:    44.1
EINECS:    200-827-9

Synonyms
PROPANE, NATURAL;PROPANECOMBUSTION;Popane;A-108;Freon 290;propyldihydride;propylhydride;R 290

Discovered in 1857 by the French chemist Marcellin Berthelot, Propane became commercially available in the US by 1911. 
Propane has lower volumetric energy density than gasoline or coal, but has higher gravimetric energy density than them and burns more cleanly.
Propane gas has become a popular choice for barbecues and portable stoves because its low −42 °C boiling point makes it vaporise inside pressurised liquid containers (it exists in two phases, vapor above liquid). 
Propane retains its ability to vaporise even in cold weather, making it better-suited for outdoor use in cold climates than alternatives with higher boiling points like butane.
LPG powers buses, forklifts, automobiles, outboard boat motors, and ice resurfacing machines, and is used for heat and cooking in recreational vehicles and campers. 
Propane is also becoming popular as a replacement refrigerant (R290) for heat pumps as Propane offers greater efficiency than the current refrigerants: R410A / R32, higher temperature heat output and less damage to the atmosphere for escaped gases—at the expense of high gas flammability.

Propane is colourless and odourless, with a mercaptan odour. 
Like all fossil fuels, propane is a non-renewable energy source. 
Propane is a gas derived from natural gas and petroleum. 
Propane is found mixed with natural gas and petroleum deposits. 
Propane is called a ‘fossil fuel’ because it was formed millions of years ago from the remains of tiny sea animals and plants. 
Propane is a clean-burning, versatile fuel. 
Propane is used by nearly everyone, in homes, on farms, by business, and in industry mostly for producing heat and operating equipment. 
Propane is one of the many fossil fuels included in the liquefied petroleum gas (LPG) family. 
Because propane is the type of LPG most commonly used in the United States, propane and LPG are often used synonymously. 
Butane is another LPG often used in lighters.

Propane is a certified reference material standard for propane, a solvent that has been used in the extraction of cannabinoids from Cannabis and has been identified as a contaminant in butane hash oil and Δ9-THC concentrates. 
Propane is designed for use as a reference standard for propane by GC- or LC-MS. 
Propane is intended for research and forensic applications.
Propane is an alkane and a gas molecular entity. 
Propane has a role as a food propellant.
A colorless gas with a faint petroleum-like odor. 
Propane is shipped as a liquefied gas under its vapor pressure. 
For transportation Propane may be stenched. 
Contact with the unconfined liquid can cause frostbite by evaporative cooling. 
Easily ignited. 
The vapors are heavier than air and a flame can flash back to the source of leak very easily. 
The leak may be either a liquid or vapor leak. 
The vapors can asphyxiate by the displacement of air. 
Under prolonged exposure to fire or heat the containers may rupture violently and rocket.

Propane Chemical Properties
Melting point: -188 °C(lit.)
Boiling point: -42.1 °C(lit.)
density: 0.564 g/mL at 20 °C(lit.)
vapor density: 1.5 (vs air)
vapor pressure: 190 psi ( 37.7 °C)
refractive index: 1.2861
Fp: -104 °C
storage temp.: -20°C
form: liquid
pka: ≈ 44 (Gordon and Ford, 1972)
Flame Color: Blue(complete combustion); Yellow or orange(incomplete combustion)
biological sourc: rabbit
Odor Threshold: 1500ppm
explosive limit: 9.5%
Water Solubility: 62.61mg/L(25 ºC)
Thermal Conductivity: 0.13 W/(m·K)
Merck: 13,7891
BRN: 1730718
Henry's Law Constant: 0.706 at 25 °C (Hine and Mookerjee, 1975)
Exposure limits: OSHA PEL-TWA:1000 ppm (1800 mg/m³)
NIOSH REL-TWA:1000 ppm
Dielectric constant: 1.6（Ambient）
Stability: Stable. Incompatible with strong oxidizing agents. Highly flammable. May form explosive mixtures with air.
Cosmetics Ingredients Functions: PROPELLANT
LogP: 2.360
Surface tension: 7.7mN/m at 293.15K
CAS DataBase Reference: 74-98-6(CAS DataBase Reference)
EPA Substance Registry System: Propane (74-98-6)

Propane is the gas is slightly soluble in H2O, moderately soluble in alcohol, and very soluble in ether. 
Although a number of organic compounds which are important industrially may be considered to be derivatives of propane, Propane is not a common starting ingredient. 
The content of propane in natural gas varies with the source of the natural gas, but on the average is about 6%. 
Propane also is obtainable from petroleum sources.
Propane is a colorless gas that is odorless when pure (a foul-smelling odorant is often added).
Propane is released to the living environment from automobile exhausts, burning furnaces, natural gas sources, and during combustion of polyethylene and phenolic resins. 
Propane is both highly inflammable and explosive and needs proper care and management of workplaces. 
Propane's use in industry includes as a source for fuel and propellant for aerosols. 
Occupational workers exposed to liquefi ed propane have demonstrated skin burns and frostbite. Propane also causes depression effects on the CNS.

Physical properties    
Propane is a colorless, odorless, flammable gas that follows methane and ethane in the alkane series. 
The root word prop comes from the three-carbon acid propionic acid, CH3CH2COOH. 
Propionic acid comes from the Greek words protos meaning first and pion meaning fat.
Propane was the smallest acid with fatty acid properties. 
Propane is the gas used to fuel barbecues and camp stoves giving it the common name bottled gas.
Propane is marketed as liquefied petroleum gas (LPG) or liquefied petroleum; it should be noted that LPG is often a mixture that may contains butane, butylene, and propylene in addition to propane. 
In addition to cooking, propane can be used as an energy source for space heating, refrigeration, transportation, and heating appliances (clothes dryer).
Propane can be stored as liquid in pressurized (approximately 15 atmospheres) storage tanks and/or at cold temperatures and vaporizes to a gas at atmospheric pressure and normal temperatures. 
This makes Propane possible to store a large volume of propane as a liquid in a relatively small volume; propane as a vapor occupies 270 times the volume of propane in liquid form. 
This makes liquid propane an ideal fuel for transport and storage until needed.

Characteristics    
Propane demonstrates that the carbon atoms have different characteristics in alkanes with more than two carbon atoms. 
The terminal carbon atoms in propane are bonded to three hydrogen atoms and one carbon atom. 
A carbon atom bonded to only one other carbon atom is referred to as a primary or 1° carbon. 
The central carbon atom in propane is bonded to two other carbon atoms and is called a secondary or 2° carbon. 
A hydrogen atom has the same classifi cation as the carbon atom to which it is attached. 
Thus the hydrogen atoms attached to the terminal carbon atoms in propane are called primary (1°) hydrogens, whereas the central atom has secondary (2°) hydrogen. 
The diff erence in bonds leads to diff erences in reactions and properties of diff erent isomers. 
For example, breaking a primary bond requires more energy than breaking a secondary bond in propane. 

This makes formation of the isopropyl radical CH3CHCH3• easier than the n-propyl radical, CH3CH2CH2•. 
Even though the formation of the isopropyl is more favorable energetically, the greater number of primary hydrogen atoms leads to approximately equal amounts of n-propyl and isopropyl radicals formed under similar reaction conditions.
Oxidation of propane can produce various oxygenated compounds under appropriate conditions, but generally alkanes are relatively unreactive compared to other organic groups. 
Some of the more common oxidation products include methanol (CH3OH), formaldehyde (CH2O), and acetaldehyde (C2H4O). 
Propane can be converted to cyclopropane by conversion to 1,3 dichloro-propane using zinc dust and sodium iodine ClCH2CH2CH2Cl--Zn. Nacl--cyclopropane.

Properties and reactions
Propane is a colorless, odorless gas. 
Ethyl mercaptan is added as a safety precaution as an odorizer, and is commonly called a "rotten egg" smell.
At normal pressure it liquifies below its boiling point at −42 °C and solidifies below its melting point at −187.7 °C. 
Propane crystallizes in the space group P21/n.
The low space-filling of 58.5% (at 90 K), due to the bad stacking properties of the molecule, is the reason for the particularly low melting point.
Propane undergoes combustion reactions in a similar fashion to other alkanes. 
In the presence of excess oxygen, propane burns to form water and carbon dioxide.

Energy content
The enthalpy of combustion of propane gas where all products return to standard state, for example where water returns to its liquid state at standard temperature (known as higher heating value), is (2,219.2 ± 0.5) kJ/mol, or (50.33 ± 0.01) MJ/kg.
The enthalpy of combustion of propane gas where products do not return to standard state, for example where the hot gases including water vapor exit a chimney, (known as lower heating value) is 2,043.455 kJ/mol.
The lower heat value is the amount of heat available from burning the substance where the combustion products are vented to the atmosphere; for example, the heat from a fireplace when the flue is open.

Density
The density of propane gas at 25 °C (77 °F) is 1.808 kg/m3, about 1.5× the density of air at the same temperature. 
The density of liquid propane at 25 °C (77 °F) is 0.493 g/cm3, which is equivalent to 4.11 pounds per U.S. liquid gallon or 493 g/L. 
Propane expands at 1.5% per 10 °F. Thus, liquid propane has a density of approximately 4.2 pounds per gallon (504 g/L) at 60 °F (15.6 °C).
As the density of propane changes with temperature, this fact must be considered every time when the application is connected with safety or custody transfer operations.
If enough headspace is not left in a tank when filling, the tank could rupture when it heats up.

Uses
Propane has been used as a transportation fuel since its discovery. 
Propane was first used as an automobile fuel in 1913. 
Propane follows gasoline and diesel as the third most popular vehicle fuel and today powers more than half a million vehicles in the United States and 6 million worldwide. 
The widespread use of propane is hampered by the lack of a distribution system, but it has been used to fuel fleets of buses, taxis, and government vehicles. 
Also, it is heavily used to power equipment such as forklifts. 
Propane is cleaner burning than gasoline or diesel and has been used to reduce urban air pollution. 
Compared to gasoline it emits 10–40% of the carbon monoxide, 30–60% of the hydrocarbons, and 60–90% of the carbon dioxide. 
An advantage of cleaner burning propane is that engine maintenance is improved because of lower engine deposits and fouling. 
Propane’s octane ratings range between 104 and 110. 
The lower emissions are somewhat compromised by propane’s lower energy value; propane has about 75% of the energy content of gasoline when compared by volume. 
Propane is separated from natural gas and is also produced during petroleum processing. 
Approximately 53% of the propane produced in the United States comes from the small fraction (less than 5%) found in natural gas and the remainder comes petroleum refining.
Propane is used as a fuel gas, as a refrigerant,and in organic synthesis.

Portable stoves
Propane is a popular choice for barbecues and portable stoves because the low boiling point of −42 °C (−44 °F) makes it vaporize as soon as it is released from its pressurized container. 
Therefore, no carburetor or other vaporizing device is required; a simple metering nozzle suffices.

Refrigerant
Blends of pure, dry "isopropane" [isobutane/propane mixtures of propane (R-290) and isobutane (R-600a)] can be used as the circulating refrigerant in suitably constructed compressor-based refrigeration.
Compared to fluorocarbons, propane has a negligible ozone depletion potential and very low global warming potential, or GWP (having a GWP 20 value of 0.072, 1⁄14 that of carbon dioxide, and a GWP 500 of 0.006, 1⁄170) and can serve as a functional replacement for R-12, R-22, R-134a, and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems.
Because its global warming effect is far less than current refrigerants, propane was chosen as one of five replacement refrigerants approved by the EPA in 2015, for use in systems specially designed to handle its flammability.

Such substitution is widely prohibited or discouraged in motor vehicle air conditioning systems, on the grounds that using flammable hydrocarbons in systems originally designed to carry non-flammable refrigerant presents a significant risk of fire or explosion.
Vendors and advocates of hydrocarbon refrigerants argue against such bans on the grounds that there have been very few such incidents relative to the number of vehicle air conditioning systems filled with hydrocarbons.
Propane is also instrumental in providing off-the-grid refrigeration, as the energy source for a gas absorption refrigerator, and is commonly used for camping and recreational vehicles.
Propane has also been proposed to use propane as a refrigerant in heat pumps.

Motor fuel
In the U.S., over 190,000 on-road vehicles use propane, and over 450,000 forklifts use it for power. 
Propane is the third most popular vehicle fuel in the world, behind gasoline and diesel fuel. 
In other parts of the world, propane used in vehicles is known as autogas. 
In 2007, approximately 13 million vehicles worldwide use autogas.
The advantage of propane in cars is its liquid state at a moderate pressure. 
This allows fast refill times, affordable fuel cylinder construction, and price ranges typically just over half that of gasoline.
Meanwhile, Propane is noticeably cleaner (both in handling, and in combustion), results in less engine wear (due to carbon deposits) without diluting engine oil (often extending oil-change intervals), and until recently was relatively low-cost in North America. 
The octane rating of propane is relatively high at 110. 

In the United States the propane fueling infrastructure is the most developed of all alternative vehicle fuels. 
Many converted vehicles have provisions for topping off from "barbecue bottles". 
Purpose-built vehicles are often in commercially owned fleets with private fueling facilities. 
A further saving for propane fuel vehicle operators, especially in fleets, is that theft is much more difficult than with gasoline or diesel fuels.
Propane is also used as fuel for small engines, especially those used indoors or in areas with insufficient fresh air and ventilation to carry away the more toxic exhaust of an engine running on gasoline or diesel fuel. 
More recently, there have been lawn-care products like string trimmers, lawn mowers and leaf blowers intended for outdoor use, but fueled by propane in order to reduce air pollution.

Production
Propane is produced as a by-product of two other processes, natural gas processing and petroleum refining. 
The processing of natural gas involves removal of butane, propane, and large amounts of ethane from the raw gas, to prevent condensation of these volatiles in natural gas pipelines. Additionally, oil refineries produce some propane as a by-product of cracking petroleum into gasoline or heating oil.
The supply of propane cannot easily be adjusted to meet increased demand, because of the by-product nature of propane production. 
About 90% of U.S. propane is domestically produced.
The United States imports about 10% of the propane consumed each year, with about 70% of that coming from Canada via pipeline and rail. 
The remaining 30% of imported propane comes to the United States from other sources via ocean transport.
After Propane is separated from the crude oil, North American propane is stored in huge salt caverns. 
Examples of these are Fort Saskatchewan, Alberta; Mont Belvieu, Texas; and Conway, Kansas. These salt caverns can store 80,000,000 barrels (13,000,000 m3) of propane.

Biochem/physiol Actions    
In addition to facilitating solubilization of lipids, apolipoproteins help to maintain the structural integrity of lipoproteins, serve as ligands for lipoprotein receptors, and regulate the activity of enzymes involved in lipid metabolism. 
Apolipoprotein E (ApoE) plays an important role in lipid metabolism. 
Propane′s interaction with specific ApoE receptor enables uptake of chylomicron remnants by liver cells, which is an essential step during normal lipid metabolism. 
Propane also binds with the LDL receptor (Apo B/E). Defects in ApoE are a cause of hyperlipoproteinemia type III.