Propane

An Introductory Note on Propane

Propane is an easily liquefied, colourless, gaseous hydrocarbon. Propane formula is C3H8. In the paraffin series, it is the third member after methane and ethane. It is also known as n-Propane, propyl hydride, Dimethylmethane. 

In 1857 it was first discovered by Marcellin Berthelot, a French chemist. It is stored and transported as a liquid, and when released from the container, this becomes gas. C3H8 is an essential part of Liquefied Petroleum Gas (LPG) and is also available as liquefied Propane. An identifying odour is mixed with it for its detection. 

It is primarily extracted as a by-product of natural gas processing and petroleum refining. 

Properties of Propane

Just like other hydrocarbons, propane is also non-polar. This feature indicates that it can mix only with other non-polar compounds. It is readily soluble in chloroform, benzene, ethyl ether and also in ethanol. Moreover, it is a non-corrosive substance. The vapours of propane can asphyxiate through the displacement of air. 

Formula 


C3H8

Molecular Weight


44.10 g/mol

Melting Point of Propane


-187.7⁰ C

Boiling Point 


-42.25⁰- 42.04⁰ C

Gas Density of Propane


2.0098 kg/m3

Critical Temperature


206.6 F

Propane Structure

Propane consists of three carbon atoms and eight hydrogen atoms. Each of them is connected with a single covalent bond, each carbon atom creating four covalent bonds. This alkane exists in chain-like structure, and the carbon structure remains as C-C-C. The carbon in the centre shares a single bond with each of the end carbon and two hydrogen atoms. Similarly, each of the end carbon shares a single bond with three hydrogen atoms and central carbon atom. 

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The number of both the hydrogen bond acceptors and hydrogen bond donors in propane is zero. 

Chemical Reactions of C3H8

Similar to other alkanes, Propane also initiates combustion reactions. In the presence of constant supply of oxygen, it reacts and produces carbon dioxide and water. 

C3H8 + 5O2 → 3CO2 + 4H2O + heat

However, in the presence of insufficient oxygen, it forms carbon monoxide or/and soot. 

2C3H8 + 9O2 → 4CO2 + 2CO + 8H2O + heat

C3H8 + 2O2 → 3C + 4H2O + heat

Also, to convert propane to propanoic acid, we have to perform the following steps

First, we have to convert propane into alcohol and then into a carboxylic acid. 

CH3-CH=CH2 +H2O----->CH3-CH2-CH2-OH

Then, 

CH3-CH2-CH2-OH -- (acidified K2Cr2O7 / alk. KMnO4)--> CH3-CH2-COOH

Besides, KCN reacts with ethyl chloride and forms propane nitrile. Following is the reaction. 

C2​H5​Cl+KCN→C2​H5​CN + KCl

Production of Propane

As we have mentioned earlier, Propane is produced in two ways, oil refining and gas processing. Both these processes start by drilling underground oil wells. 

Propane is obtained from heated crude oil through a distillation tower. Then it is pressurised and stored in liquid form in tanks and cylinders. 

However, it is extracted very little in an amount from natural gas. The raw natural gases contain several gases, including propane, when it comes out of the oil well. Also, it is separated from other gases via stripper plants that effectively strip the propane out of the gaseous mixture. Due to this increased shale gas extraction, the production of propane has reduced drastically. However, U.S has an increasing source of propane, and they have become a net exporter since 2011. 

Purity

Propane with C3H8 chemical name is not always suited for usages. Sometimes, it contains a large amount of propene or propylene, which makes it unsuitable for use as vehicle fuel. A maximum amount of 5% of propene can stay in propane, and that is standardised quantity of this kind of fuel. Since it is odourless, ethanethiol, an odorant is also added to it so that people can smell and detect it easily if leakage occurs. 

By-Product of C3H8

In the process of manufacturing propane, many by-products occur in gas, liquid or solid forms. The solids are hydrogen sulphide, bitumen, etc. and in the liquid form, we get crude oil which is further refined. Also hydrocarbons like propylene, butylenes are produced as co-product that is useful for gasoline refining, petrochemical production, etc. 

Storage 

Propane is generally stored and shipped as a liquid in steel cylinders, leaving a vapour space. Also, international ships reuse it when they transport LPG. In the presence of sunlight, propane evaporates, and then they collect this vapour and reuse it in the ship’s diesel engine, hence reducing bunker consumptions. 

Application

The usages of Propane are varied, and some of them are discussed below. 

Motor fuel- It is quite popular in several countries as fuel for motor vehicles. In U.S.A alone, over 190,000 vehicles use propane as car fuel. It is considered as the third most popular car fuel worldwide followed by gasoline and diesel. The reasons behind this are it takes less time to refill and costs almost half that of gasoline. 

Refrigeration- Propane is also used as an energy source for gas absorption refrigerators. One of the reasons behind this isthat propane has lesser ozone depletion potential than fluorocarbons. Hence, it is better for environments and can replace other harmful substances used for constructing compressor-based refrigerators.  

Other Uses

Apart from that, this compound is used for several other purposes. It includes.

  • It is used as flammable gas in soldering blowtorches. 

  • Propane acts as feedstock for the production of petrochemicals.

  • Hot air balloons also use this gas,

  • It can also extract vegetable oil and animal fat. 

  • In depositing silicon carbide, it is used. 

  • It is a component in adhesives, paint and sealants. 

  • C3H6 is also commonly used as cooking fuels and in water heaters. 

  • Also, it is used as propellants in aerosol cans. 

  • It is involved in manufacturing acrylic acid and propylene.  

Now that you know the several uses of propane, let us learn about the history behind it. 

History of Propane

The origin of this hydrocarbon can be traced back by 5000 years. However, the refined version of it was first produced in 1859, when Pennsylvania and Seneca Oil Company first drilled oil well. More specifically, it is first recognised as a significant substance in 1910 when a motor car owner of Pittsburgh asked Dr Walter Snelling to investigate why the gasoline he purchased became half when he reached the home. On investigating, Snelling found out that gasoline contains several other substances like butane, Propane and others. From that day onwards, chemists and scientists have developed several ways to procure propane in the finest form. 

Health Hazards

Being a great alternative to gasoline, it should be handled with care to avoid any accident. Since a high concentration of propane can displace oxygen, it can cause rapid breathing, clumsiness, fatigue and other symptoms. The liquefied gas form of it can cause mild to severe frostbites if it comes in contact with skin. 

Along with that, the gas leakage can cause explosion and fire if not stored properly. Often the cylinder in the basement of a boat leaks and if it comes in direct contact with water heater and other appliances, it explodes. Due to this, it is inappropriate for use as boat fuel. 

Did You Know?

Almost 10 billion litres propane is annually produced in Canada; however, half of it is exported.  

Test Your Knowledge

1. Which one of these is an isomeric pair?

  1. Propane and butane

  2. Ethane and Propane

  3. Ethane and ethane 

  4. 2-methyl Propane and butane

Ans. d) 

2. How is Propane Measured?

Ans. Usually, Propane is measured by gallons; however, pounds is also used to measure it. 

Now that you know about the important features of Propane along with its usages, try to incorporate your class notes for a detailed study note. For further information regarding several other alkanes like ethane, butane, etc. tune in to Vedantu’s website. Now you can also download our Vedantu app for enhanced access to our detailed study materials and online sessions.

FAQ (Frequently Asked Questions)

1. How long Does Propane Stay in the Air?

Ans. Propane releases in the air as alkaline and reacts with UV rays. On oxidising, it splits into carbon dioxide and water. However, this is a slow process and takes several weeks for completion. Nonetheless, the half-life of Propane at 20 C is about 14 days in air.  

2. What are the Usages of Propane?

Ans. Propane is widely used for heating, grilling and cooking purposes in households. Also, it is used as fuel in forklifts, buses, fleet vehicles and farm irrigation engines. 

3. What are the Disadvantages of Propane?

Ans. Propane is more concentrated than air. Hence, it sinks in an enclosed area and collects at the ground that cannot be detected. Moreover, it is combustible, and if it leaks and comes in contact with other flammable gases, it can explode and make fire. 

4. What Happens if Your Tank Runs Out of Propane?

Ans. If your propane tank is empty and the gas line is still open, then leakage can occur when you further fill the tank with propane. When this happens, the moisture and air enter into the empty tank which usually leads to rust-build-up.