Difference Between Propane and Butane

Main Difference – Propane vs Butane

Propane and butane are simple organic molecules. These are categorized as hydrocarbons because these molecules are only composed of carbon atoms and hydrogen atoms. Both propane and butane are gases at room temperature and under atmospheric pressure. Both these gases are combustible gases. These gases can be burnt, releasing heat energy. The burning may occur as complete combustion or incomplete combustion. In both cases, a flame is given by the burning of these gases. This combustion gives carbon dioxide, gases like carbon monoxide and water vapor as byproducts. The main difference between propane and butane is that propane molecule is composed of three carbon atoms whereas butane molecule is composed of four carbon atoms.

Key Areas Covered

1. What is Propane
      – Definition, Properties, Applications
2. What is Butane
      – Definition, Properties, Applications
3. What are the Similarities Between Propane and Butane
      – Outline of Common Features
4. What is the Difference Between Propane and Butane
      – Comparison of Key Differences

Key Terms: Butane, Carbon Dioxide, Carbon Monoxide, Combustion, Flame, Hydrocarbons, Isobutane , Propane

What is Propane

Propane is a gas that is composed of propane molecules. The chemical formula of propane is C₃H₈. Therefore, it is composed of three carbon atoms. It is a simple alkene and a hydrocarbon. The molar mass of propane is about 44 g/mol. At room temperature and atmospheric pressure, propane exists as a gas. However, it is compressible to make liquid propane that is transportable. This liquid propane can easily be vaporized due to its very low boiling point. The boiling point of propane is about -42^oC. Therefore, as soon as the lid of the container is opened, liquid propane will be converted into propane gas that can be burnt to get energy.

Propane is heavier than normal air since the relative density of propane is higher than 1. Therefore, if there is a mixture of propane and normal air in the same container, propane gas will sink to the bottom of the container.

Figure 01: A cylinder filled with propane liquid

The complete combustion of propane produces carbon dioxide, water vapor, and heat energy. But when there isn’t sufficient oxygen, incomplete combustion will take place, forming carbon monoxide along with carbon dioxide, carbon soot, and water vapor. The heat energy produced by incomplete combustion is less than the heat energy produced in complete combustion.

In addition to its use an industrial fuel, it can also be used as a motor fuel, a propellant for household aero sprays, the primary fuel for hot air balloons, etc.

What is Butane

Butane is a combustible gas that is composed of butane molecules. Butane has four carbon atoms and ten hydrogen atoms. Butane is an alkene and a hydrocarbon that is in the gaseous phase at room temperature and atmospheric pressure. The chemical formula for butane is C₄H₁₀. The molar mass of butane is about 58.12 g/mol. Butane can be found as two isomers: normal butane and isobutene. Normal butane is the simple linear structure of four carbons. Isobutane is a branched structure where one carbon atom is added as a methyl group to the three carbon backbone.

This is a colorless gas having a gasoline like odor. The boiling point of butane is about -1^oC. At room temperature, butane readily burns. Therefore, butane is considered as a highly flammable gas. The flash point of butane is about -60^oC. The flash point of a gas is the lowest temperature at which it can become ignitable following its mixture with air. This is also easily liquefied.

Figure 02: Butane fuel canisters

Butane can also undergo complete and incomplete combustion. When complete combustion occurs, it produces carbon dioxide, water vapor and heat. In the incomplete combustion, butane produces carbon monoxide along with water vapor and heat.

Butane can be used as an additive for gasoline blending, a fuel, and isobutene can be used to enhance the octane number of motor gasoline.

Similarities Between Propane and Butane

Propane and Butane are hydrocarbons.
Both are alkenes
Both are combustible gases
Both gases are compressible into their liquid form.
Both gases can undergo complete and incomplete combustion.

Definition

Propane: Propane is a combustible gas that is composed of propane molecules.

Butane: Butane is a combustible gas that is composed of butane molecules.

Chemical Formula

Propane: The chemical formula of propane is C₃H₈.

Butane: The chemical formula of butane is C₄H₁₀.

Molar Mass

Propane: The molar mass of propane is about 44 g/mol.

Butane: The molar mass of butane is 58.12 g/mol.

Flash Point

Propane: The flash point of propane is -104^oC.

Butane: The flash point of butane is -60^oC.

Boiling Point

Propane: The boiling point of propane is -42^oC.

Butane: The boiling point of butane is -1^oC.

Conclusion

Propane and butane are combustible gases that can be used as fuel. These gases can be found in natural gas. Therefore, natural gas processing is a major source to obtain these gases. The main difference between propane and butane is that propane molecule is composed of three carbon atoms whereas butane molecule is composed of four carbon atoms.

References:

1. Reid, Danielle. “Butane: Definition, Properties & Formula.” Study.com. n.d. Web. Available here. 04 Aug. 2017.2.”Propane.” Wikipedia. Wikimedia Foundation, 31 July 2017. Web. Available here.04 Aug. 2017.

Image Courtesy:

1. “propane bottle air receiver 2” by h080 (CC BY-SA 2.0) via Flickr
2. “Photo D2” By Blake Turner – Own work (CC BY-SA 4.0) via Commons Wikimedia