Liquefied Petroleum Gas

·         Discover the real difference between butane vs propane vs isobutane vs LPG. All three gases are consider to be LPG – Liquefied Petroleum Gas.

·         In some ways they are almost or exactly the same.

·         However, there are some important differences that you need to know.

First, some short summary answers:

Butane vs Propane – Choosing Butane or Propane Gas

·         Comparing butane vs propane, the most important differences are their dissimilar boiling point and vapour pressure but both are regarded as LPG – Liquefied Petroleum Gas – and commonly used for cooking, heating, hot water and autogas.

·         When considering butane or propane gas, the difference in physical properties determines which gas is best for a particular application.

·         Propane has a lower boiling point, at -42°C vs -0.4°C for butane. So, propane will continue to vaporise – turn to gas – even in colder climates, down to -42°C.

·         Butane has a lower vapour pressure at a given temperature, being about ¼ that of propane. This lower pressure is advantageous for some propellant applications.

·         Butane has a slightly higher energy content by volume while propane energy content is slightly higher by weight. This seeming inconsistency is as a result of the two liquefied gases having a different specific gravity.

What is Butane (n-butane)? Is Butane a Gas?

Ø  Butane is a gas when not under pressure and at normal room temperatures. Butane is a flammable hydrocarbon gas that is liquefied through pressurisation. Butane is a gas that also falls under the category of “LPG”. It is classified as LPG, along with propane, isobutane and mixtures of these gases.

Ø  Butane (n-butane) comes from natural gas processing and oil refining.

Ø  Butane is commonly used as a fuel, propellant and refrigerant, as well as a petrochemical feedstock.

Ø  The chemical formula for Butane is C₄H₁₀. (Butane molecule model shown)

Ø  Butane is supplied to businesses that require Butane, as opposed to propane. 

Ø  Butane has some specific applications where it has advantages over propane. 

n-Butane or n Butane

Both n-Butane or n Butane are just other names for regular butane.

What is Isobutane?

ü  Isobutane (i-butane) is an isomer of butane.

ü  So, it has the same chemical formula as butane —  C₄H₁₀  — but has a different arrangement of its atoms, as you can see in the 3-D model images. (Isobutane molecule model shown)

ü  As with normal butane, isobutane is a flammable hydrocarbon gas that is liquefied through pressurisation. 

ü  Isobutane is converted from butane in a process called isomerization.

ü  It also has different physical properties from normal butane (n-butane).

ü  In addition to being used as a fuel, isobutane is commonly used as a refrigerant and a propellant.

ü  Isobutane has very low global warming potential and insignificant ozone depletion potential.

ü  However, its main use is in refineries to increase octane of gasoline and make it cleaner burning.

ü  It is classified as LPG, along with propane, butane and mixes of these gases.

i-Butane, i Butane or Methylpropane

·         i-Butane or i Butane are just other names for isobutane.

·         Methylpropane is yet another name for isobutane.

What is Propane Gas?

Ø  Propane is a flammable hydrocarbon gas that is liquefied through pressurisation. 

Ø  It is classified as LPG – Liquefied Petroleum Gas – along with butane, isobutane and mixtures of these gases.

Ø  Propane comes from natural gas processing and oil refining.

Ø  It is commonly used for heating and cooking.

Ø  Propane is the gas that is supplied to virtually all homes and most businesses that purchase LPG in Australia.  

Ø  LPG is supplied in gas bottles that are either exchanged or refilled on site by LPG tankers. 

Ø  Large users may utilise bigger LPG storage tanks.

Ø  Propane is also frequently used in Autogas, alone or in a propane-butane mix.

Ø  LPG goes by a number of names in Australia including LPG, LPG gas, bottled gas, propane, BBQ gas, camping gas and LP gas. 

Ø  However, no worries, as it’s all the same gas. 

Ø  The chemical formula for Propane is C₃H₈.  (Propane molecule model shown)

Butane Boiling Point

·         The boiling point temperature of butane is -0.4°C.

·         This is significantly higher than propane and can be problematic in colder climates.

Propane Boiling Point

·         The boiling point temperature of propane is -42°C.

·         This boiling point temperature is sufficiently low that vaporisation can be achieved in almost all ambient temperature situations, outside of maybe the polar regions.

Butane or Propane Gas – When are they Liquid or Gaseous?

Propane, Butane & Isobutane Properties

·         This chart shows some of the physical property differences between the three gases.

·         You can refer back to the chart as we explain the importance of the numbers in the following topics…