What's the difference between propane and butane?

Propane and Butane are chemically quite similar but Propane turns to a gas at a lower temperature suiting outdoor storage and is primarily used for central heating, cooking, as a transport fuel and for numerous commercial applications. 

Butane is used mainly in cylinders for portable applications in mobile heaters in the home, and for leisure activities such as boats, caravans and barbecues. On its own, it can also be used as a propellant, refrigerant or to fuel torches. 

Often, Propane and Butane will be mixed to deliver the best energy yields and properties.

The trade association for the LPG and bioLPG industry in the UK