Propane has been used as a fuel for over 100 years and has been chemically-engineered to be efficient and safe, burning at a very high temperature, almost 2,000°C.
It’s more environmentally-friendly than many alternatives – a liquid propane spill poses no threat whatsoever to groundwater, surface water or soil – and it can be transported easily to homes in remote regions.
But how is propane gas made?
Propane - A Short History
In the late 1850s, French chemist Marcellin Berthelot first discovered propane. In 1864, English industrial chemist Edmund Ronalds isolated propane from petroleum, though it would be a further 44 years until it was understood how important propane was.
In 1910, the owner of a car in Pittsburgh asked a chemist by the name of Dr Walter Snelling why a gallon of petrol was reduced by half in the short drive to his home. The driver thought he was being cheated but in fact Snelling discovered that a large percentage of the liquid petrol was made up of hydrocarbons such as propane. He invented a machine – basically a still – using coils from an old heater and random pieces of lab equipment and separated the petrol into its liquid and gas components, thereby creating the first answer to the question ‘how is propane manufactured.’
Snelling found a way to convert gas into liquid and hence started the multi-billion pound propane industry. Today, the process of how propane is made – from both crude oil and natural gas – is slightly more technologically advanced than using old bits of metal lying around, but the core principles remain the same.
How is Propane Gas Made from Crude Oil?
When oil fields are drilled on land and at sea, the resulting product is separated into crude oil and what is known as wet gas. This is a mixture of oil, LPG and natural gas.
During the refining of crude oil, a process known as fractional distillation – separating the oil into its component parts – occurs. The heavy elements sink to the bottom and the light elements rise to the top. Propane is a light element and is removed from the top layer. The amount of propane is small compared to wet gas (around 1-4%) but it is important because it’s used as fuel to power the refineries themselves. This goes some way to answer the question ‘how is propane gas made’ but we still haven’t told you how it is extracted from the production of natural gas.
How is Propane Manufactured from Natural Gas?
The wet gas is piped to an absorption plant where it is cooled and then filtered through an absorption oil, also called a wash oil. This is a light liquid hydrocarbon that is used to remove natural gas and liquefied petroleum gases as well as impurities. What’s left is dry gas which is composed of around 90% methane – this is the gas that gets piped into your house.
Next, the absorption oil which is saturated with hydrocarbons is pumped to a processor where they are boiled off. The remaining mixture is then sent to a stabiliser tower where again, like the crude oil process, gravity plays its part. Natural liquid gasoline is heavy and falls to the bottom and the lighter LPG is drawn off the top. The LPG can be used as a blend or it can be further separated into isobutane gas, butane gas and propane gas.
Propane is 270 times more dense as a liquid than as a gas so it’s important we answer the question ‘how is liquid propane gas made?’ Liquefaction can only occur if the propane gas is completely free of impurities. It is turned from a gas into a liquid by increasing the pressure in the storage tanks as well as cooling it to -42°C.
We’ve answered the question ‘how is propane gas made’ but there is one very important fact worth knowing about propane. Propane is both colourless and odourless. In liquid form it looks like water and in gas form it is invisible. Therefore to ensure you know if there’s a leak, a deliberately revolting artificial smell called ethyl mercaptan is added.