By Adam Lusher on May 3, 2020
In 1920, isopropyl alcohol (IPA) became the world’s first commercial petrochemical. It was made from petroleum or natural gas.
For nearly 100 years IPA has been little known outside the chemical industry. Carleton Ellis, the inventor who discovered how to make it, is better remembered as the man who gave the world modern margarine, based on vegetable oils instead of animal fats.
IPA is used as a solvent in paints and printer inks, a degreaser, or in rubbing alcohol, for cleaning cuts and grazes.
Now, though, IPA is best known as the active ingredient in hand sanitiser and has emerged as a vital tool in slowing the spread of COVID-19.
We are donating 2.5 million litres of IPA – about enough to fill an Olympic-sized swimming pool – to the Dutch health-care sector.
We are also donating 125,000 litres of IPA – enough to make nearly 1 million 340g bottles of hand sanitiser – to the Canadian government, to be used in various ways in health-care facilities.
What is IPA?
IPA is a colourless liquid at room temperature. Each molecule consists of three carbon atoms, eight hydrogen atoms and one oxygen atom, giving it the chemical formula C3H8O.
How does it work?
IPA attacks viruses and bacteria in the same way it attacks grease.
The outer walls of many viruses including COVID-19 consist of greasy substances called lipids. Rather like an invading army storming a castle, IPA breaks down the outer walls and damages the material inside to render the virus harmless.
How is IPA made?
The Carleton Ellis method used propylene, obtained by subjecting crude oil or natural gas to high temperatures and pressures in what is known as a cracking process.
The hydrocarbon molecules, consisting of long chains of carbon and hydrogen atoms, are broken into smaller molecules, one of which can be propylene (C3H6).
Ellis developed a two-stage process. First, he used sulphuric acid to turn the propylene into an intermediate chemical; then he introduced water to react with the intermediate chemical to produce IPA.
Today, commercial manufacturers can choose between the Ellis method or two alternatives that were developed in the second half of the 20th Century.
The first alternative involves using modern catalysts to get the propylene and water to react and produce IPA in one go. For this single-stage process to work, however, the propylene must be purer than in Ellis’ original two-step process.
The second alternative uses acetone, which can be made from the benzene found in crude oil and propylene. Modern catalysts are used to trigger a reaction between acetone and hydrogen that produces IPA.
How can IPA help stop the spread of COVID-19?
Hand sanitiser gel is produced by mixing IPA with water, glycerol and hydrogen peroxide. It can be used to keep hands free of COVID-19, significantly reducing the risk of infection, especially where no soap and water are available.
In hospitals and care homes, disinfectant wipes containing diluted IPA can be used in a deep clean of non-porous surfaces that might be contaminated with COVID-19.