Before we explore how hydrogen peroxide is made, let’s look at what it is. Hydrogen peroxide (chemical symbol H2O2 – it’s basically water with an extra oxygen atom!) is a weakly acidic, colourless liquid which can easily be mixed with water. It can also be pale blue in its pure form, although as it is an unstable compound and decomposes when exposed to heat, it is usually kept in a slightly acidic solution in the presence of a stabiliser.
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How Is Hydrogen Peroxide Produced?
Over 99% of the world’s hydrogen peroxide is manufactured by an autoxidation process. While the overall equation for this process is fairly simple (H2 + O2 -> H2O2), there is obviously a lot more to it than that!
Hydrogen peroxide is made through the catalysis of the reaction of hydrogen (H2) with atmospheric oxygen (O2) to produce hydrogen peroxide (H2O2).
The Step-by-Step Process Of Making Hydrogen Peroxide
To put it in more complex terms, hydrogen peroxide is generally made according to this four-step process:
- Hydrogenation on a palladium catalyst creates a reaction between hydrogen and anthraquinone which produces anthrahydroquinone.
- The palladium catalyst is filtered out of the solution.
- Oxidation takes place by blowing air through the solution, forming the hydrogen peroxide.
- The hydrogen peroxide is extracted, purified, and then concentrated by vacuum distillation.
Hydrogen peroxide also occurs naturally in surface and groundwater, as well as in the atmosphere. It is also made in humans and animals as a part of biochemical processes.
Producing Hydrogen Peroxide Through the Anthraquinone Process
This process starts with the reduction of anthraquinone to the corresponding anthrahydroquinone. In the presence of oxygen, the anthrahydroquinone oxidises – this is normally done by bubbling compressed air through an anthrahydroquinone solution. Unstable hydrogen atoms transfer to the oxygen molecule and produce hydrogen peroxide. This solution is then concentrated and purified.
While this sounds complicated, the equation for this process is fairly simple:
H2 + O2 → H2O2
This method of producing hydrogen peroxide became mainstream after the 1930s. Increased demand resulted in big leaps in production: 35,000 tonnes by 1950; over 100,000 tonnes by 1960; 300,000 tonnes by 1970. In 2015, the figure stood at 4.3 million tonnes globally.
Safe Storage of Hydrogen Peroxide
Hydrogen peroxide should be stored in a cool (between 5-25°C), dry area away from heat and direct sunlight, and kept well away from anything flammable as it can increase the risk or intensity of fire even though it doesn’t burn itself. It should be stored in a stable container made of plastic or glass (metal containers should not be used as hydrogen peroxide can react with metals).
What Makes Hydrogen Peroxide Foam?
Hydrogen peroxide is used as an antiseptic as it kills bacteria. When you put hydrogen peroxide on a cut, you might notice that it starts to foam. That’s because the chemical breaks down when it comes into contact with blood. An enzyme in your blood called catalase attacks the hydrogen peroxide, turning it into oxygen and water.
How To Make Elephant Toothpaste With Hydrogen Peroxide
On a larger scale, you may have seen the science experiment called “elephant toothpaste”, a chemical reaction between hydrogen peroxide and a potassium iodide solution. When hydrogen peroxide breaks down, it turns into oxygen and water. A tiny amount of hydrogen peroxide can create a lot of oxygen and the potassium iodide removes this oxygen, producing an effervescent, bubbling foam which can leap metres into the air. Watch out!
ReAgent sells hydrogen peroxide in 6%, 30% and 35% solutions, and in 2.5 or 25 litre pack sizes – it is not suitable for bleaching straw hats or dying your hair! If you’d like to discuss your hydrogen peroxide requirements, contact our friendly team.
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