Hydrogen Peroxide

Hydrogen peroxide is corrosive and a strong oxidizer, and has a formula of H2O2. It is a clear viscous liquid and has a slightly sharp smell. It can be found in organisms and as a by-product of oxidative metabolism. Due to differences in effects of hydrogen bonding, aqueous solution of hydrogen peroxide and pure solutions differs in freezing point temperature. In aqueous solution, water and hydrogen peroxide forms a eutectic mixture and exhibits a freezing point depression.



Hydrogen peroxide is mainly used as a bleaching agent in textile industry, in the pulp and paper industry during chemical and mechanical pulping process and in cosmetics industry. They are more environmental friendly than the chlorine-based bleaches and can be used to manufacture a wide range of organic and inorganic compounds.



Manufacturing Process



The manufacturing process of hydrogen peroxide includes 4 main steps:-

1. Hydrogenation of an anthroquinone: - A solution of the 2-ethylanthraquinone in a mixed solvent system containing a non-polar hydrocarbon and a polar solvent, and a suspension of a nickel or palladium-based catalyst on a solid support, is hydrogenated using hydrogen gas at 320 K. Reduction to the 2- alkylanthraquinol occurs. The catalyst is removed by filtration and recycled.

2. Oxidation of the anthraquinol:-The solution of 2-ethylanthraquinol is then oxidized by air to a hydroperoxide, which reacts in water to reform 2-ethylanthraquinone and produce a dilute solution of hydrogen peroxide. Thus the overall reaction is:

H2 + O2 ----à H2O2

3. Extraction of hydrogen peroxide solution:-Water is added to extract the peroxide as an aqueous solution containing 40% hydrogen peroxide. The organic solvent layer is recycled to the hydrogenation unit for further reaction.

4. Purification and concentration of hydrogen peroxide:-The aqueous hydrogen peroxide solution is treated with organic solvents and by air being pumped through to remove residual quinone and solvents and produce the standard 40% product.



Hydrogen peroxide in its purest form is inherently stable. However, if brought into contact with certain contaminants (mainly heavy metals) it can decompose. Therefore, stabilisers are normally added to the product. They act by complexing with any traces of transition metal ions present which would otherwise catalyse the decomposition of hydrogen peroxide.