Previously, hydrogen peroxide was prepared industrially byhydrolysisof theammonium peroxydisulfate, which was itself obtained by theelectrolysisof a solution ofammonium bisulfate(NH4HSO4) insulfuric acid:

(NH4)2S2O8+ 2H2O→H2O2+ 2(NH4)HSO4

Today, hydrogen peroxide is manufactured almost exclusively by theanthraquinone process, which was formalized in 1936 and patented in 1939. It begins with the reduction of ananthraquinone(such as2-ethylanthraquinoneor the 2-amyl derivative) to the correspondinganthrahydroquinone, typically byhydrogenationon apalladiumcatalyst; the anthrahydroquinone then undergoesautoxidationto regenerate the starting anthraquinone, with hydrogen peroxide as a by-product. Most commercial processes achieve oxidation by bubblingcompressed airthrough a solution of the derivatizedanthracene, whereby the oxygen present in the air reacts with the labile hydrogen atoms (of the hydroxy groups), giving hydrogen peroxide and regenerating the anthraquinone. Hydrogen peroxide is thenextracted, and theanthraquinonederivative is reduced back to the dihydroxy (anthracene) compound usinghydrogengas in the presence of a metal catalyst. The cycle then repeats itself.

1. From sodium peroxide (Merck’s method)

Calculated amount of sodium peroxide (Na2O2) is gradually added to an ice-cold solution of 20% H2SO4in small lots with constant stiring.

Na2O2+H2SO4→ Na2SO4+ H2O2

Upon cooling, crystals ofNa2SO4.10H2Oseparate out and the resulting solution contains about 30% H2O2. The solution also contains some dissolvedNa2SO4, but it does not interfere with the reactions ofH2O2. A pure sample ofH2O2may, however, be prepared by vacuum distillation.