Hydrogen peroxide is now generally prepared on industrial scale by the:
(a) action of H2SO4 on barium peroxide
(b) action of H2SO4 on sodium paraoxide
(c) electrolysis of 50% H2SO4
(d) burning hydrogen in excess of oxygen
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(c) Industrial preparation of H2O2:
(A) By the electrolysis of 50% H2SO4 : 50% H2SO4 solution is electrolysed at 0°C between Pt electrodes. The perdisulphuric acid is formed. H2SO4⇌H+ + HSO4- at Anode; 2HSO4-→H2S2O8 + 2e at cathode; 2H++2e →H2 The obtained perdisulphuric acid gives H2O2 on hydrolysis. H2S2O8 + 2H2O ⇌H2O2 + 2H2SO4 This H2O2 is separated by distillation at reduced pressure and thus, 30% solution of H2O2 is obtained.(B) By the auto-oxidation of 2-ehtyle-anthraquinol(Modern Method): Anthraquinol, in a mixture of benzene and n-heptanol on treatement with air gives H2O2 and 2-ethyl-anthroquinone. This 2-ethyl-anthraquinone on hydrogenation gives 2-ethyl-anthraquinol in presence of Pd catalyst.
It is a cyclic process and in it only H2 is consumed, 2 -ethyl-anthraquinone is reobtained during reaction.