Process for producing hydrogen peroxide

A process for producing hydrogen peroxide by subjecting a working solution containing anthraquinones as the reaction medium, to reduction and oxidation alternately, which process is characterized in that (1) the anthraquinones as the reaction medium contained in the working solution are a mixture of an alkyl-substituted anthraquinone and an alkyl-substituted tetrahydroanthraquinone, wherein the molar ratio of the alkyl-substituted anthraquinone to the alkyl-substituted tetrahydroanthraquinone in the working solution is 2:1 to 8:1, that (2) in the reduction step, the total amount of the alkyl-substituted tetrahydroanthraquinone in the working solution and part or the total amount of the alkyl-substituted anthraquinone in the working solution are reduced, and (3) in the working solution after the reduction step and before the oxidation step, the content of the alkyl-substituted anthrahydroquinone formed is kept higher than the content of the alkyl-substituted tetrahydroanthrahydroquinone formed.