Process for hydrogenating an alkylated anthraquinone

In a process for producing hydrogen peroxide by the cyclic steps of reducing, oxidizing, and extracting a working solution containing as a working compound, a compound selected from the group consisting of 2-ethylanthraquinone, 2-isobutylanthraquinone, 2-amylanthraquinone, the corresponding 2-alkylanthrahydroquinone, the corresponding 5,6,7,8-tetrahydro-2-alkylanthraquinone, and the corresponding 5,6,7,8-tetrahydro-2-alkylanthrahydroquinone, the improvement which comprises increasing the mol ratio of the nuclearly-hydrogenated, tetrahydro components of the working solution by adjusting the concentration of the non-nuclearly hydrogenated working compounds to be equal to or less than the maximum solubility of the alkylated anthrahydroquinone formed in the working solution at the hydrogenation temperature, hydrogenating the working solution at a pressure of 100 to 400 kilopascals, at a temperature of 40.degree. C. to 50.degree. C., and recycling at least 90% of the working solution to the hydrogenator without oxidation and extraction thereby increasing the mol ratio of the tetrahydro components of the working compound without forming substantial quantities of undesired by-products.

A process for starting up a plant for producing hydrogen peroxide by the cyclic steps of reducing, oxidizing, and extracting a working solution containing as a working compound an alkylated anthraquinone, and the corresponding anthrahydroquinone, tetrahydroanthraquinone, and tetrahydroanthrahydroquinone comprising the steps of adjusting the concentration of the non-nuclearly hydrogenated working compounds in the working solution to be equal to, or less than, the maximum solubility of the alkylated anthrahydroquinone formed in the working solution at the hydrogenation temperature, hydrogenating the working solution in the presence of a palladium catalyst at a pressure of 50 to 400 kilopascals and at a temperature of 50.degree. C. or less, and recycling at least 90% of the hydrogenator without the steps of oxidation and extraction, thereby increasing the mol ratio of tetrahydro components of the working compound without forming substantial quantitites of undesired by-products.