Abstract: A process for preparing 1-aminoanthraquinone having high purity, which comprises either1. hydrogenating 1-nitroanthraquinone in an aqueous medium in the presence of a base using a hydrogenating catalyst, and then oxidizing the hydrogenation product, or2. hydrogenating crude 1-nitroanthraquinone containing dinitroanthraquinones as impurities or crude 1-aminoanthraquinone containing diaminoanthraquinones as impurities in an aqueous medium in the presence of a base using a hydrogenating catalyst, stopping the hydrogenation at a time when the 1-nitroanthraquinone or 1-aminoanthraquinone has been substantially reduced to 1-aminoanthrahydroquinone but the dinitroanthraquinones or diaminoanthraquinones remain substantially unreduced to diaminoanthrahydroquinones, removing water-insoluble materials from the reaction mixture, and then oxidizing the remaining water-soluble residue.

Abstract: A process for preparing aminoanthraquinones of high purity, which comprises catalytically hydrogenating nitroanthraquinones in the suspended state in an aqueous medium in the presence of a hydrogenating catalyst. In a preferred embodiment, the catalytic hydrogenation may be carried out in the presence of an organic or inorganic base, followed, if desired, by oxidizing the hydrogenation product.

Abstract: 5-Nitro-1,4,4a,9a-tetrahydroanthraquinone is suspended in water in the form of a powder and then catalytically hydrogenated in the presence both of a hydrogenation catalyst containing a metal such as palladium, platinum or the like as its effective component and of a base such as sodium hydroxide, pyridine or the like thereby to form a hydroquinone type compound of 1-aminoanthraquinone. By contacting the resultant reaction solution with air or by adding an oxidizing agent such as hydrogen peroxide to the reaction solution, the hydroquinone type compound is readily oxidized into 1-aminoanthraquinone in the suspended state.