An environmentally friendly and safe synthesis of phloroglucinol and its derivatives through the flow hydrogenation of 1,3,5-trinitrobenzenes on heterogeneous copper catalysts is reported. It was found that hydrogenation of 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene 2,4,6-trinitroxylene and 2,4,6-trinitromesitylene in methanol over Cu-Al mixed oxides derived from layered double hydroxides provides the selective formation of the corresponding triaminobenzenes, which were isolated from the reaction mixture in the form of double salts with sulfuric acid stable in storage. The subsequent hydrolysis in aqueous solution gives phloroglucinol derivatives in good yields (75–82%).