Abstract: A process is disclosed for the separation of catalyst-free working solution from working solution containing palladium black of the hydrogenation circuit of the anthraquinone process for the production of hydrogen peroxide. The problem addressed was to improve the separation of a catalyst-free working solution from the hydrogenation circuit containing Pd black, which was previously carried out using filter candles, in order to reduce the process costs. This problem is solved by the use of a microfilter operating on the crossflow principle with a filter membrane of ceramic material, more particularly .alpha.-aluminum oxide, or polyolefin with an average pore diameter of 0.1 to 3.0 .mu.m, preferably 0.1 to 1.5 .mu.m, and more preferably 0.5 to 1.5 .mu.m. The crossflow rate is generally 0.5 to 5 m/sec.