Manufacture of H.sub.2 O.sub.2

A process of hydrogenating an alkylanthraquinone working solution comprising feeding an alkylanthraquinone working solution in the oxygenated form at a temperature of from 20.degree. to 40.degree. C. to a hydrogenator containing a slurry of supported hydrogenation catalyst which is supported palladium, supported platinum or supported nickel having a median particle size of from 70 to 200 microns and less than 10% by weight particles less than 50 microns in diameter, the working solution in the hydrogenerator being maintained at from 38.degree. to 60.degree. C., and containing from 2 to 15% catalyst maintaining the pressure in the hydrogenator at from about 10 to about 100 psig, removing hydrogenated working solution from the hydrogenator through immersed filters which retain essentially all the catalyst in the hydrogenerator, dividing the hydrogenated working solution into a recycle stream which comprises from 10 to 90 percent of the hydrogenated working solution and a remaining stream which is to be oxidized, cooling the recycle stream to from 20.degree. to 40.degree. C. and recycling the cooled stream to the hydrogenator.