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NCITES
Vol. 76
Decomposition of Aqueous Hydrogen Peroxide Over Chromic Oxide Catalysts
given in Table I. In the case of the chromia gel there is a direct relationship between the surface oxidation and the catalyst acidity as determined by B Y STERLING E I'ULTZ ASD SOL15'. \TELLER the pH measurement. The oxidized catalyst RECEIVED OCTOBER 22, 1953 contains the equivalent of 1.9% CrOs; an aqueous Chromia and chromia-alumina catalysts contain suspension of 100 g. of catalyst per liter would, excess surface oxygen after oxidation a t jO0°.1-3 therefore, be expected t o have a pH corresponding The extent of surface oxidation has been found to t o a chromic anhydride concentration of 1.9 g. be qualitatively related to the activity for the per liter. The pH values of a number of pure catalytic decomposition of aqueous hydrogen chromic anhydride solutions were determined and peroxide. Figure 1 shows the results obtained for from these data the pH of one containing 1.9 g. of both oxidized and reduced samples of the three CrOl per liter was found to be 2.7-2.8. The expericatalysts tested, i.e., stabilized chromia gel, 205% mentally determined FH for the oxidized chromia chromia impregnated on alumina (Houdry Type K gel is 2.71 (Table I). The reduced chromia gel contains no excess surface oxygen, and its aqueous catalyst), and coprecipitated chromia-alumina (35% CrzO,). The reaction rates were deter- suspension is, correspondingly, almost neutral. mined from the slopes of the curves obtained by TABLE I plotting oxygen liberated us. time. I n most of the CATALYST CHARACTERISTICS runs these curves were straight lines, but in several OxidaTitrabI1 of runs with the chromia-alumina catalysts the retion table aqueous (CrOz, acidity suspenaction rate increased, and the aqueous phase Catalysts %) (meq./g.) sion turned purple, after several hundred seconds. I n Oxidized chromia gel 1 . 9 0.173 2.71 these few cases the slopes of the initial straight
