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Catalysts of varying surface properties (e.g. surface area, pore volume and crystallite size) and of varying bulk properties (e.g. metallic radius, heat of formation of oxide and percentage d‐character) were evaluated as catalysts for the decomposition of hydrogen peroxide. Surface properties were varied by studying the following catalysts: unsupported nickel oxide, nickel oxide/α‐alumina, nickel oxide/α‐alumina and nickel oxide/silica‐alumina. The bulk properties were varied by studying the oxide catalysts of different metals such as nickel, chromium, mangenese, cobalt and palladium. The results obtained from this work along with the data obtained from a search of the literature, were correlated using a compensation plot (linear relationship between the activation energy and the logarithm of the frequency factor). General correlations for bulk properties and catalytic activities are presented for the decomposition of hydrogen peroxide. The use of a “Compensation Effect” for the hydrogenation of ethylene is also discussed.

The effect of various types of irradiation, such as «-particles, neutrons, and -rays on the activity of catalysts (Coekelbergs et al., 1962;Mikovsky and Weisz, 1962;Taylor, 1965; Taylor, 1968; Weisz and Swegler, 1955) is reported. In these studies the catalytic activity increased significantly with the radiation treatment. In all cases the commercially available catalyst was irradiated. Usually, fairly large dosages of irradiation were required to produce significant changes in the catalytic activity (Mikovsky and Weisz, 1962).Recently, another type of irradiation, ultrasonics, was used to increase the activity of a catalyst (Li et al., 1964; Ranganathan et al, 1971). The ultrasonic treatment (insonation) was carried out during the manufacture of the catalyst as opposed to the irradiation of the commercially available catalyst. The information reported in the literature is as yet too scant to afford a clear picture of the subject. The situation is made complex by the several variables in the case of irradiation with ultrasonics-the frequency, intensity, duration of insonation, and the atmosphere over the catalyst system during irradiation.The literature on insonation of catalysts can be divided in three categories: (I) insonation of the catalyst during the preparation stage; (II) insonation of the already prepared catalyst; and (III) insonation of the reaction mixture (including the catalyst). Two of these systems have been discussed in detail in one of our earlier papers (Ranganathan et al., 1971). A brief introduction is in order. Case I: Insonation of Catalyst during Preparation StageThe catalyst is insonated during the preparation stage. As the ultrasonics produce cavitation and mixing at the microlevel, insonation affects the catalyst particle size, crystallite size, pore size, and the pore-size distribution (Kapustin, 1962;Li et al., 1964;Slaczka, 1964).

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