The hydrogenation of benzene has been studied over series of copper-nickel, copperpalladium, and gold-palladium alloys using a microcatalytic method. Specific activities are reported for the temperature range 98-182" (copper-nickel) and for the range 84-144" (copper-palladium and gold-palladium). Apparent activation energy values are also reported. For the copper-nickel series, the results are compared with previously published studies and are shown to be consistent with a surface composition differing from that of the bulk and dependent on temperature and/or time of reduction of the initial mixed oxide. It is postulated that a reaction mechanism change, dependent on the surface composition, determines the behavior of the kinetic parameters. For the copperpalladium and gold-palladium samples, it is concluded that their catalytic behavior indicates the formation of transition metal-group Ib metal-hydrogen ternary systems.

No abstract

The cementation of copper in alkaline zinc solution (300 g/liter normalNaOH , 60 g/liter Zn, and 0.2 g/liter Cu) was studied and a method based on mathematical simulation was used to identify the mechanisms governing the process. Results suggest that activation was the initial mechanism, since copper ions do not deposit easily on zinc. However, the mechanism changed to diffusion after a few minutes of cementation, when copper ion deposition was facilitated by the presence of metallic copper partly covering the zinc surface. The mathematical procedure as well as the results of simulation are presented. Experimental cementations were performed and the data coincided with the predictions obtained by simulation. The present simulation method can be applied also to cementation in acid media.

No abstract