1752. KHVATOV, A. D. [Dependence of the Energy of Activation on the Activity of the Catalyst.] Jour. Gen. Chem. (U.S.S.R.), vol. 9, 1939, pp. 819-824; Chem. Abs., vol. 33, 1939, p. 7653.

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Literature Abstracts

Surface of catalysts is not homogeneous. The most-active regions of the surface are first acted upon by chemical reagents, which decrease the activity of the catalyst almost 50%. In the experiments, the surface structure of Ni was changed by the reaction of Ni(CO)₄ formation, formed when a stream of CO is passed at 100°-150° over Ni, and again decomposed into Ni and CO at 300°-400° by passing definite amounts of CO and by determining the activation energy of CH₃CHO decomposition from the reaction CH₃CHO→CH₄+CO. The reaction velocity was determined by passing 1 l. of CO in 1 hr. over the catalyst at 100°. The Ni(CO)₄ formed was passed into a U tube heated to 350° where it was decomposed into metallic Ni and CO. The deposited Ni was dissolved in HNO₃ and its amount determined by the method of Chugaev as Ni dimethylglyoxime. This experiment was repeated until the activity of the catalyst (measured by the reaction velocity) remained constant or changed only slightly. The reactions were performed in a quartz tube, 500 mm. long, 18 mm. diam., with 2 gm. of the catalyst, 2 cm. long. After the 1^st action of CO a very sharp drop of the decomposition velocity was observed (26.6-47%). After the 2d CO action a smaller drop occurred at 250°-260°, and only a very small drop after the 3d CO action at 260°. It was found that a minimum of Ni formation corresponded to the maximum activity drop of the catalyst. This verifies the hypothesis that the number of active regions on the surface of the catalyst can be very small. From the experimental data, the energies of activation for the different steps of the chemical action of CO on Ni were calculated from the equation of Arrhenius, and they were found to be the same in all cases (9,000±300 cal.). This shows that the energy of activation does not depend on the activity of the catalyst. Gives 6 diagrams, 7 tables, and 17 refs.