Sept., 1962
Rsuucnos
PRODUCTS FROM THE
A1203
BUTENE-1
Temp. ("C.)
Carrier substance
Radioactivity (counts/min.)
890
CH81
3230 200 3090 700
CzHaI Platinum
CUPRIC OXIDEBY HYDROGES
T.4BLE 111 HIGHTEMPERATURE DECOMPOSITION OF
Crttalyst
OF
690
CHJ CeHjI
For the heterogeneous case, however, if two-point adsorption by the double-bonded carbons of butene-1 is assumed, only ethyl radicals would be expected. But at these elevated temperatures, it is likely that the catalytic action, particularly of alumina, results in the equilibrium or near-equilibrium concentrations of butene-1 with its isomers, butene2 arid isobutene. Both isobntene and butene-2,
1673
again assuming two-point adsorption, would yield two methyl radicals for each molecule decomposed. In fact, if two-point adsorption and equilibrium are both attained prior to the decomposition step, the ratio of methyl to ethyl radicals would be quite high, $bout 9: 1. Thus it appears from the data that these assumptions are more correct for alumina than for platinum, a substance which is not known to be a particularly good catalyst for olefin isomerization. Although allyl iodide was looked for in a few of the runs, none was detected. This may have been due to the st,rong adherence of the unsaturated allyl radical to the catalyst surface. Acknowledgment.-Acknowledgment is made to the donors of The Petroleum Research Fund, administered by the American Chemical Society, for support of this research.
THERR!IOGRAVIMETRIC STUDY OF THE KINETlCS OF THE REDUCTIOS OF CUPRIC OXIDE BY HYDROGEF BY W. D. BOND Oak RzdgP National Laboratory, Oak Ridge, Tennessee, Operated by U n i o n Carbide Nuclear Cornpang for the U . S . Atomic Energy Commission
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Received September 26,1.961
The reaction CuO(s) Hz(g) Cu(s) f HzO(g) occurs in three stages: an induction stage, an acceleration or autocatalytic stage terminating a t about 35% reduction of the oxide, and a decreasing-rate stage. The rate of reduction in each stage is dependent on the nature and the degree of subdivision of the initial oxide and on the temperature. The same mole fraction is reduced in a given time regardless of the initial mass of oxide. The acceleration and decay stages are very closely approximated by a semi-empirical equation of the €'rout-Tompkins type, which is based on the initial reaction occurring on certain active nuclei followed by a rapid growth of these nuclei by a branching-chain mechanism. As a result, the reduction rate is not necessarily proportional to the initial surface area. The reduction rate reaches a maximum and subsequently decreases, as considerable interference occurs among the branching nuclei. ilrrhenius plots give an activation energy of 13.5 f. 1.2 kcal. for the reduction. Addition of the reaction product copper has no measurableoeffect on the reaction. Tl'ater vapor in concentrations of 25 mg./l. of hydrogen completely inhibits reaction initiation a t 112 , The inhibiting effect decrewes rapidly as the temperature is increased and disappears entirely a t 190". Once reduction starts, water vapor has practically no effect.
Many studies of the nature of the reduction of copper oxide by hydrogen have been reported in the literature. All investigators agree that the reduction consists of three stages-induction, autocatalytic or acceleratory, and decay-and that the reactions occur on certain active nuclei. There are, however, several areas of disagreement in the results of these studies. Several workers2-j have reported that water vapor markedly affects the beginning of the reduction, although little effect is observed once the reaction has begun. However, Pavlyuchenko and Rubinchike report that water vapor has no measurable effect on the onset of the reaction. Some workers2p3have reported that the autoleatalysis of the reaction is primarily a result of the Egolid product, copper, whereas others6,' report (1) Presented a t the 138th National Meeting of the American Chemical Society, New York, N. Y., September 11-16, 1960. (2) (a) R. N. Pease and H. 9. Taylor. J . Am. Chem. SOC.,43, 2179 (1921); (b) A. T.Larson and F. E. Smith, tbzd., 47, 346 (1925). (3) Y . Okayama, J . SOC.Chem. Ind. J a p a n , 31, 300 (1928); Chem. Abatr., 23, 2873 (1929). ( 4 ) IG. I. Chufarov, et al., Zhur. Fzz. Khzm., 26, 31 (1952) ( 5 ) 13. Hasegawa, PTOC. I m p . Acad. Tokyo, 19, 393 (1943). (6) M. XI. Pavlyuchenko and Ya. 8. Rubinchik, J . A p p l . Chem. U S S R 24, 751 (1951). (7) ,J. S. Lewis, J . Chsm. SOL,820 (1932).
that copper has no measurable effect and that the autocatalysis is the result chiefly of the crystal structure of the initial oxide. Mathematical expressions for the reduction rate a t various per cent of reduction differ The reduction has been shown to involve adsorbed hydrogen, with the rate only slightlg affected by hydrogen pressure in the 200-700 mm. range."6 Experimental Chemicals.-Three types of CuO were uscd: a wire form of reagent grade CuO obtained from Mallinckrodt Chemical Co., CuO prepared by calcination of Cu(NOa)z~*~HzO, and CuO prepared by calcination of C U ( O H ) ~ whlch was obtained by precipitation from a copper nitrate solution with ammonium hydroxide. All chemicals used in the preparations were reagent grade. Cupric oxide was prepared from the nitrate by weighing I50 g. of Cu(NO~)2.3HzOin a 250-ml. evaporating dish, carefully heating on a hot plate until most of the water of hydration had been removed, and then heating in a muffle furnace a t 400" for 22 hr. The product wae lightly crushed and sieved. About 757, of the material was found t o be
