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The gas-phase hydrogenation of buta-1,3-diene has been studied in a static system using alumina-supported ruthenium (0-50°), rhodium (15-SO0), palladium (0-45"), osmium (25-70°), iridium (-2O-75"), and platinum (0-150').Orders of reaction and activation energies were measured. But-l-ene and cis-and trans-but-2-ene were initial products under all conditions. Palladium is completely selective for olefin formation but the other metals provide n-butane as an initial product, and it is the major product of the iridium-catalysed reaction. The dependence of the product composition on conversion, hydrogen pressure, and temperature is reported.1 : 2-Addition of hydrogen to the diene is responsible for but-l-ene formation on all of the metals. Formation of but-2-ene by a 1 : 4-addition process occurs on palladium and probably on the other metals; the relative yields of transand cis-but-2-ene formed by this process depend on the conformational characteristics of adsorbed precursors. Where n-butane formation takes place, simultaneous olefin isomerisation modifies the olefin distribution produced by 1 : 2-and 1 : 4-addition.The proportion of n-butane produced depends on the inherent activities of the metals for butene hydrogenation relative to desorption, and on the difference between the free energies of adsorption of buta-1,3-dienc and the butenes.Reaction characteristics were not dependent on the crystal structurc of the metal.

Although the catalytic properties of gold are surpassed by those of the Group Viii metals, especially palladium and platinum, possible applications of gold in catalytic processes have been widely studied, more especially for oxidative dehydrogenation. Alloys and mixtures

Over five different types of platinum catalyst the reaction of ethylene with hydrogen at 0" C or room temperature obeys the initial rate expressionThe products of the reaction between ethylene and deuterium over each catalyst have been analysed mass-spectrometrically over a range of temperatures and partial pressures. The simultaneous formation of HD and of deuterated ethylenes always occurs, but these processes are always much slower than the rate of addition : however, the rates of the exchange reactions vary very widely from one catalyst to another, particularly in their dependence on temperature and partial pressure variation.Redistribution leads to the formation of all possible isotopic ethanes, and the yield of those containing more than two D atoms declines logarithmically as the number of D atoms increases ; the ethane distributions can be accurately reproduced with the aid of two disposable parameters. Changes in the shape of the distribution due to temperature and reactant ratio variation follow the same trends with all catalysts, suggesting that the basic mechanisms are always the same. The postulation of five simple mechanisms satisfactorily explains all the observations.

The reaction between propylene and deuterium has been studied in the temperature range -18" C to 130" C over a pumice-supported platinum catalyst, and the products have been analyzed by means of a mass-spectrometer. At 18" C a redistribution of hydrogen and deuterium atoms occurs, giving rise to propanes containing from 0 to 8 deuterium atoms ; the yield of C3H6D2 increases as the relative pressure of deuterium is raised. The addition proceeds atomically, and is faster than the H2-D2 equilibration with equimolar mixtures of reactants. Equilibration between C3H6 and C3D6 is catalyzed by deuterium, but the resulting deutero-propylenes are only detected in the gas phase when deuterium is not in excess.

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The kinetics of the hydrogenation of cyclopropane have been studied over pumicesupported rhodium, palladium, iridium, and platinum catalysts between 0 and 200°C : orders of reaction, which depend on the method of catalyst preparation, indicate that the rate-controlling step involves adsorbed cyclopropane and adsorbed hydrogen atoms. Cyclopropane is probably chemisorbed as a n-complex. Activation energies and approximate adsorption coefficients are also reported.A kinetic study of the hydrogenation of methylcyclopropane over platinum-pumice shows that it is more strongly adsorbed than cyclopropane. Analysis reveals that the product is chiefly isobutane at room temperature, the proportion of n-butane rising to about 30 % at 250". These results are interpreted in terms of the electron-releasing influence of the methyl group.