Catalytic properties of the rare earth metals (Sc, Nd), their hydrides, carbides, and oxides in the reaction of high-temperature para-ortho conversion of hydrogen
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The metals scandium, neodymium, and their compounds with H, C, and O comprise the following series with respect to decreasing specific catalytic activity in the p-o conversion of hydrogen; Sc>ScH2 >ScC>Sc2O3; Nd>NdH3>NdC2>Nd2O3. It is suggested that such series are determined by the increase in the acceptor capacity of the nonmetal atoms in the series: H<C<O.
The activation energy of this reaction for each series retains satisfactory constancy; the preexponential factors A0 of the Arrhenius equation comprise series analogous to the activity series of the catalysts.
With respect to decreasing specific catalytic activity, the metals, hydrides, carbides, and oxides studied in the work comprise the series: Nd>Y> Sc; NdH3>YH3>ScH2; NdC2>YC>YC2> ScC; Nd2O3 >Y2O3>Sc2O3. It is suggested that these activity series are determined by the increasing value of the ionization potential of the metal atom.
Evidently the active centers in the reaction of p-o conversion of hydrogen are metal atoms. This agrees with the concepts of the formation of energetically stable electronic configurations for the atoms of the catalyst.
KeywordsCarbide Hydride Y2O3 Metal Atom Preexponential Factor
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