ИСТИНА

Nanoparticles of metal have special catalytic properties in comparison with massive metal. This feature is actively studied in various catalytic reactions: hydrogenation, oxidation, carbon-carbon bond formation, electrochemical reactions, electron transfer reactions et al. The purpose of this work was to study the features of catalytic reduction of hexacyanoferrate(III) ions with hydrogen in presence of Pd nanoparticles. Palladium nanoparticles were obtained by the photochemical method when a xenon lamp was irradiated solution of Pd(II) and stabilizer PANa. The effect on reduction process of stirring, acidity of solution, hydrogen pressure and amount of catalyst was studied. It was found that both change of pH (in range from 3 to 11) and stirring of solution did not significantly affect rate constant of reduction process. These results demonstrates that internal or external diffusion is not the limiting stage. In addition, it is shown that the reaction rate depends linearly on both the hydrogen pressure and the amount of nanoparticles added. This is explained by first-order of hydrogen in reaction and by proportionality from active surface of catalyst. It was also noted that pre-saturation of palladium sol with hydrogen leads to a significant acceleration of reaction. This may be due to the fact that on the surface nanoparticles occur a reversible dissociative adsorption of hydrogen and formation of a bond H–PdNP. In the early works, it was assumed that dissociative adsorption on metal surface is nonactivation process. This assumption is confirmed by the absence of an effect of temperature on rate of the reaction.