Olga Z. Didenko

Geometric and electronic approaches to size effects in heterogeneous catalysis

The influence of electronic and geometric factors is considered in the context of the manifestation of size effects in heterogeneous catalytic oxidation and hydrogenation reactions. Both of the factors are interdependent; however, the electronic factor predominates with regard to small metal and metal oxide particles (smaller than 10 nm), for which the energies of electron transitions in an activated complex are size-dependent. Only the geometry of active component nanoparticles exerts the main effect on the catalytic properties of coarser particles. In this case, the geometric factor depends on the accessibility of the active surface to reactants. The probability of the occurrence of complex active centers including several surface atoms increases as the active component particles of a catalyst become larger. The efficiency of the approach proposed to study the activating effect of nanophase catalysts is demonstrated using the oxidation and hydrogenation reactions of carbon oxides and the hydrogenation of acetonitrile and acetone as examples.

Synthesis of Nanosized ZnO/MgO Solid and Its Catalytic Activity for CO Oxidation

Abstract ZnO/MgO solid samples containing ZnO nanoparticles of controllable size were prepared using colloidal technique. The catalytic performance of the ZnO/MgO samples for CO oxidation was measured. The reaction rate of CO oxidation on the ZnO nanoparticles with variable average radius (2.01−2.29 nm) shows nonmonotonic dependence caused by the quantum-confinement effect.

Effect of temperature and small amounts of metal ions on transient chaos in the batch Belousov-Zhabotinsky system

Abstract We report an effect of temperature and small amounts of metal ions on transient chaotic regime observed in the batch Belousov–Zhabotinsky oscillating chemical reaction catalyzed by ferroin. The transient chaos is quantified by values of the largest Lyapunov exponent and induction period. We have found that these values depend through the Arrhenius equation on the temperature if the initial ferroin concentration is varied in the range of (0.87–3.5)×10 −3 M . We show that inside this range transient chaos is characterized by linear response to injection of solutions containing metal ions, e.g., cerium(III), manganese(II), vanadyl(IV) or thallium(I).