N. N. Tolkachev

The influence of the dispersion of metals on the activity of Pt/C and Pd/C catalysts in the dehydrogenation of perhydroterphenyl

The activity of Pt/C and Pd/C catalysts in the dehydrogenation of perhydroterphenyl was studied at conversions lower than 30% depending on the dispersion of platinum and palladium metals, which was estimated by two independent methods (adsorption of CO and X-ray diffraction).

Propane oxidation with chemically bound oxygen on Pt/TiO2/Al2O3 and Pt/CeO2/Al2O3 catalysts

Possible mechanisms are suggested for propane oxidation on Pt/TiO2/Al2O3 and Pt/CeO2/Al2O3 catalysts in the cyclic reactant supply mode. As compared to the steady-state process, the process conducted as catalyst oxidation-reduction cycles results in a very different product composition: it is more selective toward partial oxidation products and yields much smaller amounts of complete oxidation products. It is established by isothermal and temperature-programmed oxygen desorption that, under the reaction conditions examined, the oxygen desorbed from the catalyst surface into the gas phase makes a negligible contribution to propane oxidation. It is proved by XPS that propane oxidation is due to the chemically bound oxygen of the catalyst. The hypothetical mechanism of the process includes propane activation on Pt followed by the transfer of the activated species to the oxygen-storing component (TiO2 or CeO2), where the intermediates are oxidized by chemically bound oxygen.

Photocatalytic removal of nitrogen oxides from air on TiO2 modified with bases and platinum

The efficiency of TiO2 (Degussa P-25) modified with an alkaline admixture (urea, BaO), sulfuric acid, or platinum in the photocatalytic oxidation of NO (50 ppm) with a flowing 7% O2 + N2 mixture under UV irradiation in a flow reactor at room temperature and atmospheric pressure is reported. Because of the progressive blocking of active sites of the photocatalyst by the reaction products (NO2, NO3−), it is impossible to realize prolonged continuous removal of NOx (NO + NO2) from air without catalyst regeneration at elevated temperatures. The efficiency of the photocatalysts is characterized by specific photoadsorption capacity (SPC) calculated from the total amount of NOx adsorbed during 2-h-long irradiation. Modification of TiO2 with 5% BaO or 5% urea raises the SPC of the catalyst by a factor of 2–3. Presumably, this promoting effect is due to the basic properties of these dopants, which readily sorb NO2 and NO3−. A considerable favorable effect on SPC is also attained by adding 0.5% Pt to (5% BaO)/TiO2. The SPC of the (0.5% Pt)/TiO2 catalyst depends on the state of the platinum. The samples calcined in air at 500°C, which contain Pt+ and Pt2+, have an approximately 2 times higher SPC than unpromoted TiO2 and ensure a much larger NO2/NO ratio at the reactor outlet. Conversely, the samples reduced in an H2 atmosphere at 200°C, whose platinum is in the Pt0 state, show a lower SPC than the initial TiO2 and cause no significant change in the NO2/NO ratio.

Effect of electron beam irradiation on the formation of active sites in the Pt/H pentasil catalyst

The influence of preirradiation with an electron beam from a linear resonance electron accelerator in flowing argon on the structure and properties of the 1% Pt/H pentasil catalyst was studied. The support structure was studied by x-ray diffraction and low-temperature nitrogen adsorption. No changes in the crystal structure and pentasil specific surface area were observed in the irradiation dose range from 120 to 900 Mrad at an average electron energy of 7.7 MeV. The electron beam treatment resulted in a considerable increase in the catalytic activity of the Pt/H pentasil in gas-phase toluene hydrogenation as a model reaction. The results obtained by IR spectroscopy of adsorbed CO and X-ray diffraction data suggested that the increase in the catalyst activity after electron beam irradiation is due to changes in the size and charge of the Pt particles.