Active Sites on Nanocrystalline Tin Dioxide Surface: Effect of Palladium and Ruthenium Oxides Clusters

Active sites of nanocrystalline tin dioxide materials with variable particle size, surface area, and catalytic modifiers were studied. Effect of palladium and ruthenium oxides clusters on the activity and concentration of tin dioxide surface centers was evaluated by temperature-programmed desorption techniques using probe molecules, FTIR spectroscopy, EPR, and thermogravimetric methods. The surface site concentration decrease was observed with an increase of SnO₂ particle size and BET area decrease. The active sites of SnO₂ were found to be selectively promoted by the additives. Accumulation of surface OH groups including hydroxyl spin centers and Broensted acid sites was characteristic for SnO₂/PdO_<i>x</i> nanocomposites as a result of water chemisorption enhancement due to proposed electronic clusters–support interaction. Ruthenium oxide was shown to increase the concentration of chemisorbed oxygen species via oxygen spillover route

Active Sites on Nanocrystalline Tin Dioxide Surface: Effect of Palladium and Ruthenium Oxides Clusters

Active sites of nanocrystalline tin dioxide materials with variable particle size, surface area, and catalytic modifiers were studied. Effect of palladium and ruthenium oxides clusters on the activity and concentration of tin dioxide surface centers was evaluated by temperature-programmed desorption techniques using probe molecules, FTIR spectroscopy, EPR, and thermogravimetric methods. The surface site concentration decrease was observed with an increase of SnO₂ particle size and BET area decrease. The active sites of SnO₂ were found to be selectively promoted by the additives. Accumulation of surface OH groups including hydroxyl spin centers and Broensted acid sites was characteristic for SnO₂/PdO_<i>x</i> nanocomposites as a result of water chemisorption enhancement due to proposed electronic clusters–support interaction. Ruthenium oxide was shown to increase the concentration of chemisorbed oxygen species via oxygen spillover route

CO₂ Hydrogenation to Methanol on CuO-ZnO/SiO₂ and CuO-ZnO/CeO₂-SiO₂ Catalysts Synthesized with β-Cyclodextrin Template

A series of mixed copper (II)—zinc oxide catalysts supported on unmodified and ceria-modified silica supports were synthesized using β-cyclodextrin as a template. The novelty of this work lies in the use of cyclosextrins for the template synthesis of catalyst supports. The obtained samples were analyzed by XRD, SEM-EDX, low-temperature nitrogen physisorption, XPS, and EPR. The magnetic properties of the catalysts were also measured. The thermal decomposition of precursors was analyzed by TGA combined with mass-spectrometric analysis of the evolved gases. The effects of the support pore size, the nature of the active phase and its loading, as well as the sequence of component deposition on the catalyst performance in the CO2 conversion to methanol were studied. The catalysts with cerium added at the gelation stage demonstrated the best performance. The selectivity of these samples reaches values of more than 90% over a fairly ide temperature range, with the productivity reaching 480 g/kg cat·h at 300 °C