Деградация человеческого потенциала как фактор латентной составляющей деятельности высшей школы Украины

Рассмотрены проблемы тенизации и коррупционности функционирования украин-ской высшей школы на фоне вектора развития показателей потенциала населения страны.Розглянуті проблеми тінізації і коррупційності функціонування української вищої школи на тлі вектору розвитку показників потенціалу населення країни

Attachment of Iron Oxide Nanoparticles to Carbon Nanotubes and the Consequences for Catalysis

The attachment of colloidal iron-oxide nanoparticles (designated Fe-NPs) to pristine and surface-oxidized carbon nanotubes (CNTs and CNT-Ox, respectively) was investigated. The loadings of Fe-NPs (size 7 nm) on the CNT and CNT-Ox supports amounted to 3.4 and 2.3 wt. %, respectively; the difference was attributed to weaker van der Waals interactions between the colloidal Fe-NPs and the surface of CNT-Ox. Fischer–Tropsch to olefins (FTO) synthesis was performed to investigate the impact of support functionalization on catalyst performance. Weak interactions between the Fe-NPs and the CNT-Ox support facilitated particle growth and led to substantial deactivation of the Fe/CNT-Ox catalysts. The addition of promoters (Na+S) to Fe/CNT resulted in remarkable activity, selectivity to lower olefins, and stability, making colloidal iron nanoparticles on pristine CNTs a suitable catalyst for FTO synthesis

Attachment of Iron Oxide Nanoparticles to Carbon Nanotubes and the Consequences for Catalysis

The attachment of colloidal iron-oxide nanoparticles (designated Fe-NPs) to pristine and surface-oxidized carbon nanotubes (CNTs and CNT-Ox, respectively) was investigated. The loadings of Fe-NPs (size 7 nm) on the CNT and CNT-Ox supports amounted to 3.4 and 2.3 wt. %, respectively; the difference was attributed to weaker van der Waals interactions between the colloidal Fe-NPs and the surface of CNT-Ox. Fischer–Tropsch to olefins (FTO) synthesis was performed to investigate the impact of support functionalization on catalyst performance. Weak interactions between the Fe-NPs and the CNT-Ox support facilitated particle growth and led to substantial deactivation of the Fe/CNT-Ox catalysts. The addition of promoters (Na+S) to Fe/CNT resulted in remarkable activity, selectivity to lower olefins, and stability, making colloidal iron nanoparticles on pristine CNTs a suitable catalyst for FTO synthesis

Effects of Drying Conditions on the Synthesis of Co/SiO₂ and Co/Al₂O₃ Fischer–Tropsch Catalysts

The nanoscale distribution of the supported metal phase is an important property for highly active, selective, and stable catalysts. Here, the nanoscale redistribution and aggregate formation of cobalt nitrate during the synthesis of supported cobalt catalysts were studied. Drying over a range of temperatures in stagnant air resulted in cobalt particles (8 nm) present in large aggregates (30–150 nm). However, drying in a N₂ flow resulted in cobalt nanoparticles distributed either in aggregates or uniformly on various SiO₂ and γ-Al₂O₃ supports, critically dependent on the drying temperature. The mechanism of aggregation was studied through chemical immobilization of the precursor on a silica support after drying in a N₂ flow. The aggregation behavior upon drying in a gas flow at temperatures below 100 °C showed a remarkable similarity to distributions obtained upon the dewetting of colloidal films, suggesting a physical process. Alternatively, by inducing decomposition of the cobalt nitrate above 100 °C before drying was complete, aggregation was brought about through a chemical process that occurred both in stagnant and flowing gas. A γ-alumina support exhibited increased precursor-support interactions and displayed little cobalt aggregation upon drying in a gas flow but extensive aggregation upon drying in stagnant air. The aggregation behavior was further tested on silica supports with pore sizes between 3 and 15 nm and tested under industrially relevant Fischer–Tropsch conditions, which revealed that uniform cobalt nanoparticle distributions were up to 50% more active compared to aggregated systems. Thus, hydrodynamics and the temperature of the gas phase are critical parameters to control nanoscale distributions during drying of functional nanomaterials such as supported catalysts

Synthesis method for crystalline hollow titania micron-cubes

We report the synthesis of novel micron-sized titania cubes comprising a hematite core and a titania shell. Single core particles are entirely coated with a homogeneous titania shell of tunable thickness. Our convenient and straightforward synthesis method is mediated by the surfactant cetyltrimethylammonium bromide (CTAB) and proceeds under ambient conditions. Subsequent calcination transforms the amorphous titania shell to anatase/rutile titania; dissolution of the hematite core eventually results in hollow porous titania cubes. The resulting core–shell and hollow titania cubes display the tendency to align face-to-face, indicating their potential for utilization in close-packed arrays

Origin and prevention of broad particle size distributions in carbon-supported palladium catalysts prepared by liquid-phase reduction

Carbon-supported palladium (Pd/C) catalysts often display broad or multimodal Pd particle size distributions detrimental for their performance. Therefore, the formation of large particles during preparation should be better understood and avoided. We prepared catalysts with up to 10 wt% Pd supported on oxygen-functionalized carbon nanotubes and activated carbon via liquid-phase reduction. It was inferred that small Pd particles (∼1 nm) were formed from Pd ions adsorbed on the carbon. At higher loadings, up to 65% of the Pd ended up in larger particles (>10 nm) probably formed from Pd ions in solution, lowering the Pd-normalized activity in the hydrogenation of cinnamaldehyde 4-fold compared to samples with small particles only. Three key factors were identified for preparing Pd/C catalysts with exclusively ∼1 nm Pd particles: a support with a high density of acid sites and high specific surface area, and a metal loading at molar ratio Pd/acid sites <0.5

Effects of the Functionalization of the Ordered Mesoporous Carbon Support Surface on Iron Catalysts for the Fischer–Tropsch Synthesis of Lower Olefins

Ordered mesoporous carbon (CMK-3) with different surface modifications is applied as a support for Fe-based catalysts in the Fischer–Tropsch to olefins synthesis (FTO) with and without sodium and sulfur promoters. Different concentrations of functional groups do not affect the size (3–5 nm) of Fe particles in the fresh catalysts but iron (carbide) supported on N-enriched CMK-3 and a support with a lower concentration of functional groups show higher catalytic activity under industrially relevant FTO conditions (340 °C, 10 bar, H2/CO=2) compared to a support with an O-enriched surface. The addition of promoters leads to more noticeable enhancements of the catalytic activity (3–5 times higher) and the selectivity to C2–C4 olefins (≈2 times higher) than surface functionalization of the support. Nitrogen surface functionalization and removal of surface groups before impregnation and calcination, however, further increase the activity of the catalysts in the presence of promoters. The confinement of the Fe nanoparticles in the mesopores of CMK-3 restricts but does not fully prevent particle growth and, consequently, the decrease of activity under FTO conditions

Stability of Colloidal Iron Oxide Nanoparticles on Titania and Silica Support

Using model catalysts with well-defined particle sizes and morphologies to elucidate questions regarding catalytic activity and stability has gained more interest, particularly utilizing colloidally prepared metal(oxide) particles. Here, colloidally synthesized iron oxide nanoparticles (FexOy-NPs, size ∼7 nm) on either a titania (FexOy/TiO2) or a silica (FexOy/SiO2) support were studied. These model catalyst systems showed excellent activity in the Fischer-Tropsch to olefin (FTO) reaction at high pressure. However, the FexOy/TiO2 catalyst deactivated more than the FexOy/SiO2 catalyst. After analyzing the used catalysts, it was evident that the FexOy-NP on titania had grown to 48 nm, while the FexOy-NP on silica was still 7 nm in size. STEM-EDX revealed that the growth of FexOy/TiO2 originated mainly from the hydrogen reduction step and only to a limited extent from catalysis. Quantitative STEM-EDX measurements indicated that at a reduction temperature of 350 °C, 80% of the initial iron had dispersed over and into the titania as iron species below imaging resolution. The Fe/Ti surface atomic ratios from XPS measurements indicated that the iron particles first spread over the support after a reduction temperature of 300 °C followed by iron oxide particle growth at 350 °C. Mössbauer spectroscopy showed that 70% of iron was present as Fe2+, specifically as amorphous iron titanates (FeTiO3), after reduction at 350 °C. The growth of iron nanoparticles on titania is hypothesized as an Ostwald ripening process where Fe2+ species diffuse over and through the titania support. Presynthesized nanoparticles on SiO2 displayed structural stability, as only ∼10% iron silicates were formed and particles kept the same size during in situ reduction, carburization, and FTO catalysis

Promoted Iron Nanocrystals Obtained via Ligand Exchange as Active and Selective Catalysts for Synthesis Gas Conversion

Colloidal synthesis routes have been recently used to fabricate heterogeneous catalysts with more controllable and homogeneous properties. Herein a method was developed to modify the surface composition of colloidal nanocrystal catalysts and to purposely introduce specific atoms via ligands and change the catalyst reactivity. Organic ligands adsorbed on the surface of iron oxide catalysts were exchanged with inorganic species such as Na₂S, not only to provide an active surface but also to introduce controlled amounts of Na and S acting as promoters for the catalytic process. The catalyst composition was optimized for the Fischer–Tropsch direct conversion of synthesis gas into lower olefins. At industrially relevant conditions, these nanocrystal-based catalysts with controlled composition were more active, selective, and stable than catalysts with similar composition but synthesized using conventional methods, possibly due to their homogeneity of properties and synergic interaction of iron and promoters

Stability of Colloidal Iron Oxide Nanoparticles on Titania and Silica Support

Using model catalysts with well-defined particle sizes and morphologies to elucidate questions regarding catalytic activity and stability has gained more interest, particularly utilizing colloidally prepared metal(oxide) particles. Here, colloidally synthesized iron oxide nanoparticles (FexOy-NPs, size ∼7 nm) on either a titania (FexOy/TiO2) or a silica (FexOy/SiO2) support were studied. These model catalyst systems showed excellent activity in the Fischer-Tropsch to olefin (FTO) reaction at high pressure. However, the FexOy/TiO2 catalyst deactivated more than the FexOy/SiO2 catalyst. After analyzing the used catalysts, it was evident that the FexOy-NP on titania had grown to 48 nm, while the FexOy-NP on silica was still 7 nm in size. STEM-EDX revealed that the growth of FexOy/TiO2 originated mainly from the hydrogen reduction step and only to a limited extent from catalysis. Quantitative STEM-EDX measurements indicated that at a reduction temperature of 350 °C, 80% of the initial iron had dispersed over and into the titania as iron species below imaging resolution. The Fe/Ti surface atomic ratios from XPS measurements indicated that the iron particles first spread over the support after a reduction temperature of 300 °C followed by iron oxide particle growth at 350 °C. Mössbauer spectroscopy showed that 70% of iron was present as Fe2+, specifically as amorphous iron titanates (FeTiO3), after reduction at 350 °C. The growth of iron nanoparticles on titania is hypothesized as an Ostwald ripening process where Fe2+ species diffuse over and through the titania support. Presynthesized nanoparticles on SiO2 displayed structural stability, as only ∼10% iron silicates were formed and particles kept the same size during in situ reduction, carburization, and FTO catalysis. Instrumenten groe