Display omitted
► The introduction of yttrium in Mg,Al hydrotalcite occurs without its insertion in the Mg or Al octahedral positions. ► The lower electronegativity of yttrium led to an increase of ...the basicity. ► The memory effect plays an important role in the reconstruction of the LDH structure from the beginning of the reaction. ► Hydration of mixed oxides generates a worm texture and contributes to the decrease of the surface area. ► During reconstruction of the LDH under inert atmosphere part of carbonic anions are replaced by hydroxyl groups.
Modification of Mg,Al hydrotalcite with Y
3+ prepared following co-precipitation at low suprasaturation led to an improvement of the activity and selectivity for styrene epoxidation with hydrogen peroxide in acetonitrile. The materials were characterized using several techniques such as XRD, DRIFT, TEM, CO
2-TPD and adsorption–desorption isotherms of nitrogen at −196
°C. It was thus demonstrated that the memory effect of hydrotalcite acts very quickly even in an unfriendly environment like that generated by hydrogen peroxide. A direct correlation between the memory effect and the catalytic behavior in the epoxidation of the styrene has been demonstrated. MgO and Al
2O
3 were also prepared using the precipitation method. The investigation of MgO, Al
2O
3 and of a mechanic mixture of them showed that the activity of the catalysts in this reaction correlates very well with their basicity.
Terbium ions were introduced in SiO
2 via two different pathways: (1) grafting the terbium europium complexes with two alcoxide structures, 3-(2-imidazolin-1-yl)-propyl-triethoxysilane (IPTES) and ...aminopropyl-trimethoxysilane (APTMS) and (2) functionalization of the SiO
2 support with silicon 4-carboxylbutyltriethoxide (CABES) followed by subsequent addition of the terbium ions. The new materials were investigated by means of nitrogen adsorption isotherms at −196
°C, thermogravimetric analysis, powder X-ray diffraction, Fourier-transform infra-red, diffuse reflectance , steady-state and time-resolved photoluminescence spectroscopy. Terbium complexes are heterogeneous distributed within silica framework and show relatively strong luminescence and long average photoluminescence lifetimes. The non-radiative deactivation of terbium emission in Tb-CABES/SiO
2 is more efficient compared to Tb-APTMS /SiO
2 and Tb-IPTES/SiO
2 and this is reflected in the order of the average photoluminescence lifetimes: Tb-CABES/SiO
2 (675
±
10
μs)
<
Tb-IPTES/SiO
2 (1040
±
20
μs)
<
Tb-APTMS/SiO
2 (1265
μs
±
25
μs).
Display omitted
•Plasma treatment considerably enhances the catalytic activity of graphene oxide.•Plasma exposure leads to the formation of defects and of surface acidic species.•The electron ...temperature and the dissociation degree of H2 are important parameters.
A considerable enhancement of the catalytic activity of graphene oxide (GO) was achieved as a result of plasma treatment in a hydrogen glow discharge. The results obtained for the hydroisomerization of 1-octene, together with the catalyst characterization showed that plasma exposure leads to the formation of defects in the material and of surface acidic species. Optical emission spectroscopy diagnostics of the plasma revealed that the electron temperature and the dissociation of molecular hydrogen are important parameters that can be tuned for optimization of the treatment process.
We highlighted aspects related to the different ways of using jumps to achieve goals aimed at developing explosive force in female volleyball players. We administered a questionnaire to 64 volleyball ...players registered with different teams in the Romanian championship to determine their opinions regarding the importance of jumping exercises in the development of explosive strength in volleyball players. The data presented in the research results highlight the fact that some types of jumps are used in a greater proportion in the parts of training intended for the development of explosive force, compared with other types of jumps. Referring to the type of strength pursued as a training goal, we found that the weight of the use of jumps is different, with a significant increase in their use in the parts of training aimed at speed strength/explosive strength.
Mesoporous M-SBA-15 (M/Si = 1/10) (where M = Al, B or AlB in a ratio 0.5:0.5) were prepared via a known procedure using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) ...(P123) as template. Further deposition of platinum on these supports has been achieved by impregnation with an aqueous solution of H2PtCl6. The prepared supports and catalysts were characterized by the adsorption-desorption isotherms of nitrogen at −196 °C, XRD and TEM measurements, and temperature-programmed desorption of ammonia (TPD-NH3). All these solids were investigated for the hydro-isomerization of heptane. In the investigated range of time (24 h) and temperatures (200–300 °C) the supports exhibited no isomerization activity but only a small cracking activity. The addition of platinum to these supports provided activity in this reaction even for a weak acid support as B-SBA-15. However, the presence of both aluminum and boron in a ratio of 0.5 to 0.5 led to a more efficient catalyst. Thus, the PtAlB-SBA-15 catalyst showed a slightly higher conversion than the PtAl-SBA-15 one. All the investigated Pt-SBA-15 provided high selectivity for the isomerization to methylhexanes. Dimethylpentanes were also produced but in a different extent, depending on the acidity of the support. Cracking of heptane to C1C4 molecules accompanied the hydro-isomerization process but in a rather small extent (yields smaller than 5% after 24 h).
Display omitted
•Mesoporous M-SBA-15 (M/Si = 1/10) (where M = Al, B or AlB in a ratio 0.5:0.5) were utilized as supports for the Pt catalysts.•Pt/M-SBA-15 shown catalytic behaviour for the hydro-isomerization of heptane.•Methylhexanes are the main isomerization products.•Dimethylpentanes were also produced but in a smaller extent.
The terrestrial snail Helix pomatia (Gastropoda: Stylommatophora: Helicidae) is one of the largest gastropod species in Europe. This species is strictly protected in some European Union countries; ...however, at the same time, it is also farmed and commercialized for human consumption. Here, we describe 11 microsatellite markers that are very useful in population genetic studies for assessing the status of both wild and farmed populations of this species of community interest. The microsatellites were isolated using 454 pyrosequencing technologies and 11 primer pairs were selected and used for genotyping an H. pomatia population and also checked for cross-species amplification on H. lucorum and H. lutescens specimens. The number of alleles per locus ranged from 3 to 13 and observed heterozygosity was between 0.458 and 0.917. Seven of these loci were polymorphic in H. lucorum, and four in H. lutescens. This set of nuclear markers provides a powerful tool for population genetic studies of this species of community interest, and also for closely related species. The described microsatellite markers should also facilitate the identification of populations of conservation concern.
Display omitted
•Ru or/and Ni catalysts were prepared by coprecipitation or wet impregnation.•Ru supported on alumina led to the highest degree of lignin depolymerisation.•Presence of ruthenium led ...to dimers as dominant products.•The interaction between ruthenium and nickel had an influence in the depolymerisation performance of lignin.
The catalytic performances of two different classes of catalysts containing nickel or/and ruthenium as the active sites were studied in the depolymerisation of lignin isolated from Miscanthus × giganteus. The catalysts were prepared either by coprecipitation (ie, (RuNiMgAlO)x, (RuNiAlO)x, (NiAlO)x, (NiMgAlO)x) or by wet impregnation (ie, Ru/Al2O3) and characterized by nitrogen physisorption (BET), XRD, XPS, NH3-TPD, Raman and H2-TPR techniques. The experimental results indicate that the presence of ruthenium led to dimers as dominant products.
PDF
