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Volume 477, Nº 2 (2017)
- Ano: 2017
- Artigos: 7
- URL: https://journals.rcsi.science/0012-5016/issue/view/9232
Physical Chemistry
New catalysts of dry reforming of methane into synthesis gas
Resumo
New catalysts have been developed for the production of synthesis gas via a resource-saving and environmentally friendly process—dry reforming of methane. The catalysts are fabricated from NdCaCo1–xNixOn precursors (x = 0, 0.2, 0.4, 0.6, 0.8, 1) synthesized by a ceramic method. According to X-ray powder diffraction, when reacting with an equimolar CH4/CO2 mixture at 800–900°С, the precursors are converted into a mixture of neodymium and calcium oxides and cobalt and nickel metals. The catalyst based on NdCaNiOn at 850°С has ensured high conversions of methane (91%) and CO2 (86%) at СО and hydrogen yields of 88 and 78%, respectively. At 940°С, the yield of CO is close to the quantitative one (97%).
209-211
Rearrangement energies for radicals of azido nitroaromatic compounds
Resumo
Dissociation energies of C–N3 bonds have been determined on the basis of data on the enthalpies of formation for a series of azido nitroaromatic compounds and the enthalpies of formation of radicals. Using fundamental relationships of chemical physics, a procedure has been suggested to calculate the energy of rearrangement of molecule fragments into radicals on the basis of special properties of rearrangement energy and the sums of average thermochemical energies for bonds comprising radical fragment in molecule. This calculation procedure provided a possibility to determine the energy of the N3 moiety transformation into N3 radical and the rearrangement energies of nitroaromatic radicals.
212-215
Drift mechanism for the formation of metallic wires in liquid helium
Resumo
A drift mechanism of formation of wires in liquid helium from metal laser ablation products has been suggested. The latter are usually ionized and are attracted to any surface due to the electric image force. This is responsible for that the drift of microparticles prevail over diffusion. The formation of anisometric structures (wires) under the drift conditions is a well-known phenomenon [9], not related to the properties of superfluid helium.
216-218
Creation of a microrelief by thermally stimulated shrinkage of metal-coated polypropylene films
Resumo
A study was made of the conditions of producing micron-sized reliefs by thermally stimulated shrinkage of metallized commercial biaxially oriented polypropylene films. It was shown that, in annealing within a temperature range close to the polypropylene melting point, the film shrinks in two directions to form folded structures on the surface. The folds are about 2–8 μm in size. The shrinkage and the relief depth depend on the annealing temperature. The relief remains on the film surface after the removal of the aluminum layer.
219-221
Synthesis, photophysical properties, and photochemical activity of the water-soluble dyad based on fullerene С60 and chlorin e6 derivatives
Resumo
Chlorin e6 derivative and water-soluble dyad resulting from covalent bonding of polyanionic fullerene С60 derivative to chlorin e6 derivative were synthesized and studied for spectral properties and photochemical activity. A considerable change in the absorption spectra and pronounced fluorescence quenching for the chlorin moiety included in the dyad were identified. The singlet excited state of chlorin is quenched via electron transfer from the excited chlorin to the fullerene core. A comparison of the photochemical activities of the test compounds in aqueous solutions showed a tenfold increase in the photochemical activity of the chlorin–fullerene dyad compared with free chlorin per absorbed light quantum.
222-226
Structural transformation of silver nanoprisms in aqueous solution initiated by Cl−, Br−, and I− ions: electrochemical mechanism
Resumo
It has been found that halide ions (Cl–, Br–, and I–) in aqueous solution initiate structural transformation of silver trigonal prisms (20−50 nm in size) in the sequence prism ⇒ disc ⇒ sphere. It has been demonstrated that the change in structure is caused by the formation of poorly soluble silver salts on nanoprisms and occurs by the electrochemical mechanism. The efficiency of the process is dictated by the nature of the halide ion.
227-230
On some features of glass transition in amorphous substances
Resumo
In Bartenev’s well-known approach to determining the dependence of glass-transition temperature on melt cooling rate, it was proposed to take into account the temperature dependence of the activation energy of the liquid-to-glass transition. The physical meaning of parameters of the obtained equation is discussed.
231-234