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Vol 474, No 2 (2017)
- Year: 2017
- Articles: 7
- URL: https://journals.rcsi.science/0012-5016/issue/view/9217
Physical Chemistry
Formation of catalytically active layers on the surface of polymetallic alloys
Abstract
A new method for the synthesis of catalysts on polymetallic supports via the formation of intermetallic (aluminide) layer on the support surface followed by leaching and stabilization of the layer has been proposed. The intermetallic layer structure and distribution of elements in the layer were studied by scanning electron microscope considering a nickel chromium stainless-steel grid as an example. The morphology and elemental composition of the active phase on the catalyst surface were studied. The complex structure of this phase was found to consist of two types of entities with different composition located on the continuous highly porous substrate. The catalyst sample was tested in deep oxidation of CO and propane and demonstrated high activity. The developed method can be used to obtain new high-performance polymetallic catalysts.
85-88
Supercomputer technologies for structural-kinetic study of mechanisms of enzyme catalysis: A quantum-chemical description of aspartoacylase catalysis
Abstract
The results of modeling of the complete catalytic cycle of aspartoacylase-catalyzed N-acetylaspartate hydrolysis by the combined quantum mechanics/molecular mechanics method and with the use of umbrella sampling replica-exchange molecular dynamics simulations are reported. It has been shown that the decrease in the high-energy barriers of rate-limiting stages is achieved through the preceding equilibrium stages, such as proton transfer and conformational changes. General features of the catalytic behavior of enzymes have been formulated.
89-92
Deflagration-to-detonation transition in the gas–liquid-fuel film system
Abstract
A deflagration-to-detonation transition was experimentally detected for the first time in a channel with a thin wall liquid-fuel film and a gaseous oxidizer using a weak ignition source, which generates no primary shock wave of any significant intensity. In a number of tests, a low-velocity quasi-stationary detonationlike combustion front traveling at an average velocity of 700–900 m/s was recorded; the structure of this front included a leading shock wave and a reaction zone following after a time delay of 80 to 150 μs.
93-98
A graph theory method for determining the basis of homodesmic reactions for acyclic chemical compounds
Abstract
One of the techniques for theoretically determining enthalpies of formation of organic compounds is the method of homodesmic reactions. In this work, a graph theory interpretation of acyclic chemical compounds was presented, and an algorithm for constructing a basis of homodesmic reactions was developed, which makes it possible to use a homodesmic approach to calculating the enthalpy of formation. Using the developed algorithm was exemplified by building the basis of homodesmic reactions for the butyramide molecule.
99-102
Sources of ultrahigh creep resistance of advanced martensitic steels
Abstract
New approaches to alloying high-chromium martensitic steels have been discussed. The suggested strategy makes it possible to retain their long-term creep strength at temperatures up to 650°C and operation times up to 2 × 105 h by increasing the boron content and decreasing the nitrogen content.
103-105
Self-organization processes and synthesis of nanostructured silver microparticles in AgNO3 solutions with variable pH values
Abstract
The morphology of micrometer-sized silver particles obtained by liquid-phase chemical reduction of silver nitrate with ascorbic acid depends appreciably on the solution pH. The synthesis carried out at 100°C for 20 min at pH < 4 or pH > 9 yields anisotropic faceted nanocrystalline particles, while the synthesis at pH = 5–8 results in self-assembly to give microspheres representing close-packed aggregates of a huge number of silver nanoparticles with a cauliflower structure.
106-108
Free radicals in photolysis of mixed phosphonium–iodonium ylides and in their reactions with acetylenes
Abstract
UV irradiation of mixed phosphonium–iodonium ylide in CH2Cl2 leads to formation of free radicals with lifetimes of a few minutes detected by EPR. In mixtures of ylides with acetylenes, the structure of radicals changes, and their concentration and stability increase. In the presence of acetylenes, the radicals contain ylide and acetylene residues, and their EPR spectra have hyperfine coupling constants typical for 31P nuclei in C-radicals and for 1H nuclei, depending on the acetylene structure. It has been demonstrated that the observed radical products are formed from short-lived primary radicals.
109-113