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Том 61, № 14 (2016)
- Год: 2016
- Статей: 3
- URL: https://bakhtiniada.ru/0036-0236/issue/view/10186
Article
Phase states of Li(Na,K,Rb,Cs)/W/Mn/SiO2 composite catalysts for oxidative coupling of methane
Аннотация
This survey analyzes the results of studies into Li(Na,K,Rb,Cs)/W/Mn/SiO2 composites, which are used as catalysts for oxidative coupling of methane (OCM). The focus is on phase states. Our analysis shows that the SiO2 matrix is an active constituent of the composites and not an inert carrier of additives and the OCM heterogeneous process involves alkali-metal tungstate melts, along with polycrystalline manganese oxides. The effects of the cation ratio and synthetic routes on the phase composition of Li(Na,K,Rb,Cs)/W/Mn/SiO2 are assessed.
1689-1707
Structural features of monomeric octahedral d2-rhenium(V) monooxo complexes with oxygen atoms of bidentate-chelating acido (O,O)-ligands
Аннотация
The structural features of 39 mononuclear octahedral d2-rhenium(V) monooxo complexes (I–ХХХIХ) with oxygen atoms of bidentate-chelating (O,O) acido ligands (Lig) are considered. In 21 complexes (I–ХХI), the O(lig) atoms are both in trans and cis positions to oxo ligands. In the other 18 complexes (XXI–XXXIX), both O(lig) atoms are in cis positions to the O(oxo) ligands.
1708-1726
Symmetry and topology code of cluster self-assembly of icosahedral framework structures of boron and borides
Аннотация
The topological types of suprapolyhedral clusters composed of i-B12 icosahedra have been modeled. The models of icosahedral supraclusters have been used in analysis of the crystal structures of boron and borides (the TOPOS program package). To identify nanocluster precursors in crystal structures, there have been used special algorithms for partitioning structural graphs into disjoint substructures and constructing a basis 3D network of the structure as a graph with the nodes corresponding to the positions of the centroids of the cluster precursors. The cluster self-assembly have been modeled for 25 types of icosahedral framework structures of boron—B12-hR12, (B12)2(B2)2-oP28, (B12)4B2-P50, B196-tP196, and B333-hR333; binary borides—(B12)O2-hR14, (B12)P2-hR14, and (B12)(CBC)-hR15; templated metal borides—Na2(B12)2B6-oI64, Mg2(B12)B2-oI68, Tb(B12)(B4)-mI60, Al4(B12)4B8-oC88, (B12)4(Si4)4-oI64, (B12)4B2Be4-tP58, Ti2(B12)4B2-tP52, Sc12B180-tP192, Cu4Sc12B180-tP192, Si1.5Sc9B178-tP216, Mg28B360-oP388, Al28B352-oP384, Si28B352-oP306, Y24(B156)8(B39)8-cF1944, Sc10B315-hR339, and Li24B315-hR336. The symmetry and topology code of the crystal structure self-assembly from nanocluster precursors in the form of primary chain → microlayer → microframework has been completely restored. Frequency analysis of various topological and symmetry pathways for the formation and evolution of cluster precursors makes it possible to elucidate crystal-formation trends in inorganic systems at the microscopic level.
1727-1787