Co-Pt bimetallic catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures

The performance of a Co-Pt powder and of Co-Pt catalysts supported on γ-Al₂O₃ and on the graphite-like carbon material Sibunit in selective CO oxidation in hydrogen-containing mixtures is considered. Fine particles of metal-metal solid solutions and intermetallides were obtained by the decomposition of a Co- and Pt-containing double complex salt in a hydrogen atmosphere at ～400°C. As compared to their Pt and Co monometallic counterparts, the bimetallic catalysts are more active and allow the CO concentration in hydrogen-containing mixtures to be reduced from 1 to 10^?3 vol %. This effect is likely due to the formation of bimetallic particles of a Co-Pt solid solution on the support surface.     

Synthesis of non-equilibrium PtxOs1−x Solid solutions. Crystal structure of [Pt(NH3)4][OsCl6]

Several non-equilibrium solid solutions belonging to the platinum-osmium systems Os_0.9Pt_0.1, Os_0.8Pt_0.2, Os_0.5Pt_0.5, Os_0.7Pt_0.3, Os_0.75Pt_0.25 are prepared and studied. The thermal decomposition of [Pt(NH₃)₄][OsCl₆] in the hydrogen and helium atmosphere is investigated. It is found that the Pt_0.5Os_0.5 solid solution develops through the formation of (NH₄)₂[OsCl₆] and a metallic phase based on Pt. The crystal structure of a double complex salt [Pt(NH₃)₄][OsCl₆] is studied (X8-APEX Bruker, 1508 independent reflections, R = 2.04%). Crystal data for PtOsN₄Cl₆H₁₂ are: a = 11.6216(5) Å, b = 11.0016(5) Å, c = 10.3819(5) Å, V = 1327.4(1) ų, space group Cmca, Z = 4, d _x = 3.333 g/cm₃. The coordination polyhedron around Os is octahedral: 〈Os-Cl〉 2.357 Å, ∠Cl-Os-Cl 89.5–90.5°, while around Pt it is square-planar: Pt-N 2.046 Å, ∠ N-Pt-N 89.59° and 90.41°.     

[Ru(NH3)6](MoO4)Cl·3H2O and [M(NH3)6](ReO4)3·2H2O (M = Ru, Ir). Synthesis and crystal structure

X-ray crystallographic analysis is used to determine the crystal structures of [Ru(NH₃)₆](MoO₄)Cl·3H₂O and [M(NH₃)₆](ReO₄)₃·2H₂O (M = Ru, Ir) complex salts. The features of the fragment packing are studied.     

Solid solutions Ru<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ir<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> synthesized by thermolysis of coordination compounds

The double complex salts [Ir(NH₃)₅Cl][IrCl₆], [Ru(NH₃)₅Cl][IrCl₆], and [Ru(NH₃)₅Cl]₂[IrCl₆]Cl₂ have been synthesized and characterized. An X-ray diffraction study demonstrated that these salts are isostructural with [Rh(NH₃)₅Cl][OsCl₆] and [Ir(NH₃)₅Cl]₂[PtCl₆]Cl₂ synthesized earlier. Thermolysis of these salts in hydrogen and helium has been studied. X-ray powder diffraction analysis show that thermolysis yields stoichiometric solid solutions of metals as the final products. The unit cell parameters of these products correspond to equilibrium phases.     

Liquid-phase epitaxy of multicomponent layer-based porous coordination polymer thin films of [M(L)(P)0.5] type: importance of deposition sequence on the oriented growth

The progressive liquid-phase layer-by-layer (LbL) growth of anisotropic multicomponent layer-based porous coordination polymers (PCPs) of the general formula [M(L)(P)(0.5)] (M: Cu(2+), Zn(2+); L: dicarboxylate linker; P: dinitrogen pillar ligand) was investigated by using either pyridyl- or carboxyl-terminated self-assembled monolayers (SAMs) on gold substrates as templates. It was found that the deposition of smooth, highly crystalline, and oriented multilayer films of these PCPs depends on the conditions at the early growth cycles. In the case of a two-step process with an equimolar mixture of L and P, growth along the [001] direction is strongly preferred. However, employing a three-step scheme with full separation of all components allows deposition along the [100] direction on carboxyl-terminated SAMs. Interestingly, the growth of additional layers on top of previously grown oriented seeding layers proved to be insensitive to the particular growth scheme and full retention of the initial orientation, either along the [001] or [100] direction, was observed. This homo- and heteroepitaxial LbL growth allows full control over the orientation and the layer sequence, including introduction of functionalized linkers and pillars.     

Phase transformations of the Re<Subscript>0.3</Subscript>Ir<Subscript>0.7</Subscript> solid solution

Transformations of the nonequilibrium solid solution Re_0.3Ir_0.7 at increased pressure (1–10 GPa) and temperature (2000°C) have been studied. A phase transition from the hexagonal close-packed cell to the face-centered cubic cell without a loss of density and volume per atom has been detected.     

On quadruples of projectors connected by a linear relation

We describe the set of γ ∈ ℝ for which there exist quadruples of projectors P _i for a fixed collection of numbers α_i   ℝ₊, , such that α₁ P ₁ + α₂ P ₂ + α₃ P ₃ + α₃ P ₄ = γI. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 9, pp. 1289–1295, September, 2006.