Synthesis and structure of the complex [Mo<Subscript>3</Subscript>(μ<Subscript>3</Subscript>-S)(μ<Subscript>2</Subscript>-S<Subscript>2</Subscript>)<Subscript>3</Subscript>(Et<Subscript>2</Subscript>NCS<Subscript>2</Subscript>)<Subscript>3</Subscript>]I

The structure of tri-μ₂-disulfido-μ₃-thiotris(diethyldithiocarbamato)-S,S′-triangle-trimolybdenum iodide [Mo₃(μ₃-S)(μ₂-S₂)₃(Et₂NCS₂)₃]I was determined. The compound was characterized by differential thermal analysis and IR, Raman, and X-ray electronic spectroscopy.     

Crystal structure of Na<Subscript>3</Subscript>(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[Ir(SO<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>4</Subscript>]·4H<Subscript>2</Subscript>O

The complex Na₃(NH₄)₂[Ir(SO₃)₂Cl₄]·4H₂O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) ų, space group P2₁/c, Z = 2, d _calc = 2.547 g/cm³. In the complex anion two trans SO ₃ ^2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Crystal structure of glycine phosphite C<Subscript>2</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>·H<Subscript>3</Subscript>PO<Subscript>3</Subscript>

Single crystal X-ray diffraction study of glycine phosphite C₂H₅NO₂·H₃PO₃ was performed (monoclinic, space group P2₁/c, a = 7.401(3) Å, b = 8.465(3) Å, c = 9.737(3) Å; β = 100.73(5)°, Z = 4). It has been found that one of hydrogen atoms is located at the centre of symmetry forming two strong hydrogen bonds to yield H₄P₂O ₆ ^?2 dimers, while another hydrogen atom is statistically disordered over two positions and organizes the dimers into an infinite corrugated chain. The ordering of this hydrogen atom position and/or displacement of the other one from the centre of symmetry will lead to the loss of symmetry centre and lowering of the point group symmetry from C_2h to piezo-active group C₂ or C _s .     

Catalytic dehydrogenation of cyclohexene over MoO<Subscript>3</Subscript>/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

A series of MoO₃/γ-Al₂O₃ catalysts with different Mo surface densities (Mo atoms/nm²) has been prepared by incipient wetness impregnation method. Structural characteristics of the prepared catalysts were investigated by atomic absorption spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, N₂ adsorption at −196 °C, and temperature-programmed reduction (TPR). The catalytic activities of the prepared catalysts were tested by cyclohexene conversion between 200 and 400 °C. XRD results indicated that molybdenum oxide species were dispersed as a monolayer on the support up to 4.04 Mo atoms/nm², and the formation of crystalline MoO₃ was observed above this loading. FTIR and TPR results showed that molybdenum oxide species were present predominantly in tetrahedral form at lower loading, and polymeric octahedral forms were dominant at higher loading. Cyclohexene conversion reaction proceeded mainly through the simple dehydrogenation pathway in the studied temperature range 200–400 °C and was found to be highly dependent on MoO₃ dispersion.     

Crystal structure of [Pb<Subscript>3</Subscript>(OH)<Subscript>4</Subscript>Co(NO<Subscript>2</Subscript>)<Subscript>3</Subscript>](NO<Subscript>3</Subscript>)(NO<Subscript>2</Subscript>)·2H<Subscript>2</Subscript>O

The structure of [Pb₃(OH)₄Co(NO₂)₃](NO₃)(NO₂)·2H₂O is determined by single crystal X-ray diffraction. The crystallographic characteristics are as follows: a = 8.9414(4) Å, b = 14.5330(5) Å, c = 24.9383(9) Å, V = 3240.6(2) ų, space group Pbca, Z = 8. The Co(III) atoms have a slightly distorted octahedral coordination formed by three nitrogen atoms belonging to nitro groups (Co–N_av is 1.91 Å) and three oxygen atoms belonging to hydroxyl groups (Co–O_av is 1.93 Å). The hydroxyl groups act as μ₃-bridges between the metal atoms. The geometric characteristics are analyzed and the packing motif is determined.     

Physicochemical properties of (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>NH<Subscript>2</Subscript>Cl–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Composite solid electrolytes were synthesized from the organic salt dimethylammonium chloride (1–x)C₂H₈NCl–xAl₂O₃. Their physicochemical properties were studied. In the starting C₂H₈NCl salt, there is a phase transition at 39°C accompanied by an increase in conductivity by two orders of magnitude. The conductivity of the high-temperature phase is 9.3 × 10^–6 S/cm at 160°C. A differential scanning calorimetry study showed that the salt in the composites spreads over the oxide surface and at x > 0.6 the salt melting enthalpy decreases to zero. The conductivity of the resulting composites was studied by impedance spectroscopy. It was shown that heterogeneous doping leads to a sharp increase in ion conductivity to 7.0 × 10^–3 S/cm at 160°C and a decrease in the activation energy to 0.55 eV.     

Effect of ZrO<Subscript>2</Subscript> on Catalyst Structure and Catalytic Sulfur-Resistant Methanation Performance of MoO<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

A series of MoO₃/ZrO₂–Al₂O₃ catalysts was prepared and investigated in the sulfur-resistant methanation aimed at production of synthetic natural gas. Different methods including impregnation, deposition precipitation, and co-precipitation were used for preparing ZrO₂–Al₂O₃ composite supports. These composite supports and their corresponding Mo-based catalysts were investigated in the sulfur-resistant methanation, and characterized by N₂ adsorption–desorption, XRD and H₂-TPR. The results indicated that adding ZrO₂ promoted MoO3dispersion and decreased the interaction between Mo species and support in the MoO₃/ZrO₂–Al₂O₃ catalysts. The co-precipitation method was favorable for obtaining smaller ZrO₂ particle size and improving textural properties of support, such as better MoO₃ dispersion and increased concentration of Mo⁶⁺ species in octahedral coordination to oxygen. It was found that the MoO₃/ZrO₂–Al₂O₃ catalyst with ZrO₂Al₂O₃ composite support prepared by co-precipitation method exhibited the best catalytic activity. The ZrO₂ content in the ZrO₂Al₂O₃ composite support was further optimized. The MoO₃/ZrO₂–Al₂O₃ with 15 wt % ZrO₂ loading exhibited the highest sulfur-resistant CO methanation activity, and excess ZrO₂ reduced the specific surface area and enhanced the interaction between Mo species and support. The N₂ adsorption-desorption results indicated that the presence of ZrO₂ in excessive amounts decreased the specific surface area since some amounts of ZrO₂ form aggregates on the surface of the support. The XRD and H₂-TPR results showed that with the increasing ZrO₂ content, ZrO₂ particle size increased. These led to the formation of coordinated tetrahedrally Mo⁶⁺(T) species and crystalline MoO₃, and this development was unfavorable for improving the sulfur-resistant methanation performance of MoO₃/ZrO₂–Al₂O₃ catalyst.     

Reciprocal system 3Tl<Subscript>2</Subscript>S + Sb<Subscript>2</Subscript>Se<Subscript>3</Subscript> ⇆ 3Tl<Subscript>2</Subscript>Se + Sb<Subscript>2</Subscript>S<Subscript>3</Subscript>

Phase equilibria in the reciprocal system 3Tl₂S + Sb₂Se₃ ? 3Tl₂Se + Sb₂S₃ are investigated by DTA, X-ray powder diffraction, and emf measurements. Some polythermal sections, the isothermal section of the phase diagram at 400K, and the liquidus-surface projection for this system are constructed. The types and coordinates of invariant and univariant equilibria are determined. It is shown that the system is non-diagonal. Broad regions of solid solutions are found on the basis of the binary compounds Tl₂S and Tl₂Se and along the boundary system Sb₂S₃-Sb₂Se₃ and the sections Tl₃SbS₃-Tl₃SbSe₃, TlSbS₂-TlSbSe₂, and TlSb₃S₅-TlSb₃Se₅ of the phase diagram.     

High-temperature reactions in the Co<Subscript>3</Subscript>Cr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript>–Cr(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> system

A new dichromium(III) cobalt(II) diphosphate(V) of the formula CoCr₂(P₂O₇)₂ was detected in the Co₃Cr₄(PO₄)₆–Cr(PO₃)₃ system. The new compound was obtained as a result of high-temperature solid-state reactions between CoCO₃, Cr₂O₃ and (NH₄)₂HPO₄ as well as between Cr(PO₃)₃ and Co₃Cr₄(PO₄)₆. CoCr₂(P₂O₇)₂ was characterized using XRD, DTA and IR methods. Results demonstrated that CoCr₂(P₂O₇)₂ crystallizes in the triclinic system and its unit cell parameters were calculated. Its infrared spectrum was presented. CoCr₂(P₂O₇)₂ melts incongruently at 1270±10 °C with a formation of solid α-CrPO₄. The compound Co₃Cr₄(PO₄)₆, component of the system under study, was obtained for the first time as a pure phase. Its thermal stability was also investigated. Co₃Cr₄(PO₄)₆ is stable in air up to 1410 ± 20 °C.     

The phase diagram of CsNO<Subscript>3</Subscript>–RbNO<Subscript>3</Subscript>

The phase transitions of RbNO₃ and the binary phase diagram of (Cs,Rb)NO₃ were investigated at atmospheric pressure, using simultaneous direct and differential thermal analysis, μDTA and DSC techniques. A fourth phase transition of RbNO₃ has been observed at temperature near the melting point. The phase diagram of this system is characterised by a eutectic, two eutectoid and an azeotropic-like invariants. Three limited solid solutions and two continuous solid solutions have been detected at low temperature.     

Effect of Fe-zeolite on formation of N<Subscript>2</Subscript>O in selective reduction of NO by NH<Subscript>3</Subscript> over V<Subscript>2</Subscript>O<Subscript>5</Subscript>–WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> catalyst

An approach for significantly suppressing N₂O formation in reduction of NO by NH₃ over V₂O₅–WO₃/TiO₂ (VWT) catalyst has been studied by coating different amounts of a Fe-exchanged zeolite (FeZ) onto the catalyst. FeZ-promoted VWT samples were characterized using N₂ sorption, X-ray diffraction (XRD) analysis, and NH₃ adsorption/desorption techniques to understand the primary role of FeZ in lowering N₂O production levels. At high temperatures (≥450 °C), VWT gave N₂O production with high concentrations, while N₂O formation was noticeably reduced when using FeZ-promoted catalysts, which also showed somewhat lower NO removal activities (<5 %) at all temperatures. N₂ sorption and XRD measurements revealed no perceptible physical or chemical alterations of each constituent, even in VWT catalysts after FeZ coating following high-temperature calcination. Adsorption of NH₃ on unpromoted and FeZ-promoted catalysts and subsequent desorption yielded very complicated spectra for N₂O that might primarily come from NH₃ oxidation, and the interaction between V–NO species at temperatures >580 °C. NO on neighboring sites seems to be produced via decomposition of N₂O generated at lower temperatures. The FeZ in the promoted VWT catalysts could be responsible for N₂O decomposition and N₂O reduction with unreacted NH₃ at temperatures >400 °C, thereby significantly lowering N₂O emission levels. This promotional effect bodes well for use in many industrial deNO _x applications.     

[Ca(OPPh<Subscript>3</Subscript>)<Subscript>5</Subscript>][Mo<Subscript>6</Subscript>(μ<Subscript>3</Subscript>-Cl)<Subscript>8</Subscript>Cl<Subscript>6</Subscript>] · OPPh<Subscript>3</Subscript>: Synthesis and crystal structure

A solvatothermal reaction of the octahedral cluster molybdenum complex (H₃O)₂[Mo₆(μ₃-Cl)₈Cl₆] · 6H₂O with CaCl₂ · 6H₂O and OPPh₃ in acetonitrile gave the known polymeric complex trans-[{Ca(OPPh₃)₄}{Mo₆(μ₃-Cl)₈Cl₆}]_∞. However, a closer examination revealed that this system also produces a novel cluster complex, [Ca(OPPh₃)₅][Mo₆(μ₃-Cl)₈Cl₆] · OPPh₃, which was isolated and characterized by X-ray diffraction.     

Impedance Study of the Conductivity of Solid Oxide Electrolyte Films SrZr<Subscript>0.95</Subscript>Y<Subscript>0.05</Subscript>O<Subscript>3–δ</Subscript> and CaZr<Subscript>0.9</Subscript>Y<Subscript>0.1</Subscript>O<Subscript>3–δ</Subscript>

Information on the across-plane conductivity of films of solid-oxide electrolytes SrZr_0.95Y_0.05O_3–δ and CaZr_0.9Y_0.1O_3–δ deposited on ion-conducting supports is acquired by the impedance method. It is shown that the support/film interface and the intergrain boundaries considerably affect the across-plane charge transfer in the film. The effect of the crystallographic orientation of the YSZ support on the microstructure and conductivity of the CaZr_0.9Y_0.1O_3–δ electrolyte film is demonstrated.     

Crystal structure of Ba<Subscript>3</Subscript>[UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(NCS)]<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Single crystals of Ba₃[UO₂(C₂O₄)₂(NCS)]₂ · 9H₂O are synthesized and studied by X-ray diffraction. The crystals are orthorhombic, space group Fddd, Z = 16, and the unit cell parameters are a = 16.253(3) Å, b = 22.245(3) Å, c = 39.031(6) Å. The main crystal structural units are mononuclear complex groups [UO₂(C₂O₄)₂NCS]^3? of the crystal-chemical family (AB ₂ ⁰¹ M¹ (A = UO ₂ ²⁺ , B⁰¹ = C₂O ₄ ^2? , M¹ = NCS^?) of the uranyl complexes linked into a three-dimensional framework by electrostatic interactions and hydrogen bonds involving oxalate ions and water molecules.     

Structural and Temperature Dependent Electrical Conductivity Properties of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript>–Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> CO-Doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

In the present work, Dy₂O₃ and Sm₂O₃ double-doped Bi₂O₃-based materials are synthesized by exploiting the solid-state synthesis method. The structural and temperature dependent electrical properties of these ternary ceramic samples, which are candidate materials for solid oxide fuel cell (SOFCs) electrolyte, are determined by means of a powder X-ray diffractometer (XRD), the four point-probe method (FPPM), and the thermal-gravimetry/differential thermal analysis (TG/DTA). As a result of the XRD measurements, the fluorite-type fcc δ-phase with a stable structure is obtained for higher values of the dopant oxide material, which are the samples with the maximum content of fixed 20% Dy₂O₃ and 15% and 20% Sm₂O₃. The samples with the stable δ-phase structure have higher conductivities. The highest electrical conductivity is found for the (Bi₂O₃)0.6(Dy₂O₃)_0.2(Sm₂O₃)_0.2 sample, which was 2.5×10^–2 (Ohm cm)^–1 at 750 °C. The activation energies are also calculated from the Arrhenius charts, which were determined from the FPPM measurements. The lowest activation energy is found as 0.85 eV for the sample with the highest electrical conductivity.     

Crystal structure of α-Ag<Subscript>8</Subscript>S<Subscript>3</Subscript>SO<Subscript>4</Subscript>

The crystal structure of silver sulfide-sulfate α-Ag₈S₃SO₄ was determined by X-ray powder diffraction data. The substance crystallizes in the tetragonal system and the space group P-4 with the unit cell parameters of α = 7.2032(4) Å, c = 5.1043(5) Å, Z = 1, R _f = 5.55%, χ² = 3.45. The layers in the structure of the compound formed by trigonal prisms of Ag₆S connected to each other through the vertices are connected by the additional atoms of sulfur into a three-dimensional framework. Distorted tetrahedral anions of SO ₄ ^2? are located in the cavities of the framework, the symmetry (D _2d ) of which was confirmed by the data of IR spectroscopy.     

Thermal analysis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1−x</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>x</Subscript> pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the (Bi₂O₃)_1−x(Y₂O₃)_x type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Y³⁺ ions. The incorporation of doped ions provides the interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Oxidation of Adamantane with H<Subscript>2</Subscript>O<Subscript>2</Subscript>–CF<Subscript>3</Subscript>COCF<Subscript>3</Subscript> · 1.5 H<Subscript>2</Subscript>O in the Presence of VO(acac)<Subscript>2</Subscript>

The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)₂ to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.