Methanation of CO2 over Ru?SiO2 catalyst

Using Ru–SiO₂ catalyst, the kinetics of methanation of carbon dioxide has been studied. In the temperature range of 320–460°C a simple power law model is found to predict experimental results with a good agreement over the range of variables studied.

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Ru/SiO₂. , 320–460°C.

     

Gas-phase measurements of the surface basicity of AlPO4?TiO2 and AlPO4?ZrO2 catalysts

The amount and strength of basic sites of AlPO₄–TiO₂ and AlPO₄–ZrO₂ catalysts over a different range of AlPO₄/metal oxide weight ratios were measured by studying the adsorption of acid molecules (acrylic acid and phenol) in the gas phase (473–673 K) by using the gas-chromatographic pulse method. The results obtained show that the basicity of AlPO₄–TiO₂ and AlPO₄–ZrO₂ catalysts is far lower than that of pure AlPO₄, and with an increase in the metal oxide (TiO₂ or ZrO₂) weight ratio, the basicity decreases. Besides, the basicity of AlPO₄–ZrO₂ is fairly low compared with that AlPO₄–TiO₂. In both cases, the total basicity (measured at 473 K vs. acrylic acid) gradually decreases with the calcination temperature while the stronger basic sites (measured at 573 K vs. phenol) remained unchanged up to calcination temperatures of 1073 K. Some weak surface basic sites remained in catalysts pretreated at 1273 K.

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- AlPO₄–TiO₂ AlPO₄–ZrO₂ AlPO₄/ , ( ) (473–673 K). , AlPO₄–TiO₂ AlPO₄–ZrO₂ AlPO₄ TiO₂ ZrO₂. , AlPO₄–ZrO₂ AlPO₄–TiO₂. — 473 K — , , 573 K , 1073 K. , 1273 K, .

     

Synthesis and structures of Cs4[(UO2)2(C2O4)(SO4)2(NCS)2] · 4H2O and (NH4)4[(UO2)2(C2O4)(SO4)2(NCS)2] · 6H2O

Single crystals of Cs₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 4H₂O (I) and (NH₄)₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 6H₂O (II) have been synthesized and studied by X-ray diffraction. The crystals of both compounds are orthorhombic with the space group Pbam, Z = 2, and unit cell parameters a = 12.0177(3) ?, b = 18.6182(5) ?, c = 6.7573(10) ?, R = 0.0376 (I); a = 11.6539(9) ?, b = 18.3791(13) ?, c = 6.7216(5) ?, R = 0.0179 (II). The main structural units of crystals I and II are [(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂]⁴⁻ chains belonging to the crystal-chemical group A₂K⁰²B₂²M₂¹ (A = UO₂²⁺, K⁰² = C₂O₄²⁻, B² = SO₄²⁻, M¹ = NCS⁻) of the uranyl complexes. The uranium-containing chains are joined into a three-dimensional framework due to a system of electrostatic interactions with the cesium or ammonium ions in the structure of I. In the structure of II, this framework is additionally stabilized by hydrogen bonds involving the outer-sphere water molecules and ammonium ions. Original Russian Text ? I.V. Medrish, A.V. Virovets, E.V. Peresypkina, L.B. Serezhkina, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 7, pp. 1115–1120.     

Oxidative coupling of methane over Bi2O3?P2O5?K2O/Sm2O3

Oxidative coupling of methane over Bi₂O₃–P₂O₅–K₂O/Sm₂O₃ takes place giving more C₂H₄ as compared to C₂H₆. Sm₂O₃ supported Bi–P–K is a more active and selective catalyst, than TiO₂, -Al₂O₃, SiO₂ and MgO supported catalysts.

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Bi₂O₃–P₂O₅–K₂O/Sm₂O₃ , . Bi–P–K, Sm₂O₃, , TiO₂, -Al₂O₃, SiO₂, MgO.

     

Crystal structure of K2[Mo3(PdPPh3)S4(C2O4)3(H2O)3]·0.5H2O

By the reaction of [Mo₃S₄(C₂O₄)₃(H₂O)₃]²⁻ with PdCl₂ and NH₄H₂PO₂ as a reducing agent, followed by the addition of PPh₃, a new oxalate cuboidal cluster complex [Mo₃(PdPPh₃)S₄(C₂O₄)₃(H₂O)₃]²⁻ is obtained. It was isolated and structurally characterized as K₂[Mo₃(PdPPh₃)S₄(C₂O₄)₃(H₂O)₃]·0.5H₂O. Original Russian Text Copyright ? 2008 by A. L. Gushchin, M. N. Sokolov, D. Yu. Naumov, and V. P. Fedin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 4, pp. 775–778, May–June, 2008.     

Dehydrogenation of Isobutane Over V2O5/γ-Al2O3 Catalyst

The effect of the type of the support and the amount of V₂O₅ loading on the activity of V₂O₅/γ-Al₂O₃ catalyst for the dehydrogenation of isobutane have been investigated. Based on the experimental results of TPR, XRD and ESR spectroscopy, it is suggested that there are strong interactions between vanadia and carrier and that the V⁴⁺ species on the surface is the active site of V₂O₅/γ-Al₂O₃ for this reaction. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis, crystal structure and luminescence of a novel metal-organic polymer {Cd2(C4H2O4)2(C4H6N2)2(H2O)2 · 2H2O}n

The novel 3D coordination polymer {Cd₂(C₄H₂O₄)₂(C₄H₆N₂)₂(H₂O)₂ · 2H₂O} _n (I) has been synthesized and characterized by standard solid state methods including single-crystal X-ray crystallography. The compound crystallizes in triclinic space group P [`1]\bar 1 with a = 8.589(4), b = 10.585(3), c = 13.094(1) ?, α = 84.91(4)°, β = 79.21(0)°, γ = 83.76(4)°, V = 1159.5(1) ?³, Z = 2. The fumaric acid acts as a multimodal bridging ligand in the polymer unit. One of the fumaric acid ligands tridentately chelates to two Cd²⁺ cations in the same dinuclear unit, while the other bidentately chelates to two Cd²⁺ cations in another dinuclear unit. The two metal centers possess slightly distorted pentagonal bipyramid geometry with four Cd {(μ₄-fumarato)-(μ₂-fumarato)-bis(2-methylimidazolyl)-diaqua} units joining together to form a 28-membered ring. The whole molecule exhibits a through channel along y-axis and 2D layers in xz plane. With hydrogen bond and π-π interaction, the 2D layers construct a 3D microporous network.     

Crystal structure of metal-organic coordination polymers [Cu(bpy)2(H2O)2](NO3)2·4.5C2H5OH and [Cu2(bpy)(H2O)(L-pha)2](NO3)2·H2O

Two metal-organic coordination polymers [Cu(bpy)₂(H₂O)₂](NO₃)₂·4.5C₂H₅OH (1) and [Cu₂(bpy)(H₂O)(L-pha) ₂](NO₃)₂·H₂O (2) (L-Hpha = L-phenylalanine, bpy = 4,4′-bipyridyl) are prepared by slow evaporation of an aqueous alcoholic solution of copper nitrate, L-phenylalanine, and 4,4′-bipyridyl. The structure and composition of the obtained compounds are determined by single crystal XRD. The framework of compound 1 is positively charged and forms two types of intersecting channels. Compound 2 is a homochiral metal-organic coordination polymer whose structure contains L-phenylalanine anions.     

Diverse coordination of two ligands in ferromagnetic [Cu(μ-HCO2)2(3-pyOH)]n and [Cu2(μ-HCO2)2(μ-3-pyOH)2(3-pyOH)2(HCO2)2]n

Two novel polynuclear complexes with methanoate anions and 3-hydroxypyridine ligands [Cu(μ-HCO₂)₂(3-pyOH)]_n (1) and [Cu₂(μ-HCO₂)₂(μ-3-pyOH)₂(3-pyOH)₂(HCO₂)₂]_n (2), respectively, were synthesized and characterized. The central copper atom in 1 is surrounded by four methanoates and a 3-pyOH molecule, forming a square-pyramidal CuO₃NO chromophore. All the methanoates are bidentate and serve as bridges between the adjacent copper ions via syn-anti and anti–anti coordination. The basal square coordination axes are formed by O(syn), N(3-pyOH) (1.974(2), 2.016(2) Å) and O(anti), O(anti) (1.945(2), 1.960(2) Å), while the third O(anti) (2.247(2) Å) is on the top of the pyramid. A ferromagnetic transition with an exchange constant 2J/k_B = 9.2 cm⁻¹ is found for 1 below 20 K. This interaction probably takes place through two syn-anti methanoates extended in a chain through the 2D structure. On the other hand, two monoatomic Cu–O–Cu intra-dinuclear asymmetric (1.986(2), 2.415(2) Å) bridges of two methanoates in [Cu₂(HCO₂)₄(3-pyOH)₄] (2) are present. An elongated distorted octahedral coordination sphere around each copper(II) atom is completed by an additional monodentate terminal methanoate (1.975(2) Å), two N-coordinated 3-pyOH (2.005(2), 2.002(2) Å) and the third weakly O-coordinated 3-pyOH (2.732(2) Å). Although a shorter Cu?Cu distance is noticed in 2 than in 1 (4.690(1) Å 1, 3.442(1) Å 2), much weaker ferromagnetism is found in 2.     

Oxo Peroxo Glycolato Complexesof Vanadium (V). Crystal Structureof (NBu4)2[V2O2(O2)2(C2H2O3)2]?H2O

 Oxo peroxo glycolato complexes of vanadium(V) (M ₂[V₂O₂(O₂)₂(C₂H₂O₃)₂]ċnH₂O (n=0, 1; M=NBu₄ ⁺ (1), K⁺ (2), NH₄ ⁺ (3), Cs⁺ (4), NPr₄ ⁺ (5)) as well as (NBu₄)₂[V₂O₄(C₂H₂O₃)₂]ċ H₂O (6) have been prepared and characterized by spectroscopic methods. X-Ray structure analysis of 1 revealed the presence of dinuclear [V₂O₂(O₂)₂(C₂H₂O₃)₂]²⁻ anions with a (chemical structure) bridging core and six coordinated vanadium(V) atoms in a distorted pentagonal pyramidal array.     

Crystal structure of [Pd(NH3)4]3[Ir(NO2)6]2·H2O

A single crystal of [Pd(NH₃)₄]₃[Ir(NO₂)₆]₂·H₂O double complex salt is studied by X-ray diffraction. Crystallographic characteristics are as follows: a = 21.0335(5) ?, b = 8.0592(2) ?, c = 21.3452(5) ?, β = 91.254(1)°, V = 3617.43(15) ?³, P2₁/c space group, Z = 4, d _x = 2.714 g/cm³. Single-layer pseudohexagonal packing of complex anions is determined along the [−1 0 1] direction in the structure. Complex cations and crystallization water molecules are located between the mentioned layers.     

Sandwich-type Uranium-Substituted of Bismuthotungstate: Synthesis and Structure Determination of [Na(UO2)2(H2O)4(BiW9O33)2]13?

The sandwich-type [Na(UO₂)₂(H₂O)₄(BiW₉O₃₃)₂]¹³⁻ uranium (VI) has been synthesized by reacting the trivacant species of B-α-[BiW₉O₃₃]⁹⁻ with and investigated by IR and UV–Vis spectroscopy, and elemental analysis. The X-ray single crystal analysis was carried out on Na₁₃[Na(UO₂)₂(H₂O)₄(BiW₉O₃₃)₂] · 33H₂O (I) which crystallizes in the orthorhombic system, space group Pna2₁ with a = 33.8454(19) ?, b = 21.1484(12) ?, c = 13.2403(7) ?, α = 90°, β = 90°, γ = 90°, and Z = 4. The polyanion consists of two lacunary B-α-[BiW₉O₃₃]⁹⁻ groups which sandwich two uranyl cations and one sodium cation. The uranium atoms adopt distorted pentagonal–bipyramidal coordination, achieved by two equatorial bonds to each BiW₉O₃₃ unit and one external water ligand. The coordination of each uranium atom is evident by the shift of ν_as(W–O_b–W) and ν_as(Bi–O) stretching vibrational bonds. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Hydrothermal synthesis and crystal structures of new uranyl oxalate hydroxides: α- and β-[(UO2)2(C2O4)(OH)2(H2O)2] and [(UO2)2(C2O4)(OH)2(H2O)2]·H2O

Two modifications of the new uranyl oxalate hydroxide dihydrate [UO₂)₂(C₂O₄)(OH)₂(H₂O)₂] (1 and 2) and one form of the new uranyl oxalate hydroxide trihydrate [(UO₂)₂(C₂O₄)(OH)₂(H₂O)₂]·H₂O (3) were synthesized by hydrothermal methods and their structures determined from single-crystal X-ray diffraction data. The crystal structures were refined by full-matrix least-squares methods to agreement indices R(wR)=0.0372(0.0842) and 0.0267(0.0671) calculated for 1096 and 1167 unique observed reflections (I>2σ(I)), for α (1) and β (2) forms, respectively and to R(wR)=0.0301(0.0737) calculated for 2471 unique observed reflections (I>2σ(I)), for 3. The α-form of the dihydrate is triclinic, space group , Z=1, a=6.097(2), b=5.548(2), , α=89.353(5), β=94.387(5), γ=97.646(5)°, , β-form is monoclinic, space group C2/c, Z=4, a=12.180(3), b=8.223(2), , β=95.817(4), . The trihydrate is monoclinic, space group P2₁/c, Z=4, a=5.5095(12), b=15.195(3), , β=93.927(3), . In the three structures, the coordination of uranium atom is a pentagonal bipyramid composed of dioxo UO₂²⁺ cation perpendicular to five equatorial oxygen atoms belonging to one bidentate oxalate ion, one water molecule and two hydroxyl ions in trans configuration in 2 and in cis configuration in 1 and 3. The UO₇ polyhedra are linked through hydroxyl oxygen atoms to form different structural building units, dimers [U₂O₁₀] obtained by edge-sharing in 1, chains [UO₆]_∞ and tetramers [U₄O₂₆] built by corner-sharing in 2 and 3, respectively. These units are further connected by oxalate entities that act as bis-bidentate to form one-dimensional chains in 1 and bi-dimensional network in 2 and 3. These chains or layers are connected in frameworks by hydrogen-bond arrays.     

Solid state synthesis of CuFe2O4 from Cu(OH)2?·?CuCO3–4FeC2O4?·?2H2O mixtures: mechanism of reaction and thermal characterization of CuFe2O4

Copper Ferrite has been prepared by solid state synthesis of milled mixtures of copper basic carbonate [Cu(OH)₂ · CuCO₃] and iron (II) oxalate dihydrate [FeC₂O₄ · 2H₂O]. The reaction mechanism has been studied by simultaneous TG/DSC analysis: the different steps of the mass loss process have been individuated along with the relevant enthalpy terms starting from both physical and mechanically activated mixtures. CuFe₂O₄ has been synthesized by annealing the mechanically activated mixture at 750–800 °C while no pure CuFe₂O₄ is obtained by annealing the physical mixture at temperatures as high as 1100 °C. CuFe₂O₄ has been characterized as concerns the molar het capacity, the tetragonal–cubic transition enthalpy and the Curie point.     

Deuterium exchange reaction of ethylbenzene over an Fe2O3?K2CO3?Cr2O3 catalyst

Isotope exchange reaction of ethylbenzene with water or hydrogen has been examined over Fe₂O₃–K₂CO₃–Cr₂O₃ catalyst. The participation of the hydrogen attached to -carbon or phenyl group was observed. The exchange rate of the -hydrogen was compared for different alkylbenzenes and found that toluene was the most active, whereas cumene was inactive. This order suggested that the -hydrogen dissociated as a proton. -Adsorbed state was supposed as an intermediate of dehydrogenation, which dissociates the -hydrogen reversibly as a proton on a basic site. Including the results of exchange reaction of styrene, the overall route of dehydrogenation is discussed.     

Pyridine-2-thione (pySH) derivatives of silver(I): Synthesis and crystal structures of dinuclear [Ag2Cl2(μ-S-pySH)2(PPh3)2] and [Ag2Br2(μ-S-pySH)2(PPh3)2] complexes

Reaction of silver(I) halides with PPh₃ in acetonitrile and then with pyridine-2-thione (pySH) chloroform (1:1:1 molar ratio) has yielded sulfur bridged dimers of general formula, [Ag₂X₂(μ-S-pySH)₂(PPh₃)₂] (X = Cl, 1, Br, 2). Both these complexes have been characterized using analytical data, NMR spectroscopy and single crystal X-crystallography. The central Ag₂S₂ cores form parallelograms with unequal Ag–S bond distances (2.5832(8), 2.7208(11) Å) in 1 and (2.6306(4), 2.6950(7) Å) in 2, respectively. The Ag?Ag contacts of compounds 1 and 2 are 3.8425(8) and 3.8211(4) Å, respectively. The angles around Ag (in the range 87.19(2)–121.71(2)° in 1 and 87.81(2)–121.53(2)° in 2) reveal highly distorted tetrahedral geometry. There are inter dimer π–π stacking interactions between pyridyl rings (inter ring distances of 3.498 and 3.510 Å in complexes 1 and 2, respectively). The solution state ³¹P NMR spectroscopy has shown the existence of both monomers and dimers. The studies reveal relatively weaker intramolecular –NH?Cl hydrogen bonding in case of AgCl vis-à-vis that in CuCl which favored both a monomer and a dimer with AgCl, and only a monomer with CuCl.     

Synthesis of High-purity Fe2AlB2 and the Effect as Sintering Additive for ZrB2

Fe₂AlB₂ powder material was prepared by the direct reaction of iron,aluminum and boron powders in a tubular furnace.The effects of different Al contents,temperature and raw material pretreatment on the purity of product were studied.The mixed powder with the stoichiometric ratio of 1.5Al/2Fe/2B was processed by CIP (Cold Isostatic Pressing),and then calcined at 1150℃ for 120 min.The product containing a small amount of impurities is treated with alkaline solution to obtain high-purity Fe₂Al B₂ powder.Zr B₂-Fe₂Al B₂ composite ceramic was successfully prepared at 1250℃ by hot pressing sintering.The density,hardness and fracture toughness were 96.2%,22±0.3 GPa and 5.78±0.5 MPa·m^1/2,respectively.     

A comparison between the reaction of P2Ph4 with [{Co2(CO)6}2(μ-η:μ-η-HOCH2CCCCCH2OH)] and the reaction of [Co2(μ-PPh2)2(CO)6] with HOCH2CCCCCH2OH

Reaction of P₂Ph₄ with the diyne-diol complex [{Co₂(CO)₆}₂(μ-η²:μ-η²-HOCH₂CCCCCH₂OH)] in toluene at 65 °C gives [{Co₂(μ-P₂Ph₄)(CO)₄}{Co₂(CO)₆}(μ-η²:μ-η²-HOCH₂CCCCCH₂OH)] (1). Thermolysis of 1 at 95 °C leads to [{Co₂(CO)₅}₂(μ-P₂Ph₄)(μ-η²:μ-η²-HOCH₂CCCCCH₂OH)](2) and (μ₂-PPh₂)(μ₂-CO)(CO)₇] (3). The structures of 1-3 have been established by X-ray crystallography. In 1, a pseudoequatorial P₂Ph₄ ligand bridges the cobalt-cobalt bond of a Co₂(CC)(CO)₄ unit. By contrast, in isomeric 2, a pseudoaxial P₂Ph₄ ligand spans two Co₂(CC)(CO)₅ units, a new coordination mode for [{Co₂(CO)₅L}₂(μ-η²:μ-η²-diyne)] complexes. Complex 3 arises from dehydration-cyclocarbonylation of the diyne-diol in 1 to give a 2(5H)-furanone, a process that has not been previously reported. Reaction of HOCH₂CCCCCH₂OH with [Co₂(μ-PPh₂)₂(CO)₆] at 80 °C in toluene gave [Co₃(μ-PPh₂)₃(CO)₆], [Co₂(CO)₆(μ-η²-HOCH₂CCCCCH₂OH)] and [Co₂{μ-η⁴-PPh₂C(CCCH₂OH)C(CH₂OH)CO}(μ-PPh₂)(CO)₄] (4). The regiochemistry of 4 was confirmed by X-ray crystallography.