Theoretical investigation of the CO oxidation on Al<Subscript>12</Subscript>Zr Cluster

Equilibrium geometries of Al₁₂Zr cluster were systematically studied on the basis of density functional theory with generalized gradient approximation. To gain insights into high catalytic activity we use the CO oxidation as a benchmark probe. In Al–Zr bimetallic clusters, Zr site is the catalytically active centre, the adsorption of CO and O₂ on the same site respectively (single-site mechanism), a Langmuir-Hinshelwood (LH) mechanism is proposed, which proceed via two steps, CO + O₂ → CO₂ + O and CO + O → CO₂. Two CO oxidation mechanisms of two CO₂ molecules as product have been simulated. For the later mechanism, the key step is the O–O bond scission in the OCOO* intermediate, which is significantly accelerated due to the attack of the neighboring CO molecule. The calculated barriers for the later reactions are lower compared with the former reaction. Detailed reaction paths corresponding to this case are calculated. Our study suggests that the CO oxidation catalyzed by Al₁₂Zr cluster is likely to occur at the room temperature.     

Concentrated solar energy for thermochemically producing liquid fuels from CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O

A two-step solar thermochemical cycle for producing syngas from H₂O and CO₂ via Zn/ZnO redox reactions is considered. The first, endothermic step is the thermolysis of ZnO to Zn and O₂ using concentrated solar radiation as the source of process heat. The second, non-solar, exothermic step is the reaction of Zn with mixtures of H₂O and CO₂ yielding high-quality syngas (mainly H₂ and CO) and ZnO; the latter is recycled to the first solar step, resulting in net reactions CO₂ = CO+0.5O₂ and H₂O= H₂ +0.5O₂. Syngas is further processed to liquid fuels via Fischer-Tropsch or other catalytic reforming processes. State-of-the-art reactor technologies and experimental results are provided for both steps of the cycle.     

Zur Korrosion von unlegiertem Stahl und Aluminium in wäßrigen Lösungen von Ammoniak und Kohlensäure — 1. Mitteilung: Korrosionsprodukte

Corrosion of unalloyed steel and aluminium in aqueous solution of ammonia and carbonic acid-1. Communication:Corrosion products Two new corrosion products were detected in testing of pure iron, rimming unalloyed steel, aluminium (99,9) and Al-Mg 1,5 in aerated aequous solutions of 130 g/l NH₃ and 80/l Co₂ at 60°. On iron and unalloyed steel the compound (NH₄)₂Fe₂(OH)₄(CO)₃ · H₂O was formed and on aluminium or Al-Mg 1,5 NH₄Al(OH)₂CO₃ · H₂. Both compounds were synthesized and compared by X-ray diffraction, IR spectrum, thermoanalysis, and chemical analysis with published literature. For NH₄Al(OH)₂CO₃ · H₂O the unit cell was calculated which changes somewhat with for the corrosion product are a = 6,64 Å; b = 11,99 Å; c = 5,76 Å. Orthorhombic lattice, aspect C*c*, or (a*) = 13.29 Å; C* = 11,99 Å (hexagonal lattice, pseudohexagonal?). The measured density = 2.03 g · the calculated 2,29 g · cm for Z = 4. The infrared spectrum was partly newly coordinated. Between aluminium metal and NH₄Al(OH)₂CO₃H₂O epitaxial relations are possible, which could explain the higher resistance against corrosion in comparison with steel in the test solution.     

Theoretical investigation of water gas shift reaction catalyzed by [Ru(CO)<Subscript>3</Subscript>Cl<Subscript>3</Subscript>]<Superscript>–</Superscript> in solution

Mononuclear Ru halogen carbonyl complex was the exclusive to catalyze the water-gas reaction (WGR) according to Ken-ichi Tominaga et al. Density functional theory (DFT) is employed to study the water-gas shift reaction (WGSR) in basic solution for [RuCl₃(CO)₃]^?. Four different mechanistic pathways have been considered. The calculations indicate that formic acid mechanism to be competitive. The energetic span model (ESM) proposed by Shaik et al. has been applied to reveal the kinetic behavior of the four catalytic cycles. The one with the highest efficiency usually gives the highest TOF. The formic acid mechanism exhibits high catalytic activity towards water gas shift reaction due to the highest value of the calculated turnover frequency (1.89 × 10^–14 s^–1), which is higher than the value of TOF (1.74 × 10^–16 s^–1, Ru(CO)₅; 1.88 × 10^–15 s^–1, Fe(CO)₅). It turned out that [Ru(CO)₃Cl₃]^– is a promising candidate for an improved WGSR catalyst and a better catalyst for the industrially important reaction.     

Morphology and activity relationships of macroporous CuO–ZnO–ZrO<Subscript>2</Subscript> catalysts for methanol synthesis from CO<Subscript>2</Subscript> hydrogenation

A series of macroporous CuO–ZnO–ZrO₂ (CZZ) catalysts with different Zn/Zr ratios were successfully prepared by template method and characterized by X-ray diffraction (XRD), N₂ adsorption, reactive N₂O adsorption, scanning electron microscopy (SEM), H₂ temperature-programmed reduction (H₂-TPR), and transmission electron microscopy (TEM). The activity of the catalysts was tested for methanol synthesis from CO₂ hydrogenation. It is found that the increase in the Zn/Zr ratio could lead to the sintering of the catalysts, destroying the macroporous structure integrity. The macroporous CZZ catalysts own lower Zn/Zr ratio, exhibiting a better morphology and activity. For comparison, the conventional nonporous CZZ catalysts were also investigated. The results show that the CZZ catalysts with macroporous structure own smaller particles, higher CO₂ conversion, and CH₃OH yield. It reveals that the macroporous structure could inhibit the growth of the particle size, and the special porous structure is favorable for diffusion and penetration of CO₂, which could improve the catalytic activities.     

On the oxidation of iron in CO2 + CO mixtures. III: Coupled linear parabolic kinetics

High-purity iron has been oxidized at 1000–1200° C in CO₂ and in CO₂ + CO with different compositions and at different total gas pressures (0.1–1 atm.). The experimental work has comprised thermogravimetric reaction rate measurements and characterization of the wüstite scales by metallography and x-ray diffraction. The overall results have been analyzed in terms of a classical model for coupled linear/parabolic kinetics, where it is assumed that the surface of growing wüstite scales has exactly the same defect structure and defect concentrations as that of bulk wüstite equilibrated in the same gaseous atmospheres. Important discrepancies are found between the predicted and the experimentally observed reaction behavior. Thus, both the linear and parabolic rate constants are found to be dependent on the partial pressure of CO₂ and the total gas pressure of the CO₂ + CO gas mixtures, and furthermore, the reaction in CO₂ + CO is slower than in O₂ and in H₂O + H₂ with the same oxygen activity. In order to explain the experimental results, it is suggested that CO and CO₂ molecules interact with the wüstite surface and thereby affect the defect structure and defect concentrations in a thin surface layer, and that this, in turn, affects both the linear and parabolic reaction rates.     

An IR Spectroscopic Study of the Effect of Gamma Radiation on the Nano-ZrO<Subscript>2</Subscript> + Nano-SiO<Subscript>2</Subscript> + H<Subscript>2</Subscript>O Systems

Using the method of IR Fourier-transform spectroscopy, the radiation decomposition of water in the nano-ZrO₂ + nano-SiO₂ + H₂O system at room temperature (T = 300 K) under the influence of γ-quanta is studied. It is shown that the adsorption of water by the zirconium and silicon nanooxides proceeds by the molecular and dissociative mechanisms. The following intermediate active products of the radiation-heterogeneous decomposition of water are registered: Zr and Si hydrides, and hydroxyl OH groups. It is shown that a change in the ratio of the ZrO₂ and SiO₂ nanopowders gives rise to a change in the surface profile and in the radiation-chemical yield of molecular hydrogen.     

Equilibria in Reactions of Hydrogen,and Carbon Monoxide With Dissolved Oxygen in Liquid Iron; Equilibrium in Reduction of Ferrous Oxide With Hydrogen,and Solubility of Oxygen in Liquid Iron

Equilibria in the following reactions have been investigated in the range of 1550° to 1700°C : 1) H₂ + O_ (in liquid Fe) = H₂O, 2) CO + O_ (in liquid Fe) = CO₂, and 3) H₂ + Fe _x O (liquid wüstite) = H₂O + xFe (liquid). Solubility of oxygen in liquid iron is obtained indirectly with a high degree of accuracy from the equilibrium data on reactions 1 and 3. The results are expressed in thermodynamic functions, and correlated with new data on the standard free energies of H₂, H₂O, O₂CO, and CO₂.     

Ein dem Malachit ähnliches basisches Eisenkarbonat als Korrosionsprodukt von Stahl

A basic ferrous carbonate similar to malachite as a corrosionproduct of steel A formerly unknown basic ferrous carbonate is described, which was found on the cone of a hot water valve (temperature 180°C) together with siderite and magnetite. According to analysis the formula is Fe_1,8²⁺Fe_0,2²⁺(OH)_2,2CO₃ or “Fe₂(OH)₂CO₃” with some amorphous ferric oxidehydrate. The unit cell of said compound is orthorhombic: a = 9,39₀Å; b = 24,53 Å; c = 3,21₂ Å; Z = 8 aspect p* ab. The measured density: 3,59 g · cm^?3. An infrared spectrum was taken and the frequencies of absorption coordinated tentatively with vibrations between 800–500 cm^?1. Thermal analysis in oxygen leads to a stepwise exothermic decomposition and oxidation in course of which above 197°C an intermediate metastable compound (ferric oxidecarbonate “Fe₂O₂CO₃”) is topotactically formed. The unit cell of this compound is orthorhombic: a = 9.23 Å; b = 12,18 Å; c = 5,94 Å. Also in this case an infrared spectrum was taken and bonds coordinated. Above 360°C further decomposition leads the formation of hematite. Decomposition in argon starts at 300°C. The reaction is endothermic and the product magnetite. A structural relationship exists between “Fe₂(OH)₂CO₃” and malachite and also to siderite. In this latter case we assume epitaxial relations.     

Phase Equilibria in the System Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-CoO and Gibbs Energy of Formation of Ca<Subscript>3</Subscript>CoAl<Subscript>4</Subscript>O<Subscript>10</Subscript>

An isothermal section of the system Al₂O₃-CaO-CoO at 1500 K has been established by equilibrating 22 samples of different compositions at high temperature and phase identification by optical and scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy after quenching to room temperature. Only one quaternary oxide, Ca₃CoAl₄O₁₀, was identified inside the ternary triangle. Based on the phase relations, a solid-state electrochemical cell was designed to measure the Gibbs energy of formation of Ca₃CoAl₄O₁₀ in the temperature range from 1150 to 1500 K. Calcia-stabilized zirconia was used as the solid electrolyte and a mixture of Co + CoO as the reference electrode. The cell can be represented as: From the emf of the cell, the standard Gibbs energy change for the Ca₃CoAl₄O₁₀ formation reaction, CoO + 3/5CaAl₂O₄ + 1/5Ca₁₂Al₁₄O₃₃ → Ca₃CoAl₄O₁₀, is obtained as a function of temperature: /J mol⁻¹ (±50) = −2673 + 0.289 (T/K). The standard Gibbs energy of formation of Ca₃CoAl₄O₁₀ from its component binary oxides, Al₂O₃, CaO, and CoO is derived as a function of temperature. The standard entropy and enthalpy of formation of Ca₃CoAl₄O₁₀ at 298.15 K are evaluated. Chemical potential diagrams for the system Al₂O₃-CaO-CoO at 1500 K are presented based on the results of this study and auxiliary information from the literature.     

Magnetic properties and crystallization kinetics of Zn<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Precursor of nanocrystalline Zn0.5Ni0.5Fe2O4 was obtained by grinding mixture of ZnSO4·7H2O,NiSO4·6H2O,FeSO4·7H2O,and Na2CO3·10H2O under the condition of surfactant polyethylene glycol(PEG)-400 being present at room temperature,washing the mixture with water to remove soluble inorganic salts and drying it at 373 K.The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K.The precursor and its calcined products were characterized by differential scanning calorimetry(DSC) ,Fourier transform infrared(FT-IR) ,X-ray diffraction(XRD) ,and vibrating sample magnetometer(VSM) .The result showed that Zn0.5Ni0.5Fe2O4 obtained at 1073 K had a saturation magnetization of 74 A·m2·kg-1.Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique,and kinetic parameters were determined by Kissinger equation and Moynihan et al.equation.The value of the activation energy associated with the crystallization process of Zn0.5Ni0.5Fe2O4 is 220.89 kJ·mol-1.The average value of the Avrami exponent,n,is equal to 1.59±0.13,which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.     

热浸锌铝合金镀层表面纳米晶腐蚀产物共沉积机理

采用XRD和TEM对热浸锌铝合金镀层在动态充气海水全浸试验时所形成的白色腐蚀产物进行了研究,结果表明：腐蚀产物主要由典型的纳米级Zn4CO3(OH)6.H2O,Zn5(OH)8Cl2和Zn6Al2CO3(OH)16.4H2O微晶组成,而这种纳米晶的形成与由吸附引起的Zn^2 和Al^3 离子的共沉积有关,镀层表面腐蚀后首先生成Al(OH)3凝胶,当凝胶吸附的锌离子超过异相核的临界过饱和度时,发生锌、铝氢氧化物的共沉淀,生成双氢氧化物,由于晶体长大速度较慢不能与沉淀形核同步进行,导致镀层表面形成了微晶状态的腐蚀产物。     

Novel AgCl/Ag<Subscript>2</Subscript>CO<Subscript>3</Subscript> heterostructured photocatalysts with enhanced photocatalytic performance

A series of novel AgCl/Ag₂CO₃ heterostructured photocatalysts with different AgCl contents (5 wt%, 10 wt%, 20 wt%, and 30 wt%) were prepared by facile coprecipitation method at room temperature. The resulting products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), respectively. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of methyl orange (MO) under UV light irradiation. With the optimal AgCl content of 20 wt%, the AgCl/Ag₂CO₃ composite exhibits the greatest enhancement in photocatalytic degradation efficiency. Its first-order reaction rate constant (0.67 h^?1) is 5.2 times faster than that of Ag₂CO₃ (0.13 h^?1), and 16.8 times faster than that of AgCl (0.04 h^?1). The formation of AgCl/Ag₂CO₃ heterostructure could effectively suppress the recombination of the photo-generated electron and hole, resulting in an increase in photocatalytic activity.     

Synthesis and electrochemical performances of LiCoO<Subscript>2</Subscript> recycled from the incisors bound of Li-ion batteries

A new LiCoO₂ recovery technology for Li-ion batteries was studied in this paper. LiCoO₂ was peeled from the Al foil with dimethyl acetamide (DMAC), and then polyvinylidene fluoride (PVDF) and carbon powders in the active material were eliminated by high temperature calcining. Subsequently, Li₂CO₃, LiOH·H₂O and LiAc·2H₂O were added into the recycled powders to adjust the Li/Co molar ratio to 1.00. The new LiCoO₂ was obtained by calcining the mixture at 850°C for 12 h in air. The structure and morphology of the recycled powders and resulting samples were studied by XRD and SEM techniques, respectively. The layered structure of LiCoO₂ synthesized by adding Li₂CO₃ is the best, and it is found to have the best characteristics as a cathode material in terms of charge-discharge capacity and cycling performance. The first discharge capacity is 160 mAh·g⁻¹ between 3.0–4.3 V. The discharge capacity after cycling for 50 times is still 145.2 mAh·g⁻¹.     

Obtaining ZrO<Subscript>2</Subscript> + CeO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> + TiO<Subscript>2</Subscript>/Ti compositions by plasma-electrolytic oxidation of titanium and investigating their properties

Regularities of the effect produced by Ce₂(SO₄)₃ salt introduced in an aqueous electrolyte containing Zr(SO₄)₂ on the plasma-electrolytic formation of oxide coatings on titanium, their composition, and structure are studied. ZrO₂ + CeO _x + TiO₂ three-phase oxide coatings with a thickness about 10 μm are obtained. The coatings involve ZrO₂ cubic phase. The ZrO₂-to-TiO₂ phase ratio in the coatings can be controlled. The zirconium content in the coatings reaches 20 at %, while that of cerium is 3–5 at %. The surface layer (∼3-nm thick) contains Ce³⁺ (∼30%) and Ce⁴⁺ (∼70%). Pores in the surface part of coatings have diameters around or smaller than 1 μm and are regularly arranged. The obtained systems have a certain catalytic activity with respect to the oxidation of CO to CO₂ at temperatures above 400–450°C. The coatings are corrosion-resistant in chloride-containing environments. The thickness h of coatings depending on the charge Q supplied to the cell is described by the equation h = h ₀(Q/Q ₀) ⁿ , where n = 0.35 and h ₀ is the thickness of the coating formed at Q ₀ = 1 C/cm².     

Phase transformation and microstructural features of NiAl/Ni<Subscript>3</Subscript>Al two-phase alloys containing ternary elements

Various ternary elements were added to observe the effects on the microstructural features of β+γ′ two-phase alloys. The microstructural features of β+γ′ two-phase (Ni₆₆Al₃₄)_100-χX_χ(X=Ti, Si, Nb) depended on the A_s (austenite start) temperature of β-martensite with alloying elements. For A_s>250°C, a lamellar microstructure was found to form by the following phase transformation: Martensite→Ni₅Al₃→β+γ’. For A_s<250°C, two-type microstructures, mesh and Widmanstätten, were formed depending on the ternary element. When Ti or Nb was added as a ternary element, the β→Ni₅Al₃ transformation occurred very quickly. Conversely, this transformation proceeded very slowly in the case of Si addition, and the resultant microstructure assumed somewhat different features. Consequently, it could be suggested that the microstructures of NiAl/Ni₃Al two-phase alloys are determined by not only the A_s temperature but also by the β→Ni₅Al₃ transformation.     

CO<Subscript>2</Subscript> electrochemical reduction via adsorbed halide anions

The electrochemical reduction of CO₂ was studied utilizing halide ions as electrolytes, specifically, aqueous solutions of KCl, KBr, KI. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were a Pt wire and an Ag/AgCl electrode, respectively. The results of our work suggest a reaction mechanism for the electrochemical reduction of CO₂ where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO₂. Electron-transfer to CO₂ may occur via the X⁻ _ad(Br⁻, Cl⁻, I⁻)-C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO₂. The stronger the adsorption of the halide anion to the electrode, the more strongly CO₂ is restrained, resulting in higher CO₂ reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons; leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the over potential necessary for CO₂ reduction, and thus increase the rate of electrochemical CO₂ reduction.     

Nanocrystalline ZrO<Subscript>2</Subscript> preparation and kinetics research of phase transition

The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O,and Na2CO3·10H2O as raw materials.The nanocrystalline ZrO2 was obtained by calcining the precursor.The precursor and its calcined products were characterized using TG/DTA,FT-IR,XRD,and SEM.The results showed that the precursor dried at 353 K was a zirconyl carbonate compound.When the precursor was calcined at 673 K for 150 min,highly crystallization ZrO2 with tetragonal structure (space group P42/nmc (137)) was obtained with a crystallite size of 24 nm.However,when the precursor was calcined at 1023 K for 150 min,highly crystallization ZrO2 with monoclinic structure (space group P21/c (14)) was obtained with a crystallite size of 20 nm.The mechanism and kinetics of the thermal process of the precursor were studied using DTA and XRD techniques.Based on the Kissinger and Arrhenius equation,the values of the activation energies associated with the thermal process of the precursor were determined to be 26.80 and 566.73 kJ·mol-1 for the first and third steps,respectively.The mechanism of ZrO2 phase transition from tetragonal to monoclinic structure is the random nucleation and growth of nuclei reaction.     

Soda-fuel metallurgy: Metal ions for carbon neutral CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O reduction

The role of minerals in biomass formation is understood only to a limited extent. When the term “photosynthesis—CO₂ and H₂O reduction of sugars, using solar energy”—is used, one normally thinks of chlorophyll as a compound containing magnesium. Alkali and alkaline earth metals present in leaf cells in the form of ions are equally essential in this solar energy bioconversion coupled with nitrogen fixation. Application of some of these principles can lead to artificial carbon-neutral processes on an industrial scale close to the concentrated CO₂ emission sources.     

Resistance of High-Nickel,Heat-Resisting Alloys to Air and to Supercritical CO<Subscript>2</Subscript> at High Temperatures

The reduction behaviour of wustite-type iron oxide scale on a low-carbon, low-silicon steel by dissolved carbon in the steel at 650–900 °C under pure nitrogen was studied. It was found that dissoved carbon in the steel examined was able to react with the wustite scale on the surface, leading to reduction of this scale. It was also found that the scale reduction rate was the most rapid within 750–800 °C, followed by that at 700 °C and then at 850 °C, whereas the rates were essentially zero at 650 and 900 °C. Decarburization occurred to the steel as a result of scale reduction, and the degree of decarburization at 750–800 °C was also the most severe. The rate of scale–carbon reaction was primarily controlled by carbon diffusion through the decarburization layer as the calculated carbon permeability, defined as the product of carbon diffusivity and the carbon concentration difference across the decarburization layer, also reached its maximum within 750–800 °C. Scale reduction led to the formation of pores at the scale–steel interface as a result of volume shrinkage when wustite was reduced to iron, but the porosity volume was smaller than calculated at 800–850 °C, which could have an inhibiting effect on the scale–carbon reaction. The calculated volume of CO + CO₂ gases generated as a result of scale–carbon reactions was about 100 times the calculated porosity volume. It was believed that the wustite scale was permeable to CO and/or CO₂, allowing the much larger volume of CO and CO₂ gases to escape through the scale layer.