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.

     

Study of acid-base properties of a SiO2?AlPO4 (80∶20 W/W) catalyst

2-Methyl-3-butyn-2-ol (MBOH) transformation was used as a test reaction in order to determine the acid-base properties of a SiO₂/AlPO₄ (80∶20 w/w) catalyst. Experiments were carried out in a microcatalytic pulse reactor and in a continuous-flow reactorvia Temperature Programmed Surface Reactions-Mass Spectrometry (TPSR-MS). Results are compared to acid-base properties calculated by other instrumental techniques.     

Synthesis and characterization of P2O5–ZrO2–SiO2 membranes doped with tungstophosphoric acid (PWA) for applications in PEMFC

Homogeneous, transparent and crack-free P₂O₅–ZrO₂ and P₂O₅–ZrO₂–SiO₂ membranes have been synthesized by the sol–gel process. A first step has been oriented to the optimization of the synthesis and characterization of different compositions by TGA, FE-SEM, FTIR and EIS to choose the best inorganic composition in terms of chemical and mechanical stability, and proton conductivity. The addition of SiO₂ improves the mechanical and chemical stability. On the other hand, compositions with higher content in P₂O₅ have demonstrated lower mechanical and chemical stability against water, but higher proton conductivity. The water retention and high porosity of inorganic membranes leads to high proton conductivity, 10⁻² S/cm, at 140 °C and 100% relative humidity. The second step has been focused in the study of doped inorganic membranes of molar composition 99.65(40P₂O₅–20ZrO₂–40SiO₂)–0.35PWA. The high homogeneity, transparency and SEM-EDX analysis of these membranes indicates no phase separation suggesting that PWA is well dispersed in the inorganic structure. The incorporation of PWA in sol–gel oxides provides an increase of the proton conductivity at low relative humidity due to the adequate distribution of PWA in the inorganic network. Conductivity increases in two orders of magnitude at low humidity (10⁻⁴ S/cm at 50 °C and 62% RH) compared with undoped sol–gel oxide membranes.     

Calculation of self-absorption coefficients of calcium resonance lines in the case of a CaCl2–water plasma

The resonance escape factors for the lines emitted by a neutral calcium atom Ca I at 4226.73 Å and of ionic calcium Ca II at 3933.66 Å and at 3968.47 Å are calculated assuming a Voigt profile and in the case of CaCl₂–water plasma. The dependence of the escape factor on the optical thickness ?₀ from the line center which itself depends on the two main spectral line shape broadening mechanisms (pressure and Doppler effects) are considered. The variation of the resonance escape factors with the temperature, the CaCl₂ molar proportion and the size of the plasma are also investigated. This calculation is useful for the application of Laser-Induced Breakdown Spectroscopy in the quantitative analysis of elemental composition. Its application allows us to reduce the non-linearities in the relation between resonance lines intensities of calcium in our case and its concentration.     

Carbon/λ-MnO2 composites for supercapacitor electrodes

In the present work a composite of carbon with λ-MnO₂ have been synthesized by a simple two-step route. In the first step, to obtain LiMn₂O₄/carbon material, mesoporous activated carbon was impregnated with the solution of precursor metal salts and heated subsequently. As-prepared materials were acid treated which resulted in the formation of λ-MnO₂/carbon. Physical properties, structure and specific surface area of electrode materials were studied by TEM, X-ray diffraction and nitrogen sorption measurements. Voltammetry cycling, galvanostatic charge/discharge and impedance spectroscopy measurements performed in two- and three-electrode cells have been applied in order to measure electrochemical parameters. TEM images confirmed well dispersed λ-MnO₂ particles on the surface of carbon material. The carbon in the composite plays an important role as the surface area enhancing component and a support of pseudocapacitive material. Furthermore, the through-connected porosity serves as a continuous pathway for electrolyte transport. A synergetic effect of the porous carbon framework and of the redox properties of the λ-MnO₂ is at the origin of improvement of specific capacitance values which has been observed for composites after delithiation.     

Vapor-phase synthesis of isoprene from formaldehyde and isobutylene over CuSO4?MOx/SiO2 catalysts

Vapor-phase synthesis of isoprene from formaldehyde and isobutylene over CuSO₄–MO_x/SiO₂ catalysts has been studied. The results show that CuSO₄–MO_x/SiO₂ catalysts exhibit a good catalytic activity; especially when the metal oxides have appropriate basicity, is isoprene yield greatly enhanced. The results of product analysis indicate that there are side-reactions during isoprene production, which are isoprene hydrogenation, polymerization of isobutylene, copolymerization of isobutylene and isoprene, and reaction of C₅ aldehyde and ketone formed during isoprene production. In addition, catalytic behavior of the catalysts and probable mechanism of side-reactions are discussed.

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CuSO₄–MO_x/SiO₂. ; , . , , , , , , C₅ , . .

     

Reduction of an amorphous NiO?Al2O3/SiO2 catalyst by different olefins and hydrogen

By static magnetic measurements it was found that the ability to reduction of an amorphous NiO–Al₂O₃/SiO₂ catalyst decreases in the order: but-2-eneshydrogen isobutene>but-1-ene>propeneethene. The reduction temperatures are significantly higher than the dimerization reaction temperatures.

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, NiO–Al₂O₃/SiO₂ : -2>-1> . .

     

Selective oxidation of methanol on V2O5 and V2O5?MoO3 supported on montrmorillonite

Methanol oxidation on V₂O₅ and V₂O₅–MoO₃ catalysts supported on montmorillonite has been studied in the temperature range of 250–500°C. The V₂O₅–MoO₃ containing sample shows higher selectivity towards formaldehyde formation than the V₂O₅ catalyst.     

Solubility in the CaCl2 + Mg(NO3)2 ? Ca(NO3)2 + MgCl2-H2O system

For the first time solubility at 25 and 50°C is studied in the CaCl₂ + Mg(NO₃)₂ ↔ Ca(NO₃)₂ + MgCl₂-H₂O four-component reciprocal water-salt system in order to determine the feasibility of preparing calcium nitrate and magnesium chloride. Original Russian Text ? K.R. Matveeva, O.S. Kudryashova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1200–1204.     

Cu/MoO3-TiO2/SiO2上光催化CO2和C3H8合成异丁烯醛的研究

采用表面改性法和等体积浸渍法制备了金属修饰的负载型复合半导体材料Cu/MoO3-TiO2/SiO2, 用X射线衍射、 比表面积测定、 红外光谱、 拉曼光谱和紫外-可见漫反射等技术对固体材料的结构、 吸光性能和化学吸附性能进行了表征, 研究了该材料对CO2和丙烷合成异丁烯醛的光促表面催化规律. 结果表明, 半导体活性组分MoO3和TiO2在所制备的催化剂Cu/MoO3-TiO2/SiO2表面形成化学键, 并存在多种活性吸附位; 金属Cu的修饰拓展了固体材料对光源的响应范围, 提高了反应体系的吸光能力; 固体材料对CO2和丙烷的有效吸附使其在较低温度下就能促进异丁烯醛的紫外光化学合成, 反应选择性达到85％左右. 根据实验结果对光促CO2和丙烷表面催化合成异丁烯醛的机理进行了讨论.     

SO2, HCl, CO2, HS und S?urechloride

Ohne Zusammenfassung     

"Small amount for multiple times" of H2O2 feeding way in MoS2-Fex heterogeneous fenton for enhancing sulfadiazine degradation

In recent years, MoS₂catalyzed/cocatalyzed Fenton/Fenton-like systems have attracted wide attention in the field of pollution control, but there are few studies on the effect of H₂O₂ feeding way on the whole Fenton process. Here, we report a new type of composite catalyst（MoS₂-Fex） prepared in a simple way with highly dispersed iron to provide more active sites. MoS₂-Fexwas proved to possess selectivity for singlet oxygen（1O2） in effectively...     

Composition,structure, and functional properties of organomineral composite sorbents KU-2×8-ZnS and KU-2×8-PbS

Organomineral composite sorbents KU-2×8-ZnS and KU-2×8-PbS were synthesized on the basis of the matrix of a strongly acidic KU-2×8 cation exchanger. Scanning electron microscopy and elemental analysis were used to study their microstructure and chemical composition. With the use of potentiometric titration, their bifunctional nature was revealed and the dissociation constants and the total exchange capacities of the ionogenic groups were determined. The sorption of copper(II), zinc, and cadmium by KU-2×8-ZnS and KU-2×8-PbS sorbents from 0.005 M solutions of their salts was examined. The total dynamic sorption capacity of the composite sorbents for the above metals, found in the study, exceeds similar values for the individual KU-2×8 cation exchanger by a factor of 1.6–2.0 and that in 0.001–0.050 M solutions of potassium and calcium chlorides, by a factor of 1.3–4.5. An explanation is suggested for the sorption process of heavy nonferrous metals on composite sorbents with an active sulfide component by the mechanism of coordination copolymerization.     

Characterization of Cu?Rh/SiO2 by temperature-programmed desorption (TPD) of hydrogen

The presence of Cu on Rh/SiO₂ inhibited H₂ chemisorption at 303 K and suppressed CO hydrogenation. TPD study shows that chemisorption of H₂ on Cu–Rh/SiO₂ is an activated process at 303 K.

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Cu Rh/SiO₂ H₂ 303 CO. , H₂ Cu–Rh/SiO₂ 303 .

     

New synthetic procedure for Na NH2（BH3）2 and evaluation of its hydrogen storage properties

Tremendous efforts have been devoted to the synthesis of new light element hydrides for hydrogen storage.Ammonia borane(AB)is a promising candidate possessing high hydrogen capacity and low dehydrogenation temperature.The step-wise dehydrogenation and release of by-products,however,are obstacles to its practical application.Chemical modifications of AB to synthesize new compounds or its derivatives are of practical and fundamental importance.Here we report an improved synthesis of sodium aminodiborane(Na NH2(BH3)2,Na ABB),a derivative of ammonia borane.This procedure leads to high purity Na ABB by reacting Na NH2 and 2 eq.AB.The dehydrogenation properties have been investigated by means of temperature programmed desorption-mass spectrometry,volumetric release,nuclear magnetic resonance,Fourier transform infrared spectroscopy,and X-ray diffraction.In a closed vessel,Na ABB can release~2 eq.H2 when heated at 271°C,forming solid products of Na BH4 and highly condensed polyborazylene.     

Heat capacity and thermodynamical properties of the crystal of [RE2(Glu)2(H2O)8](ClO4)4·H2O (RE = Nd, Eu, Dy)

Thermodynamical data of rare earth complexes with amino acid are important for engineering chemistry and fundamental chemistry. However, they have rarely been reported. In this work, a series of crystalline complexes of rare earth perchlorate coordinated with glutamic acid have been synthesized in water medium, and their thermodynamical data, including the heat capacity in low temperature range and the standard enthalpy of formation, were determined. These complexes were identified to be [RE₂(Glu)₂(H₂O)₈](ClO₄)₄·H₂O (RE = Nd, Eu, Dy) by using thermogravimetric analysis (TG), differential thermal analysis (DTA), and chemical and elementary analyses. Their purity has been determined. No melting points were observed for all the three complexes. The heat capacity of the complexes was measured by an adiabatic calorimeter from 79 to 370 K. Abnormal heat capacity values were detected for two of the complexes and the decomposition range of one complex was found. The temperature, enthalpy change and entropy change of the decomposition processes of the three complexes were calculated. The polynomial equations of heat capacity in the experimental temperature range have been obtained by least squares fitting. The standard enthalpy of formation was determined by an isoperibol reaction calorimeter at 298.15 K. Supported by the Research Fund of Beijing Institute of Petro-Chemical Technology (N06-06)     

Study of self-association of water in supercritical CO2 by Monte Carlo simulation: Does water have a specific interaction with CO2?

The extent of the self-association of water in supercritical CO₂ has been investigated in a wide range of density and temperature by the test particle insertion technique. The results show that the association constant for water decreases with temperature and weakly depends on CO₂ density. This weak density dependence provides evidence for the lack of a strong specific CO₂–water interaction. Comparing calculated association constants with its gas-phase values shows that the association constant is at most ca. 38% lower than its gas-phase value in the high density–low temperature region. Inspection of the simulated radial distribution functions revealed that forming modest water–CO₂ complexes does not result in substantial interference in H-bonding of water molecules.     

Dehydrogenation of methanol to methyl formate over CuO?SiO2 gel catalyst

CuO−SiO₂ gel catalysts were prepared by sol-gel method and were characterized by UV-Visible diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD) and temperature-programmed reduction (TPR). It was found that the copper loadings have a strong influence on the reduction and catalytic properties of CuO−SiO₂ gels. A great part of copper oxide is highly dispersed as confirmed by TPR, XRD and DRS data. The catalysts are shown to be active and selective toward methyl formate formation in methanol dehydrogenation due to the presence of highly dispersed copper over SiO₂.