Methane synthesis from CO/H2O mixture on supported nickel catalysts, II. Surface species in CO?H2 and CO?D2O interaction by IR spectroscopy

The species resulting in CO, CO+H₂ or CO+D₂O adsorption on supported Ni catalysts were followed by IR spectroscopy and their role in methane synthesis mechanism is discussed.

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- , CO, CO+H₂ CO+D₂O . .

     

Methane synthesis from CO/H2O mixture on supported nickel catalysts, III. Formation of surface carbon and its role in the reaction mechanism

IR spectra of adsorbed CO species after prolonged contact with the catalyst surface show that surface carbon is formed and it participates in methane synthesis.

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- , CO , , .

     

Influence of alkaline promoters (potassium) on the properties of Mo/SiO2 catalysts for alcohol synthesis from CO and H2

Conversion mechanisms of CO, H₂ and intermediates on Mo/SiO₂ and Mo–K–SiO₂ catalysts have been studied. It appears that alkaline promoters inhibit alcohol conversion to olefins and subsequent hydrogenation to paraffins. Active phase of the selective catalyst is MoO₂ promoted by potassium.

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CO H₂ Mo/SiO₂ Mo–K–SiO₂ . . MoO₂, .

     

Influence of CO2 and H2O on methane conversion over oxide catalysts

It has been established that the introduction of CO₂ and H₂O to the reaction mixture when using freshly prepared catalysts, increases the overall methane conversion and decreases the yield of hydrocarbons. On coked MgO their effect is insignificant.

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, CO₂ H₂O . MgO CO₂ H₂O .

     

Influence of oxygen on catalytic properties of supported palladium catalysts in CO hydrogenation

It has been established that the addition of oxygen to synthesis gas has a positive effect of the activity and selectivity of supported palladium catalysts in methanol synthesis. The degree of the effect of oxygen depends on the chemical nature of the support and the conditions of catalysis, preceding the addition of oxygen to the reaction mixture. The probable causes for the influence of oxygen on the catalytic properties of palladium, supported on oxide supports, have been discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 557–563, September–October, 1989.     

The overtone spectra of H2O,D2O and mixtures of H2O in D2O ice

The overtones of the stretching vibration of OH and OD were measured in solid solutions of H₂O in D₂O over a wide range of concentration and temperatures. The observed frequencies and the overall shape of the spectra were related to excitations of single OH or OD bonds (bound excitations) and those involving neighboring OH bonds extending over the crystal (non-bound excitations). The observed large anharmonicity of the bound state is interpreted as due to a low lying barrier in the double minimum potential curve for the hydrogen motion.     

Effect of Au loading, H2O and CO concentration on the stability of Au/ZnO catalysts for room-temperature CO oxidation

Catalytic decomposition of ethanol in the presence of steam over Pd supported on a porous carbonaceous material was studied. XPS and TEM were used for the catalyst characterization. Experiments were performed under atmospheric pressure, temperature of 320-360°C and H₂O/C₂H₅OH molar ratio 8.1. It was found that the catalyst exhibited a high activity and long-term stability for the ethanol decomposition into a gas mixture containing carbon oxides, methane and hydrogen.     

Study of CO and H2 sorption on supported bimetallic Pd?Pb catalysts

With increasing the lead content both CO and hydrogen sorption drop considerably. The influence of lead can be observed starting from a concentration of 0.5%. This may indicate that the surface is enriched in lead atoms.

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CO, H₂. , 0,5%. .

     

Influence of organic reagents on alumina supported nickel catalysts. I. Preparation of catalysts

Nickel/-alumina catalysts have been prepared by a version of the impregnation technique called double impregnation. The application of different organic reagents for activation of the -Al₂O₃ support promotes the formation of nickel-aluminate and large nickel crystallites in the catalysts obtained.

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/- , . . . -Al₂O₃, -, .

     

Influence of promoter on catalytic properties of Cu-Mn-Fe/ZrO2 catalysts for alcohols synthesis

The addition of iron and manganese has a strong effect on the Cu/ZrO₂ catalyst performance for alcohols synthesis. The structures of catalysts have been investigated using X-ray adsorption spectroscopy and diffuse reflectance FTIR spectroscopy of absorbed CO. It is found that the Cu-Fe species and the interaction between them play an important role in converting the activity center for methanol synthesis to the center for higher alcohols synthesis.This revised version was published online in December 2005 with corrections to the Cover Date.     

Vibrational spectrum of I(H2O)

The infrared spectrum of the ionic cluster I⁻(H₂O) was recorded from 3170 to 3800 cm⁻¹ by vibrational predissociation spectroscopy. A strong multiplet observed at 3415 cm⁻¹ and a narrow band at 3710 cm⁻¹ were assigned as a hydrogen-bonded OH stretch and free OH stretch respectively, indicating that H₂O forms a single hydrogen bond with the iodide anion. Ab initio vibrational frequencies and intensities were computed at the second-order Møller-Plesset (MP2) level for the minimum energy configuration, a nearly linear hydrogen-bonded isomer, and for a low-lying saddlepoint, a symmetric C_2v bridged isomer. The spectrum predicted for the hydrogen-bonded isomer agreed well with experiment.     

A temperature programmed desorption study of H2 from supported nickel catalyst

The chemisorption of hydrogen on Ni/SiO₂ has been studied by measuring temperature programmed desorption on various samples under various experimental conditions. Two peaks are found, which can be related to a weakly and to a strongly bound species of chemisorbed hydrogen. Their analysis has been performed by a method which makes possible to determine whether a certain kinetic model can describe the entire desorption process or to assign a clear meaning to the corresponding kinetic parameters.

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Ni/SiO₂ - . . , , , , .

     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).

     

Ethylene polymerization over supported MAO/(nBuCp)2ZrCl2 catalysts: Influence of support properties

The catalytic system methylaluminoxane (MAO) and bis(n-butylcyclopentadienyl)zirconium dichloride ((nBuCp)₂ZrCl₂) was immobilized on commercial silica, silica-alumina and aluminophosphate calcined at different temperatures. The properties of the supports were determined by using N₂ adsorption-desorption isotherms at 77 K, FT-IR spectroscopy and SEM. After aluminium and zirconium impregnation, the catalysts were analyzed by ICP-AES, FT-IR and UV-vis spectroscopy. Ethylene polymerizations were carried out in a Schlenk tube at 70 °C and 1.2 bar of ethylene pressure. The polyethylene obtained was characterized by GPC, DSC and SEM.Catalysts supported on silica-alumina exhibited higher polymerization activity than those supported on silica and aluminophosphate. Besides, the activity of MAO/(nBuCp)₂ZrCl₂ catalytic system supported on silica-alumina and aluminophosphate decreased strongly with support calcination temperature, while remained almost constant when silica was employed as support. All these experimental features suggest a role of the support acid properties and hydroxyl group population in the generation of active polymerization species.     

The interaction of H2, CO, CO2, H2O and NH3 on ZnO surfaces: an Oniom Study

We have used the Oniom method with three layers in order to study the interaction of CO, H₂, H₂O, NH₃ and CO₂ molecules with the ZnO surfaces using a (ZnO)₃₄₈ cluster model. The layers are divided into the high layer at the CCSD level, the medium layer at the RHF level and the low level layer using the UFF force field method. The orbital and binding energies of the adsorbed molecules, Mulliken and ChelpG charges as well as geometrical parameters were analyzed and compared with the available experimental and theoretical data.     

Solvothermal synthesis, crystal structure, magnetic and luminescent properties of (H3O)6·[Co4(H2O)4(HPMIDA)2(PMIDA)2)]·2H2O

A cobalt phosphonate (H₃O)₆·[Co₄(H₂O)₄(HPMIDA)₂(PMIDA)₂)]·2H₂O, 1, has been synthesized from a mild solvothermal reaction of Co(II) ion with N-(phosphonomethyl)iminodiacetic acid (H₄PMIDA). Compound 1 crystallizes in the triclinic space group with cell parameters of , , , α=93.06(3)°, β=99.66(3)°, γ=90.34(3)° and Z=1. Compound 1 shows a novel tetra-nuclear molecular structure. In the crystal lattice, molecules of 1 hydrogen bond to each other to form two-dimensional (2D) layers, which are further linked together by the co-crystallized H₂O molecules and H₃O⁺ counter ions through hydrogen bonding to form the 3D supramolecular network. Thermogravimetric analysis, IR spectrum, magnetic susceptibility and luminescent spectra are given.     

Simultaneous N2O and NO reduction over carbon supported catalysts

The simultaneous reduction of N₂O+NO with carbon supported Ni/K catalysts was studied. High conversions of both compounds were obtained at 400°C, and a synergystic effect between Ni and K was observed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermodynamic modeling of the vapor–liquid equilibrium of the CO2/H2O mixture

In order to evaluate the feasibility of CO₂ sequestration in geological formations detailed knowledge of the mutual solubilities of the CO₂/H₂O system is required. In this work we employ three models, which all involve the well-known Peng–Robinson equation of state, to study the CO₂/H₂O phase equilibrium, with emphasis on the solubility of CO₂ in the aqueous phase and the solubility of H₂O in the CO₂-rich phase. The considered models include the Peng–Robinson equation of state coupled with the conventional van der Waals one fluid mixing rules or the universal mixing rules, and the cubic-plus-association equation of state that uses the Peng–Robinson equation of state in order to account for the usual attractive and repulsive forces and an extra association term to account for the strong hydrogen bonding interactions. The required model parameters are calibrated using experimental data up to 1500 bar for pressure, and up to 673 K for temperature. To improve the accuracy of the proposed models we consider two temperature ranges. Temperatures lower than 373 K are of interest to the geological CO₂ sequestration, while higher temperatures are of interest to fluid-inclusion studies. Good agreement is obtained between the experimental and the correlated solubilities.     

Dipole moment derivatives of H2O and H2S

The dipole and quadrupole derivatives of H₂O and H₂S are calculated analytically, using the coupled Hartree—Fock method first proposed by Gerratt and Mills. The greater efficiency, of this method allows SCF wave functions very, close to the Hartree—Fock limit to be used. Agreement, with experimental data is good.