Some peculiarities in synthesis of nitrogen-containing heterocyclic compounds on zeolite catalysts

Acid properties of some zeolite catalysts have been studied using IR spectroscopy and compared with data on the selectivity of their catalytic effect in the synthesis of nitrogen-containing compounds from monoethanolamine.

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Interaction of N<Subscript>2</Subscript> with the acid sites of oxides

Nitrogen adsorption on SiO₂, -Al₂O₃, TiO₂, and sulphated zircona (SO _2- ⁴ /ZrO₂) is studied by Fourier transform IR spectroscopy. Integrated absorption coefficients for the bands due to the N—N vibrations in nitrogen complexes with Brønsted and Lewis acid sites are determined. A general correlation between integrated absorption coefficients and the positions of N—N bands of nitrogen interacting with the above sites in zeolites and oxides is discussed. The orientation of a nitrogen molecule relative to Brønsted and Lewis acid sites is calculated ab initio using a 6-31G^** basis set.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 115–121.Original Russian Text Copyright © 2005 by Malyshev, Paukshtis, Malysheva.     

Comparative discussion of NH

A comparative study of NH ₄ ⁺ formation on aluminosilicate surface and in an aqueous solution of hydrochloric acid has been carried out in the framework of the nonempirical method with a STO-3G basis. It is suggested that the compensation mechanisms of energy consumptions to form protonated species in both cases are similar.

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-3 - NH ₄ ⁺ - . - .

     

IR spectroscopic determination of protonation heats of bases on catalyst surfaces

IR spectra of pyridine adsorbed on zirconium phosphate and zeolite HNaY were studied at temperatures of 400–500 K. Protonation heats of pyridine determined on the OH groups of zirconium phosphate and zeolite HNaY having theOH at 3640 cm^–1, are 65±6.0 and 172±16 kJ/mol, respectively.

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400–500 K , HNaY. OH (Q=65±6, /) OH HNaY cOH 3640 ^–1 (Q=172±16 /).

     

CATION/ANION MODIFIED CERIA-ZIRCONIA SOLID SOLUTIONS PROMOTED BY Pt AS CATALYSTS OF METHANE OXIDATION INTO SYNGAS BY WATER IN REVERSIBLE REDOX CYCLES

Ca and/or F-modified fluorite-like Ce-Zr-mixed oxides have been prepared by Pechinis method. The bulk structure of samples was characterized by XRD, EXAFS and FTIRS of the lattice modes. The surface properties were studied by SIMS and FTIRS of adsorbed CO and surface hydroxyls. The specific reactivity of the surface oxygen, its amount, coefficients of bulk and near-surface diffusion, as dependent upon the sample composition and temperature, were estimated using sample reduction by CO in the pulse/flow mode. Insertion of fluorine into the lattice results in decreasing the degree of oxygen polyhedra distortion, thus decreasing the amount of reactive oxygen and diffusion coefficients. Calcium and Pt addition counteracts this effect. At 500^oC for Pt-supported Ce-Zr-O samples including those modified by Ca and F, the lattice oxygen is easily removed by methane generating CO and hydrogen with high selectivity. Reoxidation of reduced samples by water or carbon dioxide at the same temperature restores the oxygen capacity producing more hydrogen or carbon monoxide.     

Stabilization of TiO<Subscript>2</Subscript>–Co<Subscript>3</Subscript>O<Subscript>4</Subscript> thin films on a glass fiber material by introduction of silica into the matrix

The TiO₂–Co₃O₄–SiO₂ oxide system supported on glass fiber was synthesized and studied. The oxide layers attached to the glass fiber surface have a porous structure. Characteristics of thin-film coatings on the glass fiber substrate (oxide layer phase composition and adhesion to the glass fiber surface) depend on the silica concentration. The obtained materials are catalytically active towards the exhaustive oxidation of propane.     

Effect of the microstructure of Pt/CeO2-TiO2 catalysts on their catalytic properties in CO oxidation

The microstructure of 2% Pt/CeO₂-TiO₂ catalysts has an effect on their catalytic properties in CO oxidation. The nanostructured catalysts as platinum clusters 0.3–0.5 nm in size are the most active. These clusters are stabilized at crystal boundaries formed by irregularly intergrown anatase particles. The catalyst containing platinum particles 2–5 nm in size is less active because of the decrease in the extent of dispersion of platinum and the change of its electron state.     

Studying the Interaction between Water Vapor and a γ-Al2O3 Surface by IR Spectroscopy

Russian Journal of Physical Chemistry A - The interaction between a γ-Al2O3 surface and vapors of H2O and D2O is studied via IR spectroscopy. It is shown that surface hydroxyl groups of...     

New Data on the Ability of Alumina–Platinum Systems to Catalyze the Methane Aromatization Reaction under Nonoxidizing Conditions

The state and size of the metal on the surface of aluminum oxide and the acidic properties of the support depending on the concentration of supported platinum were studied in this work. The effect of the Pt content of the alumina–platinum catalyst on the activation (chemisorption) of methane was investigated, and the composition of hydrocarbon fragments formed in this case was calculated. The sample most active in a reaction of the joint conversion of methane with n-pentane, which was performed for the production of aromatic hydrocarbons under nonoxidizing conditions, was established. The effect of the temperature of n-pentane supply to the reaction atmosphere was studied for the 0.6%Pt/Al₂O₃ catalyst. The degree of enrichment of the resulting aromatic hydrocarbons and the quantity of incorporated methane activated on the catalyst surface were determined with the use of isotope mass spectrometry.     

Surface modification of single-walled carbon nanotubes by functional nitrogen-containing groups and study of their properties

Treatment of single-walled carbon nanotubes (SWCNT) in a gaseous 40%NH₃–1%С₂Н₂–C₂H₄ mixture at 600 and 700°С led to “nitrogen-containing carbon coating–single-wall carbon nanotubes” composites. Single-walled carbon nanotubes after etching in aqua regia (SWCNTetch) and doped with nitrogen (N-SWCNT) were studied by XPS, electron microscopy, and IR spectroscopy. It was found that the initial SWCNTetch surface contains various oxygen-containing functional groups. Treatment of SWCNTetch in a 40%NH₃–1%С₂Н₂–C2H₄ mixture led to the formation of a thin carbon coating on the carbon nanotube surface due to polymerization and condensation of hydrocarbons. After treatment at 600°C, the formation of nitrogen-containing functional groups is insignificant; however, when the treatment temperature is increased to 700°C, the nitrogen content reaches 0.5 at % of the weight of the N-SWCNT sample.