IR spectroscopy and thermal desorption study of the transformation of phenol on hydrated manganese dioxide

An experimental basis is given for the conclusion that deep oxidation of phenol on hydrated manganese dioxide in a two-stage adsorption catalysis regime takes place via the stage of formation of surface phenoxy compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 219–222, July–August, 1994.     

Study of the adsorption of sulfur dioxide on dealuminated zeolites Y by thermal desorption and powder X-ray diffraction

Sulfur dioxide is adsorbed on zeolites Y in two forms. The amount of the stable form (T_des=350–390 K) changes in proportion to the sodium content in the zeolite The stable form is localized in a large void at a distance of 1.8 å from the S_II position and causes redistribution of sodium cations. The weakly bound form (T_des=286–300 K) makes the main contribution to the adsorption of SO₂ on highly siliceous zeolites Y and is formed by adsorbate-adsorbate interaction, and it is apparently delocalized in a large void. Out-of-framework aluminum compounds that are formed during dealumination decrease the free volume of the zeolite without changing the nature of interaction of SO₂ with the zeolite.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 535–541, March, 1991.     

纳米二氧化钛对痕量铅的吸附性能研究

提出了纳米TiO2分离富集, 火焰原子吸收光谱法测定水样中痕量铅的新方法.考察了铅在纳米TiO2上的吸附动力学、最佳酸度和吸附容量.实验结果表明：在最佳实验条件下,纳米TiO2能定量、快速地吸附水中的痕量Pb^2＋,其静态吸附容量为17.90 mg/g.吸附在纳米TiO2上的Pb^2＋可用0.1 mol/L HNO3＋0.1 mol/L CH3COOH完全洗脱.对Pb2＋的检出限为2.57 ng/mL, 相对标准偏差为2.5% （n=11, ρ=0.10 μg/mL）,加标回收率在94.5%～102.5%之间.可用于实际水样中铅的测定.     

Study of propylene adsorption and conversion on a gallium-molybdenum catalyst by IR spectroscopy and thermodesorption techniques

A study of propylene adsorption on gallium molybdate by IR spectroscopy and thermodesorption techniques has shown that propylene is adsorbed in reversible (-allyl) and irreversible (carboxyl, carbonate and formate) forms. The analysis of the spectra observed is supported by deuterated propylene adsorption. The conversion of the surface -allyl complexes into an Me–O–CH₂–CH=CH₂ type compound is followed.

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- , - : , . , . - Me–O–CH₂–CH=CH₂.

     

The adsorption properties of titanium dioxide

The adsorption properties of titanium dioxide were studied by gas chromatography. We used organic compounds from different classes, namely, n-alkanes, n-alkenes (C₆-C₈), and polar compounds (electron donors and acceptors) as test adsorbates. The differential heats of adsorption and the contributions of dispersion and specific intermolecular interaction energies were determined for the systems from the experimental retention data. The electron-donor and electron-acceptor characteristics of the ultimately hydroxylated surface of TiO₂ were evaluated.     

IR spectral study of SO2 adsorption on polysiloxane layers containing tertiary amino groups

Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 1, pp. 164–167, January–February, 1996.     

Properties of surface acid sites of ZrO2 and SO4ZrO2-based systems studied by diffuse-reflectance Fourier-transform IR spectroscopy: adsorption of acetonitrile-d3

The properties of acid sites of ZrO₂ and SO₄/ZrO₂-based systems modified by metal ions were studied by DRIFT spectroscopy using acetonitrile-d₃ as a probe molecule. In the case of ZrO₂. CD₃CN interacts with the Lewis acid sites (LAS) with moderate strength. Adsorption on the Brönsted acid sites (BAS) is very weak, which indicates the absence of strong BAS on the surface of ZrO₂. Modification of the surface by SO₄ groups results in the appearance of a new type of BAS that are capable of adsorbing CD₃CN in the polycoordinated form,i.e., stronger complexes with the adsorbate. Addition of metal ions (Fe, Ga, Zn, or Co) leads to the formation of a new type of LAS connected with Fe³⁺, Ga³⁺, Zn²⁺, and Co²⁺ promoter ions.     

Platinum catalysed nanoporous titanium dioxide electrodes in H2SO4 solutions

The preparation and electrochemistry of dispersed Pt metal on nanoporous titanium dioxide coatings is described. It is shown that photocatalytic deposition of Pt centres on a nanoporous titanium dioxide layer fabricated from TiO₂ nanoparticles leads to high surface area electrocatalysts. The reactions investigated are the evolution of hydrogen and the oxidation of carbon monoxide and methanol.     

Composition of plasma-chemical silicon dioxide films as studied by IR spectroscopy

The results of a comparative analysis of the compositions of silicon dioxide films prepared by the decomposition of tetraethoxysilane vapor in a glow discharge and the deposition of the products onto a substrate are presented. The compositions of films prepared in gas mixtures containing argon, oxygen, tetraethoxysilane vapor, and NaCl were compared using IR spectroscopy. The electric discharge was excited at a frequency of 19 kHz and in a radiofrequency range at 81.36 MHz. It was found that the additives of oxygen and sodium-containing vapors exerted a noticeable effect on the composition of the films. The compositions of the films prepared at the low-frequency and high-frequency discharge excitation were also different.     

A study of pyridine adsorption on supported vanadium-aluminium catalysts by IR and UV spectroscopy

The acidic properties of supported vanadium-aluminum catalysts have been studied by the IR and UV spectroscopy of adsorbed pyridine. Introduction of vanadium ions does not result in the appearance of acidity of the Brönsted type in the temperature range under study (25–500°C). The adsorption of pyridine on samples containing large amounts of V₂O₅ reversibly increases the transmission in the IR region, which is due to the decrease of current carrier concentration. On pure Al₂O₃, pyridine is oxidized beginning with 400°C; V₂O₅ decreases the temperature of the beginning of oxidation to 200–300°C.

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- . (25°–500°C). , V₂O₅, -, . Al₂O₃ 400°C , V₂O₅ 200–300°C.

     

Photoactivity of mechanochemically prepared nanoparticulate titanium dioxide investigated by EPR spectroscopy

Titanium dioxide nanopowders were prepared by mechanochemical synthesis in a high-energy ball mill using TiOSO₄·xH₂O and Na₂CO₃ followed by annealing in the temperature range 200–800 °C. The UVA photonic efficiency of radical processes on synthesized TiO₂ powders was determined by in situ EPR spectroscopy, using, as indicators, the N-oxide spin trapping agents (5,5-dimethyl-1-pyrroline N-oxide and 5-(diisopropoxy-phosphoryl)-5-methyl-1-pyrroline N-oxide) or the radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate, ABTS⁺). The results obtained by monitoring the photoinduced generation of hydroxyl radical spin adducts correlated with those found by the investigation of the photoreduction of ABTS⁺. The presence of iron and chromium ions, which were evidenced in samples milled in steel, decreased the photonic efficiency of radical processes. The presence of a sulfate salt matrix during the annealing process distinctly inhibits the transformation of anatase to rutile. The highest photocatalytic activity was shown by anatase samples which were prepared by milling in corundum and annealed at 700 °C. They were composed of crystallites with a mean size of 25–30 nm and well developed crystal faces.     

Analysis of organic contaminations on Si(100) by thermal desorption spectroscopy

Summary Temperature and chemical state selective analysis of organic contaminants on Si(100) present after storage in air can be performed using thermal desorption spectroscopy (TDS). Samples stored for different times in air were characterized by XPS and then subjected to TDS. Hydrocarbon fragments were observed as well as a significant partial pressure of formaldehyde occurring as a decomposition product from higher molecular contaminants. Effects of treatment with HF and heating under reduced pressures of molecular oxygen were studied. The paper describes also some general analytical features of the technique.     

Investigation of a Co-MgO-ZSM catalyst by temperature-programmed reduction,temperature-programmed desorption,and IR spectroscopy

The 32% Co-3% MgO-ZSM (SiO₂/Al₂O₃=38) system has been studied by means of temperature-programmed reduction, temperature-programmed desorption, and IR spectroscopy. The data from temperature-programmed reduction show that cobalt exists on the surface of the catalyst in the form of Co²⁺, CoO, Co₃O₄, and CoO·MgO solid solutions. Reduction of the sample results in the formation of a very inhomogeneous surface with four groups of sites.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. J. Heyrovsky Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, Prague. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 55–59, January, 1992.     

Study of the adsorption behavior of heavy metal ions on nanometer-size titanium dioxide with ICP-AES

A new method using nanoparticle TiO2 as solid-phase extractant coupled with ICP-AES was proposed for simultaneous determination of trace elements. The adsorption behavior of nanometer TiO2 towards Cu, Cr, Mn and Ni was investigated by ICP-AES, and the adsorption pH curves, adsorption isotherms and adsorption capacities were obtained. It was found that the adsorption rates of the metal ions studied were more than 90% in pH 8.0-9.0, and 2.0 mol L-1 HCl was sufficient for complete elution. Nanometer TiO2 possesses a significant capacity for the sorption of the metal ions studied which is higher than the capacity of silica, the commonly used extractant. The method has been applied to the analysis of some environmental samples with satisfactory results.     

11种吸附剂上二噁英的热吸附/脱附性能评价

筛选在低温下高效捕集并在一定的高温下可以快速完全脱附二噁英的吸附/脱附材料是二噁英在线热捕集的关键.该研究以1,2,3,4-四氯代二苯并-对-二噁英(1,2,3,4-TCDD)和1,2,3,8,9-五氯代二苯并呋喃(1,2,3,8,9-PCDF)为二噁英模型物,以电子捕获检测器(ECD)作为检测器,利用填充柱气相色谱系...