- LABORATORY SCALE DEMONSTRATION OF THE Mg-S-I CYCLE FOR THERMOCHEMICAL HYDROGEN PRODUCTION
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The Mg-S-I water splitting cycle was demonstrated on a laboratory scale by constructing an apparatus for repeated operations of chemical reactions of the whole cycle and by the circulation of reactants through purely thermochemical proceses below 1000 deg C.Electric furnaces and quartz glass reactors were used.Sixteen times of cycle operations were performed in 16 h with production rates of 0.3 liter H2/h and 0.15 liter O2/h.
- Kumagai, Toshiya,Mizuta, Susumu
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Read Online
- Synthesis, structural and magnetic characterizations of a dinuclear copper(II) complex with an (N,S,O) donor ligand: Catecholase and phenoxazinone synthase activities
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A new dinuclear Cu(II) complex (1) was synthesized and crystallographically characterized. Each of the Cu(II) centres has penta coordination and been found to adopt square pyramidal geometry. Variable temperature magnetic measurements showed that there is weak ferromagnetic interaction between the Cu(II) centres in 1. 1 shows catecholase as well as phenoxazinone synthase activities in different solvents. The turn over numbers for the catecholase activity were 4.02 × 103 h?1 (MeOH) and 9.57 × 103 h?1 (MeCN), and that of phenoxazinone synthase activity were 1.065 × 103 h?1 (MeOH), 2.13 × 102 h?1 (MeCN) and 2.844 × 103 h?1 (DCM).
- Ghosh, Ayon Kanti,Ali, Anzar,Singh, Yogesh,Purohit, Chandra Shekhar,Ghosh, Rajarshi
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p. 156 - 163
(2018/02/20)
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- Mesoporous carbon supported platinum nanocatalyst: Application for hydrogen production by HI decomposition reaction in S-I cycle
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Platinum supported on carbon as a catalyst is widely reported and have a wide range of applications ranging from fuel cell application to hydrogenation reactions, where structure and properties of carbon support play an important role in the functioning of the catalyst. Mesoporous carbon supported platinum nanocatalyst was synthesized by hard templating route using mesoporous silica as template. The catalyst prepared has been characterized by X-ray diffraction, Raman, SEM, TEM, XPS and BET surface area. This catalyst has been employed for liquid phase HI decomposition reaction of sulfur iodine thermochemical cycle for production of hydrogen. The catalyst was evaluated for its activity for HI decomposition reaction and stability in the reaction environment. From present study we conclude that Pt supported on mesoporous carbon is a suitable and stable catalyst for liquid phase HI decomposition reaction.
- Tyagi, Deepak,Varma, Salil,Bharadwaj, Shyamala R.
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p. 2177 - 2184
(2017/01/28)
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- Formation of volatile iodine compounds under hot concentrated acid conditions (nitric acid or aqua regia) and in diluted acid solutions with or without thiocyanate
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It is reported that iodine volatilization can occur in any elemental analysis of total iodine by ICP-MS. This problem affects the accuracy of the results, and it has been neither rationalized nor solved up to now. In this work, the formation of volatile iodine compounds in concentrated acid solutions (nitric acid or aqua regia) under microwave heating was studied by UV–Vis spectrophotometry, linear sweep voltammetry, and cyclic voltammetry. It was evidenced that molecular iodine (I2) can unexpectedly form in concentrated hot HNO3solutions, irrespective of the starting iodine compound (iodide, iodate, periodate, 3-iodo-L-tyrosine, 3,5-diiodo-L-tyrosine dehydrate). I2is produced by the nitrogen oxides existing in these conditions. The formation of volatile iodine is minimized in aqua regia, as chloride is able to keep iodine in solution due to the formation of charged chloro-iodo complexes (e.g. I2Cl?). The dilution of the concentrated acid solution, required prior to the ICP-MS analysis, causes the disruption of I2Cl?so that I2can again volatilize. To avoid this, 0.1 M thiocyanate can be added, as it forms a strong I2SCN?complex which keeps I2in solution as ion. Also other iodine species possibly occurring in the explored conditions, iodide and iodate, were demonstrated to be converted to I2SCN?in diluted HNO3solutions and in the presence of 0.1 M thiocyanate. Recovery tests demonstrated that iodine volatilization is minimized if samples containing iodine are treated in aqua regia and, after dilution, they are added with 0.1 M thiocyanate.
- Badocco, Denis,Romanini, Francesca,Di Marco, Valerio,Mondin, Andrea,Pastore, Paolo
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- On-site detection of phosgene agents by surface-enhanced Raman spectroscopy coupled with a chemical transformation approach
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Phosgene and its analogs are greatly harmful to the public health, environmental safety and homeland security as widely used industrial substances with extremely high toxicity. In order to rapidly evaluate the emergency risk caused by these chemicals, a new highly sensitive method based on surface-enhanced Raman spectroscopy (SERS) technique for measurement of phosgene agents was developed for the first time. Coupled with a chemical transformation approach, the highly toxic phosgene was conveniently converted to a SERS-sensitive probe, i.e. iodine (I2), with low toxicity or non-toxicity. The characteristic SERS peak in 459 cm-1 was used for quantitation and was presumed as a formation of triiodide anion (I3-), which was induced in an iodide (I-)-aggregation Au NPs system. The total measurement can be completed in ~20 min with the limits of detection of ~60 μg/l (phosgene) and ~30 μg/l (diphosgene), respectively, on a portable Raman spectrometer. This work is the first report of SERS measurement on phosgene and diphosgene in a quantitative level. This method is expected to meet the requirements of on-site detection of phosgene agents, promote emergency responses and raise more opportunities for the portable SERS applications. A sensitive surface-enhanced Raman spectroscopy method for measurement of phosgene agents with a chemical transformation approach was reported for the first time. With the transformed product iodine, a more stable triiodide anion was formed in an iodide-aggregated Au nanoparticles system appeared as a characteristic ultraviolet-visible absorption peak at 352 nm and a surface-enhanced Raman spectroscopy peak of 459 cm-1. Three phosgene agents exhibit different reaction rates.
- Gao, Haiyue,Wu, Jianfeng,Zhu, Yingjie,Guo, Lei,Xie, Jianwei
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p. 233 - 239
(2016/02/27)
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- Facile synthesis of a rare example of an iron(III) iodide complex, [FeI3(AsMe3)2], from the reaction of Me 3AsI2 with unactivated iron powder
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The reaction of Me3AsI2 with unactivated iron powder provides a synthetic entry into the coordination chemistry of iron(III) iodide, which is inaccessible by traditional routes due to the low stability of the parent halide FeI3. The reaction of iron powder with Me 3AsI2 results in the formation of a trigonal bipyramidal complex, [FeI3(AsMe3)2], which features the iodide ligands in the equatorial positions, and the Me3As groups occupying the axial positions. This complex is a rare example of an iron(III) iodide complex, and is the first iron(III) complex of a monodentate tertiary arsine ligand. The preparation of [FeI3(AsMe3) 2] via the direct oxidation of iron powder further demonstrates that complexes of soft donor ligands can be prepared with hard transition metal centres, such as iron(III), in direct contravention of the HSAB principle. The structure of [FeI3(AsMe 3)2] is isomorphous with all previously reported [MX 3(EMe3)2] (M = main group or transition metal, X = halide, E = N, P, As) trigonal bipyramidal structures.
- Barnes, Nicholas A.,Godfrey, Stephen M.,Ho, Nicholas,McAuliffe, Charles A.,Pritchard, Robin G.
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- Iodine emission in the presence of humic substances at the water's surface
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Humic substances that preferentially adsorb at the air/water interfaces of water or aerosols consist of both fulvic and humic acid. To investigate the chemical reactivity for the heterogeneous reaction of gaseous ozone, O 3(g), with aqueous iodide, I-(aq), in the presence of standard fulvic acid, humic acid, or alcohol, cavity ring-down spectroscopy was used to detect gaseous products, iodine, I2(g) and an iodine monoxide radical, IO(g). Fulvic acid enhanced the I2(g) production yield, but not the IO(g) yield. Humic acid, n-hexanol, n-heptanol, and n-octanol did not affect the yields of I2(g) or IO(g). We can infer that the carboxylic group contained in fulvic acid promotes the I2(g) emission by supplying the requisite interfacial protons more efficiently than water on its surface.
- Hayase, Sayaka,Yabushita, Akihiro,Kawasaki, Masahiro
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p. 5779 - 5783
(2012/08/28)
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- Weak acids enhance halogen activation on atmospheric waters surfaces
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We report that rates of I2(g) emissions, measured via cavity ring-down spectroscopy, during the heterogeneous ozonation of interfacial iodide: I-(surface, s) + O3(g) + H+(s) →→ I2(g), are enhanced several-fold, whereas those of IO · (g) are unaffected, by the presence of undissociated alkanoic acids on water. The amphiphilic weak carboxylic acids appear to promote I2(g) emissions by supplying the requisite interfacial protons H+(s) more efficiently than water itself, at pH values representative of submicrometer marine aerosol particles. We infer that the organic acids coating aerosol particles ejected from oceans topmost films should enhance I2(g) production in marine boundary layers.
- Hayase, Sayaka,Yabushita, Akihiro,Kawasaki, Masahiro,Enami, Shinichi,Hoffmann, Michael R.,Colussi, Agustin J.
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p. 4935 - 4940
(2011/07/29)
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- Bi2(IO4)(IO3)3: A new potential infrared nonlinear optical material containing [IO4]3- anion
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A new potential infrared (IR) nonlinear optical (NLO) material Bi 2(IO4)(IO3)3 was synthesized by hydrothermal method. Bi2(IO4)(IO3)3 crystallizes in the chiral orthorhombic space group P212 121 (No. 19) with a = 5.6831(11) A, b = 12.394(3) A, and c = 16.849(3) A. It exhibits a threedimensional framework through a combination of the IO3, IO4, BiO8, and BiO9 polyhedra and is the first noncentrosymmetric (NCS) structure containing [IO4]3- anion. Bi2(IO 4)(IO3)3 has an IR cutoff wavelength of 12.3 ?m and belongs to the type 1 phase-matchable class with a moderately large SHG response of 5 × KDP, which is in good agreement with the theoretical calculations.
- Cao, Zhenbo,Yue, Yinchao,Yao, Jiyong,Lin, Zheshuai,He, Ran,Hu, Zhanggui
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p. 12818 - 12822
(2012/03/09)
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- Organosulfur oxoacids. Part 2. A novel dimethylthiourea metabolite - Synthesis and characterization of the surprisingly stable and inert dimethylaminoiminomethane sulfonic acid
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A new metabolite of the biologically active thiocarbamide dimethylthiourea (DMTU) has been synthesized and characterized. DMTU's metabolic activation in the physiological environment is expected to be dominated by S-oxygenation, which produces, successively, the sulfenic, sulfinic, and sulfonic acids before forming sulfate and dimethylurea. Only the sulfinic and sulfonic acids are stable enough to be isolated. This manuscript reports on the first synthesis, isolation, and characterization of the sulfonic acid: dimethylaminoiminomethanesulfonic acid (DMAIMSOA). It crystallizes in the orthorhombic Pbca space group and exists as a zwitterion in its solid crystal form. The negative charge is delocalized over the sulfonic acid oxygens and the positive charge is concentrated over the planar N-C-N framework rather than strictly on the sp2-hybridized cationic carbon center. As opposed to its sulfinic acid analogue, DMAIMSOA is extremely inert in acidic environments and can maintain its titer for weeks at pH 6 and below. It is, however, reasonably reactive at physiological pH conditions and can be oxidized to dimethylurea and sulfate by mild oxidants such as aqueous iodine.
- Petersen, Jeffrey L.,Otoikhian, Adenike A.,Morakinyo, Moshood K.,Simoyi, Reuben H.
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p. 1247 - 1255
(2011/02/24)
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- CONTINUOUS PROCESS FOR CONVERTING NATURAL GAS TO LIQUID HYDROCARBONS
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A method comprising: providing a first halogen stream; providing a first alkane stream; reacting at least a portion of the first halogen stream with at least a portion of the first alkane stream in a first reaction vessel to form a first halogenated stream; providing a second alkane stream comprising C2 and higher hydrocarbons; providing a second halogen stream; and reacting at least a portion of the second halogen stream with at least a portion of the second alkane stream in a second reaction vessel to form a second halogenated stream.
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Page/Page column 78
(2010/04/03)
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- Novel and highly effective method for the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS), catalyzed by I2 generated in situ using Fe(NO3)3 · 9 H 2O/NaI under heterogeneous and neutral conditions
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Structurally diverse alcohols and phenols were trimethylsilylated in a clean and efficient reaction with hexamethyldisilazane (HMDS) based on the use of I2 generated in situ from Fe(NO3)3 · 9 H2O/NaI. The reaction occurs very rapid in good-to-high yield in CH2Cl2 at room temperature, and the use of toxic and corrosive molecular I2 is avoided.
- Khazaei, Ardeshir,Rahmati, Sadegh,Rostami, Amin
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p. 1434 - 1438
(2009/10/16)
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- Oxyhalogen-sulfur chemistry - Kinetics and mechanism of oxidation of methionine by aqueous iodine and acidified iodate
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The oxidation of methionine (Met) by acidic iodate and aqueous iodine was studied. Though the reaction is a simple two-electron oxidation to give methionine sulfoxide (Met-S=O), the dynamics of the reaction are, however, very complex, characterized by clock reaction characteristics and transient formation of iodine. In excess methionine conditions, the stoichiometry of the reaction was deduced to be IO3- + 3Met → I- + 3Met-S=O. In excess iodate, the iodide product reacts with iodate to give a final product of molecular iodine and a 2:5 stoichiometry: 2IO3 - + 5Met + 2H+ → I2 + 5Met-S=O + H 2O. The direct reaction of iodine and methionine is slow and mildly autoinhibitory, which explains the transient formation of iodine, even in conditions of excess methionine in which iodine is not a final product. The whole reaction scheme could be simulated by a simple network of 11 reactions.
- Chikwana, Edward,Davis, Bradley,Morakinyo, Moshood K.,Simoyi, Reuben H.
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p. 689 - 697
(2009/12/04)
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- Semiconductor-catalyzed solar photooxidation of iodide ion
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With natural sunlight TiO2 (anatase), ZrO2, MoO3, Fe2O3, ZnO, CeO2 and Al2O3 microparticles photocatalyze the oxidation of iodide ion but CuO, ZnS, CdO, CdS, HgO, PbO,
- Karunakaran,Anilkumar
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p. 153 - 158
(2008/10/09)
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- Generation of atomic iodine via fluorine for chemical oxygen-iodine laser
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A method of the chemical generation of atomic iodine for a chemical oxygen-iodine laser (COIL) using atomic fluorine as a reaction intermediate was studied experimentally. This method is based on the reaction between F2 and NO providing F atoms, and the reaction of F with HI resulting in iodine atoms generation. Atomic iodine was produced with efficiency exceeding 40% relative to initial F2 flow rate. This efficiency was nearly independent on pressure and total gas flow rate. The F atoms were stable in the reactor up to 2 ms. An optimum ratio of the reactants flow rates was F2:NO:HI = 1:1:1. A rate constant of the reaction of F2 with HI was determined. The numerical modelling showed that remaining HI and IF were probably consumed in their mutual reaction. The reaction system was found suitable for employing in a generator of atomic iodine with its subsequent injection into a supersonic nozzle of a COIL.
- Jirásek, Vít,?palek, Otomar,?ensky, Miroslav,Picková, Irena,Kodymová, Jarmila,Jakubec, Ivo
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p. 167 - 174
(2008/10/09)
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- Heterogeneous reactions of HX + HONO and I2 on ice surfaces: Kinetics and linear correlations
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Reaction probabilities of gaseous nitrous acid, HONO, with HCl, HBr, and HI treated ice surfaces have been investigated in a fast flow-tube reactor coupled with a differentially pumped quadrupole mass spectrometer (QMS) at 191 K. The reaction probability increases with the HX surface coverage, and the rate is the highest for the HONO reaction on the Hi-treated ice surface. Relative rate constants are correlated to the nucleophilic parameter, according to the linear free-energy relationship for this series of heterogeneous reactions on ice surfaces. The correlation was also extended to HOCl + HX(ad) reactions on the ice surface, and it can be used to treat other heterogeneous atmospheric and catalytic reactions. The reaction products ClNO and BrNO were determined by the QMS. INO was found to rapidly convert to I2 on surfaces, and I2 was observed from the reaction of HONO + HI. The uptake coefficient of I2 on the HI-treated ice surface is higher than that for I2 on the water-ice surface.
- Diao, Guowang,Chu, Liang T.
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p. 1364 - 1373
(2007/10/03)
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- METHOD OF PROCESSING OF HYDROGEN FOR REDUCTIVE ACYLATION OF NITRO, AZIDO AND CYANO ARENES
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The present invention relates to a method for processing of hydrogen for the reductive acylation of nitro, azido and cyano arenes. More particularly, this invention relates to an improved process for the preparation of amides and anilides using C3-C7 carboxylic acids as proton source/acylating agents employing Fe3+-montmorillonite as a catalyst.
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- Method of processing of hydrogen for reductive acylation of nitro, azido and cyano arenes
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A method for processing of hydrogen for the reductive acylation of nitro, azido and cyano arenes is disclosed. More particularly, improved process for the preparation of amides and anilides using C3-C7carboxylic acids as proton source/acylating agents employing Fe3+-montmorillonite as a catalyst is disclosed.
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Page column 4
(2008/06/13)
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- Spontaneous Formation of Cellular Chemical System that Sustains Itself far from Thermodynamic Equilibrium
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We report the observation of the spontaneous formation of a cellular structure in a simple inorganic system. The system is obtained by immersing a pellet of calcium and copper chlorides in an alkali solution containing sodium carbonate, sodium iodide, and hydrogen peroxide. The system produces a cell surrounded by a semipermeable membrane. Reactants diffuse and react inside the cell with copper ions serving as catalyst. The products diffuse out of the cell. The system sustains itself far from thermodynamic equilibrium.
- Maselko, Jerzy,Strizhak, Peter
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p. 4937 - 4939
(2007/10/03)
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- Spectrofluorimetric determination of both hydrogen peroxide and -O-O-H in polyethylene glycols (PEGs) using 2-hydroxy-1-naphthaldehyde thiosemicarbazon (HNT) as the substrate for horseradish peroxidase (HRP)
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2-Hydroxy-1-naphthaldehyde thiosemicarbazon (HNT) had been synthesized and used as a new kind of substrate for horseradish peroxidase (HRP) in spectrofluorimetric determination of hydrogen peroxide (H2O 2). The oxidation reaction of HNT with H2O2 under the catalysis of HRP was studied in detail. The possible reaction mechanism was discussed. Under optimum experimental conditions, the oxidized product of HNT had excitation and emission maxima at 260 and 450 nm, respectively. The linear range of this method was 1.30 × 10-9 -1.25 × 10-5 mol 1-1 with a detection limit of 3.89 × 10-10 mol 1-1. The effect of interferences, surfactants and organic solvents on the determination of H2O 2 had been investigated. A study to prove the existence of -O-O-H in PEGs was carried out. The proposed method was successfully applied to the determination of -O-O-H in polyethylene glycols.
- Tang, Bo,Wang, Yan
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p. 2867 - 2874
(2008/10/08)
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- Method and composition for the generation of chlorine dioxide using Iodo-Compounds, and methods of use
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The present invention relates to a biocidal composition, designed for the generation of chlorine dioxide, comprising at least one iodo-compound having at least one iodine atom and a source of chlorite ions. The molar ration of chlorite ions to iodine atoms is 2 or greater. The composition finds use in a variety of applications including methods of cleaning, sanitizing, deodorizing, and disinfecting various surfaces.
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Page column 17-21
(2008/06/13)
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- Inhibitors of IMPDH enzyme
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The present invention relates to a novel class of compounds which are IMPDH inhibitors. This invention also relates to pharmaceutical compositions comprising these compounds. The compounds and pharmaceutical compositions of this invention are particularly well suited for inhibiting IMPDH enzyme activity and consequently, may be advantageously used as therapeutic agents for IMPDH mediated processes. This invention also relates to methods for inhibiting the activity of IMPDH using the compounds of this invention and related compounds.
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Page column 30
(2010/02/04)
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- Quantum yields for the photodissociation of iodine in compressed liquids and supercritical fluids
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Quantum yields of photodissociation were determined for iodine in compressed liquid n-alkanes and supercritical CO2 and xenon after laser excitation at 532 nm. The quantum yield decreases nearly linearly with increasing density. No cluster effe
- Schwarzer,Schroeder,Schroeder
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p. 183 - 195
(2007/10/03)
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- Kinetics of the molybdate and tungstate catalyzed oxidation of iodide by hydrogen peroxide
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Several studies of the Mo(VI) and W(VI) catalyzed reaction of H2O2 with various substrates have been documented previously. The experiments described herein attempt to settle some apparent contradictions in these reports. Specificall
- Copper, Christine L.,Koubek, Edward
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p. 229 - 232
(2008/10/08)
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- Formation of Pd2X2(μ-S)(μ-dpm)2 by reaction of PdX2(dpm) with H2S in the presence of alumina (X = halogen, dpm - diphenylphosphinomethane)
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Alumina promotes the reaction of PdX2(dpm) (3) (X = Cl, Br, I) with H2S to form Pd2X2(μ-S)(dpm)2 (2) and HX, with chemisorption of the HX (quantified by titration) providing the driving force; althoug
- Wong, Terrance Y.H.,James, Brian R.,Wong, Philip C.,Mitchell, Keith A.R.
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p. 159 - 169
(2008/10/09)
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- The Effect of Iron(III) Sulfate on the Interaction of Hydrogen Peroxide with Potassium Iodide in Solution
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Iron(III) sulfate is shown to accelerate iodide oxidation by hydrogen peroxide in aqueous solution.
- Danilov,Krasnobaeva,Nosova,Fedulov,Georgievskaya
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p. 660 - 661
(2008/10/08)
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- Kinetics and Mechanism of the Copper(II)-Catalyzed Oxidation of the Iodide Ion by Chromate(VI) Ion in an Aqueous Solution
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Although the chromate(VI) ions, CrO42- and HCrO4- , which are described as CrVI herein, could hardly oxidize the iodide ion to iodine above pH 3.0, it was catalytically oxidized by adding traces of copper(II) ion. When a copper(II) solution of 10-7-10-5 mol dm-3 was mixed with an iodide solution, after a fast formation of iodine, the iodine concentration remained constant. After such an iodine formation had occurred, if a chromate solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2/3(d[I2]/dt)= -d[CrVI]/dt=k[CuI][CuvI], in which [CuI] is the steady-state concentration in the chain cycle CuI+/CuI. The rate of the chain reaction was independent of the time to add chromate, and the formation of iodine I2 (or triiodide ion I3-) stopped at the time when all of the chromate was consumed by the chain reaction. The stoichiometry was 3I- +CrVI→1.5I2+CrIII. The iodine formation was extremely inhibited by the presence of either radical scavengers or complex-forming reagents as well as by increasing pH. Although addition of alcohols to the reaction mixture extremely accelerated the iodine formation before adding chromate, it hardly affected on this process after the addition of chromate. The reaction mechanisms are presented in order to account for the observed results.
- Kimura, Masaru,Ikawa, Rie,Shiota, Yuko,Tsukahara, Keiichi
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p. 893 - 897
(2007/10/03)
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- Kinetics and Mechanisms of the Copper(II)-Catalyzed Oxidation of Iodide Ion in the Presence of Molecular Oxygen in Aqueous Acid Media
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Traces of copper(II) ions in 10-7 - 10-5 M (M=mol dm-3) catalytically accelerated the oxidation reactions of iodide ion to iodine in relatively strong acid solutions (pH2) in the presence of molecular oxygen under conditions containing relatively high concentrations of I-.When a copper(II) solution was mixed with an iodide solution, after a rapid formation of iodine, it gradually increased according to the reaction times.For about 5 min after mixing, plots of ->formed vs. t showed a good straight line; the formation rate of I2 (or I3-) increased proportionally with increasing concentrations of copper(II) ion and oxygen, with increasing concentrations of hydrogen ion and iodide ion, and with increasing temperature and with decreasing the ionic strength in the reaction solution.The formation rate of I2 was extremely inhibited by the presence of either radical scavengers or ethylenediaminetetraacetic acid (EDTA).A chain mechanism is presented to account for the obtained results.
- Kimura, Masaru,Tokuda, Mari,Tsukahara, Keiichi
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p. 2731 - 2735
(2007/10/02)
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- The Role of Adsorption of Iodine on the Reactor Wall in Photoinduced Nonequilibrium Phase Transition in the Briggs-Rausher Reaction
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The lengths of the induction periods for the photoinduced nonequilibrium (I) -> (II) phase transition in the Briggs-Rausher reaction were measured both in a well-stirred reactor and in artificially created unstirred regions of the reactor.In the absence of stirring, the new phase, (II), is generated irregularly at a random point in the bulk and is not initiated by the reactor walls.The magnitude of iodine adsorption from an aqueous solution on a glass surface was experimentally determined.The experimental results preclude the earlier assumption that in the nonequilibrium (I) -> (II) phase transition iodine adsorption on the reactor walls is the primary cause of the stirring effects.
- Melikhov, D. P.,Vanag, V. K.
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p. 1019 - 1022
(2007/10/02)
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- Photochemistry of alkyl halide dimers
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Dimers and other small clusters of CH3I, C2H5I, i- and n-C3H7I, HI, CF3I, CH3Br, and C2H5Br formed in a supersonic expansion are irradiated at 248 and 193 nm and the halogen molecule product probed via laser induced fluorescence spectroscopy.Both dimers and larger clusters of RI (R = H, alkyl) excited at each wavelength yield I2 in its ground electronic state with very little internal energy.Clusters of CF3I and those containing alkyl bromides do not give halogen molecule products after excitation at either wavelength.A model for the dynamics in the dimer excited state which explains these results is presented.
- Fan, Y. B.,Randall, K. L.,Donaldson, D. J.
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p. 4700 - 4706
(2007/10/02)
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- A pulse radiolysis study of the reaction of OH with I2 and the decay of I2-
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The rate constant for the reaction of the hydroxyl radical with iodine was estimated to be (9.5 +/- 1.0) * 10-9 dm3 mol-1 s-1 at 20 deg C from fitting the time dependence of the decrease in the absorption of iodine at 460 nm.A number of rate constants associated with the decay of I2- that were required for this fitting process were also determined.They were the reaction of I2- with I2- (2k = (4.60 +/- 0.05) * 10-9 dm3 mol-1 s-1) at an ionic strength of 1.2 * 10-2 mol dm-3; I2- with I (k = 4.6 +/- 1.6) * 10-9 dm3 mol-1 s-1); and I with I (2k = (3.0 +/- 1.0) * 10-10 dm3 mol-1 s-1).
- Elliot, A. John
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p. 1658 - 1661
(2007/10/02)
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- A SIMPLE METHOD TO LOCATE TRANSITION STATES OF CHEMICAL REACTIONS
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By using an appropriate coordinate system the arc length between two points on the geodesic reaction path is equal to the absolute difference between the function values (energies) belonging to the same points.This gives the possibility to avoid the tedious integration procedure necessary to get a measure of the position of the saddle point (or any other point) in the one-dimensional space of the reaction path.The method is illustrated by reaction coordinate values of transition states for a number of atom transfer reactions in comparison with those calculated by an independent method.Reaction coordinates also computed by using analytical functions are compared with those obtained by direct integration.
- Balint, Imre,Ban, Miklos I.
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p. 431 - 438
(2007/10/02)
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- Experimental and modeling study of oscillations in the chlorine dioxide-iodine-malonic acid reaction
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At pH 0.5-5.0, a closed system containing an aqueous mixture of chlorine dioxide, iodine, and a species such as malonic acid (MA) or ethyl acetoacetate, which reacts with iodine to produce iodide, shows periodic changes in the light absorbance of I3-. This behavior can be modeled by a simple scheme consisting of three component reactions: (1) the reaction between MA and iodine, which serves as a continuous source of I-; (2) the reaction between ClO2? and I-, which acts as a source of ClO2-; and (3) the self-inhibited reaction of chlorite and iodide that kinetically regulates the system. The fast component reaction between chlorine dioxide and iodide ion was studied by stopped-flow spectrophotometry. The rate law is -[ClO2?]/df = 6 × 103 (M-2 s-1)[ClO2?][I-]. A two-variable model obtained from the empirical rate laws of the three component reactions gives a good description of the dynamics of the system. The oscillatory behavior results not from autocatalysis but from the self-inhibitory character of the chlorite-iodide reaction.
- Lengyel, István,Rábai, Gyula,Epstein, Irving R.
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p. 9104 - 9110
(2007/10/02)
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- resonance enhanced multiphoton ionization of I and Br formed from the infrared multiphoton decomposition of CF3I and CF3Br
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Resonance enhanced multiphoton ionization (REMPI) has been used to study the products of the infrared multiphoton decomposition (IRMPD) of CF3I in a very low-pressure photolysis (VLPΦ) cell.The strongest REMPI signals are due to the ground state I(2P3/2) and the spin-orbit excited state I*(2P1/2).The origins of I and I* were determined from the time and IR laser fluence dependences of the REMPI signal.I* is formed by visible single photon dissociation of vibrationally excited CF3I and by visible multiphoton dissociation of I2 and thermal CF3I.The ionization efhciency of I has been determined relative to NH3 for our probe laser conditions, and the sticking coefhcient of I with gold surfaces has been determined.The REMPI spectra of the products of the IRMPD of CF3Br is also presented.
- Robertson, Robert M.,Golden, David M.,Rossi, Michel J.
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p. 2925 - 2931
(2007/10/02)
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- PHOTOCATALYTIC OXIDATION OF IODIDE IONS BY TITANIUM DIOXIDE
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The photocatalytic oxidation of aqueous I(-), usually as neutral 0.1 mol kg-1 KI, has been investigated using suspensions of pure anatase and rutile, five doped rutiles and two commercial anatase pigments.Reaction only proceeded in the presence of both O2 and u.v. radiation to yield I2, which reacted with excess I(-) to form I(-)3; there was no evidence for IO(-) or IO(-)3 formation.The dependence of initial reaction rate on the square root of the intensity of the incident 366 nm radiation, together with low quantum yields, reflect the recombinative loss of photoelectrons and photoholes greatly exceeding their consumption in productive reaction steps.No activation energy for I2 formation was observed with any of the catalysts, and in this respect the photo-oxidation of I(-) differs from that of liquid alcohols on the identical catalysts.A mechanism is proposed in which I2 and OH(-) result from electron transfer between charged and neutral species adsorbed on the TiO2 surface, leading to an overall reaction: .
- Harvey, Paul R.,Rudham, Robert
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p. 4181 - 4190
(2007/10/02)
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- Kinetics of Oxidation of Iodide Ion by Iron(III) in the Presence of 2,2'-Bipyridyl
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2,2'-Bipyridyl accelerates the reaction between iron(III) and iodide ion and the kinetics of this reaction has a different pattern from that of the uncatalysed reaction.The reaction obeys first order kinetics with respect to FeIII and a plot of k'/(I-) vs (I-) is linear with positive intercept, showing that the reaction has two rate-determining paths, one involving one iodide ion and the other two iodide ions.The hydrogen ion inhibits the reaction.A mechanism involving 1:2 ironIII-bipyridyl as the active species has been proposed.
- Rao, P. V. Subra,Saradamba, G. V.,Krishna, K. Rama
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p. 463 - 466
(2007/10/02)
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- Complex Kinetics in the Bromate-Iodide Reaction: A Clock Reaction Mechanism
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A reinvestigation of the kinetics and mechanism of the bromate-iodide reaction in acidic medium has been undertaken.The stoichiometry of the reaction in excess iodide concentrations over bromate is BrO3(1-)+9I(1-)+6H(1+)->Br(1-)+3I3(1-)+3H2O (A), and in excess bromate concentrations the stoichiometry is BrO3(1-)+6I(1-)+6H(1+)->Br(1-)+3I2+3H2O (B).In excess bromate concentrations a second reaction is observed in which the iodine produced by reaction B is consumed rapidly and suddenly in a typical clock reaction fashion according to the reaction 2BrO3(1-)+I2->2IO3(1-)+Br2 (C).Reaction C does not commence until reaction B is complete, i.e., when all the iodide ions have been consumed.This is explained via a combination of kinetic factors which favor the production of iodine and the fact that higher oxidation states of iodine are thermodinamically unstable with respect to iodine in the presence of iodide ions in acidic media.At 25+/-0.1 deg C and ionic strength 0.2 M (NaClO4), the rate low in both high iodide and high bromide environments was found to be -d/dt-k02, with k0=44.3+/-1.1 M-3 s-1.The postulated mechanism involves an initial nucleophilic attack on the protonate bromate species by iodide, followed by elimination of HOI.
- Simoyi, Reuben H.,Masvikeni, Patricia,Sikosana, Angela
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p. 4126 - 4131
(2007/10/02)
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- Studies of chemical reactivity in the condensed phase. I. The dynamics of iodine photodissociation and recombination on a picosecond time scale and comparison to theories for chemical reactions in solution
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Picosecond transient absorption measurements from 1000-295 nm are used to monitor the recombination dynamics of iodine after photodissociation in a variety of inert solvents.The high time resolution and signal-to-noise ratio of these measurements permits the development of a detailed model of this reaction, which should resolve disagreements over the time scales of geminate recombination and vibrational relaxation and over the role of excited electronic state trapping.Most of the atoms which undergo geminate recombination do so in 15 ps, in agreement with the predictions of existzng molecular dynamics simulations.The subsequent vibrational and electronic energy relaxation of the recombined molecule is relatively slow and accounts for most of the transient absorption dynamics.The relaxing X state vibrational population distribution is extracted with an approximate method using calculated spectra of the excited vibrational levels and is compared to recent models.Vibrational relaxation times vary from ca. 15 ps near the middle of the ground state well to ca. 150 ps for complete relaxation to v = 0.The vibrational relaxation rates do not provide support for the predicted role of resonant vibration-to-vibration energy transfer to chlorinated methane solvents, but some evidence for this mechanism is found in alkane solvents.B-state predissociation times of 10-15 ps and A '-state lifetimes of 65-2700 ps are found depending on the solvent.Current theory is not able to satisfactorily explain the large variation of the A '-state lifetime in various solvents.
- Harris, A. L.,Berg, M.,Harris, C. B.
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p. 788 - 806
(2007/10/02)
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- Kinetics of the Oxidation of Substrate Ligands by Transition-metal Cations
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The kinetics of the oxidation of iodide ions by CeaqIV have been investigated.The reaction is found to be first order in each of IV>, and , in contrast to the oxidation of Br(1-) by CeaqIV, which is second order in both and .Nevertheless, the direct order of one in found for the CeIV + I(1-) reaction can only be interpreted by assuming the involvement of intermediate Ce(4+) - I(1-) complexes.The second-order rate constant for the oxidation of I(1-) by CoaqIII is shown to vary with ionic strength, so the entalphy ΔH* and entropy ΔS* of activation have been determined in conditions where the rate is invariant with ionic strength.These values for ΔH* and ΔS* are compared with the values for other substrates.The oxidation of iodide ions is discussed in relation to a general mechanism for the oxidation of substrate ligands by aquatransition-metal cations.
- Nazar, Abdul Fattah M.,Wells, Cecil F.
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p. 801 - 812
(2007/10/02)
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- The Oscillatory Briggs-Rauscher Reaction. 1. Examination of Subsystems
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In acidic aqueous solution at 25 deg C, only slow or nonexistent reaction is observed for any two of three species iodate ion, hydrogen peroxide, and manganous ion.However, if all three species are present, 0.002 M Mn2+ catalyzes the iodate oxidation of peroxide at a rate almost 1000 times that in the absence of a catalyst! This remarkable observation, which has already been reported by Cooke, can be explained by postulating that the radical oxidant *IO2 is very sluggish at abstracting hydrogen atoms from the species like H2O2 but can oxidize Mn2+ by electron transfer.A detailed mechanism has been proposed that models semiquantitatively not only the manganous catalyzed iodate oxidation of peroxide but also the simultaneous induced disproportionation of the peroxide and the fact that the concentration of elementary iodine does not increase to a limiting value but rises to a maximum and then decreases toward a small value.Despite this single extremum, the subsystem does not exhibit oscillatory behavior.
- Furrow, Stanley D.,Noyes, Richard M.
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- CATALYTIC EFFECT OF SOME COMPLEX CATIONS ON THE PERSULPHATE-IODIDE REACTION
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The rate of the reaction S2O8(2-) + I(-) has been measured in the presence of different complexes of Co(III), Fe(II) and Ni(II).The catalytic effect of the complexes of Co(III) is attributed to the formation of ion pairs or to electrostatic effects.The catalytic effect of the complexes of Fe(II) and Ni(II) is attributed to the intermediate formation of the respective complexes of Fe(III) and Ni(III).
- Constante, Maria Del Mar Graciani,Ferranti, Francesco
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p. 173 - 176
(2007/10/02)
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- Studies on kinetic parameters of Briggs-Rauscher oscillatiung reaction
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The temperature dependence of Briggs-Rauscher oscillating reaction has been studied using different organic substrats.The apparent activation energy of chemical oscillation (EW) and entropy of activation (ΔSW(excit)) have been evaluated in each case in various manners using a monomolecular and first order approximation.
- Dutt, A. K.,Banerjee, R. S.
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p. 298 - 304
(2007/10/02)
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- Photoproduction of I2, Br2, and Cl2 on n-Semiconducting Powder
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The halogen molecules, Cl2, Br2, and I2, have been succesfully photoproduced in oxygen-saturated aqueous solutions containing the respective halide ion and platinized semiconducting n-TiO2 powder.While the latter is produced photocatalytically, the first two are clear examples of products of photosynthetic reactions.These photosynthetic reactions carried out on the Pt-TiO2 powders can lead to a net conversion of solar energy to storable chemical energy.The platinized TiO2 powders are considered to be many short-circuited platinum-semiconductor electrodes on which the photoassisted reactions take place (i.e., the reduction of oxygen on the platinum sites by the photoproduced electron and the oxidation of the halide ion by the photoproduced hole on the TiO2 surface).Although the oxidation of iodide ions by oxygen is thermodynamically spontaneous at pH 5.5, the oxidation rate is significantly enhanced in the presence of the Pt-TiO2 powder and UV radiation.The oxidation of bromide and chloride ions by oxygen is nonspontaneous at pH 5.5, but they are oxidized at significant rate in the presence of the Pt-TiO2 powder and UV radiation, indicating a photosynthetic process for the production of these halogens.Experiments indicate that the oxidation of the halide ions by oxygen will take place in the presence of irradiated unplatinized TiO2 powder, but the reaction rate is significantly increased by platinization of the semiconducting powder.These results suggest that platinization is effective in producing, at the TiO2-electrolyte interface, a depletion region which is important for the efficient charge separation of the photoproduced electron-hole pairs.The photooxidation of the halogens was carried out at several pH values and for various conditions, and conclusions concerning the efficiency of the overall process are discussed.
- Reichman, Benjamin,Byvik, Charles E.
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p. 2255 - 2258
(2007/10/02)
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- The Decomposition of Hydrogen Iodide and Separation of the Products by the Combination of an Adsorbent with Catalytic Activity and a Temperature-swing Method
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The decomposition of hydrogen iodide and the separation of the products by the combination of a column packed with an adsorbent with catalytic activity (platinum-supported active carbon, 2.3 wtpercent) and a temperature-swing method (450-900 K) are carried out, and the features and the problems of the method are examined.A one-step conversion of hydrogen iodide, 70percent, is obtained at 450 K, where the equilibrium conversion is 13percent.It is shown that the products of the decomposition of hydrogen iodide containing water are separated from each other.
- Oosawa, Yoshinao
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p. 2908 - 2912
(2007/10/02)
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