Reactivation of Promoted Nickel Catalysts for Deuterium Exchange between Hydrogen and Water in the Vapour Phase

Binary promoted nickel – chromium oxide and ternary promoted nickel – chromium oxide – aluminium oxide mixed catalysts were prepared for use in the present study. The catalysts were prepared by co-precipitation of the corresponding metal nitrates as carbonates followed by calcination in nitrogen atmosphere at 350 °C and reduction in hydrogen atmosphere at 320 °C. To prevent spontaneous oxidation of the catalysts, bidistilled water was added followed by heating of the catalyst mixtures at about 110 °C in hydrogen atmosphere for few hours. Deactivation of catalysts was studied by measurements of the variation of their activities with the time of contact of the reacting gas mixtures with the catalyst surface in the reaction chamber. It was found that while the catalytic activity of ternary catalysts for the isotopic exchange of deuterium between hydrogen and water vapour was higher than that of the binary one, the loss in activity of the former teas faster than the latter. Reactivation of the catalysts were carried out at different temperatures between 110–160°C in hydrogen atmosphere. Catalytic activity measurements indicated that higher temperatures are better for the reactivation process.     

Hydrogen-Water Deuterium Exchange Reaction Over Mixed Oxide Supported Nickel Catalysts

Three series of catalysts, Ni/Al₂O₃-SiO₂, Ni/Al₂O₃-Cr₂O₃ and Ni/SiO₂-Cr₂O₃, were prepared by co-precipitation. In all samples the nickel content was kept constant at 70 at.% Ni, while the support composition was varied. The nickel surface areas, which are required to measure the specific catalytic activities, were determined by hydrogen chemisorption. In the case of the single oxide supported nickel catalysts, the order of the specific catalytic activity values was: Ni/Cr₂O₃<Ni/Al₂O₃<Ni/SiO₂. The specific catalytic activity of the Ni/Al₂O₃-SiO₂ samples, as a function of the support composition, follows approximately the weighted sum of the specific activities of the single oxide supported nickel catalysts. The specific catalytic activity value of the Ni/Al₂O₃-Cr₂O₃ and Ni/SiO₂-Cr₂O₃ samples more closely resembled that of Ni/Cr₂O₃ catalyst. The presence on chromia surface of the chromic anhydride and its tendency to spread onto are supposed to be the cause of this behaviour. Due to their enhanced activity, the Ni/Al₂O₃-Cr₂O₃ catalysts can be used for the production and detritiation of heavy water.     

Separation of Deuterium Isotope by Chemical Exchange between Hydrogen and Water Vapour

The separation factor of deuterium (α) for the exchange reaction between hydrogen and water vapour at 100 °C has been measured and was found to be equals to 2.52 and 2.50, depending on the used experimental technique.

An empirical equation relating the variation of the separation factor with temperature for such isotopic exchange reaction has been deduced. The values of α were calculated from 0–800 °C and indicated close agreement with those calculated from spectroscopic data.

Comparison of the deduced empirical equation with the general equation relating the separation factor with temperature for such reaction, allowed the calculation of the zero point energy, as well as the free energy as a function of temperature.     

Nickel/Chromium oxide/Zirconium oxide Catalysts for Hydrogen/Deuterium Isotopic Exchange

Catalysts composed of nickel and promoted with different metal oxides proved to be suitable for H/D isotropic exchange between hydrogen and water vapour. They loss their activity due to water condensation on their surfaces. Several nickel/chromium oxide/zirconium oxide catalysts of different composition were prepared by the coprecipitation technique. The liquid phase activity of these catalysts were followed using the hydrogen peroxide decomposition on their surfaces at different temperatures. The surface characteristics of the examined catalysts were followed by applying the BET method. The results were discussed and lead to the required catalyst composition which resists the water condensation on its surface during operation and has relatively high activity in the vapour phase H/D isotopic exchange reaction between hydrogen and water.     

H/D Isotopic Exchange between Hydrogen and Water Vapour on Ni/Cr2O3/ThO2 Catalysts

Thoriumdioxide was selected as a second promoter for nickel catalyst in addition to chromium oxide which was proved to be suitable to accelerate the H/D isotopic exchange reaction between hydrogen and water vapour. A series of Ni/Cr₂O₃/ThO₂ catalysts were prepared by the co-precipitation technique. The amount of Ni was 70 … 90 mol%, while that of Cr₂O₃ was 0 … 20 mol% and that of ThO₂ ranges from 0 … 30 mol%. This type of catalysts is sensitive for water condensation on its surface. The total surface area, total pore volume and pore radius of the catalysts were calculated from nitrogen adsorption on their surfaces at 77 K and application of the BET-equation.     

Isotopic Exchange of Hydrogen between the Fluids of the Hydrocarbon Fields

It is presented the isotopic exchange of hydrogen in natural gas, crude oil, and underground water. The general behaviour of the isotopic exchange occuring in a system with a large number of components is given. A good agreement between the calculated and the experimental isotopic distribution factors is obtained in the case of the isotopic exchange of hydrogen between methane and underground water. The deuterium concentration of the crude oil samples inserts between the values obtained for methane and underground water. This fact is due to the presence of the isotopic exchange between these fluids.     

Liquid Phase Kinetic and Thermodynamic Studies on Promoted Nickel Catalysts used for H/D Exchange

Successful choice of the suitable catalyst composition for hydrogen/deuterium exchange reaction between hydrogen and water requires understanding of chemical kinetics as well as surface properties and activity in both liquid- and vapour phases. The present study deals with the thermodynamic and kinetic behaviour of a simple liquid phase reaction on the surface of nickel catalyst promoted with zirconium oxide used for the H/D exchange. This study helps understand the condensation of water on the catalyst surface during operation which leads to its poisoning. In this specific case water molecules are responsible for selective poisoning of this type of catalysts. The reaction rate constant, the increase in Gibb,s free energy, the enthalpy, the entropy of activation and the energy of activation were calculated.     

1H NMR Study of Hydrogen Bonding and Hydrogen to Deuterium Isotope Exchange in Ureido Sugars

Abstract

The acidic properties of ureido NH protons in two new derivatives of methyl 3,4,6-triacetyl-2-deoxy-β-D-glucopyranoside and i-butylamine (1) and L-leucine (2) were studied by ¹H NMR. Stronger influence of polar aprotic solvents, more effective interaction with nitroxyl radical and faster H/D exchange indicate that N1'-H proton which is proximate to the glucopyranose ring is more acidic than N3'-H one in both ureido sugars, this conclusion was supported by semi-empirical AM1 calculation. Hydrogen to deuterium exchange rates are 1.2 x 10^?2 to 5.5x 10^?3 M^?1 min^?l. Significantly slower exchange of N3'-H proton standing by Leu residue in 2 can be explained by the existence of internal H-bonds.     

Body Water,Lean Body and Fat Mass of Healthy Children as Measured by Deuterium Oxide Dilution

Abstract

Body composition of 165 healthy children was measured using the well-established method of deuterium oxide (²H₂O) dilution. After distribution of an oral load of 2.0 ml ²H₂O/kg body weight body water was estimated from the ²H₂O concentration in urine. Lean body mass was then calculated from body water using previously published age dependent ratios of the water content of the lean body mass. Fat mass was calculated as the difference of body weight and lean body mass. A good correlation was found between body water and body weight. Linear regression revealed TBW = 0.589 BW + 0.728 (r = 0.99). Body water, lean body mass and fat mass were found to change with age. The fat content of the body increases during the first six months of life. It then decreases until four to five years then rising again until 15 years of age.     

Hochwirksame ternäre Ni-Cr2O3-Al2O3-Mischkatalysatoren für den Deuteriumaustausch zwischen Wasserstoff und Wasserdampf

Die vorliegenden Untersuchungen basieren auf der Hypothese, daβ die spezifische Aktivität eines binären Ni-Cr₂O₃-Mischkatalysators für den Deuteriumaustausch in System Wasserstoff/Wasserdampf durch Zusatz einer geeeigeneten Drittkomponente durch Synergese gesteigert werden kann. Entsprechend den Anforderungen, die an die Drittkomponente zu stellen sind, erweist sich Al₂O₃ als besonders geeingent. Die gemessenen spezifischen Aktivitälen der untersuchten ternären Mischkatalysatoren zeigen, daβ entsprechend der angenommenen Hypothese ein bemerkenswerter synergetischer Effekt durch Zusatz von Al₂O₃ als Drittkomponente zu dem binären Ni-Cr₂O₃-Mischkatalysator innerhalb bestimmter Konzentrationsverhältnisse (80–85 Mol.% Ni, 5–15 Mol-% Cr₂O₃ und 5–15 Mol-% Al₂O₃) auftritt.     

The Origin and Evolution of Some Mineral Water Sources Estimated from Their Deuterium Content

In this paper are discussed the origin and the evolution of several mineral water sources from some places of Romania, on the basis of deuterium content variations of water which take place in time and their correlation with the total salt content.     

Deuterium,Oxygen-18 and Salt Content of Drinking Water Sources in Cairo

The contineous increase of population in Cairo exceeding 10 millions inhabitants lead to the search for supplementary potable water resources in addition to the Nile River which is the principle drinking water source. Groundwater represents the main supplementary source. Evaluation of the groundwater feeding the so-called El-America Water Treatment Station which is one of the biggest potable water supplies at the northern of Cairo was carried out. Chemical and isotopic techniques were applied to estimate the suitability of this groundwater for drinking purposes. The chemical analysis includes the determination of sodium, potasium, calcium and magnesium concentrations in addition to those of chlorides, sulphates, bicarbonates and silicates, while the isotopic analysis includes oxygen-18 and deuterium. The overall chemical- and isotopic investigations determined the conditions at which the examined groundwater is suitable for drinking purposes.     

New Methods for Fully Automated Isotope Ratio Determination from Hydrogen at the Natural Abundance Level

Abstract

A variety of methods for measurement of ²H/¹H from H₂ are evaluated for their ability to be fully automated and for applicability to automated isotopic analysis of water and organic compounds. Equilibration of water with H₂ gas with the aid of a platinum catalyst has been commercialized into a fully automated sample preparation device. A second and newer technique, involving injecting water, methane, or other volatile organic compounds onto hot chromium in a reactor attached to the dual inlet system of a gas isotope ratio mass spectrometer, can be integrated with a conventional GC-autosampler to allow automated analysis of a variety of substrates. Both techniques result in precisions around 1‰ (δ notation) on the VSMOW scale, and are fast and accurate, and with appropriate mass spectrometers require only negligible scaling for the SLAP/VSMOW difference. Several experimental methods which show considerable promise employ “isotope ratio monitoring” (irm) inlet systems, in which a carrier gas is used for transport of H₂ to the mass spectrometer. Any such method has to address the problem of He ions corrupting the measurement of the H₂ ions. One such approach uses a heated palladium membrane for selective introduction of H₂ into the mass spectrometer, and a second involves modifications to the ion optics to control the stray helium ions. Both approaches have significant limitations that must be overcome before irm techniques can be used in routine applications, in particular for measuring hydrogen isotopes from GC effluents (irm-GCMS).     

Fractionation of Oxygen and Hydrogen Isotopes at the Hydrate Gas forming in the Sea Sediments

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies shows that heavy isotope of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ¹⁸O = +1.99‰, δD = +23‰ relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading.     

A High Precision Thermostat for the Isotopic Analysis of Water by the Falling Drop Method

An a.c. bridge thermostat, using two thermistors mounted in two opposite arms as temperature sensing elements, is described. The unbalanced bridge voltage is rectified, after a previous amplification, by a phase sensitive detector, and it is applied to the input of the final stage which controls the heater. The thermostat can be used to maintain the temperature of a liquid bath with a 0.0005°C precision and can be easily reset to different temperatures in the operational range of the thermistors.     

FT-IR Study of the Interaction Between H2O,D2O,HOD, and Pyridines

Abstract

The complexes between H₂O, D₂O, HOD and pyridine have been studied in 1,2-dichloroethane by FT-IR spectrometry. Equal splittings of the stretching bands of H₂O and D₂O about their uncoupled vibrations are observed. The coupling between the asymmetric and symmetric vibrations reaches a value of zero when the band separation is greater than 500 cm^?1 for the OH vibrations and 365 cm^?1 for the OD vibrations. The v_OH stretching frequencies of the HOD ‥ complexes and the v_OD stretching frequencies of the DOH‥ complexes increase by complex formation. These features are explained by an electronic reorganization within the hydrogen bond.     

催化剂SiO_2/CNI的制备及其在光解水制氢领域中的应用

以二氰二胺和碘化铵为前驱体,采用水浴-焙烧方法首次制备了CNI与SiO_2不同质量比的SiO_2/CNI复合光催化剂。采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、光致发光光谱(PL)和紫外-可见漫反射光谱(UV-Vis DRS)等对催化剂进行了表征。实验结果表明,与CNI相比,CNI/SiO_2复合光催化剂具有更高的光催化活性。当SiO_2与CNI的质量比为1∶15时,SiO_2/CNI催化剂样品的光解水产氢活性最高,光解水产氢速率为88.6℃mol/h。SiO_2/CNI(1∶15)样品之所以具有高活性主要有两方面原因:适量的SiO_2与CNI复合可以使光生电子-空穴对的复合得到显著的抑制;SiO_2与CNI复合使得SiO_2/CNI对可见光(200~600 nm)吸收能力增强,且其吸收带边向长波方向移动。     

Laboratory Enrichment of Heavy Water by Electrolysis Part II: Effect of Current Density,Cathode Material,and Temperature on the Separation Factor

The different parameters affecting the electrolytic H-D separation factor were investigated. The separation factor α was found to increase with current density and then attains a constant value. With different α increased in the following way: Phosphated iron > iron > stainless steel > nickel. It was found that α decreased as the temperature increased. Applying Arrhenius equation it was possible to calculate the difference in the free energy of activation for proton and deuteron transfer using different cathodes. Excessive reduction in the volume of electrolyte lowered the separation factor. No marked effect on α was observed by changing the type or concentration of electrolyte.