Hydrogen Isotope Exchange Reactions Research Articles

Effects of outgassing of loader chamber walls on hydriding of thin films for commercial applications

An important aspect of understanding industrial processing is to know the characteristics of the materials used in such processes. A study was performed to determine the effects of hydriding chamber material on the degree of hydriding for the commercial production of thin film hydride targets for various research universities, commercial companies, and government national laboratories. The goal was to increase the degree of hydriding of various thin film hydrides and to study the vacuum environment during air-exposure hydriding. For this purpose, dynamic residual gas analysis during deuterium gas hydride processing was utilized with erbium thin films, employing a special set-up for direct dynamic hydride gas sampling during processing at elevated temperature and full loading gas pressure. Complete process data for (1) a copper–(1.83 wt. %)beryllium wet hydrogen fired passivated (600 °C–1 h) externally heated pipe hydriding chamber are reported. Dynamic residual gas analysis comparisons during hydriding are presented for hydriding chambers made from (2) alumina (99.8 wt. %), (3) copper (with an interior aluminum coating ∼10 k Å thick, and (4) for a stainless-steel air-fired passivated (900 °C–1 h) chamber. Dynamic data with deuterium gas in the chamber at the hydriding temperature (450 °C) showed the presence and growth of water vapor (D2O) and related mixed ion species(H2O+, HDO+, D2O+, and OD+) from hydrogen isotope exchange reactions during the 1 h process time. Peaks at mass-to-charge ratios (i.e., m/e) of 12(C+), 16(CD2+), 17(CHD2+), and 18(CD3+, OD+) increased for approximately the first half hour of a 1 h hydriding process and then approach steady state. Mass-to-charge peaks at 19(HDO+) and 20(D2O+) continue to increase throughout the process cycle. Using the m/e = 20 (D2O+) peak intensity from chamber (1)–Cu(1.83 wt. %)Be as a standard, the peak intensity from chamber (4)—stainless-steel (air-fired) was 7.1× higher, indicating that the surface of stainless-steel had a larger concentration of reactive oxygen and/or water than hydrogen. The (D2O+) peak intensity from chamber (3)—Cu (interior Al coating) was 1.55× larger and chamber (2)—alumina(99.8%) was 1.33× higher than Cu(1.83 wt. %)Be. Thus copper–(1.83 wt. %)beryllium was the best hydriding chamber material studied followed closely by the alumina (99.8 wt. %) chamber. Gas take-up by Er occluder targets processed in Cu(1.83 wt. %)Be hydriding chambers (i.e., gas/metal atomic ratios) correlate with the dynamic RGA data.

Two-chamber hydrogen generation and application: access to pressurized deuterium gas.

Hydrogen and deuterium gas were produced and directly applied in a two-chamber system. These gaseous reagents were generated by the simple reaction of metallic zinc with HCl in water for H2 and DCl in deuterated water for D2. The setup proved efficient in classical Pd-catalyzed reductions of ketones, alkynes, alkenes, etc. in near-quantitative yields. The method was extended to the synthesis and isotope labeling of quinoline and 1,2,3,4-tetrahydroquinoline derivatives. Finally, CX-546 and Olaparib underwent efficient Ir-catalyzed hydrogen isotope exchange reactions.

Process simulation for hydrogen/deuterium exchange in a packed column

The hydrogen isotope exchange reaction between hydrogen and water is a key process in water detritiation and heavy water production. To determine the optimum operating parameters and predict the exchange performance in a packed column, the hydrogen/deuterium exchange process was simulated, and the experiment results were verified by the simulation. The optimum exchange temperature was found to decrease with increased hydrogen feed flow rate. The deuterium concentration at the top of the column exhibited nonlinearity throughout all stages. The pressure drop per stage was also observed to induce no significant change in the hydrogen/deuterium exchange performance. With increased temperature, the change trend of calculated results was consistent with that of the experimental values. However, the calculated results are somewhat higher than the experimental ones, and the reason for the difference was discussed.

Evaluation of the Reactivity of L-tyrosine in the T-for-H Exchange Reaction at Low Temperature

In order to quantitatively evaluate the internal exposure of tritium(3H or T), both the reactivity of exchangeable and non‐exchangeable Organically Bound Tritium(OBT) must be observed at body temperature. In this study, we assumed the model of exchangeable OBT, and the hydrogen isotope exchange reaction(T-for-H exchange reaction) between L-tyrosine and HTO vapor was observed at 25 and 36 ℃ in the gas-solid system. Applying the A″-McKay plot method to the data obtained in the reaction, the rate constants(k) of the functional groups in the material were obtained and Arrhenius plots were also drawn. In addition, from the Arrhenius plots in the range of 50 - 70 ℃, the estimated rate constants(kex) of 36 and 25 ℃ were obtained by using extrapolation method. Comparing k and kex, following three matters have been found in the T-for-H exchange reaction. (1)Because the value of k was similar to kex, extrapolation method is useful. (2)Applying Taft's equation, polar and steric substituent constants of C7H7O were obtained. (3)The method used in this work is useful for quantitative clarification of the reactivity of the T-for-H exchange reaction, and for the estimation of the internal exposure of exchangeable OBT.

Practically convenient and industrially-aligned methods for iridium-catalysed hydrogen isotope exchange processes.

The use of alternative solvents in the iridium-catalysed hydrogen isotope exchange reaction with developing phosphine/NHC Ir(I) complexes has identified reaction media which are more widely applicable and industrially acceptable than the commonly employed chlorinated solvent, dichloromethane. Deuterium incorporation into a variety of substrates has proceeded to deliver high levels of labelling (and regioselectivity) in the presence of low catalyst loadings and over short reaction times. The preparative outputs have been complemented by DFT studies to explore ligand orientation, as well as solvent and substrate binding energies within the catalyst system.

Improved catalysts for hydrogen/deuterium exchange reactions

The hydrogen isotope exchange reaction between hydrogen and water is a key process in water detritiation and heavy water production. To improve the characteristics of hydrophobic catalysts for this type of reaction, foamed and cellular structures of hydrophobic catalysts were successfully prepared by adding a blowing agent. The mean particle size of Pt nanoparticles was 2.3 nm. The proportions of elemental Pt and Pt oxides were 62% and 38%, respectively. The addition of polymethyl methacrylate powder decreased internal diffusion of water vapor and hydrogen inside the catalyst and improved active site utilization. As a result, the catalytic activities of the hydrophobic catalysts are significantly higher than those of conventional hydrophobic catalysts for hydrogen isotope exchange. All catalysts exhibited excellent hydrophobic performances after 30 days of testing. It was reasonable to mix Pt/C catalysts, polytetrafluoroethene and polymethyl methacrylate in a ratio of 1:2:1 before hydrophobic treatment. Finally, the mechanisms of hydrogen–water diffusion and exchange were investigated.

Improvement of hydrogen isotope exchange reactions on Li4SiO4 ceramic pebble by catalytic metals

Abstract Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module (CH HCSB TBM) for the International Thermonuclear Experimental Reactor (ITER). In this paper, Li4SiO4 ceramic pebbles deposited with catalytic metals, including Pt, Pd, Ru and Ir, were prepared by wet impregnation method. The metal particles on Li4SiO4 pebble exhibit a good promotion of hydrogen isotope exchange reactions in H2–D2O gas system, with conversion equilibrium temperature reduction of 200–300 °C. The out-of-pile tritium release experiments were performed using 1.0 wt% Pt/Li4SiO4 and Li4SiO4 pebbles irradiated in a thermal neutron reactor. The thermal desorption spectroscopy shows that Pt was effective to increase the tritium release rate at lower temperatures, and the ratio of tritium molecule (HT) to tritiated water (HTO) of 1.0 wt% Pt/Li4SiO4 was much more than that of Li4SiO4, which released mainly as HTO. Thus, catalytic metals deposited on Li4SiO4 pebble may help to accelerate the recovery of bred tritium particularly in low temperature region, and increase the tritium molecule form released from the tritium breeding materials.

Kinetic estimation of hydrogen isotope exchange reaction between tritiated-water (HTO) vapor and each amino acid in a heterogeneous system

The hydrogen isotope exchange reaction between HTO vapor and each amino acid has been observed in order to establish a method of estimation of the internal exposure of organically bound tritium in a heterogeneous system at 25∼70°C. Rate constants (k) for the amino acids have been obtained by applying the A″-McKay plot method. Using these k values, Arrhenius plots for both the COOH and NH2 groups are drawn, and linearity was obtained over the range of 25∼70°C. Comparing the rate constants, the following four statements can be made regarding the T-for-H exchange reaction. (1) The reactivity of the functional groups in amino acids increases with increasing temperature. (2) Applying Taft's equation, the ratio of polar effect to steric effect is 2:8 in the COOH group and 9:1 in the NH2 group at 25°C. (3) The A″-McKay plot method is useful for studying the reactivity of materials, not only with one (or the same kind of) functional group(s) but also with two different kinds of functional groups. (4) The method used in this work may be useful to investigate the behavior of organically bound tritium, quantitatively.

Transient distributions of composition and temperature in a gas–solid packed bed reactor by near-infrared tomography

Near-infrared diffuse tomography was used in order to observe dynamic behaviour of flowing gases by measuring the 3D distributions of composition and temperature in a weakly scattering packed bed reactor, subject to wall effects and non-isothermal conditions. The technique was applied to the vapour phase hydrogen isotopic exchange reaction in a hydrophobic packing of low aspect ratio made of platinum on styrene divinyl benzene sulphonate copolymer resin. The results of tomography revealed uneven temperature and composition maps of water and deuterated water vapours in the core-packed bed and in the vicinity of the wall owing to flow maldistribution. The dynamic lag between the near-wall water vapour and deuterated water vapour compositions were observed suggesting that the convective transfer which was significant near the wall at the start, owing to high porosity, was also effective at large conversions.

Monitoring of Tritium Purity During Long-Term Circulation in the KATRIN Test Experiment LOOPINO Using Laser Raman Spectroscopy

The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95 %, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT4-nXn (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium β decay. A precision of 0.1 % was achieved for the monitoring of the T2 Q1-branch, which fulfils the requirements for the KATRIN experiment and demonstrates the feasibility of high-precision Raman measurements with tritium inside a glove box.

Monitoring of Tritium Purity During Long-Term Circulation in the KATRIN Test Experiment LOOPINO Using Laser Raman Spectroscopy

The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium {\beta} decay. A precision of 0.1% was achieved for the monitoring of the T_2 Q_1-branch, which fulfills the requirements for the KATRIN experiment and demonstrates the feasibility of high-precision Raman measurements with tritium inside a glove box.

The development and use of novel iridium complexes as catalysts for ortho‐directed hydrogen isotope exchange reactions

AbstractThe preparation and application of groups of new iridium complexes are described. In particular, iridium complexes possessing phosphine ligands and a bulky N‐heterocyclic carbene have been shown to be robust and readily handled species and have been applied in a range of directed hydrogen–deuterium and –tritium exchange processes and, in particular, with drug‐like substrates or within ADMET‐related studies. Overall, these new iridium(I) complexes are shown to be highly active catalysts and display catalytic activity far in excess of the industry standard, Crabtree's catalyst, with excellent levels of labelling being achieved over short reaction times and at low metal complex loadings, while tolerating a wide range of functional moieties. Furthermore and again in contrast to systems employing Crabtree's catalyst, the low catalyst loadings and short reaction times made possible by these emerging iridium carbene complexes have delivered tritiated products with very good levels of labelling and without any appreciable by‐product waste production. Copyright © 2010 John Wiley & Sons, Ltd.

The effect of adding Crabtree's catalyst to rhodium black in direct hydrogen isotope exchange reactions

AbstractA new catalytic system based on rhodium black using Crabtree's catalyst as an additive for direct hydrogen isotope exchange in aromatic compounds has been investigated. The level of deuterium incorporation can be improved from for example 16 to 93%. The new catalyst mixture tolerates a variety of solvents. Copyright © 2009 John Wiley & Sons, Ltd.

PH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases

The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(mu-thiolate)(mu-hydride)NiRu complexes, Ni(II)(mu-SR)(2)(mu-H)Ru(II) {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)-1,3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes has H(+) properties, and the complexes catalyse the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes. A mechanism of the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes through a low-valent Ni(I)(mu-SR)(2)Ru(I) complex is proposed. In contrast, in neutral-basic media (at pH 7-10), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes acts as H(-), and the complexes catalyse the hydrogenation of carbonyl compounds.

Application of iridium pincer complexes in hydrogen isotope exchange reactions

Iridium pincer complex catalyzed hydrogen to deuterium exchange could be achieved using aromatic and heteroaromatic substrates. The reactions proceed under mild conditions and with high regioselectivity. The efficiency of the hydrogen isotope exchange reaction depends on the electronic properties of the pincer complex catalyst.

Reactivity of hydroxybenzoic acids in the hydrogen-isotope exchange reaction

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between tritiated water vapor (HTO vapor) and 3-hydroxy-4-methoxybenzoic acid (and it's analog; 4-hydroxy-3-methoxybenzoic acid) were observed at 50 and 70 °C in a gas–solid system to reveal the reactivity of a functional group in an aromatic compound having two substituents in the aromatic ring. Further, it was shown that (a) the reactivity of the compounds used in this work follows the Hammett's rule, and (b) the reactivity of trisubstituted aromatic compound could be analyzed by applying the additive property of the Hammett's rule even if the compound contains a substituent at the ortho-position.

Tritium Separation by Electrolysis Using Solid Polymer Electrolyte

Hydrogen isotope separation effect by electrolysis of water was theoretically investigated and was compared with experimental results. The separation mechanism was analyzed as the hydrogen isotope exchange reaction between water and diatomic hydride that consists of hydrogen and cathode material. The equilibrium constants of the isotope exchange reaction were calculated from reduced partition function ratio. Using the constants, the separation factor (SF) of the isotopes was calculated according to the two-phase distribution theory for isotopes. Experimentally, light or heavy water spiked with tritiated water was electrolyzed by a device with a solid polymer electrolyte, which equipped with SUS, Ni, or carbon cathode. Thus, the SFs were experimentally obtained. Calculated SFs were well agreed with the experimentally values for SUS and Ni cathodes, and that for carbon cathode was somewhat small then the experimental value.

Fast and efficient tritium labelling of the nonsteroidal anti‐inflammatory drugs naproxen, tolmetin, and zomepirac

AbstractFast and efficient tritium labelling of the nonsteroidal anti‐inflammatory drugs naproxen, tolmetin and zomepirac is reported. Naproxen along with its (R)‐enantiomer were labelled by catalytic tritium–halogen exchange of the corresponding 5‐bromo derivatives providing [3H]naproxen with a specific activity of 25.4 Ci/mmol. Tolmetin and zomepirac were labelled by the hydrogen isotope exchange reaction using Crabtree's catalyst. This provided [3H]tolmetin and [3H]zomepirac with specific activities of 80.8 and 64.3 Ci/mmol, respectively. All compounds were obtained in high radiochemical purity (>98%). Copyright © 2005 John Wiley & Sons, Ltd.

NIR Raman spectrometer for monitoring protonation reactions in gaseous hydrogen

Spontaneous Raman spectroscopy was used to monitor molecular hydrogen isotope exchange reactions between H2, D2, and HD. A tunable 780nm, multimode laser diode with power output between 300 and 500mW served as the excitation source. Hydrogen isotopes could be detected at partial pressure of 13Pa (number density 3.2×1021m−3) at total gas pressure of 5.3×104Pa (number density 1.3×1025m−3) with signal-to-noise better than 2 during minutes long observations. The high sensitivity was achieved using multiple pass cell in conjunction with atomic vapor Rb absorption filter employed to eliminate Rayleigh scattered laser light. We have used the new spectrometer to measure the rapid isotope exchange reactions taking place in the palladium hydrogen purifier.

Hydrogen Isotope Exchange Reactions in an Atmospheric Pressure Discharge Utilizing Water as Carrier Gas

Allowing water/hydrogen or water/hydrogen/He gas mixture to flow through micro- hollow type of electrodes and applying 60 Hz AC power between the electrodes made it possible to sustain large area and atmospheric pressure discharge. The electrode assembly was constructed by sandwiching a dielectric spacer with two thin metal sheets and boring an array of micro holes through them. Another variation of the assembly was prepared by stacking thin metallic sheets so that the stack functions as an electrode through which the gas mixture flows for generating dielectric barrier discharge. A large volume of the gas mixture, while producing plasma, underwent instantaneous hydrogen isotope exchange reactions between H2O and D2O or between D2O and H2 gas molecules. The efficiency of the atmospheric pressure discharge was assessed by measuring the extent of the exchange reactions at a given flow rate of the gas mixture.