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Various methods of introducing deuterium into dopamine using isotope exchange are considered. The best result is achieved by isotope exchange with deuterated water at 190°C for 30 min using (a) trifluoroacetic acid as a catalyst and (b) 5% Pd/Al2O3 catalyst presaturated with deuterium gas. In the first case, the yield of deuterated dopamine was 65–70%, and the average deuterium content was 2.4–2.5 at./molecule. In the second case, the yield decreased to 35–40%, but the deuterium content increased to 3.50–3.60 at./molecule. The obtained result highlights the effectiveness of an integrated approach to introducing hydrogen isotopes into organic molecules, when activated hydrogen isotope species are formed on the catalyst and the substance deposited on it, which contribute to increasing the efficiency of isotope exchange with deuterated water at heating. [ABSTRACT FROM AUTHOR]

During D-T fusion operations the capture, purification, and recycling of unburned tritium will be crucial, as the formation of tritium containing molecules require additional processing. Removing the tritium can require costly processing to be unbound from the tritium-containing molecules and improvements to these processes will be necessary moving forward. Existing techniques using sorbent material beds to remove tritium-containing molecules from process gas streams undergo repeated high-heat cycling which leads to diminished bed lifespans, necessitating replacement and associated downtime. This work demonstrates the capture and isotopic exchange technique of deuterated ammonia (ND 3), used as a surrogate for tritium, at ambient temperature using a Pt catalyst-loaded 13X molecular sieve. Unmodified 13X molecular sieve is capable of adsorbing and retaining the ND 3 however, incorporation of a catalyst facilitates the isotopic exchange of the hydrogen isotopes. The effluent gas streams were analyzed in conjunction with desorbed ammonia isotopologues post-exchange to verify these results. Isotopically exchanging and removing heavier hydrogen isotopes using this technique provides an alternative to traditional removal methods. • Hydrogen isotopes successfully exchanged at ambient temperature with Pt catalyst present on support material. • Pt-loaded 13X demonstrates higher capacity for ND 3 when compared to 13X • Pt-loaded 13X requires lower temperatures for full desorption of ND 3 when compared to 13X [ABSTRACT FROM AUTHOR]

Triple oxygen isotope (Δ′17O) analysis of CO 2 or carbonate is increasingly applied in diverse fields in earth and environmental sciences. One of the widely-used analytical methods for Δ′17O of CO 2 is through Pt-catalyzed oxygen isotope exchange between CO 2 and O 2. However, large inter-laboratory inconsistencies in oxygen isotope fractionation between the two gases have been reported, potentially hindering data comparison across different laboratories. By examining the oxygen isotope fractionations in thermal diffusion experiments for pure O 2 and CO 2 gases as well as CO 2 -O 2 mixtures, we demonstrate that thermal-gradient-induced (TG-induced) isotope fractionation is the main reason for the inconsistencies. The degree of TG-induced oxygen isotope fractionation is affected by temperature contrasts and volume ratios between the hot and cold parts of the extraction line as well as gas composition. Larger thermal contrasts generated larger oxygen isotope fractionations. CO 2 fractionated less than O 2 in the same thermal gradient conditions. For CO 2 -O 2 mixtures, TG-induced oxygen isotope fractionation of O 2 was reduced while that of CO 2 was enhanced, compared with the pure gases. Based on the results of thermal diffusion experiments, we found that the anomalous mass fractionation exponents (0.2 ∼ 0.9) observed in the Pt-catalyzed CO 2 -O 2 isotope exchange experiments can be rationalized quantitatively by a combination of isotopic exchange equilibrium and TG-induced oxygen isotope fractionation. Our model suggests that by weakening TG-induced oxygen isotope fractionation and by increasing the volume fraction of hot zone of a reactor, we can achieve a high precision (<10 per meg) for Δ′17O CO2 through CO 2 -O 2 exchange. Considering the widely existing thermal-gradient conditions in nature, the findings in this study may shed light on the origin of non-mass-dependent isotope fractionation. [ABSTRACT FROM AUTHOR]

The paper deals with the mathematical simulation of separation systems with organic and inorganic ion-exchange resins in flexible manufacturing systems. The main parameters are identified for the effective operation of the separation system. The obtained experimental data and theoretical calculations provide the reduction of expenditures on isotope extraction and underlie a continuous separation process with the appropriate equipment automation and mobility, flexible enrichment of a spectrum of isotopes at minimum equipment changeover. [ABSTRACT FROM AUTHOR]

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. The use of D2O at 200°C makes it possible to introduce into GABA an average of about 0.5 deuterium atoms, D2O with trifluoroacetic acid (1 : 1) at 250°C, an average 1.49 deuterium atoms with a yield of 15%. The solid-phase method permits introducing about 3 deuterium atoms per GABA molecule. During isotopic exchange with D2O, the use of a palladium–rhodium mixture pretreated with deuterium gas made it possible to produce [D]GABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of [D]GABA were low. Preparative amounts of [D]GABA were produced engaging additional supports. The best result was obtained when applying GABA to zeolite. Using D2O with 5% Pd/BaSO4–GABA–zeolite pretreated with deuterium gas, allows producing [D]GABA with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%. [ABSTRACT FROM AUTHOR]

The rate coefficients k1 and k2 of the reaction $ \hbox{OD}^- + \hbox{HD} \mathop{\rightleftarrows}\limits_{k_2}^{k_1} \hbox{OH}^- + \hbox{D}_2 $ OD − + HD ⇄ k 2 k 1 ⁡ OH − + D 2 in the forward and reverse direction were measured in the temperature ranges of 15 K–273 K and 95 K–300 K, respectively. The experiments were carried out in a temperature-variable cryogenic linear 22-pole radio-frequency ion trap instrument. The temperature dependence of the equilibrium constant $ { {K_{{\rm eq}12}}}(T) $ K e q 12 (T) obtained from the measured data is in good agreement with the value calculated using the detailed balance principle under the Born-Oppenheimer approximation. The enthalpy and the entropy of the reaction obtained from the linear Van't Hoff equation are $ { {\Delta H}} = (20 \pm 2 \pm 3^{{\rm sys}})\,{\rm meV} $ Δ H = (20 ± 2 ± 3 s y s ) m e V and $ { {\Delta S}} = (5.9 \pm 1.8 \pm 1.4^{{\rm sys}})\,{\rm J}/{\rm mol}\,{\rm K} $ Δ S = (5.9 ± 1.8 ± 1.4 s y s ) J / m o l K , respectively. [ABSTRACT FROM AUTHOR]

Layered nickelates, as representatives of Ruddlesden-Popper phases, are widely used in electrochemical, catalytic and other applications due to their advanced transport and thermomechanical characteristics. In this work, La 2–x Sm x NiO 4+δ (x = 0.0 – 1.0) complex oxides are obtained and then comprehensively studied as potential oxygen electrode materials for solid oxide fuel and electrolysis cells (SOFCs and SOECs). These materials are synthesized by a glycerol-nitrate combustion method. The obtained compounds are single-phase up to x = 0.8 and possess a tetragonal Ruddlesden-Popper structure (I 4/ mmm sp. gr.). A combination of complementary techniques, including reverse dichromatometric titration, thermogravimetric and isotope exchange methods has been used to demonstrate that partial Sm substitution results in an increase in the over-stoichiometric oxygen content in the materials and oxygen transport kinetics. These materials are found to be mixed ionic-electronic conductors with predominantly p-type electronic conductivity exceeding 110 S/cm at 450 °C in air. The Sm-containing nickelates exhibit improved thermomechanical compatibility and show no chemical interaction with CeO 2 -based solid electrolytes compared to the undoped La 2 NiO 4+δ. The electrochemical activity of bilayer electrodes consisting of the La 2–x Sm x NiO 4+δ functional layers and LaNi 0.6 Fe 0.4 O 3–δ -based collectors are studied in air at 600 – 850 °C in the Ce 0.8 Sm 0.2 O 1.9 -based symmetrical cells. Electrochemical impedance spectroscopy study and following distribution of relaxation times analysis indicate a positive impact of the increased oxygen mobility in the La 2–x Sm x NiO 4+δ materials on the overall electrode performance. Due to their superior electrode characteristics compared to La 2 NiO 4+δ , La 2–x Sm x NiO 4+δ with a moderate dopant content (x = 0.2 – 0.3) can be recommended for use as oxygen electrodes for both SOFCs and SOECs. [Display omitted] • Single-phase La 2−x Sm x NiO 4+δ compounds are obtained by glycerol nitrate combustion. • Rising Sm content results in increasing the interstitial oxygen content and mobility. • La-to-Sm substitution improves thermomechanical and chemical compatibility with ceria. • La 1.7 Sm 0.3 NiO 4+δ electrode exhibits the lowest polarization resistance in the series. • Moderately doped materials show promise for use in solid oxide electrochemical cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • H 3 BO 3 and DL-TA formed 1:1 and 1:2 anionic complexes in aqueous solution. • H 3 BO 3 and DL-TA formed 1:1, 1:2, 2:2, 2:3, and 3:3 complexes when extracted by TOA. • Anionic complexes with B (4) –O bonds facilitate isotope exchange with H 3 BO 3. The separation of boron isotopes poses significant challenges due to their similar chemical properties. Previous studies have demonstrated that boron isotope separation can be achieved by solvent extraction of boric acid (H 3 BO 3) using trioctylamine (TOA) and tartaric acid (DL-TA), resulting in a remarkable separation factor of up to 1.04 through chemical exchange. However, the coordination mechanism among these three compounds remains elusive, impeding our understanding of the isotope exchange process. In this study, the species in the aqueous and organic phases were investigated using extraction experiments (maximum loading method), alongside various characterization techniques (FT-IR, 11B NMR, and high-resolution ESI-MS), followed by DFT computations. The results showed that H 3 BO 3 and DL-TA formed anionic complexes in the aqueous phase with stoichiometric ratios of 1:1 and 1:2, respectively. However, the stoichiometric ratios became more intricate in the organic phase, encompassing 1:1, 1:2, 2:2, 2:3, and 3:3. The average stoichiometric ratio of H 3 BO 3 to DL-TA calculated within the range of 1:1 to 1:1.5. Protonated TOA could form ion pairs with these anionic complexes, while unprotonated TOA might form hydrogen bonds with the carboxyl groups in DL-TA, contributing to the complexity of the stoichiometric ratios between H 3 BO 3 and TOA. The DFT calculations indicated that all complexes containing B (4) –O bonds, including 1:1, 1:2, 2:2, 2:3, and 3:3, effectively facilitated the exchange of isotopes with H 3 BO 3. These findings pave the way to process optimization of boron isotope separation by solvent extraction of boric acid. [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalytic efficiency upon Pt/ZSM-5 is 830 times higher that of commercial Pt-C at the optimum condition. • Water cluster creates an effective route to deliver proton to the reactive site. • The hydrogen transfer between Pt and Brønsted acid involves the spillover and reverse spillover. Liquid-phase hydrogen isotopes exchange between hydrogen and water is a promising route for the hydrogen isotopes separation from water, catalyzed by the metal Pt with hydrophobic coating to surmount the flooding of reactive sites. However, poor water activation ability on Pt has limited the catalytic efficiency of Pt-based catalysts and hindered their application. Herein, we report a bifunctional Pt/ZSM-5 catalyst with hydrophobic modification by surface silylation for H 2 -HDO isotope catalytic exchange. The integration of metallic Pt and Brønsted acid (BA) sites in the microporous ZSM-5 boosts the catalytic efficiency of deuterium extraction by two orders of magnitude compared to commercial Pt-C at the optimum condition. In-situ spectroscopic and theoretical studies demonstrated that HDO-H 2 O preferentially adsorbs on BA sites (-Si-OH-Al) to form protonated water clusters stabilized by hydrogen-bonded network or to undergo the proton exchange to leave deuterium on zeolite framework as a new acidic site ([AlO 4 D]). Under the attractive interaction, the dissociated hydrogen on Pt clusters releases partial electrons to form positively-charged hydrogen, which further transfers to the [AlO 4 D] sites or protonated water clusters by interfacial spillover to produce the overcharging intermediates. These intermediates cleave their O-D bonds to form positively charged D, which ultimately spills back to Pt cluster and combines with the remaining electron to desorb in the form of HD. The synergistic effect between Pt and BA sites creates a new pathway of hydrogen transfer, which enables the more efficient hydrogen-water isotope exchange on the bifunctional Pt/ZSM-5 catalyst. [ABSTRACT FROM AUTHOR]