Electrolysis of HBr using molten, alkali-bromide electrolytes

The electrolytic oxidation of HBr was investigated using molten alkali-bromide salts in a porous scaffold of yttria-stabilized zirconia (YSZ), with porous Pt electrodes. Despite a relatively thick (1.0 mm) and dense (35% porous) YSZ scaffold, a total cell impedance of less than 3 Ωcm² was achieved with NaBr at 1033 K. The open-circuit potentials also agreed with theoretical potentials for the reaction H₂ + Br₂ = 2HBr. Lower operating temperatures were made possible by using a eutectic mixture of alkali bromides, (Li_0.56K_0.19Cs_0.25)Br. The electrolyte losses for the (Li_0.56K_0.19Cs_0.25)Br electrolyte, determined from the ohmic component of the impedance spectra, were less than 1.5 Ωcm² at 673 and 773 K, similar to the value found for NaBr at 1033 K, indicating that the ionic conductivities of the alkali bromides are high so long as the salts are molten. However, the electrode losses were dependent on temperature, decreasing from 18.1 Ωcm² to 3.0 Ωcm² in going from 673 to 773 K. Implications of these results for recycling HBr in hydrocarbon bromination reactions are discussed.     

Thorium valency in molten alkali halides in equilibrium with metallic thorium

Metallic thorium is shown to corrode in molten alkali halides even in the absence of external oxidizing agents, alkali cations acting as oxidizing agents. Its corrosion rate grows in the series of alkali chlorides from LiCl to CsCl at constant temperature. Substituting halide anions for one another exerts a smaller influence, the rate rising slightly in going from chlorides to bromides and iodides, having the same alkali cations. Thorium valency is determined coulometrically, the metal being dissolved anodically in molten alkali halides and their mixtures. In fluoride melts it is equal to 4 but in chloride, bromide and iodide ones, as a rule, it has non-integral values between 4 and 2 which diminish as the temperature is raised, as the thorium concentration is lowered, as the radii of alkali cations decrease and those of halide anions increase. The emf of cells Th|N ThHl_n + (1 ? N) MHl|Mhl}C, Hl_2(g) where Hl is Cl, Br or I, M is Li, Na, K, Cs or Na + K, and N < 0.05, is measured as a function of concentration at several temperatures. Expressions are obtained for its concentration dependence. The emf grows in the series of alkali chlorides from LiCl to CsCl, other conditions being equal. A method is suggested for finding predominant pairs of ThHl₄, ThHl₃ and ThHl₂ in chloride, bromide and iodide metals that are in equilibrium with metallic thorium. From experimental data, ThHl₄ and ThHl₂ are ascertained to prevail over ThHl₃. Equations are derived for temperature dependence of conditional equilibrium constants for disproportionation reactions of ThCl₂ in LiCl, NaCl, NaCl + KCl and CsCl, ThBr₂ in NaBr + KBr, and ThI₂ in NaI + KI.     

Li–H<Subscript>2</Subscript> cells with molten alkali chlorides electrolyte

Li–H₂ thermally regenerative fuel cells were studied using molten alkali chlorides as the electrolyte at relatively lower temperature. The saturation solubility of LiH in three different alkali chloride eutectic melts (LiCl–KCl, LiCl–CsCl, and LiCl–KCl–CsCl) was determined based on equilibrium potential measurements for the hydrogen electrode. Both a Ni membrane electrode and porous Ni electrode were evaluated as the cathode of the cell. In addition, a single cell of a Li–H₂ fuel cell with a Ni membrane for the anode was constructed, and the electromotive force (emf) was measured. When the Ni membrane electrode performed as an anode with molten salt electrolyte saturated with LiH, the measured emf was similar to previously reported emf for other types of molten salt electrolyte. In conclusion, certain types of molten alkali chlorides can be used as the electrolyte of a thermally regenerative fuel cell at a relatively lower operating temperature at least above 598 K.     

The saturation vapour pressure and decomposition potential of ThCl4 solutions in molten alkali chlorides

The partial pressures of the components (ThCl₄, MCl and MThCl₅) in the saturated vapours of ThCl₄ solutions in molten LiCl, NaCl, KCl, RbCl and CsCl are determined as a function of temperature (900–1200 K) and ThCl₄ concentration (2–50 mol % ThCl₄) by dynamic method. Thorium tetrachloride volatility is shown to exceed that of alkali from the melts containing less than 98 LiCl or NaCl, 83 KCl, 67 RbCl and 48 mol % CsCl. From experimental observations the decomposition potential of the electrolytes under investigation was estimated in temperature and concentration ranges of our measurements. Under otherwise equal conditions, it increases in the series of alkali chlorides from LiCl to CsCl.     

Electrochemistry of room-temperature chloroaluminate molten salts at graphitic and nongraphitic electrodes

The electrochemistry of unbuffered and buffered neutral AlCl₃-EMIC-MC1 (EMIC =1-ethyl-3-methylimidazolium chloride and MC1= LiCl, NaCl or KCl) room-temperature molten salts was studied at graphitic and nongraphitic electrodes. In the case of the unbuffered 1 : 1 AlCl₃ : EMIC molten salt, the organic cation reductive intercalation at about –1.6 V and the AlCl₄ ^– anion oxidative intercalation at about +1.8 V were evaluated at porous graphite electrodes. It was determined that the instability of the organic cation in the graphite lattice limits the performance of a dual intercalating molten electrolyte (DIME) cell based on this electrolyte. In buffered neutral 1.1 :1.0:0.1 AIC1₃: EMIC : MCl (MC1= LiCl, NaCl and KCl) molten salts, the organic cation was intercalated into porous and nonporous graphite electrodes with similar cycling efficiencies as the unbuffered 1 : 1 melt; however, additional nonintercalating processes were also found to occur between 1 and –1.6 V in the LiCl and NaCl systems. A black electrodeposit, formed at –1.4 V in the LiCl buffered neutral melt, was analysed with X-ray photoelectron spectroscopy and X-ray diffraction and was found to be composed of LiCl, metallic phases containing lithium and aluminium, and an alumina phase formed from reaction with the atmosphere. A similar film appears to form in the NaCl buffered neutral melt, but at a much slower rate. These films are believed to form by reduction of the AlCl₄ ^– anion, a process promoted by decreasing the ionic radius of the alkali metal cation in the molten salt. The partially insulating films may limit the usefulness of the LiCl and NaCl buffered neutral melts as electrolytes for rechargeable graphite intercalation anodes and may interfere with other electrochemical processes occurring negative of –1 V.     

Electron transfer in an electron-ion molten mixture of CuCl-CuCl2-MeCl (Me=Li, Na, K, Cs)

Electron and ion transfer numbers, electroconductivity, density, and concentrations of Cu⁺ and Cu²⁺ in molten salt mixtures of CuCl-CuCl₂-MeCl (Me=Li, Na, K, Cs) were measured at a partial pressure of chlorine over the melt equal to the atmospheric pressure in the temperature interval from 800 to 1000 K. Partial values of ion and electron transfers and the molar volume of the melts were determined. Mobility of electrons was estimated. The electron transfer number was a maximum in the CuCl-CuCl₂ melt with t_c equal to 0.9. When chlorides of alkali metals were added to the CuCl-CuCl₂ melt, the electron component of electroconductivity was preserved up to 90, 65, 60, and 50 mol.% LiCl, NaCl, KCl, and CsCl, respectively. A mechanism of the electron transfer in the test melts was proposed.     

Theoretical evaluation of ultrasonic velocity in molten electrolytes

Significant structure theory and Flory theory are successfully applied for evaluating the ultrasonic velocity in five molten alkali halides (NaCl, NaBr, KCl, KBr, and KI). Later theory provides better estimates and the theoretical results are in fairly good agreement with experimental findings. Hard sphere models and cellular hole theory were also attempted. The results are not encouraging.     

Aggregation Behavior of Task-Specific Acidic Ionic Liquid N-Methyl-2-Pyrrolidinium Dihydrogen Phosphate [NMP][H2PO4] in Aqueous and Aqueous Salt Solutions

The effect of alkali salt (NaCl, NaBr, and KCl) addition on aggregate formation of N-methyl-2-pyrrolidinium dihydrogen phosphate [NMP][H₂PO₄] ionic liquid in aqueous solution was determined using surface tension at 298.15K and conductance from 288.15 to 308.15K. The surface parameters such as critical aggregation concentration (CAC), adsorption efficiency, surface pressure, surface tension at CAC, minimum surface cover by a single molecule, and maximum area excess concentration were calculated from surface tension measurements with and without salts. The results show that [NMP][H₂PO₄] forms aggregates at lower concentrations and is more surface active than classical cationic surfactants.     

Prediction of the viscosity of mixed electrolyte solutions from single-salt data

The viscosities of sonic mixed electrolyte solutions (NaCl + KCl, NaCl, + Nll₄NO₃, NaCl + CaCl₂, NaCl + Ca(NO₃)₂, NaCl + MgSO₄) have been measured to high concentration at 298 K. Existint: viscosity data for the single-salt solutions have been fitted, as required, to Goldsack's two-parameter equation. Mixed electrolyte data have been used to test the predictive accuracy of five simple methods of estimation. The usefulness and relative accuracies of the methods have been discussed briefly.     

Electrochemical studies of the reaction between titanium metal and titanium ions in the KCl-NaCl molten salt system at 973 K

The reaction between titanium metal and titanium ions in the KCl?NaCl molten salt system was investigated by means of electrochemical and physical methods at 973 K in an inert gas atmosphere (argon). It was found that the reaction between titanium metal and Ti³⁺ in the molten salts with TiCl₃ followed a simple reaction (I). However, in the case of the concentration of K₂ TiF₆ being higher than 2.7 mol % the reaction was (II); in the case of it being less than 0.8 mol %, reactions (III) and (III′) were followed. $$\begin{gathered} 2Ti^{3 + } + Ti = 3Ti^{2 + } (I) \hfill \\ 3Ti^{4 + } + Ti = 4Ti^{3 + } (II) \hfill \\ Ti^{4 + } + Ti = 2Ti^{2 + } (III) \hfill \\ 3Ti^{2 + } = Ti + 2Ti^{3 + } (III')(on cooling) \hfill \\ \end{gathered} $$ It was also found that these reactions were controlled by charge transfer and diffusion simultaneously.     

Na/K添加剂对SNCR脱硝及NO还原机制的影响

基于构建的Na-K-C-H-O-N-Cl化学反应机理模型，采用Chemkin动力学模拟软件，研究Na/K添加剂（NaOH、Na₂CO₃、NaCl、KOH、K₂CO₃和KCl）对选择性非催化还原（SNCR）脱硝性能影响，通过敏感性分析和产率分析，探讨Na/K添加剂对SNCR过程中NO还原的促进机理和路径。模拟结果表明，在温度为700~800℃且无Na/K添加剂条件下，SNCR脱硝效率几乎为零；Na/K添加剂能够显著提高低温区（小于800℃）SNCR脱硝效率，而其对高温区（大于900℃）SNCR脱硝的促进作用不明显。在温度为700℃和Na/K添加剂参与条件下SNCR脱硝效率可达43.86%~60.76%。不同Na/K添加剂对NO还原促进顺序为NaOH≈Na₂CO₃ > KOH≈K₂CO₃ > KCl > NaCl，但同一种Na/K添加剂的浓度变化（6.25~25.0 μmol·mol^-1）对SNCR脱硝效率影响较小。Na/K添加剂通过不同的循环路径产生OH基，进而通过NH2基团促进NO的还原，其中碱金属氢氧化物（MOH）对SNCR脱硝的促进路径为NaOH→NaO₂→Na→NaO→NaOH，碱金属氯化物（MCl）则主要通过MCl→M→MCl削弱Na/K添加剂的促进作用。     

The recovery of chlorine from by-product hydrogen chloride Part 2: Molten metal cathode method

A new method of recovering chlorine from by-product hydrogen chloride is proposed and developed. According to the reaction Me+2HC1 = MeCl₂+H_o (Me = Metal) hydrogen chloride is reduced to give hydrogen and metal chloride. Gaseous hydrogen was drawn out from the reaction system and the metal chloride dissolved in the electrolyte, where it was electrolysed to give chlorine and metal using molten metal as a cathode. The metal was recovered on the cathode in a molten state and reused for the former reaction. Bench scale tests were also carried out, where zinc was used as a molten metal cathode and the cell capacity was about 50 A. The cell voltage was 6.5 V at 50 A (working temperature 560°C, distance between anode and cathode 5 mm) and in this case, the ohmic loss was about 70%. The current efficiency was about 90% (anodic current density 200 A/dm²) when the working temperature was 500°C and electrode distance between anode and cathode was 18 mm.This method seems very promising on the basis of the above-mentioned data.     

锂电解过程中杂质元素的电化学行为

采用循环伏安法研究了锂电解过程中杂质元素的电化学行为。电解过程中杂质元素镁将优先于锂在阴极析出, 然后是金属锂的欠电位沉积形成镁锂合金, 最后才是金属锂的析出, Mg ²⁺的还原电极过程受扩散控制, 扩散系数为1.44×10 ^-5 cm ²/s;微量的Ca ²⁺即发生钙锂共沉积;在含少量氯化钠的熔盐体系中, 杂质元素钠被锂还原并形成合金, 随着电解质体系中氯化钠含量的增加, 金属锂中的钠含量有较大的增加;杂质元素铁优先于锂在阴极析出, 在阴极被还原成海绵铁使阴极钝化, 引起熔盐体系锂的析出电流急剧降低, Fe ³⁺的还原电极过程受扩散控制, 扩散系数为3.14×10 ^-5 cm ²/s。     

Stability of a boron-doped diamond electrode in molten chloride systems

Stability of a boron-doped diamond as an oxygen evolution electrode material was evaluated at 773 K in molten LiCl–KCl (58.5:41.5 mol%), LiCl–KCl (75:25 mol%), LiCl–CaCl₂ (64:36 mol%), LiCl–NaCl–CaCl₂ (52.3:13.5:34.2 mol%). In molten LiCl–KCl systems, the BDD is stable at 773 K regardless of the concentration of oxide ion and the composition of the melt. In molten LiCl–CaCl₂ and LiCl–NaCl–CaCl₂, the BDD electrode is less stable than in molten LiCl–KCl systems.     

NaBr,NaCl和KBr在几种有机溶剂中活度系数的测定

分别测定了NaBr在甲醇、乙醇、正丙醇和异丙醇中,NaCl和KBr在甲醇和乙醇中共8个体系（溶液物质的量的浓度在01 mol·L-1范围内）在29815、31315和32315 K下的电导率,利用Debye Hücker和Osager Falkenhangen 公式计算了以上溶液体系的平均离子活度系数,讨论了浓度和温度对电解质溶液活度系数的影响。其中NaBr 在乙醇中, NaCl在甲醇中和 KBr在甲醇中的平均离子活度系数的计算结果与已发表文献中的数据进行了比较。结果表明,该方法的活度系数结果与文献数据有较好的一致性。 关键词：电解质溶液;电导法;平均离子活度系数;有机溶剂;NaBr; NaCl;KBr     

Fusibility study of the magnesium cell electrolyte containing MgCl2, CaCl2, NaCl and KCl

The four-component magnesium cell electrolyte containing MgCl₂, CaCl₂, NaCl and KCl has been converted to a quasi-ternary system by keeping the proportion of NaCl and KCl in the mixture equimolecular. The triangular phase diagram has been drawn depicting the fusibility isotherms of the system. It has been possible to obtain complete liquid mixtures at temperatures as low as 400° C by suitably adjusting the proportions of the four components of the molten salt mixture.     

Internal cation mobility in molten CsCl-NdCl3 system at 1073 K

CsCl-NdCl₃ is the next of binary MCl-NdCl₃ systems (M: alkali metal) investigated for determination of relative internal mobilities of cations (b_Cs, b_Nd) by countercurrent electromigration method (Klemm's method). The results have been presented as isotherms of internal mobilities of Cs⁺ and Nd³⁺ ions on NdCl₃ equivalent fraction (y_Nd). It has been found that internal mobility of cesium cations is higher than neodymium ones in the entire composition range (what is typical for nonsymmetrical MCl-LnCl₃ systems (M: Li, Na, K; Ln: La, Nd, Dy)) and decreases with increase of NdCl₃ concentration in the melt. Generally, dependence of internal mobility of lanthanide cations in melts with alkali metal chlorides on lanthanide (i.e. its atomic number and concentration) seems strongly related to stability of chloride complex anions of lanthanides in the melt. Investigated systems may be divided into two classes. The first class includes MCl-NdCl₃ systems (M: Li, Na) characterized by decrease of b_Nd with increase of NdCl₃ concentration. The second includes KCl-LnCl₃ systems (Ln: La, Nd, Dy) and presented here CsCl-NdCl₃ system, and is characterized by increase of b_Ln with concentration of Ln³⁺ cation. The dependence of b_Nd on NdCl₃ concentration at 1073 K was fitted (as for other systems) by a simple equation of the form: , where is the internal mobility of Ln³⁺ cations in pure molten LnCl₃, a the difference between internal mobility of Ln³⁺ cations in pure molten LnCl₃ and infinitely diluted LnCl₃ in molten alkali metal chloride (extrapolated), and yLnCl₃ is the equivalent fraction of LnCl₃.     

Effect of Temperature, Salts and Ureas on the Association Behavior of an Amphiphilic Phenothiazine Drug Promethazine Hydrochloride

Association behavior of an amphiphilic phenothiazine drug promethazine hydrochloride in the presence of inorganic salts (LiCl, NaF, NaCl, NaBr, and KCl) and ureas (urea and thiourea) has been studied conductometrically at different additive concentrations (0?C100?mmol?kg^?1) and temperatures (293.15?C308.15?K). The critical micelle concentration (CMC) values showed an inverted U-shaped behavior with temperature; the maximum being at 298.15?K with or without additives. The inorganic salts decreased the CMC which is explained on the basis of nature and ion size. Ureas decreased the CMC at low concentration (0.2?mmol?kg^?1 urea and 0.1?mmol?kg^?1 thiourea) but, at higher concentrations, an increase in CMC was observed with both the additives. Relevant thermodynamic parameters were also evaluated and discussed on the basis of the nature of particular types of the additives. The thermodynamic parameters suggest dehydration of the hydrophobic part of the drug at higher temperatures.     

Thermodynamic properties and decomposition potential of HfCl4 solutions in molten alkali chlorides and their mixtures

The partial pressures of components in saturated vapours of HfCl₄ solutions in molten alkali chlorides and some of their mixtures are determined as a function of temperature (800–1300 K) and concentration (2–33 mol% HfCl₄) by dynamic (from 10 to 2 × 10⁴) and static (from 1.3 × 10³ to 2.6 × 10⁵ Pa) methods. HfCl₄ vaporization enthalpy and entropy, activity coefficients and excess partial thermodynamic functions are calculated from tensimetric observations. The relations of these quantities to temperature and concentration are obtained. Alkali cations and temperature being unchanged. HfCl₄ partial pressure and activity coefficient rise more sharply the smaller is the ionic potential of alkali cations in the series from Li⁺ to Cs⁺, as HfCl₄ concentration is increased. In dilute solutions (N_HfCl4 < 0.05) where HfCl₄ activity coefficient reaches its lowest values, positive HfCl₄ vaporaization enthalpy and negative HfCl₄ excess partial enthalpy are the greatest, which is indicative of HfCl₄ complexing in molten alkali chlorides. Alkali chloride partial pressures vary almost in proportion to their mole fractions in melts, with their activity coefficients being close to one. Making use of experimental data on the equilibrium electrode potentials of hafnium in dilute solutions of its di- and tetrachloride in molten alkali chlorides, the decomposition potential of HfCl₄ solutions in these salts and their mixtures is computed as a function of temperature and concentration up to 33 mol% HfCl₄. Quantitative expressions are derived for its temperature, concentration and alkali cation composition dependences. The relation of Gibbs energy to temperature is found for reaction Hf_(s) + 2Cl_2(g) = HfCl_4(g). ΔH²⁹⁸_T and S^o_T of gaseous HfCl₄ being evaluated as a function of temperature at 1000–1200 K.     

Performance and thermodynamic properties of Na-Sn and Na-Pb molten alloy electrodes for alkali metal thermoelectric converter (AMTEC)

An alkali metal thermoelectric converter (AMTEC) testing cell was set up, and run with molten sodium-tin (Na-Sn) and sodium-lead (Na-Pb) alloy cathodes. The Na activity, the partial molar enthalpy and partial molar entropy of sodium in molten Na-Sn and Na-Pb alloys have been determined, using a Na concentration cell: Na(1) I beta-alumina Na-Me(1), where Me= Sn or Pb. The thermodynamic results of these investigations agree with those of other authors. The electric performance of these Na-Me alloy electrodes of different Na concentration and temperatures is described, measuring current-voltage characteristics and a.c. impedance in the AMTEC test cell. The power density of the AMTEC cell with molten alloy cathodes decreases with increasing Na concentration, with the Na concentrations in molten alloys varying from 0.5 to 15 mol%. Maximum power densities of 0.21 to 0.15 W cm^–2 at 700°C for Na-Sn molten electrodes, and 0.30 to 0.15 W cm^–2 for Na-Pb molten electrodes have been obtained. The a.c. impedance data demonstrated that the molten alloy electrodes have a smaller cell resistance, 0.3–0.35 S2 cm^–2 at 700°C after 10–20 h. Comparison with the sputtered thin, porous film electrodes, showed that the contact resistance between electrode and surface of beta-alumina plays an important role on enhancing cell power density. At 700°C the power density of an AMTEC cell with the molten Na-Pb alloy electrode can be raised to values of about 0.2 W cm eat current densities of 0.8 A cm^–2, but at cell voltages not exceeding 0.2V. A model for the theoretical efficiency of the AMTEC cell with molten Na metal electrodes is also presented.