The influence of gas composition on the oxygen electrode reaction in the molten Li2CO3Na2CO3K2CO3 eutectic mixture

Several different electrochemical techniques have been used to study the redox reactions at smooth gold electrodes in molten ternary alkali metal carbonate eutectic mixture equilibrated with different atmopsheric compositions of carbon dioxide and oxygen. The diffusion controlled redox reaction

was identified by chronopotentiometry, which, together with cyclic voltammetry and normal pulse voltammetry, confirmed that both peroxide and oxide ions were present simultaneously. The ratio of peroxide to oxide ions depended on the gas composition. A simple thermodynamic model enabled concentrations of these species to be predicted and correlated with the experimental measurements. The diffusion coefficients of peroxide and oxide ions were deduced from these data.     

碳酸钾-乙醇胺复合溶液吸收烟气中CO2的实验研究

分别以不同浓度的碳酸钾溶液及不同配比的碳酸钾—乙醇胺复合溶液作为吸收剂,以吸收速率和吸收量为指标,研究了吸收剂对烟气中CO2的吸收效果.结果表明,纯碳酸钾溶液吸收效果不佳,而掺入乙醇胺后的吸收效果显著改善,部分复合溶液的吸收效果甚至好于同浓度纯碳酸钾溶液与纯乙醇胺溶液的吸收效果之和,碳酸钾与乙醇胺在吸收过程中存在正交互作用.确定0.6 mol·L-1碳酸钾-0.4mol· L-1乙醇胺复合溶液为最佳的吸收剂,其饱和吸收量最大(0.185 mol)、再生温度最低(105℃)、再生率最高(98.8％).     

In situ investigation on deformation and dissolution behavior of porous nickel during its oxidation/lithiation in Li/K2CO3 eutectic

On the basis of previous work, the home-made deformation-testing system was further applied to detect the thickness change of porous nickel materials in the various experimental condition of molten carbonate. The deformation and dissolution behavior of porous nickel and the loading effect on the behavior were in situ studied in the process of oxidation and lithiation. The results indicated that both an obvious deformation and a severe nickel dissolution occurred during the oxidation/lithiation of porous nickel in molten carbonate under loading conditions. Furthermore, the dissolution of nickel from porous nickel was still significant even if without loading. It was found that the deformation of porous nickel closely corresponded to its dissolution during the oxidation/lithiation of porous nickel in molten carbonate.     

Steam gasification of coal char catalyzed by K2CO3 for enhanced production of hydrogen without formation of methane

Steam gasification of coal char catalyzed by potassium carbonate was investigated on a laboratory fixed-bed reactor to examine the catalytic effects not only on the reaction rate but also on the reaction selectivity, and non-catalytic gasification of coal char was performed by way of contrast. It was observed that the catalytic gasification of coal char with steam occurred significantly in a temperature range of 700-750 °C, producing a hydrogen-rich gas with slight formation of carbon monoxide and virtually no formation of methane. An oxygen transfer and intermediate hybrid mechanism of the catalytic char gasification with steam is proposed for understanding of the experimental data regarding both the kinetic behaviors and reaction selectivity. The study has highlighted the advantages of the catalytic gasification of coal char over the conventional coal gasification with respect to the reaction selectivity. The catalytic steam gasification of coal char makes it possible to eliminate or simplify the methane reforming and water-gas shift processes in the traditional gas-to-hydrogen purification system.     

光照条件下Na2CO3/H2O2协同降解偶氮染料研究

本研究主要在光照条件下,利用Na₂CO₃/H₂O₂反应体系降解偶氮染料酸性橙8(AO 8),考察了光照条件对AO 8降解的影响,探究了不同活性基团对AO 8降解的贡献。结果表明,在光照条件下Na₂CO₃和H₂O₂可以产生协同效应,与单独加入Na₂CO₃或H₂O₂相比,能够有效促进偶氮染料AO 8的降解。在优化条件下,该体系中AO 8的降解率达到73.83%。同时研究分析了不同活性基团在AO 8降解过程中的作用,其中贡献率表现依次为CO₃·^->HO·>O₂·^->¹O₂。本研究结果可为偶氮染料废水的处理提供了一条新的途径。     

Solubility of Na2SO4, Na2CO3 and their mixture in supercritical water

The solubility of many salts in water decreases dramatically with temperature in the vicinity of the critical point of pure water. Examples of these salts are sulfates of sodium, potassium, lithium and sodium carbonate. These salts are usually produced during supercritical water oxidation (SCWO) and contribute to fouling. The solubility of Na₂CO₃ and Na₂SO₄ has been determined in pure form and in the presence of each other, for the temperature range relevant to SCWO. The experimental procedure was to pass the salt solution through a tube at constant temperature. After a brief initiation period during which no salt sticks to the tube, the salt above the solubility limit deposited on the tube surface. The solution leaving the section was thus at the solubility limit. A rapid decrease in the salt solubility was observed just above the pseudo-critical temperature. For supercritical conditions, the solubility of each salt in the form of a mixture was quite close to the solubility of pure salt. At the highest fluid density considered (480 kg/m³) the presence of Na₂CO₃ reduces the solubility of Na₂SO₄, as might be expected from the “common-ion effect”.     

Raman Spectroscopic Study of Gallium-Doped Ba(Zn1/3Ta2/3)O3

Resonators of Ba(Zn_1/3Ta_2/3)O₃, sintered between 1450° and 1600°C, are characterized by Raman spectroscopy, X-ray diffraction, and scanning electron microscopy. The quality factors of the resonators are found to depend on sintering temperature, and at 1600°C there is evidence of Zn loss from the surface. The frequency of the A_1g Raman mode changes from 800.9 cm⁻¹ for a sample with Q = 80000 (2 GHz), to 794.5 cm⁻¹ when Q = 44000 (2 GHz). Changes in the position of this and other Raman modes are thought to be due to distortions of the oxygen octahedra, brought about by Zn loss. The presence of a BaTa₂O₆ phase at the surface is confirmed by XRD and SEM.     

NO reduction with NH3 over chromia–vanadia catalysts supported on TiO2: an in situ Raman spectroscopic study

In situ Raman spectroscopy was used for studying the ternary 2% CrO₃–6% V₂O₅/TiO₂ catalyst, for which a synergistic effect between vanadia and chromia leads to enhanced catalytic performance for the selective catalytic reduction (SCR) of NO with NH₃. The structural properties of this catalyst were studied under NH₃/NO/O₂/N₂/SO₂/H₂O atmospheres at temperatures up to 400 °C and major structural interactions between the surface chromia and vanadia species are observed. The effects of oxygen, ammonia, water vapor and sulfur dioxide presence on the in situ Raman spectra are presented and discussed.     

Excess power and the product molecular hydrino H2(1/4) generated in a K2CO3 electrolysis cell

Novel inorganic hydride compounds KHKHCHO₃ and KH were isolated and characterized following the highly exothermic electrolysis of a K₂CO₃ electrolyte, and the hydride was shown to comprise hydrino hydride ions [R. Mills, E. Dayalan, P. Ray, B. Dhandapani, J. He, Electrochim. Acta 47 (2002) 3909; R. Mills, Int. J. Hydrogen Energy 25 (2000) 669; R. Mills, J. New Mater. Electrochem. Syst. 6 (2003) 45; R. Mills, Fusion Technology, vol. 37, no. 2, March, 2000, p. 157.]. We report further evidence of the catalysis of hydrogen to form molecular hydrino with potassium catalyst in a K₂CO₃ electrolytic cell. Excess enthalpy of a factor of 40% that of the ohmic power dissipation was observed. H₂(1/4), molecular hydrogen in a fractional Rydberg state, was predicted as a further product. From the NMR frequency, the energy state of the molecular hydrogen can be measured. The electrolysis gas was collected in a hollow nickel cathode that permitted enrichment of H₂(1/4) based on its higher mobility. The gases were dissolved in CDCl₃ and characterized by ¹H NMR. A singlet peak upfield of H₂ was observed with the predicted chemical shift of 1.25 ppm relative to tetramethylsilane (TMS). The H₂(1/4) NMR peak was further observed on samples prepared by dissolving each of the crystals that precipitated from the electrolyte and concentrated electrolyte in CDCl₃.     

Electrochemical impedance of two-phase Ni-Ti alloys during corrosion in eutectic (0.62Li, 0.38K)2CO3 at 650 °C

The corrosion of two-phase Ni-10Ti and Ni-15Ti in molten (0.62Li, 0.38K)₂CO₃ at 650 °C under the atmosphere of air has been studied by electrochemical impedance spectroscopy (EIS). The impedance spectra for both Ni-10Ti and Ni-15Ti are composed of a semi-circle at high-frequency port and a line at low-frequency port indicating a diffusion-controlled reaction. The corrosion of the alloys produces an external scale composed of NiO and TiO₂, and a wide internal oxidation region. An equivalent circuit representing the features of the corrosion of the alloys was proposed to fit the impedance spectra, and electrochemical parameters in the equivalent circuit were also calculated.     

Impact of moisture on the thermal behavior of K2CO3-impregnated respirator carbons

The effect of moisture on the kinetics of the reaction of K₂CO₃-impregnated carbons with air at elevated temperature has been studied. Differential scanning calorimetry (DSC) measurements, isothermal DSC measurements and oven exposure tests all show that the reaction of the impregnated carbons with air is accelerated by the presence of moisture adsorbed by the impregnated carbon. Reaction kinetics extracted from isothermal DSC measurements show that this acceleration is caused by an increase in the frequency factor (γ₂) while the activation energy (E_a2) remains unchanged. For example, for an impregnated carbon containing 22.4% by weight moisture, the frequency factor was found to increase by about 65% compared to that of the dry precursor. X-ray diffraction experiments show that the increase in frequency factor is caused by a decrease in the particle size of the impregnant through a series of steps initiated by the adsorbed water. First, the deliquescent K₂CO₃ impregnant dissolves in sufficient adsorbed water; then this solution dries during heating to initially form KHCO₃, which subsequently decomposes to form small nano-particles of K₂CO₃ that apparently have a larger specific surface area and hence more catalytic activity. We suspect that the adsorbed moisture will cause such impregnant redistribution, and hence accelerated reaction kinetics with air, whenever deliquescent impregnants on hydrophilic surfaces are used.     

Electrochemical formation of Yb-Ni alloy films by Li codeposition method in a molten LiCl-KCl-YbCl3 system

Electrochemical formation of Yb-Ni alloy films at a Ni cathode was investigated in a molten LiCl-KCl-YbCl₃ (0.5 mol%) at 723 K. A very thin YbNi₂ film (∼100 nm) was formed by potentiostatic electrolysis at 0.10 V (vs. Li⁺/Li) for 24 h. A much thicker YbNi₂ alloy film (∼7 μm) was formed by Li codeposition method (cathodic galvanostatic electrolysis at 50 mA cm⁻²) for 1 h. The formed YbNi₂ films were changed to Yb₂Ni₁₇ and α-Ni phases by anodic potentiostatic electrolysis depending on the applied potentials. The formation potentials of Yb₂Ni₁₇ and YbNi₂ were found to be 0.75 and 0.25 V, respectively.     

Interpreting the effects of operating variables on the induction period of CaCl2-Na2CO3 system by a cluster coagulation model

In this article the effects of several operating variables, including supersaturation, temperature, and the presence of additive and seeds on the induction period of CaCO₃ were studied experimentally and theoretically. In experimental, the induction period was measured by a conductivity method so that the induction period was well identified. The results show that the induction period increases with decreasing supersaturation and temperature. The presence of Mg²⁺ in solution prolongs the induction period and the addition of seeds reduces the induction period. In theoretical, a cluster coagulation model, which brings together the current nucleation models and the theories describing the behavior of colloidal suspensions, was applied to estimate the induction period under various operating variables. A comparison between the two results shows that the present model is a suitable one to interpret the effects of various operating variables on the induction period of aqueous CaCl₂-Na₂CO₃ solution.     

XPS study of Li ion intercalation in V2O5 thin films prepared by thermal oxidation of vanadium metal

The intercalation and deintercalation mechanisms of lithium into V₂O₅ thin films prepared by thermal oxidation of vanadium metal have been studied by X-ray photoelectron spectroscopy (XPS) using a direct anaerobic and anhydrous transfer from the glove box (O₂ and H₂O < 1ppm), where the samples were electrochemically treated, to the XPS analysis chamber. Vanadium in the as-prepared oxide films is mostly (from 93 to 96% depending on samples) in a pentavalent state (V⁵⁺) with a stoichiometric O/V concentration ratio fitting that of V₂O₅. Four to seven percent of VO₂ is also observed. After the 1st and the 2nd intercalation steps at E = 3.3 and 2.8 V versus Li/Li⁺, respectively, the V2p core level spectra evidence a partial reduction to V⁴⁺ states with a remaining concentration of 73 and 56% of V⁵⁺, in agreement with the intercalation of about 1/2 mol of Li per V₂O₅ mol at each intercalation step. Intercalated lithium was observed at a binding energy of 56.1 eV for Li1s. Changes of the electronic structure of the V₂O₅ thin film after intercalation are evidenced by the observation, at a binding energy of 1.3 eV, of occupied V3d states (V⁴⁺) originally empty in the pristine film (V⁵⁺). The V2p and Li1s core level spectra show that the process of Li intercalation is partially irreversible. In the first cycle, 34 and 14% of the vanadium ions remain in the V⁴⁺ state after deintercalation at E = 3.4 and 3.8 V versus Li/Li⁺, respectively, indicating a partially irreversible process already after the 1st deintercalation. The analyses of C1s and O1s XP spectra show the formation of a solid-electrolyte interface (SEI). The analyzed surface layer includes lithium carbonate and Li-alkoxides.     

Comparative study of Li(Li1/3Ti5/3)O4 and Li(Ni1/2−xLi2x/3Tix/3)Ti3/2O4 (x = 1/3) anodes for Li rechargeable batteries

A solid solution of spinel (2/3)Li(Li_1/3Ti_5/3)O₄–(1/3)Li(Ni_1/2Ti_3/2)O₄ was prepared, and its structural/electrochemical properties were compared with Li(Li_1/3Ti_5/3)O₄ to identify the effect of doping to the structural invariance of Li(Li_1/3Ti_5/3)O₄. The solid solution retained the zero strain characteristic of Li(Li_1/3Ti_5/3)O₄ during discharge/charge with an excellent cycle stability, while the rate capability was notably improved. However, a reversible broadening of the XRD peak was observed at the end of discharge, indicating some structural changes. XANES measurements showed that the oxidation state of Ti was +4 and that of Ni was +2 in the solid solution.     

A study on electrochemical characteristics of LiCoO2/LiNi1/3Mn1/3Co1/3O2 mixed cathode for Li secondary battery

In this study, the LiCoO₂/LiNi_1/3Mn_1/3Co_1/3O₂ mixed cathode electrodes were prepared and their electrochemical performances were measured in a high cut-off voltage. As the contents of LiNi_1/3Mn_1/3Co_1/3O₂ in the mixed cathode increases, the reversible specific capacity and cycleability of the electrode enhanced, but the rate capability deteriorated. On the contrary, the rate capability of the cathode enhanced but the reversible specific capacity and cycleability deteriorated, according to increasing the contents of LiCoO₂ in the mixed cathode. The cell of LiCoO₂/LiNi_1/3Mn_1/3Co_1/3O₂ (50:50, wt.%) mixed cathode delivers a discharge capacity of ca. 168 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of ca. 152 mAh/g was obtained at a 2.0 C rate. However, the cell shows very stable cycleability: the discharge capacity of the cell after 20th charge/discharge cycling maintains ca. 163 mAh/g.     

Hydrothermal upgrading of wood biomass: Influence of the addition of K2CO3 and cellulose/lignin ratio

The hydrothermal treatment of two different wood biomass samples such as cherry (hard wood) and cypress (soft wood), whose composition is different i.e. lignin, cellulose and hemicellulose were performed at 280 °C for 15 min with aq. K₂CO₃ with different concentrations (0–1 M). The soft wood biomass contains higher lignin content than hard wood biomass. The cellulose rich cherry wood biomass produced higher proportion of acetic acid than cypress. The lignin rich cypress produced the hydrocarbons with major portion of phenolic hydrocarbons and derivatives than cherry. The total oil yields from both cherry and cypress wood biomass produced 50 wt% of liquid hydrocarbons at 280 °C for 15 min with 0.5 M K₂CO₃ solution. The volatility distribution of liquid hydrocarbons showed the characteristic features of soft and hard wood biomasses.     

Hydrothermal synthesis of Li(Ni1/3Co1/3Mn1/3)O2 for lithium rechargeable batteries

Ultrafine powders of Li(Ni_1/3Co_1/3Mn_1/3)O₂ cathode materials for lithium-ion secondary batteries were prepared under mild hydrothermal conditions. The influence of the molar ratio of Li/(Ni + Co + Mn) was studied. The products were investigated by XRD, TEM and EDS. The final products were found to be well crystallized Li(Ni_1/3Co_1/3Mn_1/3)O₂ with an average particle size of about 10 nm.     

Electrochemical formation of Sm-Co alloy films by Li codeposition method in a molten LiCl-KCl-SmCl3 system

Electrochemical formation of Sm-Co alloy films at a Co cathode was studied in a molten LiCl-KCl-SmCl₃ (0.5 mol.%) at 723 K. Very thin film (∼100 nm) of SmCo₂ alloy was obtained by potentiostatic electrolysis at 0.20 V (vs. Li⁺/Li) for 24 h. Much thicker alloy film (∼5 μm) was formed by Li codeposition method (cathodic galvanostatic electrolysis at 50 mA cm⁻²) for 1 h. The formed alloy phase was suggested as Li_xSm₄Co₆ (x∼3). The formed alloy film was changed to various Sm-Co alloy phases by anodic potentiostatic electrolysis depending on the applied potentials. The formation potentials of Sm₂Co₁₇, SmCo₃, SmCo₂ and Li_xSm₄Co₆ were found to be 1.40, 0.80, 0.30 and 0.05 V, respectively.     

Kinetic studies of CH4 oxidation over Pt–NiO/δ-Al2O3 in a fluidised bed reactor

The oxidation of CH₄ over Pt–NiO/δ-Al₂O₃ has been studied in a fluidised bed reactor as part of a major project on an autothermal (combined oxidation–steam reforming) system for CH₄ conversion. The kinetic data were collected between 773 and 893 K and 101 kPa total pressure using CH₄ and O₂ compositions of 10–35% and 8–30%, respectively. Rate–temperature data were also obtained over alumina-supported monometallic catalysts, Pt and NiO. The bimetallic Pt–NiO system has a lower activation energy (80.8 kJ mol⁻¹) than either Pt (86.45 kJ mol⁻¹) and NiO (103.73 kJ mol⁻¹). The superior performance of the bimetallic catalyst was attributed to chemical synergy. The reaction rate over the Pt–NiO catalyst increased monotonically with CH₄ partial pressure but was inhibited by O₂. At low partial pressures (<30 kPa), H₂O has a detrimental effect on CH₄ conversion, whilst above 30 kPa, the rate increased dramatically with water content.