Alkali Metals Sodium Research Articles

Comparison of Catalysts Based on Individual Alkali and Alkaline Earth Metals with Their Composites Used for Steam Gasification of Coal

One-component catalysts based on alkali and alkaline earth metals (sodium, potassium, and calcium) as well as their composites were applied to the surface of coal samples used in the gasification process. The aim of this work was to compare the impact of these catalysts on the steam gasification of coal by analyzing the results of catalytic and noncatalytic measurements. The use of composites was intended to check whether it is possible to accomplish the synergistic effects (an effect arising between two or more substances interacting together to produce an effect greater than the sum of their individual effects) and overcome the shortcomings of individual metal catalysts. Measurements of steam gasification were conducted by a thermovolumetric method under isothermal conditions at an elevated pressure of 1 × 106 Pa and at four temperatures ranging from 1073 to 1273 K. On the basis of the obtained results, curves of the formation rate of gasification products were developed and yields of main products (hyd...

Effect of Na poisoning catalyst (V 2 O 5 –WO 3 /TiO 2 ) on denitration process and SO 3 formation

Abstract This paper aims to study the effect of alkali metal sodium (Na) poisoning on the performance of the Selective Catalytic Reduction (SCR) catalyst. The result showed that Na2SO4 poisoning leads to a reduced denitration rate of the SCR catalyst and an increase in the SO3 generation rate. Na2O poisoning leads to a significant reduction in the denitration rate of the SCR catalyst and marginally improves the formation of SO3. The maximum of the SO3 generation rate for a Na2SO4-poisoned catalyst reached 1.35%, whereas it was only 0.85% for the SCR catalyst. When the SO2 was contained in flue gas, the denitration rate for the Na2O-poisoned catalyst clearly increased by more than 28%. However, the effect of SO2 on the Na2SO4-poisoned catalyst was very slight. The denitration rate of the SCR catalyst decreased with an increase in the Na content. The BET and XRD results showed that Na poisoning of the catalyst decreased the number of acid sites, the reducibility of the catalyst, the surface area, and pore volume. The H2-TPR and NH3-TPD results show that Na decreases the number of acid sites and the reducibility of the catalyst. The FT-IR and XPS results showed that Na2O poisoning led to the decrease of V5+ O bonds and the consumptions of oxygen atoms. Na2SO4 poisoning can improve surface adsorbed oxygen, which was beneficial for the SO2–SO3 conversion reaction.

Predicted novel insulating electride compound between alkali metals lithium and sodium under high pressure**Project supported by the National Natural Science Foundation of China (Grant Nos. 11672274, 11274281, and 11174214), the China Academy of Engineering Physics Research Projects (Grant Nos. 2012A0101001 and 2015B0101005), the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics

The application of high pressure can fundamentally modify the crystalline and electronic structures of elements as well as their chemical reactivity, which could lead to the formation of novel materials. Here, we explore the reactivity of lithium with sodium under high pressure, using a swarm structure searching techniques combined with first-principles calculations, which identify a thermodynamically stable Li–Na compound adopting an orthorhombic oP8 phase at pressure above 355 GPa. The formation of Li–Na may be a consequence of strong concentration of electrons transfering from the lithium and the sodium atoms into the interstitial sites, which also leads to open a relatively wide band gap for LiNa-oP8. This is substantially different from atoms sharing or exchanging electrons in common compounds and alloys. In addition, lattice-dynamic calculations indicate that LiNa-oP8 remains dynamically stable when pressure decompresses down to 70 GPa.

Sulfur-Microporous Carbon Composite Positive Electrodes for Rechargeable Lithium Sulfur Batteries

Over the decades, researching on sulfur as a positive electrode material for the lithium-sulfur (Li-S) battery has widely been studied. The sulfur has a high theoretical capacity (1672 mAh g-1) and reasonable discharge voltage (ca. 2 V vs Li/Li+), and is an abundant material as a by-product of fossil fuel. However, it is well known that a sulfur positive electrode has some crucial problems for realistic application as Li-S battery, which are mainly dissolution of intermediate product species in its charge-discharge processes, insulation property of sulfur and lithium sulfide, and relatively large volume change of a sulfur positive electrode. Upon discharge process of a sulfur positive electrode, S8 molecule goes through a series of lithium polysulfides (Li2S n [n =1-8]). At this time, Li2S8, Li2S6, and Li2S4 can easily dissolve to a liquid electrolyte. Moreover, insoluble Li2S2 and Li2S also transform to a soluble lithium polysulfide by being oxidized during a charge process. These processes cause a redox shuttle reaction in a liquid electrolyte, which may induce rapid capacity decay and low charge-discharge efficiency. Also, a dissolved lithium polysulfide into a liquid electrolyte reacts with various electrolyte components (carbonate solvent, BF4 anion, and bis(fluorosulfonyl)imide (FSI) anion, etc.) and hence generates unnecessary products. Therefore, a simple sulfur positive electrode limits the choice of liquid electrolytes, which is one of some problems preventing from practical using Li-S batteries. There have been at least two approaches to overcome the above issue. One is embedding sulfur into less than about 1 nm-sized micro pores by a diffusion melt method; the other is covalently bonding sulfur onto de-hydrogenated polyacrylonitrile (S-PAN) by heat treatment. These types of sulfur composite electrodes show better cycle stability and higher charge-discharge efficiency than those of other types of sulfur composite positive electrodes and avoid the necessity to use a special electrolyte because they can completely prevent dissolution of a lithium polysulfide into a liquid electrolyte. This should be an advantage for a Li-S battery. It is interesting to note that these types of composites show similar charge-discharge behavior in spite of undergoing different synthesis routes, where their mechanisms have not been clarified yet. Sulfur loading to the composites depends on micro-pore volume of a porous material; for instance, the most suitable content of sulfur were about < 50 % in S-PAN composites, which should be improved. Therefore, in order to enhance the energy density of a Li-S cell, we think that sulfur-microporous material composites would be more investigated as a potentially better choice. In this study, we synthesized a sulfur-microporous activated carbon (AC) composite material and systematically investigated fundamental battery performance of the sulfur-microporous AC composite positive electrodes with different particle size AC, electrolyte, and negative electrode material. We confirmed that the sulfur-AC positive electrode shows relatively better low-temperature performance and prevents self-discharge at 60ºC by blocking dissolution of lithium polysulfide, which induces a redox shuttle reaction. According to the present results, a micro pore structure of 1 nm-sized strongly retains sulfur inside the pores, which indicates that some problems of sulfur as positive electrode material should be overcame by this simple synthesis method. Moreover, safety and reliability of the battery containing a sulfur positive electrode will be further improved by changing negative electrode material from alkali metal (lithium or sodium) to silicon or carbon material. Further research on sulfur-microporous AC positive electrode is currently proceeding in our laboratory and will be reported in this presentation. In our opinion, our efforts would open up a possibility of a sulfur-microporous composite as positive electrode material for a next generation rechargeable battery.

Alkali Metal Re-Distribution after Oxidation of 4H-SiC

Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n-and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 oC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO2 surface. Close to the moving SiO2/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For p-type 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na+&lt;K+&lt;Cs+, but the sodium mobility is substantial already at 1150 °C.

Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

In order to determine the chemical states of radioactive cesium (137Cs or 134Cs) sorbed in clay minerals, chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by X-ray photoelectron spectroscopy (XPS). Since the number of atoms in radioactive cesium is extremely small, we specially focused on chemical states of trace-level alkali metals. For this purpose, we have measured XPS under X-ray total reflection (TR) condition. For cesium, it was shown that ultra-trace amount of cesium down to about 100pgcm−2 can be detected by TR-XPS. This amount corresponds to about 200Bq of 137Cs (t1/2=30.2 y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.

First-principles calculations for thermodynamic properties of type-I silicon clathrate intercalated by sodium atoms

The ground state properties of the silicon clathrate [Formula: see text] intercalated by alkali metal sodium atoms [Formula: see text] are investigated by first-principle methods. Birch–Murnaghan equation of state is fitted to two sets of the [Formula: see text]–[Formula: see text] data calculated by density functional theory based on the plane-wave basis set within both the local density approximation (LDA) and the generalized gradient approximation (GGA). Through quasi-harmonic Debye model, some thermodynamic properties comprise the heat capacity, the thermal expansion coefficient, Debye temperature and the Grüneisen parameter for this clathrate compounds [Formula: see text] are obtained, which agree well with experimental results. Comparing the calculated heat specific in two ways with experimental results, we find that it is more accurate to describe the “rattle” modes of gust Na atoms in the cages as Einstein oscillators. Moreover, the effects of high pressure on these thermodynamic properties are also investigated which will be very helpful for a synthesis of these clathrate compounds in experiments under high pressure and high temperature condition.

Ion polarization behavior in alumina under pulsed gate bias stress

Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K+), sodium (Na+), and lithium (Li+), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔVth) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔVth over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔVth from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.

Release and transformation of sodium during combustion of Zhundong coals

Zhundong coalfield is one of the super-huge coalfields newly discovered in Xinjiang Autonomous Region of China. Zhundong coal is characterized by high content of sodium. This study deals with the release and transformation of sodium during combustion of two Zhundong coals. The volatilization of sodium and evolution of its occurrence modes in resultant ash were investigated in a laboratory-scale reactor. Experimental results show that sodium is the principal alkali metal and water-soluble sodium is the predominant chemical form in Zhundong coals. Combustion temperature has a pronounced effect on the release and transformation of sodium. The fraction of water-soluble sodium in residual ash decreases significantly and more HCl-soluble form is generated with the increase of combustion temperature. The tendency of ash deposition during coal combustion is closely related to occurrence mode of alkali metals. In addition, halite (NaCl) is clearly present in ash of Zijin coal at low temperature, while most sodium in form of NaCl is released into gas phase and the remainder is transformed into aluminosilicates with increasing temperature. Chlorine has a significant influence on transformation of sodium and NaCl(g) is the main form of sodium volatized from coal between 600 and 800 °C.

Research on Separating Rubidium from Deep Potassium-Rich Old Brine by Solvent Extraction

A deep potassium-rich old brine in Hubei Province contains a large number of rubidium resource. Separation of rubidium is very difficult due to the similar physical and chemical properties of rubidium with the other coexisting alkali metals (potassium, sodium, and lithium). The process of extracting and separating Rb from the old brine with 4-tert-butyl-2-(α-methylbenzyl) phenol(t-BAMBP) as the extraction agent and sulfonated kerosene as diluents was systematically studied in this paper. The concentration of extraction agent, alkalinity of the old brine, phase ratio, the extracting time and other related factors were investigated. The optimal extraction conditions were obtained as follows: the concentration of t-BAMBP was 1.0mol/L, the concentration OH- was 0.6mol/L, the phase ratio was 3, the extraction time was 3 minutes. The percentage extraction of Rb could reach 91% for single-stage extraction, the separation coefficient of Rb and K reached up to 16.15. Sulfonated kerosene as diluent is non-toxic, high flash point, non-environmental pollution. A high extraction rate and separation factor for the development of rubidium resource of deep potassium-rich brine provided a reliable basis.

Weak electron–phonon coupling in the early alkali atomic wires

The structural, electronic and vibrational properties of atomic wires composed of the early alkali metals lithium and sodium are studied using the density functional perturbation theory. The s-like electronic states near the Fermi level couple very weakly to longitudinal acoustic phonons and not at all to the transverse acoustic phonons, which results in a weak overall electron–phonon coupling. The results are compared to earlier studies on the electron–phonon coupling in metallic atomic wires and reinforce the idea that s-like states at the Fermi level give rise to weak electron–phonon coupling in one-dimension, in contrast with materials containing d-like states at the Fermi level which have correspondingly larger electron–phonon coupling due to interactions with transverse phonons.

Synthesis and characterization of dysprosium-doped magnesium tetraborate

We have identified optimal conditions for the synthesis of highly sensitive MgB4O7:Dy thermoluminescent phosphor and examined the effect of alkali metals (lithium and sodium) as additional dopants that improve the performance of the thermoluminescent phosphor.

Dibutylphosphinoylmethyloxythiacalix[4]arenes. Synthesis, structure, americium, europium and technetium extraction

A series of thiacalix[4]arenes bearing one, two or four chelating dibutylphopshinoylmethoxy groups have been synthesised and studied in the context of this paper. The synthesis consisted of precise Williamson alkylation of thiacalixarene tetrols with tosylate of dibutylhydroxymethyl phosphine oxide in the presence of alkali metal carbonates or sodium hydride. Stereochemical yield of the reaction (cone or 1,3-alternate conformer) depends on the nature of alkali metal. Small-sized ‘hard’ sodium cation organises the macrocyclic platform in the cone conformation, but larger and ‘soft’ potassium and cesium cations stabilise the macrocycle in the 1,3-alternate conformation. All synthesised compounds (except monophosphine monoxide) possess either moderate or high extraction ability towards pertechnetate ion. The cone-shaped thiacalix[4]arene tetraphosphine tetraoxide due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups effectively extract spherical americium, europium cations due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups. The extraction ability is very similar to that of calix[5]arene pentaphosphine pentaoxide existing in the cone conformation.

Preparation and Photocatalytic Performance Study of Na+/K+-WO3 by Ultrasonic Micro Method

With n-butanol/CTAB/cyclohexane as micro emulsion system, sodium tungstate and hydrochloric acid as raw material, alkali metals (Na+, K+) nitrate as dopant, pure WO3、Na+-WO3, K+-WO3 and Na+/K+-WO3 powders were prepared by ultrasonic micro-emulsion method; And performances of samples were analyzed by visible spectrophotometer. Photocatalytic activity study show that alkali metal sodium ion and potassium ion doped, photocatalytic activities of WO3 are improved markedly; When doping amount is 1.0%, catalyst amount is 2g/L, methyl orange concentration is 20mg/L, degradation time is 80 min, Na+-WO3 powder has the best photocatalytic degradation performance at 460nm, and the degradation rate is as high as 65%.

Correlation between Chemical Glass Components and the Glass Sticking on Sputtered PtIr Physical Vapour Deposition Coatings for Precision Blank Moulding

The increasing demand on high quality optical systems with complex geometries, low tolerances and a low installation space necessitates new replicative production systems for complex optical glass elements. The technology precision blank moulding shows promising properties to comply with these demands on an industrial bulk production. Due to the required high surface quality and low surface roughness of produced optical elements, moulding dies must have comparable low roughness and defect-free surfaces. To reduce wear and chemical interaction with the hot glass, moulding dies are often coated with a thin sputtered physical vapour deposition (PVD) coating. The objective of this research work was to analyze the diffusion behaviour inside different industrially used low-Tg (transformation point) glasses and their interaction with three different noble metal coating systems during an application oriented heating test. Therefore, three different PtIr coating systems with different interlayers (50 nm nickel as reference, 20 nm chromium, without interlayer) were deposited and tested in combination with six different industrially used low-Tg glasses. Using energy-dispersive X-ray spectroscopy (EDS) a diffusion of the light alkali and alkaline earth metals (sodium, potassium, calcium) was detected. The interaction between glass and coating was analyzed by EDS, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The different chemical compositions of the glasses have a significant influence on the interaction between glass and coating system. Several correlations between the chemical composition of the glasses and the amount of glass adhesion on the three coating systems were identified. The percentage of ions allocated to network modifiers lithium oxide, sodium oxide and potassium oxide correlates with the intensity of the interaction between coating and glass. The intensity of glass adhesion on the reference coating system PtIr/Ni is related with the zinc content in the glasses. Due to a diffusion process of the nickel interlayer, a direct correlation between the zinc content in the glasses and glass adhesion exists. The coating system with chromium interlayer showed comparable results to the system without interlayer.

A convenient method to prepare a novel alkali metal sodium doped carbon nitride photocatalyst with a tunable band structure

Sodium doped into a g-C3N4 crystal lattice can tune the position of CB and VB potentials, influence the structural and optical properties, and thus improve the Rhodamine B photodegradation and mineralization performances.

Phase Diagram of Olivine NaxFePO4 (0 &lt; x &lt; 1)

The composition–temperature phase diagram of cathode material NaxFePO4 in the olivine phase for sodium-ion battery has been determined. Samples were prepared by solid-state synthetic, electrochemical and chemical oxidation/reduction methods. Powder X-ray diffraction and Mossbauer spectroscopies were employed to investigate the phase behavior. At room temperature, despite the resemblance to the LixFePO4 structure, the solubility limit of alkali metal (sodium) vacancy in NaxFePO4 is found to be large. In the range 2/3 < x < 1 NaxFePO4 is found to be a solid-solution phase. Two distinguished Fe2+ sites in the solid-solution phase were found by Mossbauer spectroscopy. Ab initio calculations reproduce the quadrupole splitting constants and suggest large distortion of the Fe2+ octahedra. High-temperature in situ X-ray diffraction suggests a completely different phase diagram of sodium olivine with a much more stable nature of the intermediate at x = 2/3 in comparison to the lithium one.

Alkali metal deactivation of Mn–CeOx/Zr-delaminated-clay for the low-temperature selective catalytic reduction of NOx with NH3

Mn–CeOx/Zr-delaminated-clay has proven to be a promising low-temperature selective catalytic reduction (SCR) catalyst. To investigate the effects of alkali metals (potassium and sodium) on Mn–CeOx/Zr-delaminated-clay for the low-temperature SCR of NOx by NH3, fresh and alkali-deactivated Mn–CeOx/Zr-delaminated-clays were prepared under laboratory conditions. The SCR activity of each catalyst was measured for the removal of NO with NH3 in a fixed-bed flow reactor. The properties of the catalysts were characterized by XRD, H2-TPR, NH3-TPD, BET and XPS analyses. These results indicate that alkali metals seriously reduced catalytic activity, with potassium having a stronger deactivation effect than sodium. The addition of alkali metals to the catalysts lowered manganese oxide reducibility, allowed decrease of specific surface areas, increased Mn binding energy and lowered the number of acidic sites on the surface. Dissolution of Na, K from the catalysts by washing with water was found to be the best method for regenerating catalysts that were not greatly deactivated by alkali metals.

Emissions and deposit properties from combustion of wood pellet with magnesium additives

This work studies the amount of gaseous and particle emissions and deposits on heat exchanger surfaces in a boiler fired with commercially available pellets and with pellets primed with magnesium oxide and magnesium hydroxide. The combustion experiments were performed on a residential boiler of 20 kW. Substrates placed in the heat exchanger was analysed with SEM-EDX-mapping to evaluate the chemical composition of the deposits. The results show that particle emissions (PM 2.5) using the additives increased by about 50% and the mass of the deposits in the flue gas heat exchanger (excluding loose fly ash) increased by about 25% compared to the combustion of pellets without additives. The amount of additives was found to be eight times higher than the amount of the main alkali metals potassium (K) and sodium (Na) which leads to the assumption that the additives were overdosed and therefore caused the problems reported. The SEM analysis of the substrates placed in the flue gas heat exchanger indicate that the deposits of sodium (Na), potassium (K), chlorine (Cl) and sulphur (S) decrease using the additives. If this was due to the expected chemical reactions or due to the loose fly ash covering the substrates after the test, could not be determined in this study.

Structure of endohedral complexes of carbon nanotubes encapsulated with lithium and sodium

The article provides the results of ab initio calculations employing density functional theory of carbon nanotubes that contain clusters of lithium and sodium atoms. Stable positions of interstitial atoms, the electron density distribution in the system and the density of electronic states are determined. It is shown that the amount of charge transferred from the interstitial atoms in a cluster significantly differs from the corresponding value for a single atom. It is established that the density of electronic states of the system at low concentrations of atoms of the introduced element is determined by the electronic structure of a hollow nanotube, and as the concentration of interstitial atoms increases, this quantity becomes virtually independent on the type of alkali metal (lithium or sodium) and the initial type of the nanotube conductivity.