Sodium Species Research Articles

Selective conversion of lactic acid into acrylic acid over hydroxyapatite catalysts

Lactic acid conversion into acrylic acid was carried out over Ca-HAP catalysts at 623K. Stoichiometric Ca-HAP catalyst gave a high acrylic acid yield of about 60C-%. Furthermore, non-stoichiometric calcium deficient Ca-HAP catalysts containing the specific amounts of sodium ions, which were prepared under hydrothermal conditions, exhibited remarkably high acrylic acid yields of about 80C-%. In contrast, non-stoichiometric Ca-HAP catalysts with vacancy sites and Ca-HAP catalysts with excess amounts of sodium species showed relatively low acrylic acid yields and high selectivities into acetaldehyde and 2,3-pentanedione.

XPS and Raman studies of electron irradiated sodium silicate glass

The microstructure modifications of sodium silicate glass induced by 1.2-MeV electron irradiation are studied by x-ray photoelectron spectroscopy and Raman spectroscopy. Depth profile analyses are also performed on the irradiated glass at 109 Gy. A sodium-depleted layer with a thickness of a few tens of nanometers and the corresponding increase of network polymerization on the top surface are observed after electron bombardment, while the polymerization in the subsurface region has a negligible variation with the irradiation dose. Moreover, the formation of molecular oxygen after electron irradiation is evidenced, which is mainly aggregated in the first two-micron-thick irradiated glass surface. These modifications are correlated to the network relaxation process as a consequence of the diffusion and desorption of sodium species during electron irradiation.

A global model of meteoric sodium

A global model of sodium in the mesosphere and lower thermosphere has been developed within the framework of the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM). The standard fully interactive WACCM chemistry module has been augmented with a chemistry scheme that includes nine neutral and ionized sodium species. Meteoric ablation provides the source of sodium in the model and is represented as a combination of a meteoroid input function (MIF) and a parameterized ablation model. The MIF provides the seasonally and latitudinally varying meteoric flux which is modeled taking into consideration the astronomical origins of sporadic meteors and considers variations in particle entry angle, velocity, mass, and the differential ablation of the chemical constituents. WACCM simulations show large variations in the sodium constituents over time scales from days to months. Seasonality of sodium constituents is strongly affected by variations in the MIF and transport via the mean meridional wind. In particular, the summer to winter hemisphere flow leads to the highest sodium species concentrations and loss rates occurring over the winter pole. In the Northern Hemisphere, this winter maximum can be dramatically affected by stratospheric sudden warmings. Simulations of the January 2009 major warming event show that it caused a short‐term decrease in the sodium column over the polar cap that was followed by a factor of 3 increase in the following weeks. Overall, the modeled distribution of atomic sodium in WACCM agrees well with both ground‐based and satellite observations. Given the strong sensitivity of the sodium layer to dynamical motions, reproducing its variability provides a stringent test of global models and should help to constrain key atmospheric variables in this poorly sampled region of the atmosphere.

Crystal growth, structural, optical, thermal and NLO studies of γ-glycine single crystals

In the present work, single crystals of γ-glycine possessing nonlinear optical properties were successfully grown at ambient temperature in the presence of sodium sulphate for the first time by using the slow evaporation method. Bulk growths of α-glycine and γ-glycine single crystal were grown by slow evaporation method and top-seeded solution growth method. The grown crystal was subjected to powder X-ray diffraction analysis to determine the characteristic peak of γ-glycine and lattice parameters. The chemical composition of the γ-glycine crystal was determined by elemental analysis. The results of the Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) study show the presence of a small amount of sodium species in the grown γ-glycine crystal. The presence of functional groups was confirmed by FTIR spectroscopic analysis. The UV–vis–NIR spectrum indicates that the crystal has 75 percentage of transmittance in the entire visible and near IR region spectrum suggesting the suitability of the material for NLO applications. Differential scanning calorimetry (DSC) technique was employed to find the possible phase transition and to determine the thermal stability of γ-glycine. The second-order nonlinear optical property of the powdered sample of γ-glycine crystal was investigated by Kurtz and Perry powder technique and the relative second harmonic generation efficiency was found to be higher than that of standard inorganic material potassium dihydrogen phosphate (KDP).

Influence of Feedstock on the Release of Potassium, Sodium, Chlorine, Sulfur, and Phosphorus Species during Gasification of Wood and Biomass Shells

The objective of this work was to investigate the influence of feedstock on the release of trace elements during gasification. Therefore, different types of woody biomass and biomass residues (shells) were thermochemically converted in an atmospheric flow channel reactor furnace at different temperatures (900, 1200, and 1400 °C) under gasification-like conditions. For the determination of the composition of the hot gas, the flow channel reactor was coupled to a molecular beam mass spectrometer. The focus was set on the release of alkali metals (K and Na) and non-metals (S, Cl, and P), which are known for their high volatility and influence on the solid- and gas-phase chemistries, as well as the volatility of the other elements. The main gaseous species were 36HCl+, 58NaCl+, 74KCl+, 64SO2+, 60COS+, and 63PO2+. After quantification, the data set was correlated with the elemental composition of the biomass and likely release mechanisms are discussed.

Release of potassium and sodium species during combustion of various rank coals, biomass, sludge and peats

In this study, release characteristics of potassium and sodium species during combustion of various rank coal, biomass and sludge and peats with different physicochemical properties were examined. Most types of K and Na contained in the fuel were ionized and released, and existed as the KCl and NaCl form in the fuel. An increase in the chloride content in the fuel resulted in a decrease in the emission of KCl, and an increase in the emission of NaCl. In contrast, the KCl release increased and NaCl release decreased with increasing the combustion temperature.

Study of Na/Cu/TiO2 catalysts for the storage and reduction of NO

A Pt-free system based on Na/Cu/TiO2 catalysts was used to study the adsorption of NO under lean conditions. The results show that the NO adsorption activity dramatically increased when both sodium and copper are in intimate contact. Although copper is the active phase in the oxidation of NO to NO2, it was found that the addition of sodium species is of vital importance on the subsequent adsorption of NO2, which mainly occurs on the surface of the alkali in the form of nitrates and nitrites. It was found that a loading increase of the alkali led to an increase in the reduction temperature of the copper phase, which is ascribed to a close interaction between the copper and the sodium phases. Among the Na loadings that were studied, the addition of 5% Na gave the optimum adsorption of NO. After successive cycles of adsorption, the catalysts were fully regenerated at temperatures higher than 250°C using either CO or H2 as a reducing agent.

Ros and CaMKII Modulate Sodium Overload-Induced Calcium Leak from Ryanodine Receptors in Ventricular Myocytes

Introduction: Elevation of the diastolic free calcium concentration ([Ca2+]cyt) alters excitation-contraction coupling and contractility in cardiac myocytes. It is known that Na+ overload increases the levels of diastolic [Ca2+]cyt and induces arrhythmias via reverse mode of Na+/ Ca2+ exchanger. We hypothesized that Ca2+ leak induced by oxidation/phosphorylation of ryanodine receptors (RyRs) contributes to the rise in [Ca2+]cyt during Na+ overload. Methods: We used confocal fluorescence imaging of intact and membrane-permeabilized isolated rabbit and rat ventricular myocytes to study Ca2+ transients, cytosolic sodium ([Na+]cyt ) and intracellular reactive oxygen species (ROS) levels. Cellular Na+ overload was induced using 5 nM anemone toxin-II (ATX-II), a late Na+ current (INaL) enhancer. Results: ATX-II-induced [Na+]cyt overload caused abnormal Ca2+ transients in intact rabbit and rat myocytes. Additionally, high cytosolic Na+ increased ROS levels and activated CaMKII. These effects were abolished by the INa inhibition with ranolazine and TTX, CaMKII inhibition with KN93 and AIP or by the application of antioxidants such as DTT and coenzyme Q10. In the experiments with membrane-permeabilized myocytes, rapid elevation of [Na+]cyt from 5 mM to 20 mM resulted in an increase of ROS production in mitochondria and Ca2+ leak from RyRs by measuring the frequency of spontaneous Ca2+ waves. The CaMKII inhibitors, KN-93 and AIP, attenuated the effects of high [Na+]cyt on Ca2+ signaling. Conclusions: These data suggest that [Na+]cyt regulates RyRs activity. An increase in [Na+]cyt induces ROS production; ROS activates CaMKII leading to altered Ca2+ transients and abnormal Ca2+ handling.

Investigations on the influence of steam on the release of sodium, potassium, chlorine, and sulphur species during high temperature gasification of coal

Basic investigations on the release of alkali metal, chlorine, and sulphur species form a crucial element in designing control measures and to develop hot gas cleaning strategies for coal gasification systems. Together with other experimental approaches a large body of useful data has already been delivered in this area, but the underlying reaction mechanisms are not yet sufficiently understood. Therefore, release experiments were done in lab-scale with six hard coals and four lignites at 1400°C, 1atm and a gas stream of He/7.5% O2 and He/7.5% O2 and additional steam, respectively. The molecular beam mass spectrometry technique used for hot gas analysis is well established and is able to detect and differentiate key chemical species released during the different phases of gasification. Main species detected by MBMS were 23Na+, 34H2S+, 36HCl+, 39K+/39NaO+, 56KOH+, 58NaCl+, 64SO2+, and 74KCl+. The release of these inorganic species occurred for the most part during devolatilisation phase and is strongly influenced by steam. Especially, the amount of alkali metal hydroxide compounds increased significantly under the influence of steam.

Hydrothermal preparation of tobermorite incorporating phosphate species

Slurries of quartz, slaked lime, and sodium dihydrogen phosphate containing hydrochloric acid as the solvent were hydrothermally treated to prepare tobermorite incorporating phosphate species. X-ray diffraction and X-ray fluorescence analyses showed that tobermorite with a trace of phosphate species formed after the treatment. The sizes of plate-like tobermorite depended on the sodium phosphate additive and solvent. There were almost no effects observed of the additive and solvent on the morphology of tobermorite. Sodium and/or phosphate species promoted the transformation from calcium silicate hydrate gel as the precursor to tobermorite. Phosphate species were introduced into the tobermorite structure, resulting in the distortion of its structure.

Exploring in Situ Functionalization Strategy in a Hard Template Process: Preparation of Sodium-Modified Mesoporous Tetragonal Zirconia with Superbasicity

An in situ functionalization strategy was developed in a hard template process to fabricate mesoporous solid superbases, and sodium-modified mesoporous zirconia (NaMZ) was successfully prepared. The obtained materials were characterized by various methods including XRD, TEM, N2 adsorption, IR spectroscopy, XRF, and CO2 TPD. The results show that the NaMZ materials exhibit well-defined mesostructure, tetragonal crystalline frameworks, and superbasicity with a high strength of 27.0. The NaOH solution plays a double role by removing the silica template SBA-15 and functioning as the guest. The sodium species is thus coated onto the mesoporous zirconia formed in situ. Hence, the fabrication and functionalization of mesoporous zirconia can be realized in one step, which avoids the possible structural damage of nonsiliceous mesoporous oxides in post-treatment. The stability of metastable tetragonal zirconia was found to be due to the confined space provided by the mesoporous silica template and the formation of Si–O–Zr linkages. It was also demonstrated that the NaMZ materials exhibited excellent basic catalytic performance. The turnover frequency (TOF) value on the material NaMZ-2 can reach 95.0 h–1 with 100% selectivity to the target product dimethyl carbonate, which is much higher than the value for the extensively used homogeneous catalyst CH3ONa (45.8 h–1).

Simulating the Formation of Sodium:Electron Tight-Contact Pairs: Watching the Solvation of Atoms in Liquids One Molecule at a Time

The motions of solvent molecules during a chemical transformation often dictate both the dynamics and the outcome of solution-phase reactions. However, a microscopic picture of solvation dynamics is often obscured by the concerted motions of numerous solvent molecules that make up a condensed-phase environment. In this study, we use mixed quantum/classical molecular dynamics simulations to furnish the molecular details of the solvation dynamics that leads to the formation of a sodium cation-solvated electron contact pair, (Na(+), e(-)), in liquid tetrahydrofuran following electron photodetachment from sodide (Na(-)). Our simulations reveal that the dominant solvent response is comprised of a series of discrete solvent molecular events that work sequentially to build up a shell of coordinating THF oxygen sites around the sodium cation end of the contact pair. With the solvent response described in terms of the sequential motion of single molecules, we are then able to compare the calculated transient absorption spectroscopy of the sodium species to experiment, providing a clear microscopic interpretation of ultrafast pump-probe experiments on this system. Our findings suggest that for solute-solvent interactions similar to the ones present in our study, the solvation dynamics is best understood as a series of kinetic events consisting of reactions between chemically distinct local structures in which key solvent molecules must be considered to be part of the identity of the reacting species.

Ground Water in Certain Sites in Egypt and Its Treatments Using a New Modified Ion Exchange Resin—Characterization of Water and Modified Ion Exchange

The present work is a comprehensive of drinking water quality. Eleven groundwater samples were taken from various rural regions of Egypt, the groundwater samples were investigated for chemical, radiometric and heavy metals analyses, the major cations including; sodium ( ), potassium ( ), calcium ( ) and magnesium ( ) ions species, the major anions of chloride ( ), sulphate ( ), nitrite ( ), phosphate ( ). Radiometric analyses in water expressed as the gross alpha and beta activity concentrations, heavy metals analyses including arsenic ( ), lead ( ), cobalt ( ), manganese ( ), iron ( ) and cadmium ( ) ions. The groundwater samples were found to contain high concentrations of heavy metals than the limited values of the world health organization (WHO). Heavy metals speciation were performed using MinteqA2 geochemical code. A modified exchange resin was prepared by polymerization of the condensed dioxalayl p-sulphanilamide with phenol, this ion exchange resin was examined by the different techniques such as; x-ray diffraction, infra red spectra (IR), and electronic microscopic, it was found a good adsorbent material that used for the reduction of heavy metals from contaminated groundwater samples.

Synthesis of a Strain Molecule, 1-Azabicyclo [1.1.0] butane

1-Azabicyclo [1.1.0] butane (ABB) bearing the highly strained bicyclic structure, which is synthetically useful for the preparation of 3-substituted azetidines, was obtained by the cyclization of 2,3-dibromopropylamine hydrobromide derived from inexpensive allylamine only with organolithium compounds and lithium amides. When other bases were employed, such as potassium, sodium, and magnesium species, the reaction yielded almost no ABB. It was speculated that a lithium cation played an important role in the cyclization. Thus, we proposed that this reaction proceeded by the consecutive cyclization to aziridines via the SN2 process involving the activation of the C-Br bond based on the intermolecular Br…Li(+) coordination, as a result of studies of reaction mechanisms.

Thermal transformation of Na-LTA zeolite into low-carnegieite: The influence of residual sodium and aluminium species

The influence of residual sodium and aluminium species on the mechanism of commercial and laboratory-synthesized Na-LTA zeolite thermally induced transformation (ZTIT) was investigated. A phase transformation route between zeolite and low-temperature carnegieite (lt-carn) during heating, is evolving in two different pathways. In one aspect, Na-LTA zeolite transforms directly into lt-carn, while in the other, transformation unfolds through amorphous state. The samples with significant amount of sodium and aluminium residues: (1.05–1.06) Na 2O:(1.02–1.07) Al 2O 3:2SiO 2 did not show intermediate amorphous state during heat treatment. It was implicitly shown that investigated ZTIT process is enhanced by residual species. The residues are extracted from all investigated samples during refluxing treatment at 100 °C. The intermediary amorphous states were created from all refluxed Na-LTA samples. Common characteristics of such prepared amorphous NaAlSiO 4 states are narrow temperature stability range (cca. 50 °C) and low-density.

Searching for solvent cavities via electron photodetachment: The ultrafast charge-transfer-to-solvent dynamics of sodide in a series of ether solvents

It was recently predicted by simulations and confirmed by neutron diffraction experiments that the structure of liquid tetrahydrofuran (THF) contains cavities. The cavities can be quite large and have a net positive electrostatic potential, so they can serve as pre-existing traps for excess electrons created via photodetachment from various solutes. In this paper, we use electron photodetachment via charge-transfer-to-solvent (CTTS) excitation of sodide (Na(-)) to probe for the presence of pre-existing cavities in a series of ether solvents: THF, diethyl ether, 1,2-dimethoxyethane (DME), and diglyme (DG). We find that electrons photodetached from sodide appear after a time delay with their equilibrium spectrum in all of these solvents, suggesting that the entire series of ethers contains pre-existing solvent cavities. We then use the variation in electron recombination dynamics with CTTS excitation wavelength to probe the nature of the cavities in the different ethers. We find that the cavities that form the deepest electron traps turn on at about the same energy in all four ether solvents investigated, but that the density of cavities is lower in DG and DME than in THF. We also examine the dynamics of the neutral sodium species that remains following CTTS photodetachment of an electron from sodide. We find that the reaction of the initially created gas-phase-like Na atom to form a (Na(+),e(-)) tight-contact pair occurs at essentially the same rate in all four ether solvents, indicating that only local solvent motions and not bulk solvent rearrangements are what is responsible for driving the partial ejection of the remaining Na valence electron.

Microcrystalline Hexagonal Tungsten Bronze. 1. Basis of Ion Exchange Selectivity for Cesium and Strontium

The structural basis of selectivity for cesium and strontium of microcrystalline hexagonal tungsten bronze (HTB) phase Na(x)WO(3+x/2).zH(2)O has been studied using X-ray and neutron diffraction techniques, 1D and 2D (23)Na magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and radiochemical ion exchange investigations. For the HTB system, this study has shown that scattering techniques alone provide an incomplete description of the disorder and rapid exchange of water (with tunnel cations) occurring in this system. However, 1D and 2D (23)Na MAS NMR has identified three sodium species within the HTB tunnels-species A, which is located at the center of the hexagonal window and is devoid of coordinated water, and species B and C, which are the di- and monohydrated variants, respectively, of species A. Although species B accords with the traditional crystallographic model of the HTB phase, this work is the first to propose and identify the anhydrous species A and monohydrate species C. The population (total) of species B and C decreases in comparison to that of species A with increasing exchange of either cesium or strontium; that is, species B and C appear more exchangeable than species A. Moreover, a significant proportion of tunnel water is redistributed by these cations. Multiple ion exchange investigations with radiotracers (137)Cs and (85)Sr have shown that for strontium there is a definite advantage in ensuring that any easily exchanged sodium is removed from the HTB tunnels prior to exchange. The decrease in selectivity (wrt cesium) is most probably due to the slightly smaller effective size of Sr(2+); namely, it is less of a good fit for the hexagonal window, ion exchange site. The selectivity of the HTB framework for cesium has been shown unequivocally to be defined by the structure of the hexagonal window, ion exchange site. Compromising the geometry of this window even in the slightest way by either (1) varying the cell volume through changes to hydration or sodium content or (2) introducing disorder in the a-b plane through isomorphous substitution of molybdenum is sufficient to reduce the selectivity. Indeed, it is our hypothesis that this applies for all cations which are strongly bound by the HTB framework.

Imaging the sources and full extent of the sodium tail of the planet Mercury

Observations of sodium emission from Mercury can be used to describe the spatial and temporal patterns of sources and sinks in the planet's surface‐boundary‐exosphere. We report on new data sets that provide the highest spatial resolution of source regions at polar latitudes, as well as the extraordinary length of a tail of escaping Na atoms. The tail's extent of ∼1.5 degrees (nearly 1400 Mercury radii) is driven by radiation pressure effects upon Na atoms sputtered from the surface in the previous ∼15 hours. Wide‐angle filtered‐imaging instruments are thus capable of studying the time history of sputtering processes of sodium and other species at Mercury from ground‐based observatories in concert with upcoming satellite missions to the planet. Plasma tails produced by photo‐ionization of Na and other gases in Mercury's neutral tails may be observable by in‐situ instruments.

Effect of lanthanum addition on the properties of potassium-free catalysts for ethylbenzene dehydrogenation

The ethylbenzene dehydrogenation in the presence of steam is the dominant technology for styrene production, one of the most important high value chemicals. The most widely used industrial catalyst comprises potassium-promoted iron oxide, which deactivates with time, due to potassium loss. In order to find alternative free-potassium catalysts, the effect of lanthanum on hematite-based catalysts was studied in this work. Samples with different amounts of lanthanum and prepared with different precipitants (ammonium hydroxide, sodium carbonate and sodium hydroxide) were obtained. It was found that lanthanum led to the production of solids with small particles when ammonium hydroxide was used, a fact which was assigned to lanthanum species on the surface where they keep the hematite particles apart avoiding sinterization. On the other hand, bigger particles were produced when sodium hydroxide and sodium carbonate are used, which resulted in solids with small specific surface areas. This was related to the sodium species which covered the surface impairing the lanthanum action. The most promising catalyst was that prepared with ammonium hydroxide and with La/Fe = 0.1, which showed the highest specific activity and the highest activity per area. In this solid, lanthanum acts as a structural promoter.

Satellite measurements of the global mesospheric sodium layer

Abstract. Optimal estimation theory is used to retrieve the absolute Na density profiles in the mesosphere/lower thermosphere from limb-scanning measurements of the Na radiance at 589 nm in the dayglow. Two years of observations (2003 and 2004), recorded by the OSIRIS spectrometer on the Odin satellite, have been analysed to yield the seasonal and latitudinal variation of the Na layer column abundance, peak height, and peak width. The layer shows little seasonal variation at low latitudes, but the winter/summer ratio increases from a factor of ~3 at mid-latitudes to ~10 in the polar regions. Comparison of the measurements made at about 06:00 and 18:00 LT shows little diurnal variation in the layer, apart from the equatorial region where, during the equinoxes, there is a two-fold increase in Na density below 94 km between morning and evening. This is most likely caused by the strong downward wind produced by the diurnal tide between ~02:00 and 10:00 LT. The dramatic removal of Na below 85 km at latitudes above 50° during summer is explained by the uptake of sodium species on the ice surfaces of polar mesospheric clouds, which were simultaneously observed by the Odin satellite.