Search results for "Alkaline earth metal"
showing 10 items of 26 documents
Phase diagram of calcium at high pressure and high temperature
2018
Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murn…
Catalytic effect of Ca and K on CO2 gasification of spruce wood char
2015
Abstract Gasification is one route to produce chemicals and liquid fuels from biomass. The gasification of the char is catalyzed by alkali and alkaline earth metals in the biomass. In this work the catalytic effect of calcium (Ca) and potassium (K) on CO2 gasification of spruce wood was studied using a thermo gravimetric analyzer (TGA). The ash-forming elements were first removed from the wood using an acid leaching method. Then, various concentrations of K and Ca were absorbed to the wood by ion-exchange to carboxylic and phenolic groups, impregnation of K2CO3 or physically mixing of CaC2O4. The prepared spruce samples were placed in a mesh holder and gasified in the TGA at 850 °C in 100% …
Weak alkali and alkaline earth metal complexes of low molecular weight ligands in aqueous solution
2008
This work is aimed at reviewing the chemical literature dealing with thermodynamic aspects of the weak complex formation (species with log K values less than about 3) between alkali and alkaline earth metal ions with low molecular weight inorganic and organic ligands in aqueous solution. The following ligands (up to hexavalent anions) were examined in detail: (i) hydroxide, chloride, sulfate, carbonate and phosphate as inorganic, and (ii) carboxylates, amines, amino acids, complexones and nucleotides as organic ligands. The paper also identifies the main reasons responsible for the dispersion of the stability data on ion pairs in the literature. When possible, the trend of stability for the…
Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study
2008
The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These…
A model of biomass char gasification describing the change in catalytic activity of ash
2012
A comprehensive description of catalytic effects during char gasification under various conditions relevant to biomass gasification was made. A three-parallel reaction model was proposed to describe the dynamic change in catalytic activity of ash during gasification of biomass char particles. Three different regimes of conversion were identified by analyzing char reactivity experiments conducted in a vertical TGA with nine biomasses under a wide range of operating conditions (temperature: 1023–1123 K, pressure: 0.1–3.0 MPa and gasification mixtures of CO2–CO–H2O–H2): (1) catalytic char gasification with deactivation of catalyst, (2) non-catalytic char gasification, and (3) catalytic char ga…
Quantitative parameters for the sequestering capacity of polyacrilates towards alkaline earth metal ions
2002
The complex formation constants of polyacrylic (PAA) ligands (1.4</=logN</=2.4, N=number of monomer units) with calcium and magnesium ions were determined in different ionic media at different ionic strengths, 0</=I</=1 mol l(-1), at t=25 degrees C. Experimental pH-metric data in the presence of Ca(2+) or Mg(2+) were firstly analysed in terms of apparent protonation constants, logK(H*), using the "three parameter model" proposed by Hogfeldt; differences in logK(H*), determined in different ionic media, were interpreted in terms of complex species formation. The only species present in the system M-PAA (M=Ca(2+) or Mg(2+)) is ML(2): attempts to find species of different stoichiometry were un…
Muon knight shift measurements in the alkali and alkaline earth metal series
1979
Importance of ligand speciation in environmental research:A case study
2001
The speciations of EDTA and DTPA in process, waste and river waters are modelled and simulated, specifically to the mode of occurrence in the pulp and paper mill effluents and subsequently in receiving waters. Due to relatively short residence times in bleaching process and waste water treatment and slow exchange kinetics, it is expected that the thermodynamic equilibrium is not necessarily reached. Therefore, the initial speciation plays a key role. As such, the simulations have been extended to the process waters of the pulp and paper industry taking into account estimated average conditions. The results reveal that the main species are; Mn and Ca complexes of EDTA and DTPA in pulp mill p…
Halogenomercury Salts of Sterically Crowded Triazenides - Convenient Starting Materials for Redox-Transmetallation Reactions
2010
Diaryl-substituted triazenides Ar(Ar′)N3HgX [Ar/Ar′ = Dmp/Mph, X = Cl (2a), Br (3a), I (4a); Ar/Ar′ = Dmp/Tph, X = Cl (2b), I (4b) with Mph = 2-MesC6H4, Mes = 2,4,6-Me3C6H2, Tph = 2′,4′,6′-triisopropylbiphenyl-2-yl and Dmp = 2,6-Mes2C6H3] were synthesized by salt-metathesis reactions in ethyl ether from the readily available starting materials Ar(Ar′)N3Li and HgX2. These compounds may be used for redox-transmetallation reactions with rare-earth or alkaline earth metals. Thus, reaction of 4b or 2b with magnesium or ytterbium in tetrahydrofuran afforded the triazenides Dmp(Tph)N3MX(thf) (5b: M = Mg, X = I; 6b: M = Yb, X = Cl) in good yield. All new compounds were characterized by melting poin…
Effects of illumination on the dielectric response of barium-strontium niobate ceramics
2013
A study of the effects of white light on the low and infra-low frequency relaxation of polarization in the barium-strontium niobate (SBN) ceramics is reported. The light is found considerably decreasing the contribution of space charge at temperatures corresponding to the range of the relaxor phase (it is, around the Tm).