Effects Of Alkali Metal Salts Research Articles

Ultrathin porous graphitic carbon nanosheets activated by alkali metal salts for high power density lithium-ion capacitors

Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors (LICs). In this work, onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering, and the effects of alkali metal salts on the structure, morphology and performance of the samples are focused. The results show that alkali metal salts as activator can etch graphitic carbons, and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt. Moreover, it also affects the graphitization degree of the materials. The porous graphitic carbons (S-GCs) obtained by NaCl activation exhibit high specific surface area (77.14 m2·g−1) and appropriate graphitization degree. It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy. High-performance LICs (S-GCs//AC LICs) are achieved with high energy density of 92 Wh·kg−1 and superior rate capability (66.3 Wh·kg−1 at 10 A·g−1) together with the power density as high as 10020.2 W·kg−1.

Alkali Metal Salt Catalyzed Carbothermic Reduction for Sustainable Recovery of LiCoO2: Accurately Controlled Reduction and Efficient Water Leaching

Recycling of spent lithium-ion batteries (LIBs) is essential for both environmental protection and natural resource conservation. Carbothermic reduction of active materials has been a research hotspot for spent LIB recycling. However, the high reaction temperature and the limited solubility of Li2CO3 in the reduced product seriously restricted its industrial application. Here, based on the catalytic effect of alkali metal salts on carbothermic reduction, a novel process that features lower reduction temperature, accurately controlled reduction products, high concentration of lithium containing solution, and facile-treated CoO product was developed. With the catalysis of 10% NaOH, LiCoO2 can be controllably reduced to Li2O and CoO through catalytic carbothermic reduction. Afterward, lithium in the reduction products can be leached by deionized water with leaching efficiency higher than 93%, leaving cobalt in the leaching residue in the form of CoO. The lithium concentration in the lixivium can be up to 14....

Studies on the sol-gel transition entropy of κ-carrageenan/water system

The sol-gel transition entropy is estimated by using a modified Clapeyron-type equation for κ-carrageenan hydrogel systems under load. The effect of alkali metal salts on the sol-gel transition behavior is also investigated. The transition temperature decreases with increasing compressional stress, while the transition entropy remains unchanged. Both the transition entropy and the transition temperature at the zero stress limit vary almost in accordance with the Hofmeister series, but the inversion occurs for RbCl and CsCl. For the gels examined, a positive correlation exists between the transition entropy and the transition temperature at the zero stress limit.

Effect of alkali metal salts on decomposition of ionic liquid like organic salt

N1,N1,N2,N2-tetramethylethane-1,2-diamine-based ionic salts (TMEDA), N1,N1,N1,N2,N2,N2-hexamethylethane-1,2-diaminium dicyanamide (HMEDA-(DCA)2) were prepared following the quaternization and subsequent ion exchange. The chemical structure of the HMEDA-(DCA)2 was confirmed using 13C NMR spectrum and elemental analysis. The corresponding viscosity of its 60 wt% solution was found to be lower than 5 cP at room temperature, which was critical for propellant application. The ignition delay of 40 wt% HMEDA-(DCA)2 solution was decreased to 20–30 ms dramatically using alkali metal salts, Li(CH3COO), Mg(CH3COO)2, and Ca(CH3COO)2 as a co-catalyst when white fume nitric acid was utilized as an oxidizer.

Direct nucleophilic trifluoromethylation using fluoroform: a theoretical mechanistic investigation and insight into the effect of alkali metal cations

Prakash and co-workers recently reported a direct trifluoromethylation of Si, B, S, and C centers using fluoroform (CF3H) and dramatic effects of alkali metal salts of hexamethyldisilazane in this reaction (Science, 2012, 338, 1324). Herein, the detailed mechanisms of trifluoromethylation of Si and C centers in the presence of (Me3Si)2NK as a base have been studied using the DFT method. It has been found that the origin of the dramatic effect of the alkali metals is the stability of an intermediate MCF3. More interestingly, a linear relationship has been found between the chemical hardness of M+ (M = Li, Na, K, Rb, Cs) and the difference between the values of ΔGdec and ΔGtfm (ΔGdec, decomposition energy of the key intermediate MCF3; ΔGtfm, relative energy barrier for the formation of a Si–CF3 or C–CF3 bond). These results may help to both theoretically and experimentally search for better bases to develop more atom-economic and environmentally benign protocols to achieve trifluoromethylation using CF3H.

Synthesis, characterization and coordination chemistry of a new phosphite–ether ligand: The effects of alkali metal salts and the ligand/Rh molar ratio on the catalytic activity and regioselectivity of a Rh(I) complex of this ligand in the hydroformylation of styrene

We have recently reported that the addition of alkali metal salts to styrene hydroformylation reactions catalyzed by Rh(I) complexes of bis(phosphite) ligands can significantly improve the iso/ n regioselectivity. To better understand the effects of the alkali metal salts on these styrene hydroformylation reactions, a monodentate phosphite–ether ligand, (2,2′-C 12H 8O 2)POCH 2CH 2OCH 3, 1 has been prepared, and its Rh(I) complex has been evaluated as a catalyst for the hydroformylation of styrene. Both the activity and regioselectivity of the catalyst are sensitive to the ligand:Rh molar ratio and to the presence of salts such as LiBPh 4·3dme, NaBPh 4 and HgCl 2. The most active catalyst has a 1:2.5 Rh:1 molar ratio and a 1:8 Rh:Li + molar ratio, but the most regioselective catalyst has a 1:8.2 Rh:1 ratio and a 1:4 Rh:Li + ratio. Model complexes for various steps in the catalytic cycle, cis-Mo(CO) 4( 1) 2, 6, cis-PtCl 2( 1) 2, 7, and PdCl 2( 1) 2, 8, have been synthesized and characterized by multinuclear NMR spectroscopy and X-ray crystallography to provide insight into the factors that may affect the rates and regioselectivities of the hydroformylation catalysts. The cis– trans isomerization of 6 in the presence of catalytic amount HgCl 2 has been carried out to determine the cis– trans preference of 1 in the octahedral coordination geometry.

Study of the Effects of Alkali Metal Salts on Styrene Hydroformylation Reactions Catalyzed by Rhodium(I) Complexes of Bis(phosphite) Ligands

A functionalized α,ω-bis(phosphite-donor) ligand containing two amido groups, 8, has been prepared from tartaric acid. An in situ formed rhodium(I) metallacrown ether complex of 8 has been compared to an in situ formed rhodium(I) complex of (R,R)-Chiraphite for the hydroformylation of styrene. Both Rh(I) complexes are active catalysts, but the complex of (R,R)-Chiraphite exhibits a higher regioselectivity than does the metallacrown ether catalyst (iso/n of 10.1 versus 3.9) as expected. The additions of alkali metal salts to the hydroformylation reactions cause increases in the regioselectivities (approximately 2-fold for both LiBPh4·3dme and NaBPh4 for ligand 8; 3-fold for both LiBPh4·3dme and NaBPh4 for (R,R)-Chiraphite) with virtually no effect on the activity. The facts that (1) no change in the iso/n ratio is observed upon addition of the noncoordinating salt, TBA·BPh4, (2) LiBPh4·3dme has little effect on the regioselectivity of an in situ formed rhodium(I) complex of diphos, and (3) the increase in regioselectivity levels out at high salt:Rh ratios suggest the increase in regioselectivity is due to coordination of the alkali metal salt to the oxygen of a carbonyl ligand and to the phosphite oxygens during the regioselectivity-determining step. This proposal is consistent with the observation of only weak 1:1 coordination of LiBPh4·3dme with a model metallacrown ether, cis-Mo(CO)4(8) in acetonitrile-d3.

Practical Preparation Method of Polymer-Incarcerated (PI) Palladium Catalysts Using Pd(II) Salts

[reaction: see text]. Polymer-incarcerated (PI) palladium catalyst was practically prepared from inexpensive Pd(II) salts and a polystyrene-based copolymer under reducing conditions. Remarkable effects of alkali metal salts on the palladium loading were observed. PI Pd thus prepared showed high catalytic activity in Mizoroki-Heck reactions and Suzuki-Miyaura couplings with a range of substrates including an aryl chloride. In all cases, the Pd catalyst was recovered quantitatively without leaching, and reused several times without significant loss of activity.

Iron-Catalyzed Propylene Epoxidation by Nitrous Oxide: Studies on the Effects of Alkali Metal Salts

SBA-15-supported iron catalysts with and without alkali metal salt modifications were studied for propylene oxidation by nitrous oxide. The reaction route could be dramatically changed from allylic oxidation to epoxidation by modification of the FeOx/SBA-15 catalyst with alkali metal salts. The KCl-1 wt % FeOx/SBA-15 (K/Fe = 5) catalyst exhibited the best catalytic performances for propylene epoxidation, over which ca. 50% propylene oxide selectivity could be gained at a 10% propylene conversion at 648 K. Characterizations with diffuse reflectance UV-Vis, XANES, and Raman spectroscopic techniques revealed that the modification with KCl increased the dispersion of the iron species and changed the local coordination of iron into a tetrahedral configuration on the inner surface of SBA-15. This tetrahedrally coordinated iron site, which was probably stabilized by potassium ions, was proposed to account for the epoxidation of propylene by nitrous oxide. At the same time, the reactivity of lattice oxygen was inhibited, and the acidity of the FeOx/SBA-15 was eliminated. These changes should also contribute to the increase in the selectivity to propylene oxide. The counteranions in the alkali metal salts exerted a significant influence on the catalytic behaviors probably via an electronic effect.

Stabilization of polyamides. V. Thermo-oxidation of hexano-6-lactam in the presence of copper salts

The effect of Cu(I) and Cu(II) salts, halides and acetates on the kinetics and mechanism of the branched chain oxidation of hexano-6-lactam was studied. The effect of Cu salts on the oxidation is independent of the oxidation state of Cu ions and is similar to the effect of alkali metal salts; Cu cations do not seem to be oxidized or reduced in the course of the process. Similarly to alkali metal salts, Cu salts also affect the rates of the initiation and termination reactions of the chain oxidation, namely by their ability to coordinate with hydroperoxides and their peroxy radicals. Thus the Cu salts are able to induce homolysis of 6-hydroperoxyhexano-6-lactam, the branching reaction of the chain oxidation, the bimolecular termination of 6-peroxyhexano-6-lactam radicals leading to adipimide and peroxyadipamic acid, and most probably also the redox reaction of 6-hydroperoxyhexano-6-lactam with the aldehyde O CH(CH 2) 4CONH 2 formed from alkoxy radicals resulting from 6-hydroperoxyhexano-6-lactam homolysis via unstable hydroxy compound. All the above reactions can participate in the final effect of Cu salts on the kinetics and mechanism of N-alkyl amide oxidation.

Ionic conductivity of a novel solid polymer electrolyte

AbstractA novel kind of solid polymer electrolyte, the solvation unit of which is OCNHR, has been studied. The effects of host polymer structure, ion species, salt concentration, and plasticizers on ionic conductivity are discussed in detail. The solvability of host polymers is a very important factor that affects the ionic conductivity of electrolytes and is fully decided by the structure of solvation units and their density in polymer chain. The latter two rest with monomers structure and copolymerization ratio. Effects of alkali metal salts and divalent metal salts on ionic conductivity are different because of their different leading factor of cation radius. Salt concentration dependence of ionic conductivity appears as a double‐peak shape when alkali metal salts are added because of the total contribution of two kinds of ionic conductance modes, and appears as similar shapes when divalent metal salts are added. Different influences of plasticizers on ionic conductivity result from their different action ways. Ethylene glycol acts well because of its effective action from three different modes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2176–2184, 2001

Medium effects on the dimerization of coproporphyrin-I free base

Equilibrium constants of dimerization of the tetraanion of coproporphyrin-I free base were determined spectrophotometrically in aqueous solution at pH 9.0 in the presence of nine electrolytes, including salts of alkali metal, tetraalkylammonium and Ca(II) cations. Additions of all electrolytes promoted dimerization and the effect increased in the order tetraalkylammonium ≪ alkali metals ≪ Ca(II) salts. The Effects of alkali metal salts at concentrations below 0.1 M were quantitatively described in terms of Debye–Hückel model assuming an effective charge of the porphyrin monomer of −3. At higher salt concentrations salting-out/in effects must be taken into account. Addition of tetraalkylammonim salts to solutions containing 0.1 M NaCl produced the monomerization effect attributed to strong salting-in behavior of these salts. The effect of Ca(II) was described by complexation-induced dimerization of the porphyrin. Addition of organic co-solvents (methanol, ethanol, acetone, dioxane) to aqueous electrolyte solutions of the porphyrin produced a strong monomerization effect. Logarithms of dimerization constants extrapolated to the zero ionic strength in each mixed solvent roughly correlated with inverse dielectric constant with a negative slope considerably exceeding, however, that expected on the basis of a purely electrostatic model. Correlations with empirical solvent parameters (δH, ETN, SP) were less satisfactory than the correlation with­1/ε. A satisfactory description of solvent effects on dimerization constants was found in terms of a specific solvation model, which takes into account association of porphyrin monomer and dimer with several co-solvent molecules. Logarithms of the association constants were linear functions of the partial molar volume of the hydrocarbon portion of co-solvent molecules. Copyright © 1999 John Wiley & Sons, Ltd.

Ru-catalyzed hydrogenation of aromatic diamines: The effect of alkali metal salts

The influences of added alkali metal nitrates and nitrites on the performances of ruthenium catalysts in the liquid phase ring hydrogenation of 4,4′-methylenedianiline (MDA) and 1,4-phenylenediamine (PDA) have been examined. Sodium nitrate and sodium nitrite were shown to be the most effective promoters in enhancing the catalytic activity and in suppressing the formation of by-products. The effects of various solvents and the added water on the hydrogenation activity have also been investigated. The promoting effects of sodium nitrate and sodium nitrite were considerably enhanced in the presence of small amounts of water. XRD patterns of the Ru/Al 2O 3 catalyst sample obtained from the reaction performed in the presence of NaNO 3 or NaNO 2 revealed that the sodium aluminate (NaAlO 2) phase appears indicating that the cations of metal salts are interacting with the supporting material. An active species, NaOCH(CH 3) 2, was isolated and identified by spectroscopic and elemental analyses.

The effect of alkali metal salts on [formula omitted] and MnO 2 catalysts for the oxidative coupling of methane

A series of alkali metal halides/ZnO(60 wt.-%)/α-Al 2O 3 and NaCl MnO 2 were tested for the oxidative coupling of methane to ethylene and ethane. Sodium halides such as NaF, NaCl, NaBr and NaI were used as alkali metal halides. Recorded activities were associated with the apparent molal enthalpy of formation of sodium halides. The activity order was NaBr > NaCl > NaI > NaF. NaCl and NaBr played a role as promoters. NaF and NaI played a role as inhibitors. A kinetic study showed the reaction over NaCl(30 wt.-%)/ZnO(60 wt.-%)/α-Al 2O 3 was of the dual site Langmuir-Hinshelwood type. The obtained activation energy for the methyl radical formation was ca. 39 kcal/mole. The active oxygen species responsible for methyl radical formation seems to be a diatomic oxygen such as O 2 2− or O 2 − adsorbed on the surface of the catalyst.

The effect of alkali metal salts promoted MgO catalysts for the oxidative coupling of methane

Catalytic activities of the alkali metal salts are discussed based on experimental observations in a fixed bed flow reactor at atmospheric condition and instrumental analysis. LiCl (30 wt%) and NaCl (30 wt%) promoted MgO catalyst showed superior activity to mono alkali metal salts promoted MgO catalysts based on the C2 yield. This suggests that the bialkali metal salts neutralize the nonselective acid sites due to synergistic effect. Moreover, it is estimated that the active sites is O- ions.

Alkali metal salts as set accelerators for high alumina cement

The effect of alkali metal salts on the setting time of high aluminia cement (HAC) has been studied. The influence of concentration of the salts, chemical nature of anion and the type of alkali metal cation have been investigated. The results of the research indicate that alkali metal salts are set accelerators of HAC. The lithium cation has more effect on the setting time than other alkali cations because of its ability to form tetrahedral symmetry while the others will form the octahedral type. Lithium salts remove the nucleation barrier, caused by an initially fast precipitation. The influence of pH in mixing water is not important. The effect of hydroxyl group is greater than effect of other investigated anions due to the replacement leading to a further centre for oxobridge formation. The lithium salts cause decreasing of flexural and compressive strength of HAC mortars but also cause the strength development at early ages.

Phase behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends containing alkali metal salts

The effect of alkali metal salts on the phase behaviour of poly(methyl methacrylate) (PMMA)/poly(ethylene oxide) (PEO) blends was studied using d.s.c. Addition of lithium trifluoromethane sulfonate (LiT) to the normally miscible PEO/PMMA blends induced phase separation with the formation of a crystalline PEO phase, a crystalline PEO/salt complex phase and an amorphous PMMA phase. When potassium thiocyanate was used instead of LiT the mixture separated into two amorphous phases. Phase separation in these blends was not merely a result of the expected PEO/salt interaction, but also of the interaction of the salt with the PMMA. The evidence for this second interaction comes from an observed increase in the PMMA glass transition temperature with the addition of salt. Weak shifts in the carbonyl peaks in the i.r. spectra of the PMMA in the PMMA/salt mixtures suggest that the oxygen atom in the carbonyl interacts with the cation in the salt.

Coal analysis using thermogravimetry

Thermogravimetric analysis is being used increasingly today to obtain kinetic data related to coal decomposition. However, this method is open to criticism on the basis that the meaning of the activation energy of solid state reactions obtained from TG experiments is not clear. In this study a linear relationship between procedural activation energy and heat of reaction is developed. This is typical of elementary reactions of atoms and small radicals. The effects of alkali metal salts on the decomposition of coal under three gas atmospheres (N 2, CO 2 and air) are investigated. Several features are reported such as the effect of the catalysts on coal conversion and CH 4, CO and CO 2 emission. These are related to observed changes in activation energy.

Cationic Oligomerization of Ethylene Oxide

The oligomerization of ethylene oxide (EO) was investigated with several cationic catalysts to find a method for producing cyclic oligomers (crown ethers). The reactions were monitored by NMR spectroscopy (1H and 19F) and gas chromatography. The composition of oligomers was found to change during the reactions, and the production of 1,4-dioxane increased at the later stage of the reactions. This indicates that the composition of oligomers is kinetically controlled. The formation of higher cyclic oligomers was favored by the addition of tetrahydropyran or 1,4-dioxane to the system catalyzed by an oxonium salt; the maximum yield of cyclic tetramer was 16.8%. The effect of alkali metal salts was also examined. A template effect was observed to increase the amount of cyclic oligomer production.

Mechanisms of the alkali metal catalysed gasification of carbon

The catalytic effects of alkali metal salts in the gasification of carbonaceous materials by oxygen, steam and carbon dioxide are described. The most effective catalysts are generally the carbonates, oxides and hydroxides; other active salts tend to convert to these species under gasification conditions. Current theories of the mechanism of this type of catalysis are reviewed. Thermodynamic considerations, the results of thermal analysis and the magnitude of kinetic isotope effects suggest that cyclic sequences of elementary reactions are responsible for the catalytic phenomena.