Ethylene and propylene adsorption and the formation of hydrocarbon complexes with NO2 upon interaction of adsorbed olefins with an NO + O2 mixture over HZSM-5 and CuZSM-5 zeolites studied by TPD and ESR

Adsorption of C₂H₄ and C₃H₆ on copper in oxidized samples of CuZSM-5 is found to increase with the copper concentration; simultaneously, olefin adsorption on the Br?nsted acid sites decreases. The Cu²⁺ cations in the square-planar coordination exhibit higher reactivity in olefin adsorption than copper cations in the square-pyramidal coordination. Thermal treatment of CuZSM-5 with hydrogen results in regeneration of the Br?nsted acid sites for olefin adsorption and the disappearance of Cu²⁺ cations, the active sites of adsorption, due to the reduction of Cu²⁺ to Cu⁺ and Cu⁰. Desorption peaks appear in the TPD spectra upon the interaction between the adsorbed hydrocarbons and NO₂. These peaks are not observed upon separate adsorption of the reactants, and they are likely due to decomposition of NO₂-hydrocarbon complexes over both the Br?nsted and copper-containing sites of the zeolite     

Chemisorption and physisorption of CO2 on cation exchanged zeolitesA,X and mor

Calorimetric measurements of the heat of adsorption of CO₂ on zeolites with variable content of mono- and divalent cations lead to common conclusions. High initial heats (up to 120 kJ·mol^–1 for NaA), generally associated with a slow and activated rate of adsorption, are found for high contents of Na⁺, Li⁺ or Ca²⁺. They are attributed to a limited number of chemisorption sites (0.3 per cage in NaA).Physisorption results in lower heats (25–50 kJ·mol^–1). The lowest values are obtained with partially or totally decationized zeolites. Transition metal cations induce frequently weaker interactions than IA or IIA. Finally the stronger the energy of adsorption is, the larger the adsorbed amount is.

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Zusammenfassung Kalorimetrische Messungen der Adsorptionswärme von CO₂ an Zeolithen mit einem unterschiedlichen Gehalt an ein- und zweiwertigen Kationen führen zu allgemeinen Schlußfolgerungen. Für einen hohen Gehalt an Na⁺, Li⁺ oder Ca²⁺ werden hohe Initiierungswärmen (bis zu 120 kJ·mol^–1 für NaA) gefunden, die immer in Verbindung mit langsamen und aktivierten Adsorptionsgeschwindigkeiten auftreten. Dies wird einer begrenzten Anzahl an Stellen für die Chemisorption zugeschrieben (0.3 pro -Cage in NaA). Physisorption verursacht niedrigere Wärmen (25–50 kJ·mol^–1). Die niedrigsten Werte erhält man mit teilweise oder total entkationisierten Zeolithen. Kationen von Übergangs-metallen verursachen häufig schwächere Wechselwirkungen als IA-oder IIA-Kationen. Je höher die Adsorptionsenergie, um so größer ist die adsorbierte Menge.

     

Polarographic and voltammetric investigations in N-methylpyrrolidinone(2) and N-methylthiopyrrolidinone(2)

Polarographic and voltammetric methods were employed to study the influence of N-methylpyrrolidinone(2) (NMP) and N-methylthiopyrrolidinone(2) (NMTP) towards a series of cations. In NMP reversible electrode reactions were observed for Na⁺, K⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu²⁺, Ag⁺ and irreversible reductions for Ba²⁺, Mn²⁺, Co²⁺ and Ni²⁺. 0.1 mol l^?1 tetraethylammoniumperchlorate solutions served as supporting electrolytes. Li⁺ was not electroactive in the supporting electrolyte mentioned, but yielded an irreversible cathodic wave in tetra-n-butylammonium perchlorate. In NMTP, Li⁺, Na⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu⁺ and Ag⁺ gave reversible cathodic waves on the DME, while Mn²⁺, Co²⁺ and Ni²⁺ were reduced in an irreversible electrode process. Bisbiphenylchromium iodide serving as a reference system throughout this study showed reversible behaviour in both solvents. A comparison of E_1/2 for given ions in both solvents showed a shift of about 0.5 V to more positive values in the case of a typically hard cation such as Na⁺ whereas soft cations such as Ag⁺ and Cu⁺ shifted by more than 0.8 V to more negative values. The effects of these two solvents on the cations studied is discussed in terms of donor acceptor interactions between the cation and the solvent molecules with special respect to the changes caused by replacing the oxygen atom in NMP by a sulphur atom.     

C-C and C-H bond activation in the fragmentation of the [M + Ni]+ adducts of aliphatic amino acids

The major metal-containing species formed upon fast atom bombardment of amino acid/Ni⁺² mixtures is the [M + Ni]⁺ adduct, involving reduction of the Ni⁺² to the +1 oxidation state. By contrast, electrospray ionization of amino acid/Ni⁺² mixtures produces predominantly [Ni(M ? H)M]⁺; this species, on collisional activation, produces predominantly [M + Ni]⁺ by elimination of [M - H], presumably a carboxylate radical. The unimolecular fragmentation reactions occurring on the metastable ion time scale for the [M + Ni]⁺ adducts of a variety of α-amino acids have been recorded. The adducts with phenylalanine, α-aminoisobutyric acid and α-aminobutyric acid fragment by elimination of H₂O, H₂O + CO and, to a minor extent, by elimination of CO₂. These reactions are similar to those observed for the [M + Cu]⁺ adducts of α-amino acids. A reaction distinctive for the [M + Ni]⁺ adducts involves formation of the immonium ion RCH=NH ₂ ⁺ . By contrast, the [M + Ni]⁺ adducts with leucine, isoleucine, and norleucine show extensive metastable ion fragmentation by elimination of H₂, CH₄, C₂H₄, C₃H₆, and C₄H₈, with the relative importance of the different fragmentation channels depending on the configuration of the C₄H₉ side chain. These results are interpreted in terms of C-C and C-H bond activation of the C₄H₉ side chain by the Ni⁺. The adducts with valine and norvaline fragment in a fashion similar to the adduct with phenylalanine, except that minor elimination of C₃H₆ is observed.     

Preparation of core-shell magnetic Fe3O4@SiO2-dithiocarbamate nanoparticle and its application for the Ni2+, Cu2+ removal

A typical superparamagnetic nanoparticles-based dithiocarbamate absorbent (Fe₃O₄@SiO₂-DTC) with core-shell structure was applied for aqueous solution heavy metal ions Ni²⁺, Cu²⁺ removal.     

Behaviour of Li+ and Cu2+ in heated montmorillonite: Evidence from far-, mid-, and near-IR regions

Infrared spectroscopy in the far (FIR), mid (MIR), and near (NIR) regions was used to study the structural changes of a thermally treated clay mineral montmorillonite saturated with Li⁺ or Cu²⁺ cations (Li-JP and Cu-JP samples). Cation exchange capacity (CEC) values decreased by 89 and 64% in Li- and Cu-samples, respectively, heated at 300 °C. The IR spectra confirm that the charge of exchangeable cations significantly affect their final position after fixation upon heating. No absorption bands related to the vibrations of interlayer cations were observed in the FIR spectra of unheated or heated samples; however, different modification of the complex vibrational mode involving motion of octahedral aluminium relative to the tetrahedral sheet was observed near 197 cm⁻¹. The vibrations of OH groups in both MIR (ν_OH, 3630–3670 cm⁻¹) and NIR (2ν_OH, 7070–7170 cm⁻¹) regions proved that the Li⁺ migrated into the octahedral vacancies, thus creating local trioctahedral domains, such as AlMgLiOH. Though Cu²⁺ has similar ionic radius as Li⁺, no spectral features indicating its presence in the octahedral positions have been found even in the sample heated at 300 °C. Fixed Cu(II) is supposed to be located deep in the ditrigonal cavities of the tetrahedral sheets of Cu-JP. The NIR spectra of heated Cu-JP samples show new components near 7045 and 5170 cm⁻¹. These modes are believed to correspond to overtone bands associated with hydrated Cu²⁺ ions tightly bound in close proximity to the ditrigonal cavities of the basal surface (O_basalCu²⁺H₂O). The NIR spectra confirm that in Cu-JP heated at 200 °C, then saturated with Li⁺ and Cu²⁺ and heated again at 300 °C small Li⁺ ions migrate into the vacant octahedral sites even though Cu(II) have been trapped in the hexagonal cavities of the tetrahedral sheets in the course of previous heat treatment.     

Synthesis and adsorption properties of the cation exchange forms of OFF-type zeolite

The possibility of the ion-exchange of Na⁺ and K⁺ cations contained in OFF-type zeolite for H⁺, Ni²⁺, Cu²⁺, Co²⁺, and La³⁺ cations is investigated. Chemical and phase compositions, the morphology of crystals, and the adsorption properties of synthesized samples are studied via X-ray fluorescence and X-ray diffraction analysis, IR spectroscopy, scanning electron microscopy, and adsorption measurements.     

HTO/Cellulose Aerogel for Rapid and Highly Selective Li+ Recovery from Seawater

To achieve rapid and highly efficient recovery of Li⁺ from seawater, a series of H₂TiO₃/cellulose aerogels (HTO/CA) with a porous network were prepared by a simple and effective method. The as-prepared HTO/CA were characterized and their Li⁺ adsorption performance was evaluated. The obtained results revealed that the maximum capacity of HTO/CA to adsorb Li⁺ was 28.58 ± 0.71 mg g⁻¹. The dynamic k₂ value indicated that the Li⁺ adsorption rate of HTO/CA was nearly five times that of HTO powder. Furthermore, the aerogel retained extremely high Li⁺ selectivity compared with Mg²⁺, Ca²⁺, K⁺, and Na⁺. After regeneration for five cycles, the HTO/CA retained a Li⁺ adsorption capacity of 22.95 mg g⁻¹. Moreover, the HTO/CA showed an excellent adsorption efficiency of 69.93% ± 0.04% and high selectivity to Li⁺ in actual seawater. These findings confirm its potential as an adsorbent for recovering Li⁺ from seawater.     

Fluorescent chemosensor for Cu2+ ion based on iminoanthryl appended calix[4]arene

Calix[4]arene based podands 1a of cone conformation and 1b of 1,3-alternate conformation possessing imine units and bearing anthracene moieties have been synthesized by a 1 + 2 Schiff base condensation in good yields and examined for their cation recognition abilities towards cations such as lithium, sodium, potassium, nickel, cadmium, copper, zinc, lead, silver and mercury ions by UV–vis and fluorescence spectroscopy. The calix[4]arene derivative 1b shows a selective fluorescence enhancement in presence of Cu²⁺ ions among the various metal ions tested (Li⁺, Na⁺, K⁺, Ni²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Ag⁺ and Hg²⁺ ions). The colour of the solution changes from colourless to light yellow in the presence of Cu²⁺ ions. The stoichiometry of the complex formed between 1b and Cu²⁺ was found to be 1:1 as established by Job’s plot.     

A Conductometric Study of Complexation Reactions Between Dibenzo-18-Crown-6 (DB18C6) with Cu2+, Zn2+, Tl+ and Cd2+ Metal Cations in Dimethylsulfoxide–Ethylacetate Binary Mixtures

The complex formation between Cu²⁺, Zn²⁺, Tl⁺ and Cd²⁺ metal cations with macrocyclic ligand, dibenzo- 18-crown-6 (DB18C6) was studied in dimethylsulfoxide (DMSO)–ethylacetate (EtOAc) binary systems at different temperatures using conductometric method. In all cases, DB18C6 forms 1:1 complexes with these metal cations. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, Genplot. The non-linear behaviour which was observed for variations of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity order of DB18C6 for the metal cations in pure ethylacetate and pure dimethylsulfoxide is: Tl⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ but the selectivity order is changed with the composition of the mixed solvents. The values of enthalpy changes (ΔH°_C) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard enthalpy (ΔS°_C) were calculated from the relationship: ΔG°_C,298.15=ΔH°_C − 298.15 ΔS°_C. The obtained results show that in most cases, the complexes are enthalpy stabilized, but entropy destabilized and the values of ΔH°_C and ΔS°_C depend strongly on the nature of the medium.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

Studying the adsorption and activation of benzene and chlorobenzene on Ni(12%)/Al2O3 by means of gas chromatography and quantum chemistry

In studying the surface and adsorption properties of Al₂O₃ and Ni(12%)/Al₂O₃ with respect to C₆H₆ and C₆H₅Cl, it is found that adsorbate-adsorbent interaction is stronger than adsorbate-adsorbate interaction. It is shown that the calculated isosteric heats of adsorption vary in a range of 61 to 45 kJ/mol depending on adsorption magnitude; for Ni(12%)/γ-Al₂O₃, as in the case of γ-Al₂O₃, the heat of adsorption of chlorobenzene is higher at low degrees of filling than that of benzene. According to density functional theory quantum-chemical calculations of the structures of complexes (NinC₆H₅Cl) ^z and (Ni _n C₆H₆) ^z (n = 1, 4; z = ?1, 0, +1), a nickel atom can penetrate into C₆H₅Cl along the C-Cl bond. It is concluded that a negative charge on nickel contributes to the efficient activation of the C-Cl bond and to an increase in the rate of desorption of benzene, a key step in the hydrodechlorination of chlorobenzene.     

Probing the interaction of alkali and transition metal ions with bradykinin and its des-arginine derivatives via matrix-assisted laser desorption/ionization and postsource decay mass spectrometry

The complexes of the peptides (Pep) bradykinin (RPPGFSPFR), des-Arg¹-bradykinin, and des-Arg⁹-bradykinin with the metal (M) ions Na⁺, K⁺, Cs⁺, Cu⁺, Ag⁺, Co²⁺, Ni²⁺, and Zn²⁺ are generated in the gas phase by matrix-assisted laser desorption/ionization and the structures of the corresponding [Pep + M⁺]⁺ or [Pep − H⁺ + M²⁺]⁺ cations are probed by postsource decay (PSD) mass spectrometry. The PSD spectra depend significantly on the metal ion attached; moreover, the various metal ions respond differently to the presence or absence of a basic arginine residue. The Na⁺ and K⁺ adducts of all three peptides mainly produce N-terminal sequence ions upon PSD; the fragments observed point out that these metal ions are anchored by the PPGF segment and not the arginine residue(s). In contrast, the adducts of Cu⁺ and Ag⁺ show a strong dependence on the position of Arg; complexes of des-Arg¹-Pep (which contains a C-terminal Arg) produce primarily y_n ions whereas those of des-Arg⁹-Pep generate exclusively a_n and b_n ions. These trends are consistent with Cu⁺ ligation by Arg’s guanidine group. The [Pep + Cs⁺]⁺ ions mainly yield Cs⁺; a second significant fragmentation occurs only if a C-terminal arginine is present and involves elimination of this arginine’s side chain plus water. This reaction is rationalized through a salt bridge mechanism. The most prominent PSD products from [Pep − H⁺ + Co²⁺]⁺ and [Pep − H⁺ + Ni²⁺]⁺ contain at least one phenylalanine residue, revealing a marked preference for these divalent metal ions to bind to aromatic rings; the fragmentation patterns of the complexes further suggest that Co²⁺ and Ni²⁺ bind to deprotonated amide nitrogens. The coordination chemistry of Zn²⁺ combines features found with the divalent Co²⁺/Ni²⁺ as well as the monovalent Cu⁺/Ag⁺ transition metal ions. Generally, the structure and fragmentation behavior of each complex reflects the intrinsic coordination preferences of the corresponding metal ion.     

Formation and Dissociation Mechanism of Amide Complexes,IV. Protonation and deprotonation of the Cu2+ and Ni2+ complexes of 3,7-diazanonanediamide and 3,7-diazanonane-N,N′-diethylamide

The protonation and deprotonation rates of the coordinated amide groups in the Ni²⁺ and Cu²⁺ complexes of 3,7-diazanonanediamide (DANA) and in the Cu²⁺ complex of 3,7-diazanonane-N,N′-diethylamide (DANEA) have been studied by stopped-flow techniques. For the interconversion M(H_?2L) ? ML, two consecutive reactions are observed in the case of Cu²⁺ with DANA or DANEA, whereas there is only one reaction for Ni²⁺ with DANA. Cu(H_?2DANEA) is unusually labile, indicating a strong interaction between the N-ethyl groups. The conversion of the O- into the N-coordinated amide groups in NiDANA²⁺ is 25 times slower than in CuDANA²⁺. In the case of Ni²⁺ this excludes a step with water substitution, which is involved in one of the reaction paths observed for the Cu²⁺ complexes, since the rates of water exchange differ by a factor of 10⁵ for the two metal ions.     

Electrochemical properties of a network polymer based on tetra(sulfonatophenyl)-meta-cyclophanoctol

Conductivity of the network polymer based on tetra(sulfonatophenyl)-meta-cyclophanoctol in the H⁺, Na⁺, Cu²⁺, Zn²⁺, and Ni²⁺ forms is studied, and the self-diffusion coefficients and activation energies of diffusion of the metal cations in the polymer phase are estimated.     

The features of the Cu2+-entry into the structure of tourmaline

EPR and optical absorption spectra of Cu²⁺ ion were investigated in natural elbaites from Brazil and Zambia and in synthetic olenite single crystal. In elbaite from Zambia, the content of Cu²⁺ ions was found to be about 0.006 pfu, whereas in Brazilian elbaite the amount of this ion can approach up to 0.2 pfu. The rose color of elbaite from Zambia is mainly due to optical absorption at 515 nm related to Mn³⁺ ions. The blue color of Brazilian elbaite is related to Cu²⁺ absorption bands at 695 nm and 920 nm. Spin Hamiltonian parameters of Cu²⁺ calculated from the angular dependence of the EPR spectra are: g _x = 2.054, g _y = 2.092, g _z = 2.374; A _x = 27.8·10^?4 cm^?1, A _y = 59.3·10^?4 cm^{? 1}, A _z = 133.2·10^?4 cm^?1. We propose that Cu²⁺ ions enter into Y octahedra with common edges; the symmetry of these Y octahedra is lowered because of local disorder induced by occupancy of the Y site by cations of very different size and charge, such as Li⁺, Al³⁺, and Cu²⁺.     

Dynamic Renner effect in collisions of C+ with H2

The dynamic Renner effect is shown to permit formation of CH⁺₂ in its first excited (²B₁) state from low energy collisions of C⁺ + H₂. The consequences for C⁺ + H₂. The consequences for C⁺ + H₂ radiative association are discussed.     

Thermodynamic characteristics of ion-exchange sorption of Co2+ cations on Na-vermiculite

The exchange of Na⁺ ions of vermiculite for Co²⁺ cations is measured by sorption-analytical and microcalorimetric methods. The previously revealed growth of the equilibrium constant with a rise in the degree of filling θ of vermiculite exchange sites with Co²⁺ cations is confirmed. This result is explained by the segregation of Co²⁺ and Na⁺ cations being exchanged in separate interlayer regions of vermiculite. The negative heats of exchange of Na⁺ cations for Co²⁺ cations are associated with the energy consumption for the rearrangement of the segregated interlayer regions in vermiculite. The positive entropy changes resulting from the exchange indicate the formation of a more disordered Co-Na-layered “cake” in comparison with the initial Na-form vermiculite. A decrease in the integral molal free-energy change ΔG _m of the mixed form of the mineral is determined by the entropy factor. It is shown that, as θ increases, the ΔG _m(θ) dependence passes from a positive to a negative range of values. This pattern of the curve may be interpreted as a gradual phase transition from the Na-form to the mixed Co-Na-segregated form. The first derivatives of the enthalpy and entropy changes with respect to the degree of filling θ exhibit distinct maxima at θ ～ 0.20 as a result of the transition from the ideal mixing of Co²⁺ and Na⁺ cations being exchanged to their segregation.     

Partially substituted lithium manganese oxides as 3 V cathode materials for secondary lithium batteries

Low temperature synthesis and electrochemical properties of partially substituted lithium manganese oxides are reported. We demonstrate various metallic cations (Cu²⁺, Ni²⁺, Fe³⁺, Co³⁺) can be incorporated in the 3 V layered cathodic material Li_0.45MnO_2.1. New compounds Li_0.45Mn_0.88Fe_0.12O_2.1, Li_0.45Mn_0.84Ni_0.16O_2.05, Li_0.45Mn_0.79Cu_0.21O_2.3, Li_0.45Mn_0.85Co_0.15O_2.3 are prepared. These 3 V cathode materials are characterized by the same shape of discharge-charge profiles but different values of the specific capacity, between 90 mAh g⁻¹ and 180 mAh g⁻¹. The best results in terms of capacity and cycle life are obtained with the selected content of 0.15 Co per mole of oxide, as the optimum composition. The high kinetics of Li⁺ transport in Li_0.45Mn_0.85Co_0.15O_2.3 compared to that in the Co-free material is consistent with a substitution of Mn(III) by Co(III) in MnO₂ sheets.     

The stereochemistry of Tutton's salts X2[M(H2O)6](YO4)2

Neutron structure determinations have been made of Tutton's salts, X₂[M(H₂O)₆] (YO₄)₂, where Y = Se, X = K⁺, M = Cu²⁺; Y = S, X = K⁺, M = Ni²⁺, Cu²⁺, Zn²⁺; X = Rb⁺, Cs⁺, M = Cu²⁺. This work has shown that there are extensive hydrogen networks with almost linear hydrogen bonds from [M(H₂O)₆]²⁺ to (YO₄)^2?. The (H … O) distance increases in the Cu²⁺ series for X = K⁺ to Cs⁺ but there is no difference for the potassium copper salts when Y = Se or S. Three different distorted [M(H₂O)₆]²⁺ octahedra were found in the series (orthorhombic, tetragonal with two long and four short, or four long and two short bonds). The interatomic distances from X⁺ to the neighboring O in a distorted XO₈⁺ dodecahedron increases with increased cation size, implying that the X⁺ polyhedron is maintaining its shape.