Copper Ion Exchange Research Articles

Widening Synthesis Bottlenecks: Realization of Ultrafast and Continuous-Flow Synthesis of High-Silica Zeolite SSZ-13 for NOx Removal.

Characteristics of zeolite formation, such as being kinetically slow and thermodynamically metastable, are the main bottlenecks that obstruct a fast zeolite synthesis. We present an ultrafast route, the first of its kind, to synthesize high-silica zeolite SSZ-13 in 10 min, instead of the several days usually required. Fast heating in a tubular reactor helps avoid thermal lag, and the synergistic effect of addition of a SSZ-13 seed, choice of the proper aluminum source, and employment of high temperature prompted the crystallization. Thanks to the ultra-short period of synthesis, we established a continuous-flow preparation of SSZ-13. The fast-synthesized SSZ-13, after copper-ion exchange, exhibits outstanding performance in the ammonia selective catalytic reduction (NH3 -SCR) of nitrogen oxides (NOx ), showing it to be a superior catalyst for NOx removal. Our results indicate that the formation of high-silica zeolites can be extremely fast if bottlenecks are effectively widened.

Ion exchange of copper(II), lanthanum(III), thallium(I), and mercury(II) on the “polysurmin” substance

Interaction of copper, lanthanum, thallium and mercury salts solutions with an inorganic ion exchanger “polysurmin” was investigated. It was shown that the ion exchanger adsorbs the ions of these metals and exhibits specific selectivity for Hg2+ ions demonstrating abnormally high capacity.

Solid-State Ion-Exchange of Copper into Zeolites Facilitated by Ammonia at Low Temperature

The effect of the gas phase during solid-state ion-exchange of copper into zeolites was studied by exposing physical mixtures of copper oxides (CuI2O and CuIIO) and zeolites (MFI, *BEA, and CHA) to various combinations of NO, NH3, O2, and H2O. It is shown that heating these mixtures to 250 °C results in active catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR), indicating that the Cu has become mobile at that temperature. Such treatment allows for a fast (<5–10 h) preparation of copper-exchanged zeolites. Scanning transmission electron microscopy analysis of Cu-CHA prepared using this method shows homogeneous distribution of the Cu in the primary particles of the zeolite. In situ XRD reveals that the Cu ion-exchange is related to the formation of CuI2O. When the zeolite is mixed with CuIIO, addition of NO to the NH3-containing gas phase enhances the formation of CuI2O and the Cu ion-exchange. The mobility of Cu at low temperatures is proposed to be related to the formation of [CuI(NH3)x]+ (x ≥ 2) complexes.

The role of external acid sites of ZSM-5 in deactivation of hybrid CuZnAl/ZSM-5 catalyst for direct dimethyl ether synthesis from syngas

Direct synthesis of dimethyl ether (DME) from syngas was investigated on a series of hybrid Cu–ZnO–Al2O3/ZSM-5 catalysts prepared by kneading. It was found that the initial performance of the catalysts was a function of both zeolite crystallite sizes and Si/Al ratio. The activity of the hybrid catalysts gradually decreased with time on stream because of simultaneous copper sintering, copper oxidation and ion exchange with zeolite hydroxyl groups. Copper sintering led to the decrease in the number of metal active sites, while ion exchange of Cu2+ ions with the hydroxyl groups of the zeolite resulted in lower concentration of acid sites for methanol dehydration. Copper sintering and ion exchange could be slowed down by selective neutralization of the acid sites on the zeolite outer surface by silylation. Both catalyst stability and dimethyl ether productivity were significantly improved.

Selective catalytic reduction of NO by NH3 over copper-hydroxyapatite catalysts: effect of the increase of the specific surface area of the support

The influence of the increase of the specific surface area of the support Ca-HAp on the dispersion of copper species and their activity in the NO-SCR by NH3 has been studied. The copper ion exchange does not alter the Ca-HAp structure whatever the copper concentration. The increase of the specific surface area of the support changed the dispersion and the reducibility of copper species. The high NO conversion in the whole temperature range for the catalyst with the lowest specific surface area (35 m2/g) was related to the highly dispersed CuO particles that are easily reduced. Nevertheless, the increase of the specific surface area of the support (76 m2/g), induces an increase of the size of CuO particles that become less active in NO-SCR by NH3. The addition of 2.5 % of H2O to the reaction gas feed strongly affects the NO conversion in the whole temperature range. This deactivation can be related to the change of the nature of copper species rather than to the destruction of the Ca-HAp structure.

Polyaniline/Montmorillonite Nanocomposites Obtained by In Situ Intercalation and Oxidative Polymerization in Cationic Modified-Clay (Sodium, Copper and Iron)

Polyaniline/montmorillonite nanocomposites (PANI/M) were obtained by intercalation of aniline monomer into M modified with different cations and subsequent oxidative polymerization of the aniline. The modified-clay was prepared by ion exchange of sodium, copper and iron cations in the clay (Na–M, Cu–M and Fe–M respectively). Infrared spectroscopy confirms the electrostatic interaction between the oxidized PANI and the negatively charged surface of the clay. X-ray diffraction analysis provides structural information of the prepared materials. The nanocomposites were characterized by transmission electron microscopy and their thermal degradation was investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites have higher thermal stability than pure PANI. The electrical conductivity of the nanocomposites increased between 12 and 24 times with respect to the pure M and this increase was dependent on the cation-modification. The electrochemical behavior of the polymers extracted from the nanocomposites was studied by cyclic voltammetry and a good electrochemical response was observed.

Photorefractive properties of lithium niobate single crystals doped with copper

Raman scattering with excitation in the ultraviolet, visible, and near infrared and electron paramagnetic resonance are used to study the photorefractive properties of nominally pure, stoichiometric (R = Li/Nb = 1) single crystals of lithium niobate grown from a melt with 58.6 mol% Li2O (LiNbO3stoich), nominally pure crystals with a congruent composition (LiNbO3congr, R = 0.946), and Cu-doped crystals with a congruent composition (LiNbO3:Cu, [Cu] = 0.015 mass%). Optical irradiation is found to cause charge exchange of copper cations, Ca2+ → Cu, in the LiNbO3:Cu ([Cu] = 0.015 mass%) crystals. Thus, crystalline LiNbO3:Cu ([Cu] = 0.015 mass%) manifests photorefractive properties as a result of charge exchange of copper ions during laser irradiation, in addition to the contribution from intrinsic defects with localized electrons previously observed in LiNbO3stoich and LiNbO3congr.

UZM-9 제올라이트에서 메탄올의 올레핀으로 전환반응: 전이금속 이온 교환이 촉매의 활성저하에 미치는 영향

구리, 코발트, 니켈, 철의 전이금속 이온을 교환한 LTA 골격구조의 UZM-9 제올라이트에서 메탄올이 저급올레핀으로 전환(Methanol-to-Olefin: MTO)되는 반응을 조사하여 전이금속 이온 교환이 촉매의 활성저하에 미치는 영향을 고찰하였다. 전이금속 이온 교환에 따른 UZM-9의 결정구조, 결정 모양, 세공구조, 산성도 변화는 크지 않았다. UZM-9은 둥지 입구가 작아 MTO 반응에서 저급올레핀에 대한 선택도가 높지만, 둥지가 커서 활성중간체인 헥사메틸벤젠 등 폴리메틸벤젠이 쉽게 고리화축합되어 다고리 방향족화합물이 많이 생성되므로 활성저하가 빠르다. 그러나 구리와 코발트 이온을 교환하면 MTO 반응에서 UZM-9의 활성저하가 느려졌다. MTO 반응 중 생성되는 폴리메틸벤젠 양이온 라디칼과 전이금속 이온의 상호작용으로 활성중간체가 안정화되어 활성저하가 느려졌다. The effect of transition metal ion exchange into UZM-9 zeolite with LTA framework on its deactivation in methanol-to-olefin (MTO) conversion was discussed. The ion exchange of copper, cobalt, nickel, and iron did not induce any notable change in the crystallinity, crystal morphology, and acidity of UZM-9. The small cage entrance of UZM-9 caused the high selectivity to lower olefins in the MTO conversion, while its large cages allowed the rapid further cyclecondensation of active intermediates, polymethylbenzenes including hexamethylbenzene, resulting in a rapid deactivation. The UZM-9 containing copper and cobalt ions showed considerably slow deactivations. The interaction between transition metal ions and polymethylbenzene cation radicals, the active intermediates, generated in the MTO conversion stabilized the radicals and slowed down the deactivation of UZM-9.

NO reduction with NH3 under oxidizing atmosphere on copper loaded hydroxyapatite

Copper loaded hydroxyapatite catalysts were prepared by ion exchange in aqueous phase. The copper ion exchange capacity of hydroxyapatite host structure is highly dependent on the initial copper concentration of the solution. For the lowest concentration, a pH variation of the exchange solution is observed. This change in pH may allow the deposition of a small amount of copper hydroxide at the expense of cationic substitution of copper. The increase in copper content exchanged has no effect on the profile of conversion of NO by NH3. From this, it is assumed that the copper cations substituted for calcium are not active in the reaction. The profiles of NO conversion obtained, are in agreement with the presence of a small amount of copper oxide clusters deposited on the surfaces of the apatite.

ChemInform Abstract: The State of Excessively Ion-Exchanged Copper in Mordenite: Formation of Tetragonal Hydroxy-Bridged Copper Ion.

ChemInform Abstract: The State of Excessively Ion-Exchanged Copper in Mordenite: Formation of Tetragonal Hydroxy-Bridged Copper Ion.

Influence of Surfactant Adsorption on the Leaching of Copper Sulfides

Electrochemical impedance spectroscopy was used to investigate the adsorption of several surface active substances at the surface of copper sulfides and the influence of that adsorption on the reaction of exchange of copper ions between crystal lattice of the sulfide and the solution of copper (II) ions. Simultaneously the influence of several possible inhibitors on the leaching rate of non-stoichiometric copper sulfide was investigated. Among all investigate compounds the strongest inhibiting effect showed sodium oleate. However that compound does not adsorb at the surface of copper sulfide, and the inhibition is due to the precipitation of the insoluble copper oleate at the surface of the sulfide.

Enhanced Catalytic Performance of Copper-Exchanged SAPO-34 Molecular Sieve in Methanol-to-Olefin Reaction

Methanol-to-olefin (MTO) reaction over copper-exchanged SAPO-34 catalysts was investigated in order to extend their catalyst life. The exchange of copper ions into the cages of an SAPO-34 molecular sieve was confirmed by ESR, XPS, and 129Xe NMR techniques. Copper ions located in its cages considerably reduced its deactivation rate in the MTO reaction, while those dispersed on the external surface of the SAPO-34 molecular sieve accelerated the deactivation due to the limited mass transfer through the pore entrances. The 13C NMR and UV-VIS spectroscopy investigations of the materials occluded on the copper-exchanged SAPO-34 catalysts during the MTO reaction clearly showed that the copper ions exchanged in the cages suppressed the further condensation of alkyl aromatics to large, fused polycyclic aromatic hydrocarbons (PAHs). Theoretical calculations for the SAPO-34 and copper-exchanged SAPO-34 molecular sieves supported this observation because copper ions located in the cages stabilized the alkyl aromatics. Therefore, the exchange of copper ions into the SAPO-34 molecular sieve stabilized the reactive intermediates, alkyl aromatics, of the MTO reaction and suppressed their further condensation to PAHs, thereby slowing the deactivation.

Comparison of Amberlite IRC-748 Resin and Zeolite for Copper and Ammonium Ion Exchange

A sodium-form chelating ion-exchange resin, Amberlite IRC-748, and a natural zeolite were investigated for the exchange of copper and ammonium ions from aqueous solutions at three temperatures ((4.0, 20.0, and 40.0) ± 0.2) °C. Maximum exchange capacities were determined, and a temperature-dependent, semi-empirical thermodynamic ion exchange model used to describe the ion exchange behavior of the binary systems. It was found that the model selected fitted the data well for both systems. The resin was significantly more selective toward copper compared to zeolite, and the zeolite preferred ammonium to copper cations. Both systems exhibited an increase in selectivity toward copper or ammonium with an increase in temperature.

Redox properties of (1-(2-pyridylazo)-2-naphthol)copper(II) encapsulated in Y Zeolite

The electroactivity of zeolite-encapsulated redox-active transition metal complexes was explored for copper(II)-PAN (PAN = 1-(2-pyridylazo)-2-naphthol) complex encaged in the supercages of Y zeolite. Copper(II)-PAN complex and the zeolite boundary were investigated electrochemically by dispersion with a Nafion/water solution on carbon Toray as supporting electrode. Encapsulation was achieved by: (i) ion exchange of copper(II) in NaY zeolite and (ii) coordination of the intrazeolite metal ion with the PAN ligand using an L:copper(II) molar ratio of 2:1. The resulting materials were characterized by cyclic voltammetry in zeolite modified electrodes, surface analysis (XPS, SEM and XRD), spectroscopic methods (EPR and FTIR) and chemical analysis, which indicated that the copper(II)-PAN complex was effectively encapsulated inside the supercages of NaY, without any modification of the morphology and structure of the zeolite. The coordination geometry of Y-encapsulated copper(II)-PAN complex has been obtained with preferentially 1:1 stoichiometry analogous to the model complex, [CuCl(PAN)], by molecular simulations. For the cyclic voltammetry studies, the electrochemical behavior of free complex was compared with copper(II)-PAN complex encapsulated in Y zeolite. The results show evidence for electroactivity restricted to the boundary associated to the copper(II)-PAN complex.

A New Strategy for the Improvement of the N2Adsorption Properties of Copper-Ion-Exchanged MFI-Type Zeolites at Room Temperature

A copper-ion-exchanged MFI-type zeolite, CuMFI, which exhibits an extremely efficient adsorption of the dinitrogen (N2) molecule at room temperature, has been successfully prepared by ion exchange in an aqueous solution of Cu(CH3COO)2 containing a component of NH4CH3COO. This ion-exchange method has unique characteristics as follows; first, the copper ion exchange takes place exclusively on the ion-exchangeable site that acts as the active site for N2 adsorption, and second, the extent of the reduction of the divalent copper ion exchanged attains a high value of 88%. In addition, the CuMFI sample thus prepared exhibits a high efficiency for N2 adsorption at 298 K where the monovalent copper ions act as adsorption sites; approximately 86% of them are effective for N2 adsorption. In this case, the heats of adsorption of N2 were large, 87−60 kJ mol-1. These observations were rationalized as showing that the site-selective ion exchange with copper ions occurs, accompanying acetate ligands by which the effect ...

Electrochemically controlled ion exchange: Copper ion exchange with sodium zeolite Y

An electrochemically controlled method to drive ion exchange within zeolites is applied to the incorporation of Cu 2+ into NaY. The technique uses the polarised liquid/liquid interface to transfer sodium ions selectively – and controllably – from the exchange medium, into an adjacent organic phase. The electrochemical removal of the unwanted ions from the exchange medium drives equilibrium toward greater exchange of the desired ion. Analytical data in support of the ion-exchange process is presented and an approximate calculation of the extent of ion exchange, as a function of charge passed, is described. This method has the potential to be very effective for the exchange of ions with low affinity for the parent zeolites, and to reach 100% exchange.

Development of a new approach for microbial decontamination of water using modified Fenton's reaction

Microbial decontamination of water was carried out using a novel radical generating system consisting of ion exchange resin, copper and hydrogen peroxide. The system was successful in reducing the microbial load in water by more than 99% in 15 min and is effective against all the microorganisms tested. The method was also successful in decontaminating the flood water obtained from Industrial Canal and 17th Street Canal in New Orleans. Decontamination is due to the formation of hydroxyl radicals, formed during the decomposition of hydrogen peroxide by the metal-polymer complex.

Observation of characteristic IR band assignable to dimerized copper ions in montmorillonite

Copper ion-exchanged montmorillonite clays, which had been prepared by ion exchange in an aqueous solution of CuCl 2 at a temperature above 323 K, exhibited the characteristic IR band in the region 3360–3310 cm −1. No such bands were observed for the samples prepared by using different ion-exchange solutions and at different temperatures. From the spectroscopic observations, it was revealed that the ion-exchanged copper ions (Cu 2+) are in the form of dimerized species by bridging two hydroxyls, [ Cu 2 + < ( OH − ) 2 > Cu 2 + ], in montmorillonite.

Modification of layer charge in smectites by microwaves

The layer charge reduction of two Li-saturated montmorillonites is referred to application of microwave radiation at 2.45 GHz for dispersions and 30.0 GHz for the solid powders. Efficiency of these treatments was compared to the same conditions applying conventional heating. The samples were heated in the temperature and time windows corresponding to 190–270 °C and 30–120 min, respectively. Changes in the mean layer charge were monitored by the determination of cation exchange capacity values using exchange of triethylene tetraamino copper ions. The charge reduction of the montmorillonites in aqueous dispersions was rather low (<30%) despite the fact, that high Li+ concentration dissolved in solution was selected (1 mol L−1). This behaviour was attributed to the very high water content in used dispersions and high hydration enthalpy of Li+ cations. Nevertheless, the microwave heated dispersions (2.45 GHz) showed detectable layer charge reduction as compared to conventionally heated dispersions, where no significant changes were found.Solid powders with different content of exchangeable lithium ions were prepared with solutions having different molar fraction of Li+ and Na+ cations (0%, 20%, 40%, 60%, 80%, 100% of Li+). Final composition of interlayer cations was analysed with ICP-OES. In contrary to dispersions, the microwave treatment of the prepared powders revealed high layer charge reduction, which was much higher than for conventionally heated powders. The efficiency was enhanced with increasing interlayer lithium content but reached a limiting value depending on the montmorillonite used. Migration of the lithium into the structure of the montmorillonite supported with microwaves was extremely fast, finished probably within the few minutes of the treatments. The exchangeable Li+ cations are accelerated through alternating electric field of microwaves and highly efficient layer charge neutralisation occurs. Infrared spectroscopy showed that the products obtained with microwave treatments correspond to the materials heated conventionally for much longer periods of time. Hence, applying microwaves the time and energy requirement can be significantly reduced. The X-ray diffraction showed that montmorillonite layers were able to swell in ethyleneglycol upon charge reduction, if the cation exchange capacity was not reduced more than 20–40%.

Effects of some drugs on purified human erythrocyte CuZnSOD and in vitro inhibitiory effect of 5-fluorouracil on leukocyte total SOD activity

The inhibition and activation effects of some drugs on the activities of superoxide dismutase enzymes (SOD) in human erythrocyte and leukocyte cells was investigated. Firstly, CuZnSOD enzyme was purified 837–fold and 12% efficiency from human erythrocytes by ethanol-chloroform treatment to remove hemoglobin and then ion exchange chromatography (DEAE-Sepharose) and copper chelate affinity chromatography techniques. Inhibition or activation effects of fourteen drugs on CuZnSOD was investigated. None of the studied drugs except for 5-fluorouracil showed any effects on the enzyme. 5-fluorouracil showed activation effects on CuZnSOD at 3.33 mg/ml and 4 mg/ml concentrations with 33% and 32% activation, respectively. Leukocytes were isolated from healthy human blood, lysed in liquid nitrogen and the effect of 5-fluorouracil on the lysate SOD activity investigated. 5-Fluorouracil showed inhibition effects on total SOD activity of human leukocytes at 2 mg/ml and 4 mg/ml concentrations with 42% and 62% inhibition, respectively.