Mineral formation from aqueous solution. Part III. The stability of aurichalcite, (Zn,Cu)5(CO3)2(OH)6, and rosasite (Cu,Zn)2(CO3)(OH)2

Summary The stabilities of rosasite, (Cu, Zn)₂ (CO₃)(OH)₂, and aurichalcite, (Zn, Cu)₅(CO₃)₂(OH)₆, have been determined by solution experiments with computer calculations of aqueous species in equilibrium with the solid phases. G _f ^o values for rosasite and aurichalcite have been calculated as –1100 and –2766 kJ mol^–1 respectively for specific samples of the two minerals. Most of the difference between the free energies of the compounds and those of malachite, Cu₂(CO₃)(OH)₂, and hydrozincite, Zn₅(CO₃)₂(OH)₆ arises from substitution of the minor cation in the crystal lattice. Malachite, zincian malachite and rosasite should be considered as a single isomorphous series.Part II: A. K. Alwan and P. A. Williams,Transition Acct. Chem., 4, 319 (1979).     

Zur Thermodynamik der Metallcarbonate. 2. Mitteilung [1]. Löslichkeitskonstanten und Freie Bildungsenthalpien von Cu2(OH)2CO3 (Malachit) und Cu3(OH)2(CO3)2 (Azurit) bei 25°C

The solubilities of Cu₂(OH)₂CO₃ (malachite) and Cu₃(OH)₂(CO₃)₂ (azurite) have been studied at 25° C in solutions of the constant ionic strength 0,2 M consisting primarily of sodium perchlorate. From experimental data the following values for equilibrium constants and Gibbs energies of formation are deduced: Predominance area diagrams for the ternary system Cu²⁺ H₂O-CO_2(g), including CuO, Cu(OH)₂, Cu₂(OH)₂CO₃, Cu₃(OH)₂(CO₃)₂, Cu²⁺ and Cu (CO₃)₂²⁻, are given.     

微波辐射对浆态床合成甲醇CuO/ZnO/Al2O3催化剂前驱体晶相转变的影响

在微波辐射条件下,对CuO/ZnO/Al2O3催化剂的沉淀母液进行老化,通过XRD、TG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂微观结构的进行表征,探讨了CuO/ZnO/Al2O3催化剂前驱体晶相转变过程中微波辐射的作用。结果表明,微波辐射有利于Cu2+取代Zn5(CO3)2(OH)6中Zn2+的同晶取代反应。微波辐射的老化过程中,首先发生Cu2+取代Zn5(CO3)2(OH)6中Zn2+生成(Cu,Zn)5(CO3)2(OH)6的同晶取代反应,并于1.0 h内基本完成;随着老化时间继续延长,主要进行Zn2+取代Cu2(CO3)(OH)2中Cu2+生成(Cu,Zn)2(CO3)(OH)2的同晶取代反应,同时(Cu,Zn)5(CO3)2(OH)6进一步结晶。与常规老化1 h制备的前驱体相比,微波辐射老化1.0 h制备的前驱体含有较多的(Cu,Zn)5(CO3)2(OH)6物相,有助于增强焙烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用,提高表面铜含量,进而提高CuO/ZnO/Al2O3催化剂在浆态床合成甲醇的催化活性和稳定性,在400 h浆态床合成甲醇评价期间,甲醇时空收率最大达318.9 g.kg-1.h-1,失活率仅为0.11%.d-1。     

Synthesis of the mixed oxide catalysts based upon the nickel-copper hydrotalcites of the type Ni<Subscript>x</Subscript>Cu<Subscript>6-x</Subscript>Cr<Subscript>2</Subscript>(OH)<Subscript>16</Subscript>(CO<Subscript>3</Subscript>)×4H<Subscript>2</Subscript>O

Summary High resolution TG coupled to a gas evolution mass spectrometer has been used to study the thermal properties of a chromium based series of Ni/Cu hydrotalcites of formulae Ni_xCu_6-xCr₂(OH)₁₆(CO₃)×4H₂O where x varied from 6 to 0. The effect of increased Cu composition results in the increase of the endotherms and mass loss steps to higher temperatures. Evolved gas mass spectrometry shows that water is lost in a number of steps and that the interlayer carbonate anion is lost simultaneously with hydroxyl units. Differential scanning calorimetry was used to determine the heat flow steps for the thermal decomposition of the synthetic hydrotalcites. Hydrotalcites in which M²⁺ consist of Cu, Ni or Co form important precursors for mixed metal-oxide catalysts. The application of these mixed metal oxides is in the wet catalytic oxidation of low concentrations of retractable organics in water. Therefore, the thermal behaviour of synthetic hydrotalcites, Ni_xCu_6-xCr₂(OH)₁₆CO₃×nH₂O was studied by thermal analysis techniques in order to determine the correct temperatures for the synthesis of the mixed metal oxides.     

Reactive adsorption of hydrogen sulfide by promoted sorbents Cu‐ZnO/SiO2: active sites by experiment and simulation

In the Cu_x‐Zn_(1‐x)O/SiO₂ sorbents for ultradeep adsorptive removal of H₂S from gaseous fuel reformates for fuel cells at room temperature, Cu promoter sites significantly increase sulfur uptake capacity of the sorbents. We report characterization of the family of Cu_x‐Zn_(1‐x)O/SiO₂ sorbents for reactive adsorption of H₂S using X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET) surface area analysis, electron spin resonance (ESR), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS) and calculations by the density functional theory (DFT). Both the supported ZnO phase and Cu promoter sites in the Cu_x‐Zn_(1‐x)O/SiO₂ sorbents are nano‐dispersed, as shown by XRD. The Cu_x‐Zn_(1‐x)O/SiO₂ sorbents contain Cu promoter as the Cu²⁺ site of octahedral geometry, as found by the complementary ESR and UV–vis DRS. Mechanism of the promoter effect of the Cu²⁺ site in the Cu_x‐Zn_(1‐x)O/SiO₂ sorbents in reaction with H₂S is proposed based on DFT calculations. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Crystal Structure of [Cu2(H2O)2(phen)2(OH)2][Cu2(phen)2(OH)2(CO3)2] · 10 H2O with phen = 1,10‐phenanthroline

The blue copper complex [Cu₂(H₂O)₂(phen)₂(OH)₂][Cu₂(phen)₂(OH)₂(CO₃)₂] · 10 H₂O, which was prepared by reaction of 1,10‐phenanthroline monohydrate, CuCl₂ · 2 H₂O and Na₂CO₃ in the presence of succinic acid in CH3OH/H₂O at pH = 13.0, crystallized in the triclinic space group P1 (no. 2) with cell dimensions: a = 9.515(1) Å, b = 12.039(1) Å, c = 12.412(2) Å, α = 70.16(1)°, β = 85.45(1)°, γ = 81.85(1)°, V = 1323.2(2) ų, Z = 1. The crystal structure consists of dinuclear [Cu₂(H₂O)₂(phen)₂(OH)₂]²⁺ complex cations, dinuclear [Cu₂(phen)₂(OH)₂(CO₃)₂]^2– complex anions and hydrogen bonded H₂O molecules. In both the centrosymmetric dinuclear cation and anion, the Cu atoms are coordinated by two N atoms of one phen ligand, three O atoms of two μ‐OH groups and respectively one H₂O molecule or one CO₃^2– anion to complete distorted [CuN₂O₃] square‐pyramids with the H₂O molecule or the CO₃^2– anion at the apical position (equatorial d(Cu–O) = 1.939–1.961 Å, d(Cu–N) = 2.026–2.051 Å and axial d(Cu–O) = 2.194, 2.252 Å). Two adjacent [CuN₂O₃] square pyramids are condensed via two μ‐OH groups. Through the interionic hydrogen bonds, the dinuclear cations and anions are linked into 1D chains with parallel phen ligands on both sides. Interdigitation of phen ligands of neighboring 1D chains generated 2D layers, between which the hydrogen bonded water molecules are sandwiched.     

Thermal decomposition of copper(II) and zinc carbonate hydroxides by means of TG-MS

Summary For the quantitative analyses of evolved CO₂and H₂O during the thermal decomposition of solids, calibration curves, i.e. the amounts of evolved gases vs. the corresponding peak areas of mass chromatograms measured by TG-MS, were plotted as referenced by the reaction stoichiometry of the thermal decomposition of sodium hydrogencarbonate NaHCO₃. The accuracy and reliability of the quantitative analyses of the evolved CO₂and H₂O based on the calibration curves were evaluated by applying the calibration curves to the mass chromatograms for the thermal decompositions of copper(II) and zinc carbonate hydroxides. It was indicated from the observed ratio of evolved CO₂and H₂O that the compositions of copper(II) and zinc carbonate hydroxides examined in this study correspond to mineral malachite, Cu₂CO₃(OH)₂, and hydrozincate, Zn₅(CO₃)₂(OH)₆, respectively. Reliability of the present analytical procedure was confirmed by the fairly good agreement of the mass fraction of the evolved gases calculated from the analytical values with the total mass-loss during the thermal decompositions measured by TG.     

溶剂极性对微波辐射老化制备前驱体及CuO/ZnO/Al2O3催化剂结构的影响

在制备CuO/ZnO/Al2O3催化剂的老化过程中,采用微波辐射老化技术,着重研究了溶剂极性对前躯体物相组成,烧后CuO/ZnO/Al2O3催化剂结构及其在浆态床合成甲醇工艺中催化性能的影响。通过XRD、DTG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂表征表明,沉淀母液在微波辐射条件下进行老化,溶剂的极性对前躯体物相组成及催化剂结构影响显著。随着溶剂极性的增大,Zn2+/Cu2+取代Cu2(CO3)(OH)2/Zn5(CO3)2(OH)6中Cu2+/Zn2+的取代反应增强,使得前躯体中(Cu,Zn)5(CO3)2(OH)6和(Cu,Zn)2(CO3)(OH)2物相的含量增多,结晶度提高,导致烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用增强,且CuO晶粒减小,表面Cu含量增加,催化剂活性和稳定性提高。水溶剂的极性最大,制备的催化剂活性和稳定性最好,甲醇的时空收率(STY)和平均失活率分别为320 mg.g-1.h-1和0.11%.d-1。     

Copper/Zinc Oxide Catalysts. Part XII. Solid Solution Formation in the CuO/ZnO System. X-Ray Powder Diffraction Study

Summary. Coordination compounds Zn(mal)(H₂O)₂ (ZMH) (mal=maleate anion (C₂H₂(CO₂)₂^2-)), Cu_0.06Zn_0.94(mal)(H₂O)₂ (ZCMH), Cu(mal)(H₂O) (CMH), and physical mixtures of CMH and ZMH were used as precursors for calcination experiments in air at 500 and 1000°C lasting 18 hours. The obtained oxides were investigated by X-ray powder diffraction technique. Calcination at 500°C yielded pure zincite phase (ZnO), tenorite phase (CuO), or their mixtures. The calcination of the Zn-rich sample ZCMH at 1000°C lead to zincite phase displaying a slightly lower cell volume than the pure zincite phase obtained from Zn-only containing precursor (ZMH). These results suggest that the assumed solid solution Cu_xZn_1–xO (x=0.01–0.02) exhibits a solubility limit lower than the copper content in the ZCMH precursor (6mol-%). On the other hand, the calcination of the Cu-rich samples at 1000°C, in the presence of Zn(II), yielded tenorite phase exhibiting cell parameters significantly different from those reported for the pure tenorite phase, due to the formation of Zn_0.03Cu_0.97O solid solutions. All these results are corroborated by intensity analysis of the diffraction peaks.     

Copper/Zinc Oxide Catalysts. Part XII. Solid Solution Formation in the CuO/ZnO System. X-Ray Powder Diffraction Study

Coordination compounds Zn(mal)(H₂O)₂ (ZMH) (mal=maleate anion (C₂H₂(CO₂)₂^2-)), Cu_0.06Zn_0.94(mal)(H₂O)₂ (ZCMH), Cu(mal)(H₂O) (CMH), and physical mixtures of CMH and ZMH were used as precursors for calcination experiments in air at 500 and 1000°C lasting 18 hours. The obtained oxides were investigated by X-ray powder diffraction technique. Calcination at 500°C yielded pure zincite phase (ZnO), tenorite phase (CuO), or their mixtures. The calcination of the Zn-rich sample ZCMH at 1000°C lead to zincite phase displaying a slightly lower cell volume than the pure zincite phase obtained from Zn-only containing precursor (ZMH). These results suggest that the assumed solid solution Cu_xZn_1–xO (x=0.01–0.02) exhibits a solubility limit lower than the copper content in the ZCMH precursor (6mol-%). On the other hand, the calcination of the Cu-rich samples at 1000°C, in the presence of Zn(II), yielded tenorite phase exhibiting cell parameters significantly different from those reported for the pure tenorite phase, due to the formation of Zn_0.03Cu_0.97O solid solutions. All these results are corroborated by intensity analysis of the diffraction peaks.     

Two polymorphic forms of a mixed zinc/copper biquinoline dihydrogenphosphate

Two polymorphic forms of a mixed zinc/copper biquinoline dihydrogenphosphate are presented, showing almost identical monomeric units, viz. (2,2′‐biquinoline‐κ²N,N′)bis(dihydrogenphosphato‐κO)copper(II)/zinc(II), formulated as [Zn_xCu_1−x(H₂PO₄)₂(C₁₈H₁₂N₂)], with x = 0.88 (1) and 0.90 (2). The cation is tetrahedrally coordinated to a chelating biquinoline system and two diprotonated phosphate anions. The structures differ mainly in their intermolecular hydrogen‐bonding interactions, leading to different packing schemes. No significant evidence of stress due to the Zn/Cu solid solution formation was detected.     

The first di‐μ‐hydro­xo‐bridged binuclear copper complex containing a bis‐guanidine ligand

The present structure determination of di‐μ‐hydroxo‐bis{[N,N′‐bis­(dipiperidino­methyl­ene)­propane‐1,3‐di­amine‐κ²N,N′]copper(II)} bis­(hexa­fluoro­phosphate), [Cu₂(OH)₂(C₂₅H₄₆N₆)₂](PF₆)₂, is the first to crystallographically characterize a Cu₂(μ‐OH)₂ complex with a bidentate guanidine ligand. The cation lies on a crystallographic inversion centre and shows planar fourfold coordination of the copper centres. The Cu₂(μ‐OH)₂ species can be distinguished from Cu₂(μ‐O)₂ by the Cu—O bond lengths. The packing is determined by strong intermolecular anion–cation hydrogen bonds.     

Mass spectrometric and thermal analyses of the salt system Zn<Subscript>2</Subscript>(OH)<Subscript>2</Subscript>CO<Subscript>3</Subscript> · <Emphasis Type="Italic">x</Emphasis>H<Subscript>2</Subscript>O-NaCl

The gas phase over nanocomposites consisting of zinc carbonate hydroxide (ZCH) Zn₂(OH)₂CO₃ · xH₂O(x = 1, 3) dispersed in a NaCl matrix has been characterized by high-temperature mass spectrometry and on-line FTIR spectroscopy coupled with thermal analysis. Volatile zinc-sodium chloro complexes are in equilibrium with ZCH-rich nanocomposites at 20–700°C under mass spectrometric conditions. This is evidence that sodium chloride reacts readily with zinc oxide nanoparticles. The thermal events in the ZCH-NaCl (Li₂CO₃) system have been investigated by differential scanning calorimetry.     

Preparation and thermal analysis of synthetic malachite CuCO3·Cu(OH)2

The synthesis of malachite CuCO₃·Cu(OH)₂ or Cu₂CO₃(OH)₂ was studied through titrations of copper(II) salt solutions with a solution of sodium carbonate at different temperatures. The precipitates were characterized by TG, IR and chemical analysis. The composition varies depending on thepH of the solution and the temperature. Purer malachite was synthesized by simple mixing of a solution of copper(II) nitrate or sulfate with a solution of sodium carbonate at 50°C.The kinetics of the thermal decomposition of synthetic malachite was described by eitherR ₃ orA _m(m=1.2–1.4) law, according to TG analysis, both isothermal and nonisothermal. The Arrhenius parameters determined using three different integral methods showed the kinetic compensation effect, which is correlated to the working temperature interval analyzed.The authors thank Mr. H. Takemoto for analyzing kinetics of the thermal decomposition of synthetic malachite.     

Thermodynamic Investigation of Phase Equilibria in Metal Carbonate–Water–Carbon Dioxide Systems

 Solubility measurements as a function of temperature have been shown to be a powerful tool for the determination of thermodynamic properties of sparingly-soluble transition metal carbonates. In contrast to calorimetric methods, such as solution calorimetry or drop calorimetry, the evaluation of solubility data avoids many systematic errors, yielding the enthalpy of solution at 298.15 K with an estimated uncertainty of ±3 kJ · mol⁻¹. A comprehensive set of thermodynamic data for otavite (CdCO₃), smithsonite (ZnCO₃), hydrozincite (Zn₅(OH)₆(CO₃)₂), malachite (Cu₂(OH)₂CO₃), azurite (Cu₃(OH)₂(CO₃)₂), and siderite (FeCO₃) was derived. Literature values for the standard enthalpy of formation of malachite and azurite were disproved by these solubility experiments, and revised values are recommended. In the case of siderite, data for the standard enthalpy of formation given by various data bases deviate from each other by more than 10 kJ · mol⁻¹ which can be attributed to a discrepancy in the auxiliary data for the Fe²⁺ ion. A critical evaluation of solubility data from various literature sources results in an optimized value for the standard enthalpy of formation for siderite. The Davies approximation, the specific ion-interaction theory, and the Pitzer concept are used for the extrapolation of the solubility constants to zero ionic strength in order to obtain standard thermodynamic properties valid at infinite dilution, T = 298.15 K, and p = 10⁵ Pa. The application of these electrolyte models to both homogeneous and heterogeneous (solid-solute) equilibria in aqueous solution is reviewed.     

Heterometallic copper-lanthanum complexes of 4-(1H)-pyridone

Summary Reaction of Cu(OAc)₂, 4-(1H)-pyridone (LH) and Dy or Gd nitrate in MeOH resulted in the formation of the heterometallic complexes [Cu₂LnL₂(LH)₂(NO₃)(OH)₄· xH₂O], Ln = Dy (1) or Gd (2). Reaction of Cu(OH)₂ with 4-(1H)-pyridone and Dy(NO₃)₃ in DMF resulted in the formation of the heterometallic compound [Cu₂DyL₂(LH)₂(NO₃)₂(OH)₃·DMF] (3). The Cu complexes [Cu(OAc)L]₂ and [CuL₂·DMF] _x have also been prepared from the reaction of 4-(1H)-pyridone with Cu²⁺ in MeOH and DMF, respectively. All the complexes were characterized by elemental analyses, and i.r. and X-band e.s.r. spectroscopies.     

Mineral formation from aqueous solution,part II. The stability of langite,Cu4So4(OH)6 · H2O

Summary Naturally occurring waters in the vicinity of complex Cu orebodies have been collected where they are responsible for the precipitation of solid langite, Cu₄SO₄(OH)₆ · H₂O, and malachite, Cu₂CO₃(OH)₂. The solutions were analysed and from computer fitting of results the solubility product of langite has been calculated as log K_sp=–17.3 (0.2). This value has enabled the stability field of langite to be estimated and the relationship of this compound to other basic cupric sulphates is discussed.Part I. A. K Alawn and P. A Williams,Transition Met. Chem., 78/104     

Cu‐Based Catalyst Resulting from a Cu,Zn,Al Hydrotalcite‐Like Compound: A Microstructural,Thermoanalytical, and In Situ XAS Study

A Cu‐based methanol synthesis catalyst was obtained from a phase pure Cu,Zn,Al hydrotalcite‐like precursor, which was prepared by co‐precipitation. This sample was intrinsically more active than a conventionally prepared Cu/ZnO/Al₂O₃ catalyst. Upon thermal decomposition in air, the [(Cu_0.5Zn_0.17Al_0.33)(OH)₂(CO₃)_0.17] ? mH₂O precursor is transferred into a carbonate‐modified, amorphous mixed oxide. The calcined catalyst can be described as well‐dispersed “CuO” within ZnAl₂O₄ still containing stabilizing carbonate with a strong interaction of Cu²⁺ ions with the Zn–Al matrix. The reduction of this material was carefully analyzed by complementary temperature‐programmed reduction (TPR) and near‐edge X‐ray absorption fine structure (NEXAFS) measurements. The results fully describe the reduction mechanism with a kinetic model that can be used to predict the oxidation state of Cu at given reduction conditions. The reaction proceeds in two steps through a kinetically stabilized Cu^I intermediate. With reduction, a nanostructured catalyst evolves with metallic Cu particles dispersed in a ZnAl₂O₄ spinel‐like matrix. Due to the strong interaction of Cu and the oxide matrix, the small Cu particles (7 nm) of this catalyst are partially embedded leading to lower absolute activity in comparison with a catalyst comprised of less‐embedded particles. Interestingly, the exposed Cu surface area exhibits a superior intrinsic activity, which is related to a positive effect of the interface contact of Cu and its surroundings.     

Thermodynamic Investigation of Phase Equilibria in Metal Carbonate–Water–Carbon Dioxide Systems

Summary.  Solubility measurements as a function of temperature have been shown to be a powerful tool for the determination of thermodynamic properties of sparingly-soluble transition metal carbonates. In contrast to calorimetric methods, such as solution calorimetry or drop calorimetry, the evaluation of solubility data avoids many systematic errors, yielding the enthalpy of solution at 298.15 K with an estimated uncertainty of ±3 kJ · mol⁻¹. A comprehensive set of thermodynamic data for otavite (CdCO₃), smithsonite (ZnCO₃), hydrozincite (Zn₅(OH)₆(CO₃)₂), malachite (Cu₂(OH)₂CO₃), azurite (Cu₃(OH)₂(CO₃)₂), and siderite (FeCO₃) was derived. Literature values for the standard enthalpy of formation of malachite and azurite were disproved by these solubility experiments, and revised values are recommended. In the case of siderite, data for the standard enthalpy of formation given by various data bases deviate from each other by more than 10 kJ · mol⁻¹ which can be attributed to a discrepancy in the auxiliary data for the Fe²⁺ ion. A critical evaluation of solubility data from various literature sources results in an optimized value for the standard enthalpy of formation for siderite. The Davies approximation, the specific ion-interaction theory, and the Pitzer concept are used for the extrapolation of the solubility constants to zero ionic strength in order to obtain standard thermodynamic properties valid at infinite dilution, T = 298.15 K, and p = 10⁵ Pa. The application of these electrolyte models to both homogeneous and heterogeneous (solid-solute) equilibria in aqueous solution is reviewed. Received June 26, 2001. Accepted July 2, 2001     

Synthesis and thermolysis of substitutional solid solutions (Cu1?yMy)2(OH)PO4·xH2O (x = 0.1?0.2; M = Zn, Co, Ni)

Substitutional solid solutions (Cu_1−y Zn _y )₂(OH)PO₄·xH₂O (0 ≤ y ⩽ 0.26, x = 0.1−0.2), (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2), and (Cu_1−y Ni _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.08, x = 0.1−0.2) were synthesized. The unit cell parameters of the resulting phosphates were determined, and their IR absorption spectra were measured. The reactants were H3PO4 and mixtures of hydrous carbonates of the appropriate metals. Thermolysis of the solid solutions was examined with (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2) as an example.