Quantitative Analysis of Phases Formed During The Oxidation of Covellite (CuS)

A sample of covellite of particle size 45–90 μm was heated in air at 20°C min^–1 in a simultaneous TG-DTA apparatus. The phase compositions of the products at various temperatures were determined quantitatively by XRD and FTIR. By 500°C, 5.8% of Cu₂ O had formed, and this increased to a maximum of 44.8% at 585°C after which it decreased to zero by 750°C. 10% of CuO had formed by 680°C, and then steadily increased to 83.6% at 1000°C. 5.9% of CuO⋅CuSO₄ was found at 610°C, and increased to a maximum value of 79% after which it decomposed completely by 820°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of basic copper sulphate monohydrate

The thermal decomposition of copper sulphate hydroxide hydrate, (CuO·CuSO₄). 2Cu(OH)₂·H₂O, to copper oxysulphate and CuO was investigated by X-ray phase analysis, IR spectroscopy, complex thermal analysis and electron microscopy. The effect of water vapour and time of treatment on the formation of decomposition products with a large surface area is studied. The strong decrease in specific surface area of the precipitate (from 80 m²/g to 20 m²/g) thermally treated at a temperature above 250°C is associated with the elimination of water having a coordination bond with the Cu²⁺ ion. During this process, the interplanar distances of the crystal lattice of copper sulphate hydroxide hydrate decrease. The time of decomposition of this compound essentially affects the decrease of the specific surface area. When the decomposition proceeds in an atmosphere containing water vapour sintering processes are predominating and the phase obtained has a considerably smaller specific surface area than in cases of decomposition under dry air.     

Quantitative determination of phases present in oxidised chalcocite

A sample of chalcocite (Cu₂S) of particle size 45–75 m was heated in air at 10°C min^–1 in a simultaneous TG-DTA apparatus. The phase compositions of the products at various temperatures were quantitatively determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and wet chemical analyses. Copper(II) sulfate, of amount 1.7% by mass, was observed at 435°C and increased rapidly in concentration to 56% at 570°C. From 570–670°C, there was a rapid decrease in CuSO₄ content to 9.8% as the phase converted to CuSO₄·CuO, with the CuSO₄ not being detected at 775°C. From 435–570°C, Cu₂O formed, but at a rather slower rate, reaching 47% at 570°C. The Cu₂O level then decreased to 38% over the range 570–670°C. CuSO₄·CuO was first detected at 570°C by FTIR, although it was not detected by XRD at this temperature. The content of this species reached 41% at 670°C, decreased to 24% at 775°C, and was not detected at 840°C. CuO first appeared at 670°C and rose steadily in concentration until at 840°C it was the only compound present.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Formation and characterization of Cu<Subscript>x</Subscript>S layers on polyethylene film using the solutions of sulfur in carbon disulfide

Results of the formation of copper sulfide layers using the solutions of elemental sulfur in carbon disulfide as precursor for sulfurization are presented. Low density polyethylene film can be effectively sulfurized in the solutions of rhombic (α) sulfur in carbon disulfide. The concentration of sulfur in polyethylene increases with the increase of the temperature and concentration of sulfur solution in carbon disulfide and it little depends on the duration of sulfurization. Electrically conductive copper sulfide layers on polyethylene film were formed when sulfurized polyethylene was treated with the solution of copper (II/I) salts. Cu_xS layer with the lowest sheet resistance (11.2 Ω cm⁻²) was formed when sulfurized polyethylene was treated with copper salts solution at 80°C. All samples with formed Cu_xS layers were characterized by X-ray photoelectron spectroscopy. XPS analysis of obtained layers showed that on the layer’s surface and in the etched surface various compounds of copper, sulfur and oxygen are present: Cu₂S, CuS, CuO, S₈, CuSO₄, Cu(OH)₂ and water. The biggest amounts of CuSO₄ and Cu(OH)₂ are present on the layer’s surface. Significantly more copper sulfides are found in the etched layers.     

Study on thermal decomposition of copper(II) acetate monohydrate in air

The thermal decomposition of copper(II) acetate monohydrate (CuAc₂·H₂O) under 500 °C in air was studied by TG/DTG, DTA, in situ FTIR and XRD experiments. The experimental results showed that the thermal decomposition of CuAc₂·H₂O under 500 °C in air included three main steps. CuAc₂·H₂O was dehydrated under 168 °C; CuAc₂ decomposed to initial solid products and volatile products at 168–302 °C; the initial solid products Cu and Cu₂O were oxidized to CuO in air at 302–500 °C. The copper acetate peroxides were found to form between 100 and 150 °C, and the dehydration of these peroxides resulted in the presence of CuAc₂·H₂O above 168 °C. The initial solid products were found to be the admixture of Cu, Cu₂O, and CuO, not simply the single Cu₂O as reported before. Detailed reactions involved in these three steps were proposed to describe the complete mechanism and course of the thermal decomposition of CuAc₂·H₂O in air.     

Synthesis of CuO nanoparticles via one-pot wet-chemical method and its catalytic performance on the thermal decomposition of ammonium perchlorate

Sphere-like CuO products aggregated by numerous nanoparticles were fabricated by a low-temperature (50°C) wet chemical method using CuSO₄·5H₂O as precursor. The possible formation processes of CuO were investigated by a series of single-factor experiments. The CuO was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selectedarea electron diffraction. Furthermore, the application of CuO nanoparticles on the thermal decomposition of ammonium perchlorate was studied with 2 wt % CuO nanoparticles at heating rates of 10, 15, 20, and 25°C min^–1 from 35 to 500°C.     

Solid-state reactions in the system Cu—Sb—O; Formation of a new copper(I) antimony oxide

The solid-state reactions in the system Cu—Sb—O were investigated by thermogravimetry and X-ray diffraction. Equimolar mixtures of CuO and Sb₂O₃ form Cu(II)Sb₂O₆ when slowly heated in air up to 1000°C. The firt step in this reaction is the oxidation of Sb₂O₃ to Sb₂O₄ at 380–500°C, followed by further oxidation of Sb₂O₄ and the formation of CuSb₂O₆ at 500–1000°C. Thermal decomposition of CuSb₂O₆ in a flowing nitrogen atmosphere occurs in three stages; the first, with an activation energy of 356 kJ mole^?1, results in the formation of a new copper(I) antimony oxide, with a composition of Cu₄SbO_4.5, as determined by atomic absorption analysis and X-ray fluoresecence. Confirmation of predominantly monovalent copper and pentavalent antimony in the new compound was by ESR and ESCA, respectively. Two forms of Cu₄SbO_4.5 have been distinguished; one of these (form II) has a structure of lower symmetry, and decomposes when heated in air at 600°C to a mixture of CuO and another new copper antimony oxide, as yet uncharacterized. On further heating to 1100°C in air, Cu₄SbO_4.5 (form I) gradually reforms. Details of these reactions are summarized and X-ray powder data presented for Cu₄SbO_4.5.     

Hybrid silica-organic material with immobilized amino groups: surface probing and use for electrochemical determination of nitrite ions

A sol–gel based hybrid process was developed by manipulating different techniques in sol–gel process to synthesize γ-alumina and (CuO, CuO + ZnO) doped γ-alumina spherical particles. Catalysts having spherical geometry have an important advantage over powders or pellets which are impervious to fluids, when packed in a reactor. Boehmite sol was used as alumina precursor for synthesizing porous γ-alumina and doped materials. γ-alumina particles having 5 wt% CuO, 4 wt% CuO + 1 wt% ZnO, 3 wt% CuO + 2 wt% ZnO and 2 wt% CuO + 3 wt% ZnO were prepared by adding required amounts of Cu(NO₃)₂ and Zn(NO₃)₂ solutions prior to gelation of the sol. Methanol dehydration studies were carried out by employing these synthesized catalysts. Hundred percent conversion of methanol to dimethyl ether was observed with (4 wt% CuO + 1 wt% ZnO)-γ-alumina and (5 wt% CuO)-γ-alumina microspheres at 325 and 350 °C, respectively.     

Über Kupfer(I)-sulfat Cu2SO4. Darstellung und thermische Eigenschaften

Preparation and Thermal Properties of Copper(I) Sulfate Cu₂SO₄ Copper(I) sulfate Cu₂SO₄ can be prepared in high purity by reaction of Cu₂O with dimethyl sulfate (CH₃)₂SO₄ at 160°C in an argon atmosphere. Using an extremely fine grained Cu₂O, as obtained by reduction of cupric acetate with hydrazine, and a reaction time of 10 minutes a Cu₂SO₄ is obtained that contains less than 1% Cu₂O. Longer reaction times lead to partial decomposition of the Cu₂SO₄ to Cu(met.) and CuSO₄. In a closed system Cu₂SO₄ melts at about 400°C, however, the melt rapidly decomposes to Cu and CuSO₄, solidifying simultaneously. When heated in a thermoanalyzer in flowing argon or in a vacuum, Cu and CuSO₄ react under liberation of SO₂. Increasing the temperature leads to CuO in three steps, which converts to Cu₂O when heated to 1000°C. The question of formation of Cu₂SO₄, occasionally mentioned in the literature, being responsible for the liquid phases observed in the system Cu? S? O at temperatures below 500°C, is discussed.     

Synthesis and characterisation of phenoxo bridged dinuclear complexes of copper(II)

A series of model complexes for the type III site, in oxidised hemocyanin, containing Cu₂(μ-0Ph)³⁺ core have been synthesised using a heptadentate ligand (H₃L) formed from the Schiff base condensation of triethylenetetramine and salicylaldehyde. The ligand provides one imine and one inbuilt imidazole nitrogen and two phenolic oxygen donors with both five- and six-membered chelate rings to each metal centre. In the pentacoordinated complexes [Cu₂(L)X]·nH₂O, a third exogenous bridging ligand is present. The TG curve indicates the loss of lattice water molecules between 70 and 125°C. The residue after decomposition is CuO above 550°C. Theg values of theX-band EPR spectrum of [Cu₂L(μ-OAc)]·2H₂O in methanol glass (77 K) are typical of a variety of bridged copper(II) dimers. The copper-copper magnetic interaction is dependent on the presence and nature of X in these complexes.     

Mechanism of CO oxidation in excess H2 over CuO/CeO2 catalysts: ESR and TPD studies

The oxidation of CO with oxygen over (0.25–6.4)% CuO/CeO₂ catalysts in excess H₂ is studied. CO conversion increases and the temperature range of the reaction decreases by 100 K as the CuO content is raised. The maximal CO conversion, 98.5%, is achieved on 6.4% CuO/CeO₂ at 150°C. At T > 150°C, the CO conversion decreases as a result of the deactivation of part of the active sites because of the dissociative adsorption of hydrogen. CO is efficiently adsorbed on the oxidized catalyst to form CO-Cu⁺ carbonyls on Cu₂O clusters and is oxidized by the oxygen of these clusters, whereas it is neither adsorbed nor oxidized on Cu⁰ of the reduced catalysts. The activity of the catalysts is recovered after the dissociative adsorption of O₂ on Cu⁰ at T ～ 150°C. The activation energies of CO, CO₂, and H₂O desorption are estimated, and the activation energy of CO adsorption yielding CO-Cu⁺ carbonyls is calculated in the framework of the Langmuir-Hinshelwood model.     

Beiträge zum thermischen Verhalten von Sulfaten. VI. Zum chemischen Transport von CuSO4, Cu2OSO4 und CuO

Contributions on the Thermal Behaviour of Sulfates. VI. On the Chemical Transport of CuSO₄, Cu₂OSO₄, and CuO A powder of anhydrous CuSO₄ can be prepared by heating CuSO₄ · 5 H₂O in air or in an argon atmosphere. In the same way it is possible to get a powder of Cu₂OSO₄. But up to now, it was difficult to get crystals of CuSO₄ and there was no method known to synthesize crystals of Cu₂OSO₄. Investigations concerning chemical transport reactions of anhydrous heavy metal sulfates showed, that it is possible to get well formed crystals of CuSO₄ and Cu₂OSO₄ by deposition from a vapour phase. As transport agents for CuSO₄, Cl₂ and HgCl₂ are especially suitable. Less appropriate are HCl, NH₄Cl, and I₂. The chemical vapor deposition of Cu₂OSO₄ proceeds well with HgCl₂. In course of these investigations we recognized, that for CuO in addition to the well approved transport agents also Cl₂, HgCl₂ or I₂ (NH₄Cl less suitable) can successfully be used.     

Co oxidation with oxygen in the presence of hydrogen on CoO/CeO<Subscript>2</Subscript> and CuO/CoO/CeO<Subscript>2</Subscript> catalysts

The catalytic activity of the CoO/CeO₂ and CuO/CoO/CeO₂ systems in selective CO oxidation in the presence of hydrogen at 20–450°C ([CuO] = 1.0–2.5%, [CoO] = 1.0–7.0%) is reported. The maximum CO conversion (X) decreases in the following order: CuO/CoO/CeO₂ (X = 98–99%, T = 140–170°C) > CoO/CeO₂ (X = 67–84%, T = 230–240°C) > CeO₂ (X = 34%, T = 350°C). TPD, TPR, and EPR experiments have demonstrated that the high activity of CuO/CoO/CeO₂ is due to the strong interaction of the supported copper and cobalt oxides with cerium dioxide, which yields Cu-Co-Ce-O clusters on the surface. The carbonyl group in the complexes Co^δ+-CO and Cu⁺-CO is oxidized by oxygen of the Cu-Co-Ce-O clusters at 140–160°C and by oxygen of the Co-Ce-O clusters at 240°C. The decrease in the activity of the catalysts at high temperatures is due to the fact that hydrogen reduces the clusters on which CO oxidation takes place, yielding Co⁰ and Cu⁰ particles, which are inactive in CO oxidation. The hydrogenation of CO into methane at high temperatures is due to the appearance of Co⁰ particles in the catalysts.     

Effect of the microstructure of the supported catalysts CuO/TiO<Subscript>2</Subscript> and CuO/(CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>) on their catalytic properties in carbon monoxide oxidation

The effect of the microstructure of titanium dioxide on the structure, thermal stability, and catalytic properties of supported CuO/TiO₂ and CuO/(CeO₂-TiO₂) catalysts in CO oxidation was studied. The formation of a nanocrystalline structure was found in the CuO/TiO₂ catalysts calcined at 500°C. This nanocrystalline structure consisted of aggregated fine anatase particles about 10 nm in size and interblock boundaries between them, in which Cu²⁺ ions were stabilized. Heat treatment of this catalyst at 700°C led to a change in its microstructure with the formation of fine CuO particles 2.5–3 nm in size, which were strongly bound to the surface of TiO₂ (anatase) with a regular well-ordered crystal structure. In the CuO/(CeO₂-TiO₂) catalysts, the nanocrystalline structure of anatase was thermally more stable than in the CuO/TiO₂ catalyst, and it persisted up to 700°C. The study of the catalytic properties of the resulting catalysts showed that the CuO/(CeO₂-TiO₂) catalysts with the nanocrystalline structure of anatase were characterized by the high-est activity in CO oxidation to CO₂.     

Construction of Cu-Ce interface for boosting toluene oxidation: Study of Cu-Ce interaction and intermediates identified by in situ DRIFTS

A facile hydrothermal method was applied to gain stably and highly efficient CuO-CeO₂ (denoted as Cu1Ce2) catalyst for toluene oxidation. The changes of surface and inter properties on Cu1Ce2 were investigated comparing with pure CeO₂ and pure CuO. The formation of Cu-Ce interface promotes the electron transfer between Cu and Ce through Cu²⁺ + Ce³⁺ ↔ Cu⁺ + Ce⁴⁺ and leads to high redox properties and mobility of oxygen species. Thus, the Cu1Ce2 catalyst makes up the shortcoming of CeO₂ and CuO and achieved high catalytic performance with T₅₀ = 234 °C and T₉₉ = 250 °C (the temperature at which 50% and 90% C₇H₈ conversion is obtained, respectively) for toluene oxidation. Different reaction steps and intermediates for toluene oxidation over Cu1Ce2, CeO₂ and CuO were detected by in situ DRIFTS, the fast benzyl species conversion and preferential transformation of benzoates into carbonates through C=C breaking over Cu1Ce2 should accelerate the reaction.     

Preparation of highly dispersed copper oxide by thermal destruction of binuclear CuII monofluoroacetate in zeolite Y cavities

Thermal destruction of the binuclear monofluoroacetate complex Cu₂(CH₂FCOO)₄ deposited on zeolite Y was studied by the TG-DTA and ESR methods. Large particles of copper oxide are not formed and fine dispersion of CuO in the matrix is observed due to low temperatures of the destruction of the supported complex (240–250°C) and restriction of the process mainly to large cavities of the zeolite. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1371–1374, August, 2000.     

纳米复合氧化物CuO·SnO2的制备与结构表征

0引言由于纳米材料在热学、电学、磁学、光学等方面具有的独特性能,使其在新功能材料、催化、光电能转换等许多领域引起了人们浓厚的研究兴趣[1]。近年来,纳米催化剂对固体推进剂的燃烧性能影响研究已成为热点[2～9]。但是由于固体推进剂燃烧的特殊性,要求不仅提高燃速,而且降低压力指数,因此并非所有的纳米催化剂都是有效的。大量实践已证明[10],多种催化剂的复合使用,将可获得远远优于单一催化剂的效果。研究已发现[11],纳米复合氧化物是由多种元素复合而成,使其在结构和性能上得到互补和叠加,加上纳米粒子所具有的各种效应,从而产生独特…     

Preparation,Characterization, and Catalytic Behavior of Nanostructured Mesoporous CuO/ZrO2 Catalysts for Low-Temperature CO Oxidation

High-surface area mesoporous 20 mol% CuO/ZrO₂ catalyst was prepared by a surfactant-assisted method of nanocrystalline particle assembly, and characterized by x-ray powder diffraction (XRD), N₂ adsorption, transmission electron microscopy (TEM), H₂-TPR, TG-DTA, and x-ray photoelectron spectra (XPS) techniques. The catalytic properties of the CuO/ZrO₂ nanocatalysts calcined at different temperature were evaluated by low-temperature carbon monoxide oxidation using a CATLAB system. The results showed that these mesoporous nanostructured CuO/ZrO₂ catalysts were very active for low-temperature CO oxidation and the CuO/ZrO₂ catalyst calcined at 400°C exhibited the highest catalytic activity.     

Studies on thermal oxidation of chalcopyrite from Chitradurga,Karnataka State,India

When chalcopyrite is heated in air, up to 350? there is no marked change. Between 350 and 440?, surface material is oxidised to iron sulphate, CuSO₄ and Fe₂O₃, while in regions not accessible to oxygen the formation of Cu₅FeS₄, FeS and S takes place. From 440 to 500? oxidation and sulphation phenomena occur. Stable compounds between 500 and 650? are iron sulphate, CuSO₄ and Fe₄O₃, with a minor amount of 6CuO.Cu₂O indicated at 650?. After the decomposition of iron sulphate, CuSO₄ decomposes, first to CuO.CuSO₄ and then to CuO. By 750? the sulphur has been totally lost from all compounds, while the oxides of copper and iron partly react to form CuFe₂O₄. Final products of oxidation between 800 and 850? are CuO, CuFe₂O₄ and Fe₃O₄.     

Phase equilibria and thermodynamics of the double oxide phase Cu3TiO4

Phase equilibria in the system CuCu₂OTiO₂ were investigated in the temperature range of 1160–1270 K by means of thermogravimetry and measurements of the oxygen partial pressure. The tie lines on the isothermal phase diagram run from the phase Cu₃TiO₄ to CuO, Cu₂O, and TiO₂. The existence of Cu₃TiO₅ and Cu₂TiO₃ could not be confirmed in this temperature range. The phase “Cu₃TiO₄” is only stable above about 1140 K and its composition fluctuates between about Cu₃TiO_4.3 and Cu₃TiO_3.9. The formation of Cu₃TiO_4.3 according to the reaction 1.6 CuO + 0.7 Cu₂O + TiO₂ = Cu₃TiO_4.3 is endothermic: (1160 < T < 1270 K) ΔH° = (7600 ± 450 J-mole^?1; ΔS° = (6.7 ± 0.4) J·K^?1·mole^?1. The standard Gibbs free energy, enthalpy, and entropy of formation of Cu₃TiO_4.3 at 1200 K are ΔG°_f = ?101.39 kJ, ΔH°_f = ?1115.84 kJ, and S°_f = 466.76 J·K^?1. Rather similar values were found for Cu₃TiO_3.9.