Copper Hydroxycarbonate Research Articles

Substitution of Copper by Magnesium in Malachite: Insights into the Synthesis and Structural Effects.

The phase width of the copper hydroxycarbonate malachite, Cu2CO3(OH)2, upon substitution with magnesium has been studied in detail. In extension of a previous study on amorphous precursors, the introduction of a hydrothermal aging step allowed the retrieval of crystalline hydroxycarbonate samples with up to 37 atom % Mg (metal content) that are suitable candidates as precursors to Cu/MgO catalysts for CO hydrogenation. Simultaneous refinements of X-ray powder diffraction and pair distribution function (PDF) data as well as complementary spectroscopic insight (X-ray absorption and infrared spectroscopy) revealed that samples with up to 18 atom % Mg are phase-pure magnesian malachites but the magnesium content can be increased beyond this threshold when mcguinnessite (CuMgCO3(OH)2) is accepted as a side phase. In a complementary study, a continuous increase of the magnesium fraction was found during aging and the corresponding structural evolution was studied by means of PDF. These findings add significant insight into the aging chemistry of crystalline Cu,Mg hydroxycarbonates. Furthermore, both phase-pure magnesian malachite and mcguinnessite-containing samples with up to 37 atom % Mg have been examined by thermogravimetry, X-ray powder diffraction, and N2 physisorption and were found to be promising candidates for use as precursors for the preparation of Cu/MgO catalysts.

Combustion and Decay Resistance Performance of Scots Pine Treated with Boron and Copper Based Wood Preservatives

Boron compounds in the form of boric acid, borax or disodiumoctaborate tetrahydrate have been used as insecticide, fungicide and fire retardant in wood preservatives industry for decades. Also, copper is the most commonly used component in most of relatively modern preservatives as it is highly effective against fungi. The objective of this study was to investigate the combustion and decay resistance of boron-copper based solutions which were developed by our group. These solutions contain boric acid, sodium borate decahydrate, copper hydroxy carbonate, ethanolamine, quaternary ammonium compound (benzalkonium chloride), and/or organic acid (octanoic acid). Scots Pine (Pinus sylvestris) woods were treated with the preservatives according to ASTM D1413-07 standard by vacuum-pressure impregnation system, which was developed by our group. Decay resistance performances against white and brown rot fungi were determined according to EN 113 standard and combustion tests were performed with respect to ASTM E160-50 standard. All the impregnated wood samples were found highly resistant to both white (Trametes versicolor L.) and brown (Coniophora puteana L.) fungi. Besides, they gave better results than the control samples in terms of combustion tests.

CO Hydrogenation to Methanol over Cu/MgO Catalysts and Their Synthesis from Amorphous Magnesian Georgeite Precursors

AbstractThe synthesis of Mg‐substituted copper hydroxycarbonates by constant‐pH co‐precipitation with subsequent ageing of the precipitate has been studied in detail. This allowed the retrieval of crystalline magnesian malachite samples, which showed a “radical‐sign‐shaped” pH drop and the blue/green color change during ageing that is well‐known from the analogous Cu/Zn system. The crystallization of Cu‐rich samples has been studied elaborately by means of powder diffraction, pair distribution function (PDF), and infrared spectroscopy, thus elucidating the ageing chemistry of Cu,Mg hydroxycarbonates in general. It was found that up to 17 % Mg can be incorporated into the crystalline malachite using a synthesis route comparable to that established for Cu/ZnO catalysts, but with drastically elongated precipitate ageing times. For higher Mg contents, a step‐like pH drop was observed instead, and an amorphous variant of the hydroxycarbonate, referred to as “magnesian georgeite”, could be isolated. From such a Mg‐rich sample (Cu/Mg 70 : 30 at. %), a Cu/MgO catalyst has been prepared that shows high activity and good stability in CO hydrogenation to methanol over 800 hrs. time on stream.

Geochemical factors affecting the solubility of copper in seawater

Environmental contextMany trace metals, including copper, are only sparingly soluble in seawater and may exist in both dissolved and particulate forms (e.g. as precipitates). Aquatic organisms may experience different toxic effects from exposure to dissolved and particulate trace metals. This study investigates how concentration, reaction time and changes to precipitate composition/mineral formation affect copper solubility in seawater, thus influencing metal bioavailability and toxicity in the field and laboratory. AbstractA lack of knowledge on the solubility of metals such as copper affects the ability to predict the forms (dissolved and particulate) that organisms are exposed to in field and laboratory waters. Laboratory tests were conducted where copper (total concentrations of 0.5 to 20mg L−1) was added to natural and artificial seawater (pH 8.15, 22°C), equilibrated for 28 days and dissolved copper monitored at periodic intervals. At 0.5mg L−1, dissolved copper concentrations remained stable over 28 days and no precipitates were detected. However, at higher total copper concentrations, an initial rapid precipitation phase was followed by the establishment of a metastable equilibrium that persisted for periods of days to weeks, and whose solubility concentrations and duration were influenced by the total copper concentration and typically in the range 0.6 to 0.9mg L−1. After 5 to 15 days, a step change decrease in dissolved copper concentration followed by a slow decline was observed in the >2mg L−1 total copper treatments. The minimum solubility measured after 28 days was 0.053mg L−1. Elemental and X-ray diffraction analyses indicated that the copper precipitates comprised similar proportions of amorphous copper hydroxycarbonate and amorphous dicopper trihydroxide chloride after 1 day and transformed to predominantly mineralised dicopper trihydroxide chloride in the clinoatacamite polymorph form after 28 days. These observations have particular relevance for toxicity tests of less sensitive organisms and highlight the need to consider metal solubility, exposure to precipitates and changes in precipitate mineral phases.

Claraite, (Cu,Zn)15(AsO4)2(CO3)4(SO4)(OH)14·7H2O: redefinition and crystal structure

Since the beginning of the 2000s, several authors reported the occurrence of As and S as chemical components of the hydrated copper hydroxy-carbonate claraite, originally described with the formula (Cu,Zn) 3 (CO 3 )(OH) 4 ·4H 2 O. Owing to the lack of knowledge about the crystal structure of this mineral, the structural role played by these chemical elements was unknown. The crystal structure of claraite has now been solved from single-crystal X-ray diffraction data by using a specimen from the marble quarries of Carrara, Apuan Alps, Tuscany, Italy. Electron-microprobe analyses gave (in wt% – average of eight spot analyses): SO 3 4.00, As 2 O 5 13.16, CuO 52.64, ZnO 9.03, CO 2(calc) 9.08, H 2 O (calc) 12.56, total 100.47. On the basis of 15 (Cu + Zn) and 45 O atoms per formula unit, the chemical formula of claraite could be written as (Cu 12.85 Zn 2.15 ) Σ15.00 (AsO 4 ) 2.22 (CO 3 ) 4 (SO 4 ) 0.97 (OH) 13.40 ·6.83H 2 O, ideally (Cu,Zn) 15 (AsO 4 ) 2 (CO 3 ) 4 (SO 4 )(OH) 14 ·7H 2 O. Raman spectrometry shows bands related to bending and stretching vibrations of AsO 4 and SO 4 groups, as well as the stretching mode of CO 3 groups and O–H bonds. The unit-cell parameters of claraite are a = 10.3343(6) A, b = 12.8212(7) A, c = 14.7889(9) A, α = 113.196(4)°, β = 90.811(4)°, γ = 89.818(4)°, V = 1800.9(2) A 3 , space group P 1 ¯ . The crystal structure has been refined to R 1 = 0.111 on the basis of 6956 reflections with F o > 4σ( F o ) and 363 refined parameters. Claraite shows a layered structure, with {0 0 1} heteropolyhedral layers formed by Cuϕ 5 and Cuϕ 6 polyhedra as well as AsO 4 and CO 3 groups. These layers are stacked along c through edge-sharing Cu 2 ϕ 10 and Cu 2 ϕ 8 dimers, the former being decorated by corner-sharing SO 4 groups hosted within intra-framework channels together with H 2 O groups. Claraite is the only known mineral showing the simultaneous occurrence of essential AsO 4 , CO 3 , and SO 4 groups.

Six new 3d–4f heterometallic coordination polymers constructed from pyrazole-bridged CuIILnIII dinuclear units

Reactions of lanthanide chlorides, copper hydroxycarbonate and 3,5-pyrazole dicarboxylic acid (H3pdc) under hydrothermal conditions result in six new 3d-4f heterometallic coordination polymers with two types of structures. Compounds [CuLn2(pdc)2(Hpdc)(H2O)4]·2H2O (Ln = Tb (1), Dy (2), Er (3), and Y (4) exhibit a layered porous structure, made up of Cu(II)Ln(III) di-nuclear units which are connected by protonated Hpdc(2-) ligand, while the others [Cu3Ln4(pdc)6(H2O)8] (Ln = Eu (5), Gd (6)) display a three-dimensional (3-D) framework structure, in which six Cu(II)Ln(III) di-nuclear units are cross-linked by two coordinated lanthanide atoms. The catalytic properties of 3 are investigated showing its activity and recyclability in the reaction of cyclopropanation of styrene.

Thermal activation of copper carbonate

Much interest focuses on the use of nano-scale copper and copper oxide for catalyst use. These nano-scale chemicals are produced through the thermal decomposition of copper salts such as copper carbonate, copper hydroxy-carbonate either synthetic or natural. This paper presents some of the studies undertaken of copper carbonates.

TPR and XPS study of cobalt–copper mixed oxide catalysts: evidence of a strong Co–Cu interaction

In this work the results of a TPR and XPS investigation of CoxOy–CuO mixed oxides in the range of composition Co : Cu=100:0–8:92 are reported and compared. The final catalysts were obtained by thermal decomposition in air and N2 at 723 K for 24 h of single‐phase cobalt–copper hydroxycarbonates prepared by coprecipitation at constant pH. The Co : Cu=100 : 0 specimen calcined in air formed the Co2+[Co3]2O4 (Co3O4) spinel phase. The copper‐containing catalysts (Co : Cu=85 : 15–8 : 92) showed mainly two phases: (i) spinels, like Co2+[Co3+]2O4, Co 1-x 2+ Cu x 2+ [Co3+]2O4 and (ii) pure CuO, the relative amount of each phase depending on the Co : Cu atomic ratio. The results of the XPS study are consistent with the bulk findings and revealed the presence of Co2+, Co3+ and Cu2+ species at the catalyst surface. Moreover, the surface quantitative analysis evidenced a cobalt enrichment, in particular for the most diluted cobalt samples. The TPR study showed that the catalyst reduction is affected by a strong mutual influence between cobalt and copper. The reducibility of the mixed oxide catalysts was always promoted with respect to that of the pure Co3O4 and CuO phases and the reduction of cobalt was markedly enhanced by the presence of copper. Cobalt and copper were both reduced to metals regardless of the catalyst composition. On the other hand, the Co : Cu=100 : 0 specimen calcined in N2 formed, as expected, CoO. The initial addition of copper resulted in the formation of the Cu+Co3+O2 compound, besides CoO, up to a Co/Cu=1 atomic ratio at which the CuCoO2 phase was the main component. A further addition of copper led to the formation of CuCoO2 and CuO phases. The XPS results were in good agreement with these findings and the surface quantitative analysis revealed a less enrichment of cobalt with respect to the catalysts calcined in air. The TPR analysis confirmed that the reduction of the N2‐calcined catalysts was also remarkably promoted by the presence of copper. Also in this case cobalt and copper metal were the final products of reduction.

Steam reforming of methanol on binary [formula omitted] catalysts: Effects of preparation condition upon precursors, surface structure and catalytic activity

Precursors for Cu ZnO catalysts, with Cu Zn molar ratios in the range from 100 0 to 0 100 , were prepared by two coprecipitation methods. These methods differ by the addition rate of a mixed Cu(NO 3) 2 Zn(NO 3) 2 solution to a NaHCO 3 solution. Characterisation by powder X-ray diffraction (PXRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), FT-IR and UV/VIS spectroscopies indicated that the structure of precursors with Cu Zn ratios in the range of 30 70 to 70 30 depends greatly upon the addition rate of the mixed solution. Amorphous copper hydroxycarbonate and sodium zinc carbonate were formed prior to the various precursors such as malachite, aurichalcite and hydrozincite. The u ZnO catalysts subsequently formed from the precursors showed the activity for steam reforming of methanol to vary with its composition. Based on the results of temperature programmed oxidation (TPO) with N 2O and an infrared spectra of CO chemisorption, the TOF of the reaction is proposed to be associated with the surface of metallic Cu.

Mechanism of the formation of precursors for the Cu/ZnO methanol synthesis catalysts by a coprecipitation method

Precursors of Cu/ZnO catalysts with various Cu/Zn molar ratios were prepared by a coprecipitation method. It was found that amorphous copper hydroxycarbonate and sodium zinc carbonate were intermediates for the formation of various precursors such as hydrozincite, malachite and aurichalcite. Aurichalcite having a high Cu/Zn ratio was prepared from a mechanical mixture of these intermediates.

Surface characterization of copper(II) oxide-zinc oxide methanol-synthesis catalysts by x-ray photoelectron spectroscopy. 1. Precursor and calcined catalysts

A surface characterization of the precursor and calcined copper oxide-zinc oxide (CuO-ZnO) catalysts prepared both by coprecipitation and by impregnation methods was carried out by using x-ray photoelectron spectroscopy (XPS). Strong oxide-oxide interactions were found to result in the formation of several surface copper species in the coprecipitated catalysts. With the catalysts containing 80-30 wt % CuO, it is proposed that the CuO structure is distorted to produce amorphous copper oxide phases in the surface layer. The copper species in the catalysts with > 80 wt % CuO are composed of the Cu/sup 2 +/ ions in crystalline CuO and the amorphous phases. As for the catalysts containing less than 30 wt % CuO XPS results showed the presence of Cu/sup 2 +/ ions, which dissolved substitutionally in the ZnO lattice and formed highly covalent bondings with oxygen anions. In contrast to the coprecipitated catalysts, the impregnated catalysts showed no appreciable interactions between copper and zinc oxides. The surface copper species in the precursor catalysts were attributed to copper hydroxycarbonate in the high copper content catalysts and to the copper in zinc hydroxycarbonate in the low copper content catalysts. 5 figures, 3 tables.