Thermal Decomposition Of Cu Research Articles

In situ XPS investigations of Cu1−xNixZnAl-mixed metal oxide catalysts used in the oxidative steam reforming of bio-ethanol

A series of CuNiZnAl-multicomponent mixed metal oxide catalysts with various Cu/Ni ratios were prepared by the thermal decomposition of Cu1−xNixZnAl-hydrotalcite-like precursors and tested for oxidative steam reforming of bio-ethanol. Dehydrogenation of EtOH to CH3CHO is favored by Cu-rich catalyst. Introduction of Ni leads to CC bond rupture and producing CO, CO2 and CH4. H2 yield (selectivity) varied between 2.6–3.0mol/mol of ethanol converted (50–55%) for all catalysts at 300°C. The above catalysts were subjected to in situ XPS studies to understand the nature of active species involved in the catalytic reaction. Core level and valence band XPS as well as Auger electron spectroscopy revealed the existence of Cu2+, Ni2+ and Zn2+ ions on calcined materials. Upon in situ reduction at reactions temperatures, the Cu2+ was fully reduced to Cu0, while Ni2+ and Zn2+ were partially reduced to Ni0 and Zn0, respectively. On reduction, the nature of ZnO on Cu-rich catalyst changes from crystalline to amorphous, relatively inert and highly stabilized electronically. Relative concentration of the Ni0 and Zn0 increases upon reduction with decreasing Cu-content. Valence band results demonstrated that the overlap between 3d bands of Cu and Ni was marginal on calcined materials, and no overlap due to metallic clusters formation after reduction. Nonetheless, the density of states at Fermi level increases dramatically for Ni-rich catalysts and likely this influences the product selectivity.

Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazole

Complex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL 3) and copper(II) bromide with 5-amino-4-carboxamide-1-phenylpyrazole (L 2), 4-acetyl-3-amino-5-methylpyrazole (HL 4) and 1-carboxamidine-3,5-dimethylpyrazole (HL 5), was studied. The obtained compounds, CuBr 2 (L 2 ) 2 , Cu(L 3 ) 2 , CuBr 2 (HL 4 ) 2 , CuBr 2 (HL 5 ) 2 and [CuBr(HL 1 )(L 3 )] 2 (HL 1 denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS and DSC. The X-ray structure of [CuBr(HL 1)(L 3)] 2 and Cu(L 3) 2 is discussed. For [CuBr(HL 1 )(L 3 )] 2 a dimeric penta-co-ordinated structure has been found; the co-ordination around the metal in Cu(L 3 ) 2 is trans-square planar. To CuBr 2 (L 2 ) 2 and CuBr 2 (HL 4 ) 2 a nearly tetrahedral, while for CuBr 2 (HL 5 ) 2 an octahedral geometry may be assumed. It means that the geometry of the compounds in the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be explained on the basis of Pearson's theory, taking into account the steric factors. A low stability intermediate formation was observed in the thermal decomposition of Cu(L 3 ) 2 .

Thermal decomposition of Cu(NO 3) 2·3H 2O at reduced pressures

Thermolysis of Cu(NO 3) 2·3H 2O is studied by means of XRD analysis in situ and mass spectral analysis of the gas phase at P=1/10 Pa at low heating rate. It is shown that stage I of the dehydration (40–80 °C) results in the consecutive appearance of crystalline Cu(NO 3) 2·2.5H 2O and Cu(NO 3)·H 2O. Anhydrous Cu(NO 3) 2 formed during further dehydration at 80–110 °C is moderately sublimed at 120–150 °C. Dehydration is accompanied by thermohydrolysis, leading to the appearance of Cu 2(OH) 3NO 3 and gaseous H 2O, HNO 3, NO 2, and H 2O. The higher pressure in the system, the larger amount of thermohydrolysis products is observed. The formation of the crystalline intermediate CuO x (NO 3) y was observed by diffraction methods. Final product of thermolysis (CuO) is formed at 200–250 °C.

Preparation, Structure and Thermal Decomposition of Cu(II) Complexes with 2-Chloro- and 2,3-Dichlorobenzoic Acids and Imidazole

The reaction products of Cu(II) 2-chlorobenzoate and imidazole (1), and of Cu(II) 2,3-dichlorobenzoate and imidazole (2) formulated as CuL'2·3imd and CuL"·3imd (L' = C7H4ClO2, L" = C7H4Cl2O2 −, imd = imidazole), were prepared and characterized by means of structural and spectroscopic measurements and thermochemical properties. The blue (1) and green (2) compounds crystallize in the monoclinic system with space group C2/c, cell parameters a = 20.753(4), b = 8.414(2), c = 14.429(3) Å, β = 90.15(3)°, V = 2519.5(9) Åsup3;, Z = 4 for (1) and a = 21.335(4), b = 8.417(2), c = 15.030(3) Å, β = 94.11(3)°, V = 2692.1(10) Åsup3;, Z = 4 for (2). The complexes decompose at 483 K.

Preparation, Structure, and Thermal Decomposition of Cu(II) 3,5-Dichlorobenzoate Trihydrate

The title compound was studied. Its solubility in water at 293 K was determined (4ċ10−4 molċdm−3). The IR spectrum of the prepared complex was recorded, and its thermal decomposition in air was investigated. The trihydrated complex starts to lose its crystallization water at 343 K; it then decomposes either to CuO (5 K min heating rate) or to gaseous products (10 K min heating rate). [Cu(C7H3Cl2O2)2ċ(H2O)3] crystallizes in the monoclinic system (space group P21n (No. 14)); cell parameters: a=16.854(3) A, b=8.330(2) A, c=13.655(3) A, β=104.20(3)°, V=1858(5) A3, Z=4, D C=1.778 g/cm3, D m=1.78 g/cm3.

Kinetics and Mechanism of the Thermal Decomposition of M(NO3)2·nH2O (M=Cu, Co, Ni)

This paper presents the results of simultaneous DTA-TG-DTG and DSC studies on the thermal decomposition of Cu(NO3)2·3H2O, Co(NO3)2·6H2O and Ni(NO3)2·6H2O in an air atmosphere. The mechanism and enthalpies of the investigated processes were determined, as well as the kinetic parameters of the processes run under non-isothermal conditions by means of Kissinger's method. The dependence of the activation energy on the ionic radius of the cations building up the crystal lattices of the investigated compounds was also studied.

Thermal decomposition of transition metal carboxylates

Dynamics of changes in microstresses during thermal decomposition of Cu(HCOO)2 crystals and their effect on the thermal decomposition kinetics were studied by IR spectroscopy at 105 to 120 °C. The formation of solid intermediate HCOOCu was observed, and the dynamics of its accumulation was followed. Kinetic regularities of transformation of HCOO groups were compared with those for gas evolution.

Characterization of the decomposition course of Cu(II) 3,5-diisopropyl salicylate hydrate and chemical reactivity of the final products — spectrothermal investigation

The thermal decomposition of Cu(II) 3,5-diisopropyl salicylate hydrate in dry nitrogen was studied thoroughly. Thermal events involved throughout the decomposition range (room temperature up to 600 °C) were monitored by means of thermogravimetry, differential thermal analysis and IR gas-phase analyses. The corresponding activation energy values were determined non-isothermally. Intermediate and final solid products were characterized by X-ray diffractometry and IR spectroscopy. The results showed Cu 2(C 13H 17O 3) 4 · 8H 2O melts at 115 °C, followed by the release of 8 mol of isopropyl alcohol (C 3H 7OH) to yield Cu 2(C 7H 5O 3) 4 (copper salicylate) through two endothermic processes at 130 °C and 210 °C. Subsequently, the copper salicylate released phenol, CO and CO 2 to give CuO as a final product at 250 °C. The IR spectra of the gaseous products revealed that a marked chemical reactivity of the gas/solid interface was present throughout the decomposition course. As a result, C 3H 7OH was involved in dehydrogenation/dehydration reactions over the freshly generated CuO surface, producing acetone and propene in the gas phase. Moreover, the byproduct acetone was involved in bimolecular interactions over the CuO surface, producing CH 4 and (CH 3) 2C = CH 2 (isobutene) in the gas phase.

Mechanism of thermal decomposition of hydrated copper nitrate in vacuo

The general scheme of three-stage thermal decomposition of Cu(NO 3) 2·3H 2O to CuO has been refined based on evolved-gas-analysis data with a quadrupole mass analyzer (Jackson et al., Spectrochim. Acta Part B, 50 (1995) 1423). Quantitative evaluation of the composition of the gaseous products shows that the first stage involves primarily deaquation, and the second stage, primarily denitration of the original hydrated nitrate. The basic nitrate formed in the second stage most probably has the formula Cu(NO 3) 2·3Cu(OH) 2. It has been established that the molecular oxygen observed in the third stage of decomposition is produced by catalytic decomposition of NO 2 on the surface of CuO. The presence of Cu-containing ions in all stages of the process is consistent with the gasification mechanism of thermal decomposition.

Behaviour of Cu(II) hydroxide during mechanical treatment

It has been established that Cu(II) hydroxide (Cu(OH) 2) can be decomposed mechanochemically to CuO. After dry grinding, Cu(OH) 2 is dehydrated for 3 h, while wet grinding (in a cyclohexane medium) for the same period of time cannot ensure that the decomposition process will be completed. During mechanical treatment, the samples are activated, which is confirmed by the broadening of the X-ray lines, the decrease in the temperature of thermal decomposition of Cu(OH) 2, and the appearance of additional exothermic peaks on the differential thermal analysis curve. The CuO obtained by mechanochemical decomposition is reduced more easily than CuO produced by thermal decomposition of Cu(OH) 2, regardless of the fact that Cu(OH) 2 has a larger specific surface area.

Thermal decomposition of Cu(II) complexes with salicylaldehyde S-methyl thiosemicarbazone

The thermal decomposition of copper(II) complexes with salicylaldehyde S-methylthiosemicarbazone of general formula Cu(HL)X·nH2O (X=Py+NO3, NCS, 0.5SO4) and [Cu(L)NH3]·H2O was investigated in air atmosphere in the interval from room temperature to 1000°C. Decomposition of the complexes occurred in several successive endothermic and exothermic processes, and the residue was in all cases CuO.

Kinetics of the non-isothermal decomposition of Cu-and Co-itaconato complexes

The kinetics of the thermal decomposition of Cu- and Co-itaconato complexes were studied using dynamic thermogravimetric techniques. The dehydration process was found to proceed in a one-stage reaction, while the thermal decomposition of the anhydrous salts was followed a two-stage reaction. The first stage is the decomposition of the complex to metal carbonate, whereas the second stage is the decomposition of the formed carbonate to the oxide. Kinetic analysis of the dynamic TG curves were discussed with reference to a composite integral method on comparison with the integral methods of Coats and Redfern and Ozawa. The activation parameters were calculated and discussed for each decomposition step.

Preparation and thermal decomposition of Cu 2(OH) 3NO 3

The decomposition of basic copper nitrate is studied using TG-FTIR. The product is decomposed between 160 and 235°C at a heating rate of 10°C min −1. The solid residue is CuO and the gases evolved during decomposition are HNO 3, H 2O, NO 2 and O 2. Decomposition seems to occur in one step.

Thermal decomposition kinetics of Cu(II) chelates of substituted chalcones

The thermal decomposition of Cu(II) complexes of 3-(phenyl)-1-(2'-hydroxynaphthyl)-2-propen-1-one (PHPO), 3-(4-chlorophenyl)-1-(2'-hydroxynaphthyl)-2-propen-1-one (CPHPO), 3-(4-methoxyphenyl)-1-(2 '-hydroxynaphthyD-2-propen-1-one (MPHPO), 3-(3,4-dimethoxy-phenyl) -1-(2'-hydroxynaphthyl)-2-propen-l-one (DMPHPO) was studied by thermogravimetry. Mathematical analysis of the data has allowed us to determine various parameters using the Freeman-Carroll equation, the integral method using the Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation. The trend of the kinetic parameters was found to be different from that of the thermal stability order. The low values of Z suggest the slow nature of the reactions.

Non-linear compositional dependence of the thermal stability of copper-cobalt hydroxide nitrates

A study of the thermal decomposition of Cu x Co 2- x (OH) 3NO 3 solid solutions, 0.0 ⩽ x ⩽ 2.0, was performed by differential thermal analysis, thermogravimetric analysis and differential scanning calorimetry under non-isothermal conditions. It was found that the onset temperature, the endothermic peak temperature and the enthalpy of decomposition increase non-linearly with x. Kinetic analysis of the thermal decomposition was also made by the Flynn and Wall, Kissinger and Takhor methods. The values of the activation energy determined by the three methods are very close and also indicate non-linear dependence of the thermal stability on composition. It is suggested that the behaviour of the investigated thermodynamic and kinetic parameters is related to the variation of the strength of the hydrogen bonds in the structure and the polarisation ability of the cations.

In situ infrared absorption spectroscopy on the thermal decomposition process of MOCVD source gases for YBCO thin films

Thermal decomposition of Cu(DPM) 2 (bis(dipivaloylmethanato)copper (II)) in the gas phase was studied by in situ infrared spectroscopy combined with a MOCVD (metalorganic chemical vapor deposition) apparatus. Decomposition was observed above 500 o C of substrate temperature at a reactor pressure of 20 Torr. Changes in the IR spectra when raising the substrate temperature show that the C-C-C (carbon chain) bond in the chelate-ring structure or the carbon-tertiary-butyl bond is first broken in the decomposition process

FT-IR study of the surface of copper oxide

The surface properties of CuO prepared by thermal decomposition of Cu(OH) 2·CuCO 3 have been studied by FT-IR spectroscopy of CO, CO 2, pyridine, pivalonitrile, methanol and formic acid adsorbed in the 200–420 K temperature range. The surface, after activation in vacuo, exposes different metal centers, developing a very weak Lewis acidic activity, identified as Cu 2+ and Cu + sites. A relevant surface basic strength is also detected. The very strong surface reactivity causes degradation even at room temperature of adsorbed pyridine and pivalonitrile, while methoxy groups already start to decompose at 270 K.

Thermal properties of copper(II) dimers with onsaturated carboxylic bridges

Thermal decomposition of Cu[in2](RCOO)4 and Cu2(RCOO)4L2 where RCOO− = acrylate, crotonate, methacrylate and 3.3'-dimethylacrylate ions, L = py, quin, acd, pic, lut) type of copper(II) dimers have been studied up 1000°C in the air. The mechanism of decomposition of these type copper(II) dimers has been proposed.

Particle-size distribution in very fine copper powders produced by the thermal decomposition of Cu(II) complexes with monoethanolamine

Particle-size distribution in very fine copper powders produced by the thermal decomposition of Cu(II) complexes with monoethanolamine

Kinetic parameters of the thermal decomposition of Cu(II) and Zn(II) salts of carboxylic acids

The kinetic parameters of thermal decomposition of Cu(II) and Zn(II) salts of carboxylic acids were investigated on the basis of the respective thermal curves. The values of the activation energy (Ea) of thermal decomposition, reaction order (n), frequency factor (A) and velocity constant (k) (in the Arrhenius kinetic equation), established from thermal data, were compared. Based on the initial decomposition temperature, the following sequences of stabilities of the studied compounds have been proposed: 1. Cu(CH3COO)2 (235°)>Cu(C6H5O7)2 (220°)>Cu(HCOO)2 (150°)>>Cu(OH)2·Cu(CO3) (50°) 2. Zn(C18H35O2)2 (305°)>ZnCO3 (210°)>Zn(CH3COO)2 (170°)