The non-isothermal decomposition of cobalt acetate tetrahydrate

The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N₂, H₂ and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N₂, and Co₃O₄ was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO₂ and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C _p and °S) were calculated for the different decomposition steps. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Mechanism of thermal decomposition of cobalt acetate tetrahydrate

The thermal decomposition of cobalt acetate tetrahydrate (Co(CH₃COO)₂ · 4H₂O) has been studied via thermogravimetric (TG) analysis, in situ X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results of TG and XRD showed that the parent salt melted and then the dissolved crystalline water was vaporized in two steps. The dehydration process was followed by a major step concerning the decomposition of the acetate group, leading to basic acetate as an intermediate, which then produced CoO and Co in N₂ and H₂ atmosphere, respectively. Three decomposition intermediates Co(CH₃COO)₂ · 0.5H₂O, Co(CH₃COO)₂, and Co(OH)(CH₃COO) were presumed. In situ XRD experiments revealed that the intermediate basic acetate was poorly crystallized or even amorphous. Evolved gases analysis indicated that the volatile products of acetate decomposition were water vapor, acetic acid, ethylenone, acetone, and CO₂. A detailed thermal decomposition mechanism of Co(CH₃COO)₂ · 4H₂O was discussed.     

Spectrothermal investigation of the decomposition course of lanthanum acetate hydrate

Thermogravimetry, differential thermal, X-ray diffraction and infrared spectroscopy analyses showed La(CH₃COO)₃·1.5H₂O to decompose completely at 700°C yielding La₂O₃. The results revealed that the compound dehydrates in two steps at 130 and 180°C, and recrystallizes at 210°C. Water thus produced hydrolyzes surface acetates (at 310°C), releasing acetic acid into the gas phase. At 334°C, the anhydrous acetate releases gas phase CH₃COCH₃ to give La₂(CO₃)₃ residue, which decomposes to La₂O₂(CO₃) via the intermediate La₂O(CO₃)₂. On further heating up to 700°C, La₂O₃ is formed. IR spectroscopy of the gaseous products indicated a chemical reactivity at gas/solid interfaces formed throughout the decomposition course. As a result, CH₃COCH₃ was involved in a surface-mediated, bimolecular reaction, releasing CH₄ and C₄H₈ (isobutene) into the gas phase. Non-isothermal kinetic parameters, the rate constantk, frequency factorA, and activation energy ΔE, were calculated on the basis of temperature shifts experienced in the thermal processes encountered, at various heating rates (2–20 deg·min^?1).     

Kinetics and mechanism of non-isothermal dehydration of nickel acetate tetrahydrate in air

The non-isothermal decomposition of nickel acetate tetrahydrate in air was studied using thermogravimetry (TG)–DTG, differential scanning calorimetry (DSC) and XRD techniques. The decomposition occurs in two major steps and the final product is NiO. The dependence of mass loss on heating rates in TG measurements imply that the dehydration and hydrolysis concur at temperature below 240 °C; the apparent activation energies calculated by Flynn, Wall and Ozawa (FWO) isoconversional method indicate the existence of a consecutive process. The kinetics of the first major decomposition step (below 240 °C) was obtained with multivariate non-linear regression of four measurements at different heating rates. According to the kinetics results from non-linear regression, the dehydration reaction (F1 type with an activation energy E of 167.7 kJ/mol) goes first. After the loss of almost half of water, the retained water and acetate are linked to each other by hydrogen bonding, so dehydration and hydrolysis concur. The pathway with a lower E is related to the hydrolysis process and the other is corresponding to the dehydration process. The simulations of reactants at different heating rates were used to verify the correctness of the reaction model. With the kinetics results, the dehydration mechanism was discussed for the first time.     

Effects of alkali metal ions on the thermal decomposition of ammonium heptamolybdate tetrahydrate

The thermal decomposition of pure ammonium heptamolybdate tetrahydrate (AHMT), and doped with Li⁺, Na⁺ and K⁺ ions was investigated using thermogravimetry, differential thermal analysis, infrared and X-ray diffraction techniques. Results obtained revealed that the decomposition of AHMT proceeded in three decomposition stages in which both NH₃ and H₂O were released in all stages. The presence of 0.5 mol % alkali metal ions enhances the formation of the intermediateb (NH₄)₂MO₇O₂₂·2H₂O while the decomposition of this intermediate into MoO₃ is slightly affected in the presence of all dopant concentrations used. The infrared absorption spectra of the thermal products of AHMT treated with 10 mol% alkali metal ions (AMI) at 350°C indicated a reduction of some Mo⁶⁺ ions. By heating of AHMT above 500°C in presence of 5 or 10 mol % of AMI, a solid-solid interaction between alkali metal oxides and MoO₃ giving rise to well crystallized alkali metal molybdates. finally the activation energies accompanied various decomposition stages were calculated.     

Thermal decomposition of nicotinate complexes of cobalt and nickel in dynamic nitrogen atmosphere

Thermal decomposition of cobalt and nickel nicotinate was studied by TG, DTG and DSC. The mechanism of decomposition has been established from TG and DSC data. The kinetic parameters namelyE, A together with ΔH were calculated from DSC curves using mechanistic and non-mechanistic integral equations.

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Zusammenfassung Mittels TG, DTG und DSC wurde die thermische Zersetzung von Cobaltund Nickelnikotinat untersucht. Der Zersetzungsmechanismus wurde anhand der TG-und DSC-Daten entwickelt. Die kinetischen ParameterE, A wurden zusammen mit ΔH anhand der DSC-Kurven mit Hilfe von mechanistischen und nichtmechanistischen Integrationsgleichungen berechnet.

     

Study of thermal decomposition of silver acetate

Thermal decomposition of silver acetate was studied (TG, DSC, mass-spectrometry, X-ray analysis, electron microscopy). Non-isothermal thermogravimetric data (obtained at two different rates of linear heating) were used for kinetic studies. Kinetic parameters were calculated only for the chosen decomposition step.     

An investigation of the thermal decomposition of gold acetate

The thermal decomposition characteristics of gold acetate to produce gold nanoparticles were investigated. A rapid and violent fragmentation of the gold acetate particles was observed at approximately 103±20°C when a rapid heating rate of 25°C min⁻¹ was used, leading to formation of nanosized spherical and partially coalesced gold particles. Particle size analysis was used to investigate possible relationships between the gold acetate crystallite size and the gold nanoparticles produced by thermal decomposition. The results indicate rapid (<0.14 ms) coalescence of the gold particles occurs for fragments in close proximity.     

Thermoanalytical investigations of the decomposition course of copper oxysalts

The thermal decomposition course of copper acetate monohydrate (CuAc) was examined on heating up to 600°C at various rates, by TG, DTA and DSC. Non-isothermal kinetic and thermodynamic parameters were determined in air or nitrogen. SEM was used to describe the decomposition course and the solid products were identified by IR and XRD analysis. The results indicated that CuAc was dehydrated at 190°C and then partially decomposed at 220°C, giving rise to CuO in addition to a minor portion of Cu₂O and Cu₄O₃. The last two oxides seemed to facilitate the decomposition of the rest of the anhydrous acetate. Cu₂O and Cu₄O₃ were oxidized in air at >400°C, in a process that did not occur in nitrogen.It is a pleasure to thank the Queen's University of Belfast, particularly the staff of the Electron Microscope Unit for assistance in obtaining the electron micrographs. Thanks are also due to the Egyptian Government for the granted fellowship.     

Mechanism and kinetics of thermal decomposition of nickel(II) sulfate(VI) hexahydrate

This work presents results of research on thermal decomposition of nickel(II) sulfate(VI) hexahydrate in air and in helium atmosphere. On the base of TG and XRD results a mechanism of thermal decomposition of NiSO₄ hydrate was established. For calculations of kinetic parameters of the Arrhenius equation, the Coats-Redfern approximation was applied. Choice of g(a) function and thus of a mechanism best describing given stage of decomposition was performed by testing 12 kinetic models. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of Ni(II) and Fe(III) acetates and their mixture

The thermal decomposition of the ferric and nickel acetate salts has been followed. It was found that the heating rate affects the decomposition steps. For a heating rate of 1 K min^–1 the product is either Fe₂O₃ or NiO. For a higher heating rate the suboxides are obtained and reoxidized again on further heating. The decomposition of the mixed salt is an overlap of the DTA for the separate salts but the decomposition reactions are shifted to lower temperatures.We would like to thank Prof. Dr. N. Afify, Phys. Dept., Fact. Science, Assiut University, for experimental assistance and valuable discussions.     

Kinetics of thermal decomposition of nickel sulfate hexahydrate

The paper describes the kinetics of all the recorded steps of thermal decomposition of nickel sulfate hexahydrate in air. The thermal decomposition of the salt in air led to NiO at about 1060 K. The kinetic parameters, the activation energyE and the preexponential factorA, and the thermodynamic parameters, the entropy, enthalpy and free energy of activation were evaluated for the dehydration and decomposition reactions. Tentative reaction mechanisms are suggested for each step of the thermal decomposition.     

乙酸烯丙酯的氢硅化反应

本文在对芳醛及环酮的氢硅化反应研究基础上, 进一步研究乙酸烯丙酯的氢硅化反应。(Ph~3P)~3RhCl作催化剂, 反应可在均相进行。采用假一级动力学方法, 以气相色谱法鉴测氢硅化产物生成的速率, 求得其反应速度常数, 进而分析其反应活性与反应物结构的关系, 并提出相应的可能机理。     

Thermal degradation of ethylene (vinyl acetate)

Ethylene (vinyl acetate), EVA, is a copolymer which is thermally degraded at high temperatures, with acetic acid release at approximately 620 K. This release can be studied by using thermal methods, and in particular thermogravimetric analysis.The present work was focused on establishing the polymer weight loss with temperature in order to calculate the activation energy of the overall deacetylation process. To obtain the final results, a Mettler TC50 instrument coupled with a Mettler TC11 microprocessor was used.The activation energies of four different industrial EVA formulations were calculated. The results obtained by applying different kinetic methods reported in the literature agreed reasonably well; they were compared in order to select the best method of reporting EVA deacetylation results.The authors wish to express their appreciation to DGICYT (Spain), Project AMB 94-107, for financial support of this study.     

Thermal and kinetic study of nickel trifluoromethanesulphonate,trifluoroacetate and acetate

The reason of comparing thermal behaviour and kinetics of some nickel compounds, is justified by the influence of anion on it, besides supplying information on the stability of the salts. In this work, Ni(TMS)₂·6H₂O, Ni(TFA)₂·3H₂O and Ni(Ac)₂·2H₂O, were synthesized and characterized by microanalysis, atomic absorption molar, conductance and thermal analysis. Thermogravimetric curves indicate that the decomposition of the salts occurs in the range 295–1169 K and the NiO is the final residue. Non-isothermal kinetic evaluation from thermogravimetric data was used to determine energies of activation and pre-exponential factors.     

Kinetics of thermal decomposition of nickel oxalate dihydrate in air

Thermal decomposition taking place in solid state complex, NiC₂O₄·2H₂O, has been investigated in air by means of TG–DTG/DTA, DSC, XRD. TG–DTG/DTA curves showed that the decomposition proceeds through two well-defined steps with DTA peaks closely corresponding to the weight loss obtained. XRD showed that the final decomposition product of NiC₂O₄·2H₂O was NiO. Kinetics analysis of NiC₂O₄·2H₂O decomposition steps was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Flynn–Wall–Ozawa (FWO) methods, and the most possible kinetic model function has been estimated through the multiple-linear regression method. The activation energies for the two decomposition steps of NiC₂O₄·2H₂O were 171.1 ± 4.2 and 174.4 ± 8.1 kJ/mol, respectively.     

2，2''''－对苯二甲硫基二乙酸与醋酸镍在低热温度下的固－固相反应

２，２′－对苯二甲硫基二乙酸与醋酸镍在低热温度下的固－固相反应＊张卫华＊＊（湖北师范学院化学系黄石４３５００２）忻新泉（南京大学配位化学国家重点实验室南京２１００９３关键词２，２′－对苯二甲硫基二乙酸醋酸镍固－固相反应动力学有机硫醚酸类化合物近年来除...     

Thermal dehydration of dipotassium tetraborate tetrahydrate and crystallization of amorphous dehydration product

Summary As one of the typical examples of producing an amorphous dehydration product, the thermal dehydration process of K₂B₄O₇·4H₂O was subjected to thermoanalytical and morphological studies. An anhydrous glass was formed via three distinguished dehydration stages. The overall thermal dehydration process was characterized as a self-induced sol-gel process to form anhydrous glass. The as produced anhydrous glass exhibited glass transition at around 700 K and subsequently crystallized via two consecutive exothermic peaks at around 770 and 900 K. The final crystallization product, triclinic K₂B₄O₇, melted at 1072 K.     

2,2'-对苯二甲硫基二乙酸与醋酸钴在低热温度下的固-固相反应

２，２－对苯二甲硫基二乙酸与醋酸钴在低热温度下的固－固相反应张卫华＊忻新泉（湖北师范学院化学系黄石４３５００２）（南京大学配位化学国家重点实验室南京）关键词２，２－对苯二甲硫基二乙酸，醋酸钴，固－固相反应，动力学１９９６－０８－０４收稿，１９９７...