Thermal decomposition kinetics of aluminum sulfate hydrate

The kinetics of individual stages of thermal decomposition of Al 2 (SO 4 ) 3 •18H 2 O were studied by TG method. It is found that Al 2 (SO 4 ) 3 • 18H 2 O decomposes to Al 2 O 3 in four major stages, all of endothermic. Some of these major stages are formed by sub-stages. The first three major stages are dehydration reactions in which two, ten and six moles water are lost, respectively. The last major stage is sulfate decomposition. In this study the kinetic parameter values of these major and sub-stages were calculated by integral and differential methods. The alterations of activation energies with respect to the decomposition ratio and to the method were investigated. © 2009 Akadémiai Kiadó, Budapest, Hungary

Thermal and kinetic analyses of 2,5-bis(2-hydroxyphenyl)thiazolo[5,4-d]thiazole

Thermal behavior and UV-Vis absorption properties of 2,5-bis(2-hydroxyphenyl)thiazolo[5,4-d]thiazole were investigated in the present study. It was found that decomposition occurs in two stages which correspond to removal of both phenolic rings and degradation of remaining core structure, respectively. After the characterization of decomposition stages, apparent activation energy values of each stage were calculated using model-free isoconversional methods (FWO and KAS). Apparent activation energies of decomposition stages are determined by both methods. Their averages are calculated as 98.232 and 123.253 kJ mol -1 in consecutive order. UV-Vis absorption properties of this compound have been determined with using different solvents. © 2014 Akadémiai Kiadó, Budapest, Hungary

Thermal and kinetic analysis of uranium salts: Part 1. Uranium (VI) oxalate hydrates

The thermal decomposition kinetics of UO 2 C 2 O 4 ·3H 2 O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO 2 C 2 O 4 ·3H 2 O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (ΔH * , ΔS * , and ΔG * ) were calculated. © 2011 Akadémiai Kiadó, Budapest, Hungary

Thermal Behaviors of Bisazocalix[4]arene Derivatives

In this article, calix[4]arene (4) was prepared by debutylation and hydrolyses reacting from 25,27-dibenzoyl-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (2). Azocalix[4]arenes (6a-c) were coupled by linking 4-methoxy, 4-ethyl, and 4-nitroaniline to calix[4]arene (4) through a diazo-coupling reaction. Thermal behavior characteristics and decomposition routes of 25,26,27,28-tetrahydroxy-11,23-di(tert-butyl)-5,17-(p-substitue phenyl)azocalix[4]arene (6a-c) were investigated in air atmosphere by means of thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA) analyses. It was found that the decomposition of all compounds complete with two exothermic stages which corresponded to removal of substitute groups (methoxy-, ethyl-, nitro-) and second stage rest of structure decomposition. © 2017 Taylor & Francis Group, LLC

Thermal and kinetic analysis of uranium salts: Part III. Uranium(IV) oxalate hydrates

Thermal decomposition of U(C 2 O 4 ) 2 · 6H 2 O was studied using TG method in nitrogen, air, and oxygen atmospheres. The decomposition proceeded in five stages. The first three stages were dehydration reactions and corresponded to removal of four, one, and one mole water, respectively. Anhydrous salt decomposed to oxide products in two stages. The decomposition products in nitrogen atmosphere were different from those in air and oxygen atmospheres. In nitrogen atmosphere UO 1.5 (CO 3 ) 0.5 was the first product and U 2 O 5 was the second product, while these in air and oxygen atmospheres were UO(CO 3 ) and UO 3 , respectively. The second decomposition products were not stable and converted to stable oxides (nitrogen: UO 2 , air-oxygen: U 3 O 8 ). The kinetics of each reaction was investigated with using Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods. These methods were combined with modeling equations for thermodynamic functions, the effective models were investigated and thermodynamic values were calculated. © 2013 Akadémiai Kiadó, Budapest, Hungary

Structural analysis of calix[n]arene-iron(III) complexes (n=4,∈6,∈8) and thermal decomposition of the parent calix[n]arenes

In this study, six new calix[n]arene-Fe3+ complexes (n∈=∈4,∈6,∈8) were synthesized with parent calix[n]arenes in a DMF solution of FeCl3∈•∈H2O. The properties and coordination characteristics of the six parent calix[n]arene-Fe3+ complexes were determined by elemental analyses, TG-DTA, UV-vis, FT-IR and 1H NMR spectroscopy. According to UV-vis analysis, in the six complexes the iron(III) coordinated by oxygen donor atoms from calix[n]arene ligands and DMF molecules. The complexes behave as 1∈:∈1 and 1∈:∈2 electrolytes in the case of calix[n]arenes (n∈=∈4,∈6) (1-4) and calix[8]arene (5, 6), respectively. 1H NMR studies demonstrate that 1 and 2 are more stable than 3, 4, 5 and 6 in DMF, and indicate cone conformation of the calix[4]arene ligands (1 and 2)

A brief review on the thermal behaviors of calixarene-azocalixarene derivatives and their complexes

Calixarenes have been widely regarded as an important class of macrocyclic host molecules, due to their efficient and highly selective binding properties towards specific metal ions. Azocalixarenes, containing single conjugated chromophore azo (-N=N-) group in p- positions are synthesized by one-pot procedures with satisfactory yields. Their structures (as solid and liquid) are elucidated by UV-Vis, FT-IR, 1H and 13C-NMR spectroscopic methods, as well as elemental analysis techniques. Thermal stability of calixarenes is very important because of their potential applications in high temperature processes such as the dyeing of textile fibers, ink-jet printing and photocopying and in high technology areas such as lasers and electro-optical devices. In this paper all the thermal studies of parent calix[n]arenes, azocalix[4]arene derivatives and their complexes containing lower and upper rim functionalized groups are reported. All the thermo analytical results such as the temperature ranges and peak temperatures of thermal decomposition steps and amount of volatile pyrolysis products were emphasized. The effect of substituted groups and their positions on the thermal stability of calixarenes were investigated. © 2012 Copyright Taylor and Francis Group, LLC

Thermal and kinetic analysis of uranium salts: Part 2. Uranium (VI) acetate hydrates

In this study the thermal decomposition kinetics of uranyl acetate dehydrate [UO 2 (CH 3 COO) 2 ·2H 2 O] were studied by thermogravimetry method in flowing nitrogen, air, and oxygen atmospheres. Decomposition process involved two stages for completion in all atmosphere conditions. The first stage corresponded to the removal of two moles of crystal water. The decomposition reaction mechanism of the second stage in nitrogen atmosphere was different from that in air and oxygen atmospheres. Final decomposition products were determined with X-ray powder diffraction method. According to these data, UO 2 is the final product in nitrogen atmosphere, whereas U 3 O 8 is the final product in air and oxygen atmospheres. The calculations of activation energies of all reactions were realized by means of model-free and modeling methods. Kissinger-Akahira- Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were selected for model-free calculations. For investigation of reaction models, 13 kinetic model equations were tested. The model, which gave the highest linear regression, the lowest standard deviation, and an activation energy value which was close to those obtained from KAS and FWO equations, was selected as the appropriate model. The optimized value of activation energy and Arrhenius factor were calculated using the selected model equation. Using these values, thermodynamic functions (ΔH, ΔS, and ΔG) were calculated. © 2012 Akadémiai Kiadó, Budapest, Hungary

Ferrocenyl dithiophosphonate functionalized inorganic-organic hybrid conductive polymer with green color in neutral state

We report the synthesis and the characterization of the first electroactive ferrocenyl dithiophosphonate functionalized inorganic-organic hybrid conductive polymer. Electropolymerization was realized in boron trifluoride diethyl etherate (BFEE) with an applied potential of 1.5 V. Surface morphological, spectroelectrochemical, colorimetric and redox properties of polymer were investigated. Spectroelectrochemical and colorimetry studies have shown that ThFc has green color in neutral state. The reaction of the ferrocenyl dithiophosphonate and nickel(II) acetate gave rise to square-planar nickel(II)complex (ThFc-Ni). ThFc-Ni complex copolymerize with thiophene and spectroelectrochemical properties of copolymer were also investigated

The thermal and detailed kinetic analysis of dipicolinate complexes

The [Cu(pydc)(eim)3]·H2O (1), [Cu(pydc)(4hp)(H2O)] (2) and [Ni(pydc)(3hp)(H2O)2][Cu(pydc)(3hp)(H2O)2]·3H2O (3) complexes (H2pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, eim = 2-ethylimidazole, 4hp = 4-hydroxypyridine, 3hp = 3-hydroxypyridine) were studied by thermo-gravimetric analysis at an ambient temperature up to 1000 K under nitrogen atmosphere. The complexes are stable about 350 K, and the decomposition reactions were carried out in seven, three and four stages for the complexes 1, 2 and 3, respectively. Following detailed thermo-gravimetrical analysis of the complexes, the decomposition mechanism was suggested for all complexes. The kinetic analysis of all decomposition stages of each compound was performed except for the final stages. The values of the activation energy, Ea, were obtained using model-free Kissinger–Akahira–Sunose and Flyn–Wall–Ozawa methods for all decomposition stages. © 2016, Akadémiai Kiadó, Budapest, Hungary