Dynamic Air Atmosphere Research Articles

Recovering palladium from its surplus complexes in research laboratories by solid state thermal treatment

The residue of heating to 900 °C in dynamic air atmosphere palladium coordination/organometallic complexes that do not contain P-donor ligands is Pd in purity close to 95%. This is a suitable method for recovering palladium from excess samples produced in research laboratories. When P-containing ligands, free or coordinated to palladium, are included in the blend of complexes subjected to this oxidant thermal treatment, unexpected inhibition of PdO formation takes place. A thorough study of the thermal decomposition in air of Pd complexes described to date supports the general trends reported here.

Thermal decomposition of ammonium paratungstate hydrate in air and inert gas atmospheres

In this study, the thermal decomposition of ammonium paratungstate hydrate was investigated in dynamic air and inert gas (nitrogen and argon) atmospheres by simultaneous thermo-gravimetric analysis (TGA), differential thermal analysis (DTA) and mass spectroscopy (MS). The intermediate and end products obtained during thermal decomposition of ammonium paratungstate hydrate were characterized by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).It was found that the kind of gas was not effective on the thermal decomposition mechanism of ammonium paratungstate hydrate below 665K. In the first decomposition step, anhydrous ammonium paratungstate was obtained by dehydration. In the second decomposition step, only deammoniation occurred and ammonium hydrogen tungstate was obtained. During the third decomposition step, dehydration, deammoniation and reduction of some tungsten atoms to lower valences were observed. At this stage, first, ammonium hydrogen tungsten oxide bronze and later ammonium tungsten oxide bronze were formed by two serial reactions. In the fourth step which occurs after 665K, ammonium tungsten oxide bronze formed stoichiometric tungsten oxide in air atmosphere and tungsten suboxide in inert gas atmosphere.

Monitoring of Thermal Degradation of Fireproof Coating

Under the fire conditions, the resistance of cable distribution is required for a fixed period, depending on the intended use of the cable. To increase the fire resistance of cables a fireproof coating may be applied. Article deal with the behavior of the fireproof coating during elevated temperature. Concretely, the aim is monitored a coating weight change under the conditions of dynamically increasing temperature and with or without using air-flow. It is also monitored the change in weight, depending on the isothermal temperatures in dynamic air atmosphere.

Surface and related bulk properties of titania nanoparticles recovered from aramid–titania hybrid films: A novel attempt

5 and 10wt%-TiO2-containing aramid–titania hybrid films were prepared using sol–gel processing improved by the inclusion of 3-isocyanato-propyltriethoxysilane (ICTOS) to strengthen bonding of the titania species to the polymer backbone and, hence, lessen its agglomeration. The films were thermally degraded by heating at 450°C in a dynamic atmosphere of air. The solid residues were found by thermogravimetry, X-ray diffractometry and electron microscopy to consist dominantly of uniformly agglomerated rod-like anatase-TiO2 nanoparticles, irrespective of the titania content of the film. The recovered titania particle morphology and surface microstructure were examined by field emission scanning and high-resolution transmission electron microscopy, respectively. Whereas, the particle surface chemistry and texture were assessed, respectively, by means of X-ray photoelectron spectroscopy and N2 sorptiometry. The recovered titanias were found, irrespective of the film content of titania, to enjoy not only a high temperature (up to 800°C) stable nanoscopic anatase bulk structure, but also a high-temperature stable surface chemical composition (lattice Ti4+ and O2−, and adsorbed OH/CHx species), (101)-faceted microstructure and highly accessible (145–112m2/g), uniform mesoporous texture with average pore diameter in the narrow range of 3.9–6.3nm. Increasing the calcination temperature up to 1100°C enhances an anatase→rutile transition, the extent of which is larger the higher the titania content of the film.

Thermal decomposition kinetics of Brazilian limestones: effect of CO2 partial pressure

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E α) were 197.4 kJ mol−1 and 188.1 kJ mol−1 for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E α for 15% CO2 were 378.7 kJ mol−1 for the CI, and 299.8 kJ mol−1 (first decomposition) and 453.4 kJ mol−1 (second decomposition) for the DP, showing that the determination of E α for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.

Thermal and spectroscopic studies of solid oxamate of light trivalent lanthanides

Solid-state LnL3·1.25H2O compounds, where L is oxamate and Ln is light trivalent lanthanides, have been synthesized. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), experimental and theoretical infrared spectroscopy, TG–DSC coupled to FTIR, elemental analysis, complexometry, and X-ray powder diffractometry were used to characterize and to study the thermal behavior of these compounds. The results led to information about the composition, dehydration, thermal stability, thermal decomposition, and gaseous products evolved during the thermal decomposition of these compounds in dynamic air atmosphere. The dehydration occurs in a single step and through a slow process. The thermal decomposition of the anhydrous compounds occur in a single (Ce), two (Pr), and three (La, Nd to Gd) steps with the formation of the respective oxides, CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd to Gd). The theoretical and experimental spectroscopic study suggests that the carboxylate group and amide carbonyl group of oxamate are coordinate to the metals in a bidentate chelating mode.

Thermal and spectroscopic data to investigate the oxamic acid, sodium oxamate and its compounds with some bivalent transition metal ions

Abstract Synthesis, characterization, and thermal behavior of transition metal oxamates, M(NH2C2O3)2·nH2O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as the thermal behavior of oxamic acid and its sodium salt (NaNH2C2O3) were investigated employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), experimental and theoretical infrared spectroscopy, TG-DSC coupled to FTIR, elemental analysis and complexometry. The results led to information about the composition, dehydration, thermal stability, thermal decomposition, as well as of the gaseous products evolved during the thermal decomposition of these compounds in dynamic air and N2 atmospheres.

Thermal decomposition course of Eu(CH 3COO) 3·4H 2O and the reactivity at the gas/solid interface thus established

The thermal decomposition course of europium acetate tetrahydrate (Eu(CH 3COO) 3·4H 2O) was probed on heating up to 1000 °C in a dynamic atmosphere of air by thermogravimetry and differential thermal analysis. The solid- and gas-phase decomposition products were identified by X-ray diffractometry, ex- and in situ infrared spectroscopy and mass spectrometry. Results obtained showed the acetate to dehydrate stepwise at 145–283 °C, and then decompose stepwise to yield eventually cubic-Eu 2O 3 at ≥663 °C encompassing the formation of intermediate oxycarbonate (Eu 2O(CO 3) 2/Eu 2O 2(CO 3) solid products (at 347–466 °C)) and H 2O, (CH 3) 2CO and CO 2 as primary gaseous products. A considerable enhancement of the production of the primary gas phase products at 400–450 °C and the emergence of (CH 3) 2C CH 2, CH 4 and CO molecules in the gas phase are ascribed to reactions occurring at the gas/solid interface at the expense of some of the primary products. These interfacial activities impart application-worthy adsorptive and catalytic functions for the associated solid products.

Macro-TG Reactor and Thermogravimetric Analysis for Cooking Oil Tar Samples

The combustible material of fire in fog discharge pipe is the cooking oil tar. Cooking oil tar was conducted on a specially designed laboratory-scale thermobalance (Macro-TG) with sample loading of 15g under dynamic air atmosphere. The effects of heating rate (5, 10, 15, 20 and 25°C/min) was examined. A simple kinetic description, named in this work as ‘First Order Reaction and Three-dimensional Diffusion Separate-stage Model (O1+D3)’ model, was developed based on the experimental results and integral analysis method. Experimental results shows that large amount of sample has a pyrolysis reaction retardancy. The distributed activation energy model was used to study the pyrolysis kinetics. Science the reaction occurred in small activation energy told us that if the cooking oil tar put on fire it will be spread rapidly and hard to put out.

Solid-state compounds of 2-methoxybenzylidenepyruvate and 2-methoxycinnamyllidenepyruvate with thorium (IV)

Solid-state compounds of general formula ThL4·nH2O, where L represents 2-methoxybenzylidenepyruvate and 2-methoxycynamylidenepyruvate, were synthesized. Complexometric titrations with EDTA, thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffractometry, elemental analysis (EA), and infrared spectroscopy have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. The results led to informations about the composition, dehydration, crystallinity, and thermal decomposition of the isolated compounds. The performed molecular calculations in this study were done using the Gaussian 03 routine. Theoretical calculations help in interpretations of FT-IR spectra supplying structural and physicochemical parameters.

Thermal studies on solid 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene of lighter trivalent lanthanides

Solid-state compounds of general formula Ln2L3·nH2O, where L represents 1,4-bis(3-carboxy-3-oxo-prop-1-enyl)benzene and Ln = La, Ce, Pr, Nd, Sm, were synthesized. Complexometric titrations with EDTA, thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. The results led to information about the composition, dehydration, crystallinity, and thermal decomposition of the synthesized compounds.

Thermo-oxidative Degradation of Polymers Containing Phosphorus in the Main Chain

In the present study the thermal behavior of some polyphosphonates and polyphosphates was studied. The polymers were synthesized by the inverse phase-transfer catalysis method. The thermal behavior was tested on a Perkin-Elmer DIAMOND device, in a dynamic air atmosphere and with heating rates of 5, 7, 10 and 12 °C min-1. By inspecting the thermogravimetric curves, a remarkable thermal stability up to 200 °C was observed. Between 240 and 380 °C, an endothermic decomposition occurred, with the tendency to a maximum at the end of the process. The end of the thermo-degradation was connected with an oxidative process. A kinetic analysis of the thermogravimetric/differential thermogravimetric results by means of the Friedman, Flynn—Wall—Ozawa, and non-parametric kinetic methods is the basis of discussions on the influence of the molecular architecture on the thermal behavior.

Thermal decomposition kinetics of rice husk: activation energy with dynamic thermogravimetric analysis

The trend for energy and material recovery from wastes along with the need to reduce greenhouse gases has led to an increased interest in the study of thermal degradation of biomass. In this study, the thermal degradation of four rice husk (agricultural biomass) of varieties (Pusa, Parmal, HBC-19 and Basmati) was studied under non-isothermal heating in dynamic air atmosphere by using a simultaneous thermal analyser. Thermal degradation of rice husk had two different stages: 'cellulose and hemicellulose conversion' and 'lignin conversion.' Friedman, Ozawa–Flynn–Wall (O–F–W) and Kissinger methods were used to determine kinetic parameters. The results showed that the activation energy obtained from the Friedman method was in good agreement with the value obtained using O–F–W method. The values of activation energies calculated by using Kissinger method were much lower than those calculated by Friedman and O–F–W method. The results obtained in this study were compared with those of the literature.

Thermo-kinetics study of orange peel in air

Thermal degradation of orange peel was studied in dynamic air atmosphere by means of simultaneous TG-DSC and TG-FTIR analysis. According to the obtained thermal profiles, the orange peel degradation occurred in at least three steps associated with its three main components (hemicellulose, cellulose and lignin). The volatiles compounds evolved out at 150–400 °C and the gas products were mainly CO2, CO, and CH4. A mixture of acids, aldehydes or ketones C=O, alkanes C–C, ethers C–O–C and H2O was also detected. The Eα on α dependence reveled the existence of different and simultaneous processes suggesting that the combustion reaction is controlled by oxygen accessibility, motivated by the high evolution low-molecular-mass gases and volatile organic compounds. These results could explain the non-autocatalytic character of the reactions during the decomposition process.

Thermal behavior of a sol–gel system containing aniline and organic phosphonates

Samples of an organic–inorganic hybrid were prepared by solvolysis and polycondensation in formic acid of tetraethoxysilane and diethylbenzyl phosphonate, simultaneous with the oxidative polymerization of aniline. The thermal behavior of the samples in dynamic air atmosphere and non-isothermal conditions was determined by a coupled thermogravimetric/evolved gas analysis. Two significant thermal events were established: the elimination from the polymeric matrix of low mass molecules, respectively the thermooxidative degradation of the organic part of the matrix. The kinetic analysis was performed with the Flynn-Wall-Ozawa, Friedman and modified Non-Parametric-Kinetic methods. Only the last one allowed an objective analysis of the first process as a process of two simultaneous thermally induced phenomena with the kinetic functions of the type αm(1 − α)n.

TG, EGA and kinetic study by non-isothermal decomposition of a polyaniline with different dispersion degree

Polyaniline was obtained by oxidizing aniline in hydrochloric acid media with ammonium peroxidisulfate as oxidizing agent. Molar ratio aniline/oxidant was 1 and ani- line/acid ratio: ,a t-5 and 400 C, respectively, 800 mL water. The both compounds were studied using two different experimental strategies: the coupled TG-EGA (FTIR) tech- nique by decomposition in dynamic air atmosphere and the kinetic analysis of TG data obtained at four heating rates (5, 7, 10 and 15 K min -1 ). The kinetic analysis of the TG non-isothermal data was performed with the Flynn-Wall- Ozawa, Friedman's, and modified non-parametric kinetic (NPK) methods. By means of the coupled techniques spec- troscopic arguments on the reaction mechanism were obtained, i.e. the oxidative degradation of the quinoine ring as the first step. The values of the activation energy by the three used methods are in good agreements. According to the NPK method, the termodegradation process consist in physical (diffusion) and chemical steps.

Thermo-mechanical characteristics of thermally aged polyethylene/polypropylene blends

Polyethylene (PE), polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications. Therefore, the current work has been carried out with the main objective of investigating the impact of the thermal aging/treatment and blend ratio (composition range) on the mechanical (tensile and hardness) and thermal characteristics (using thermogravimetric analysis in a dynamic air atmosphere) of PE, PP and PE/PP binary blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 wt.% were prepared via injection moulding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however, thermal aging at 100 °C has not affected the polymers hardness which holds also true for the tensile properties, showing a good correlation between tested mechanical properties. The thermogravimetric analysis (TGA) in a dynamic air atmosphere and derivative thermogravimetric analysis (DTA) were conducted to study the thermal degradation and stability of thermally unaged and aged PE, PP and PE/PP blends in terms of the initial ( T d and T d(1%)) and final ( T d(99%)) decomposition temperatures and maximum decomposition rate temperature ( T max). All polymers start to decompose at no less than 365 °C. As for mechanical properties, the blend ratio has affected the thermal properties however, aging time has not.

Kinetics and thermodynamics of thermal decomposition of synthetic AlPO4·2H2O

Abstract The non-isothermal kinetics of dehydration of AlPO4·2H2O was studied in dynamic air atmosphere by TG–DTG–DTA at different heating rates. The result implies an important theoretical support for preparing AlPO4. The AlPO4·2H2O decomposes in two step reactions occurring in the range of 80–150 °C. The activation energy of the second dehydration reaction of AlPO4·2H2O as calculated by Kissinger method was found to be 69.68 kJ mol−1, while the Avrami exponent value was 1.49. The results confirmed the elimination of water of crystallization, which related with the crystal growth mechanism. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the dehydration reaction are calculated by the activated complex theory. These values in the dehydration step showed that it is directly related to the introduction of heat and is non-spontaneous process.

Thermal analysis of azoic dyes: Part I. Non-isothermal decomposition kinetics of [4-(4-chlorobenzyloxy)-3-methylphenyl]( p-tolyl)diazene in dynamic air atmosphere

Thermal analysis of [4-(4-chlorobenzyloxy)-3-methylphenyl]( p-tolyl)diazene dye, was performed in dynamic air atmosphere. The compound behavior was investigated using TG, DTG, DTA and DSC techniques, under non-isothermal linear regime. Kinetic parameters of the two decomposition steps were evaluated by means of multi-heating rates methods, such as “mode-free” kinetic methods, IKP method, Perez-Maqueda et al. criterion and Master plot procedure. It was shown that the conversion function which describes the process it is not necessary one of the best-fitting functions (when using single-heating rate methods). IKP method can however reduce the possibilities of choosing the true function which can be precisely obtained by applying discrimination methods.

Synthesis and characterization of mesoporous and nano-crystalline phosphate zirconium oxides

In this work the preparation and characterization of the materials such as zirconia (ZrO 2) and zirconia promoted with phosphate ion (ZrO 2–PO 4 3−) is presented. Pure zirconium hydroxide [Zr(OH) 4] was synthesized by the sol–gel method using precursors such as zirconium n-butoxide and 1-butanol maintaining a pH 8 during the synthesis. Zr(OH) 4 was impregnated with 15 wt.% of the acid agent. Both were calcined in a dynamic air atmosphere for 3 h at 400, 500 and 600 °C. The supports were characterized by thermal analysis, X-ray diffraction, nitrogen physisorption as well as infrared spectroscopy. The results showed a positive effect on the physicochemical properties of the catalytic supports after Zr(OH) 4 impregnation with the dopping agent (H 3PO 4). Phosphate zirconium oxides remained thermically stable after calcination. It was observed that the dopping agent remained firmly attached to the zirconium oxide surface, inhibiting the particle growth and delaying the syntherization of the material and the apparition of the monoclinic phase, obtaining mesoporous and nano-crystalline materials (crystallite size 1.0–6.5 nm) with high surface areas (210–329 m 2/g) and tetragonal structure defined for the calcination temperature of 600 °C.