Thermal Dehydration Kinetics Research Articles

Thermal dehydration kinetics involved during the conversion of gadolinium hydroxide to gadolinium oxide

Non-isothermal dehydration kinetics of gadolinium hydroxide (Gd(OH)3) was studied by thermogravimetry analysis (TGA), and differential thermal analysis (DTA). It was observed that the dehydration of Gd(OH)3 occurred in two steps. In step I, Gd(OH)3 dehydrates to GdOOH at ∼ 596 K. Finally, Gd2O3 is formed after complete dehydration of GdOOH at ∼710 K. The kinetic triplets (activation energy, pre-exponential factor and reaction mechanism) were calculated for step I and step II. The activation energy was determined by using the Kissinger–Akahira–Sunsose (KAS) iso-conversional method. The results indicated that the average activation energy was higher for step II (91.29 kJ/mol) as compared to step I (77.94 kJ/mol). The reaction mechanism was estimated by following two different master plot methods such as Criado and integral master plot method. Both the master plot methods have shown similar results. It was found that the Avrami–Erofeev A3 nucleation reaction mechanism dominated in both the dehydration steps.

Kinetic study of the multistep thermal behaviour of barium titanyl oxalate prepared via chemical precipitation method

This study describes the physico-geometrical mechanism and overall kinetics for the multistep thermal dehydration of barium titanyl oxalate tetrahydrate (BTO). The thermal dehydration kinetics of BTO was studied at four different linear heating rates under non-isothermal conditions. The reaction kinetics was performed using differential scanning calorimetry (DSC) and the curves obtained were analysed using different isoconversional model-free equations and the values are found to be compatible with each other. The kinetic deconvolution principle is used for identifying the partially overlapped kinetic processes of the thermal dehydration of BTO, and it occurs in two stages. The overall reaction kinetics parameters calculated via kinetic deconvolution of the sample indicate the multistep nature of the process and the kinetic analysis of the non-isothermal data of this reaction model shows that the reaction is best described by Sestak–Berggren (m, n) empirical kinetic model. The prepared sample was identified and characterized by means of FT-IR, XRD, SEM, and TEM.

The influence of water-soluble impurities on thermal dehydration kinetics of phosphogypsum in self-generated atmosphere

The paper presents the results of studies of the effect of water-soluble impurities on the thermal dehydration of phosphogypsum in a self-generated atmosphere, which are obtained by thermogravimetry and differential scanning calorimetry. For comparison, the results of the thermal dehydration of gypsum are given. The information about the change in activation energy depending on the extent of the dehydration and the effect of temperature on the mechanism of the dehydration is obtained by the use of integral isoconversional and model-fitting methods. It has been established that water-soluble impurities have a significant influence on the kinetics of the dehydration. It has been shown that in the thermal dehydration of gypsum an abnormal change in the reaction rate and activation energy is observed. In the dehydration of phosphogypsum, this phenomenon is not observed. This is due to the impact of the water-soluble impurities on the recrystallization of an intermediate amorphous phase during the thermal decomposition.

Thermal dehydration kinetics and characterization of pandermite

Thermal dehydration kinetics and characterization of pandermite

A Novel Synthesis of Zinc Borates from a Zinc Oxide Precursor via Ultrasonic Irradiation.

In this study, zinc borate hydrate (Zn3B6O12 · 3.5H2O) was synthesized from zinc oxide (ZnO) and boric acid (H3BO3) via a novel method of ultrasonic irradiation. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Raman spectroscopy were used to characterize the synthesized products. Scanning electron microscopy (SEM) was used to determine the effects of reaction time and reaction temperature on the morphology of the products. Thermal dehydration kinetics were studied using thermal gravimetry and differential thermal gravimetry analysis (TG/DTA). The Doyle and Kissinger non-isothermal kinetic methods were used to analyse the TG/DTA data. The XRD results confirmed the successful synthesis of Zn3B6O12 · 3.5H2O at a range of reaction temperatures and times. Additionally, FT-IR and Raman analysis of the products identified peaks specific to zinc borate. Using the methods of Doyle and Kissinger, the activation energies of thermal dehydration of zinc borate were found to be 341.61 kJ/mol and 390.17 kJ/mol, respectively.

Effect of Ca(II) additive on the thermal dehydration kinetics of cerium oxalate rods

Kinetics of the thermal dehydration of solid-state reaction between cerium oxalate microrods and calcium oxalate has been studied using non-isothermal TG–DTA technique. With the introduction of calcium oxalate in varying compositions, the diffusional removal of the incorporated water molecules is impeded due to the blocking action of the surface product layer and the interaction of Ca(II). The procedure of kinetic deconvolution is used as a tool for identifying the partially overlapped kinetic processes of the thermal dehydration of pure and mixed oxalates. Mixed oxalates take more complex reaction pathways for the dehydration rather than pure oxalates of calcium and cerium. The thermal dehydration of pure cerium oxalate decahydrate and calcium oxalate dihydrate occurs in two stages, whereas that of mixed oxalates occurs in three stages. The amount of activation energy needed for the removal of 10 molecules of water from pure cerium oxalate rods and its mixture with calcium oxalate was determined by the isoconversional methods such as KAS, FWO and iterative isoconversional procedure. Significant effect in the thermal stability was observed for the compositions containing lower mass% of calcium oxalate. The average values of \(E_{{{\text{a}}_{\text{i}} }}\) for each independent process of the thermal dehydration of the mixed oxalates follow the order CC4 < CC3 < CC2.

Synthesis, characterization and thermal dehydration and degradation kinetics of chitosan Schiff bases of o-, m- and p-nitrobenzaldehyde

The chitosan Schiff bases were synthesised through the condensation reaction of chitosan with o-, m- and p-nitrobenzaldehyde (abbreviated as CSB-o, CSB-m and CSB-p) in the ratio 1:1 and were characterised by means of FTIR, UV, XRD and SEM. The thermal dehydration and degradation kinetics of all these Schiff bases were studied using different isoconversional and maximum rate (peak) methods, viz. Kissinger–Akahira–Sunose (KAS), Tang, Starink, Flynn–Wall–Ozawa (FWO) and Bosewell from DSC data and the thermal stability from TG. The activation energy values of thermal dehydration and degradation reactions obtained from isoconversional methods of FWO and Bosewell are slightly higher than that obtained from other methods. All the isoconversional and maximum rate (peak) methods yielded consistent values of E α for both the dehydration and degradation reactions and is in the order CSB-o < CSB-m < CSB-p. The Schiff bases observed (from TG) the same order of thermal stability.

Thermal dehydration kinetics and characterization of synthesized potassium borates

In this study, potassium pentaborate (santite: KB5O8·4H2O), with a powder diffraction number of 01-072-1688 was synthesized from potassium carbonate (K2CO3), boric acid (H3BO3) and boron oxide (B2O3) with reaction efficiencies between 84.88 and 95.11 %, through a hydrothermal route. Reaction temperatures and times were varied between 60–90 °C and 15–120 min. Synthesized minerals were characterized by X-ray diffraction, Fourier transform infrared and Raman spectroscopies, while surface morphologies were determined by scanning electron microscopy. Thermal dehydration behavior of santite was determined by thermal gravimetry and differential thermal analysis. From the results, santite lost its crystal water via a two-step process between 50 and 450 °C. Activation energies (E a) were calculated by using four non-isothermal kinetic methods and found to be 110.12 and 202.43 kJ/mol by the Coats–Redfern method, 107.77 and 304.18 kJ/mol by the Doyle method, 158.82 and 154.50 kJ/mol by the Kissinger–Akahira–Sunose method, and 158.07 and 156.76 kJ/mol by the Ozawa–Flynn–Wall method for the steps 1 and 2, respectively.

Effects of fly ash on thermal dehydration kinetics of cement paste

This paper presents a study of the fly ash's impact on thermal dehydration kinetics of cement paste using many types of testing and analysing methods, such as thermogravimetry analysis and Flynn–Wall–Ozawa method. The addition of fly ash can reduce the content of hydration products like calcium silicate hydrate (C-S-H). This is because fly ash reduces the content of cement. Moreover, a case of pozzolanic reaction between fly ash and Ca(OH)2 contributes to the decrease of Ca(OH)2. The results have shown that if cement paste contains as much as 10 wt-% fly ash, it has the highest Ea of Peak 3 for a period of 28 days. However, it has the smallest Ea of Peak 1 for a period of 3 days. The thermal dehydration Ea of Peak 2 increases along with the increasing fly ash content for a period of 7 days.

Characterization and thermal dehydration kinetics of zinc borates synthesized from zinc sulfate and zinc chloride

Zinc borate hydrate (Zn3B6O12·3.5H2O) was synthesized from zinc sulfate heptahydrate (ZnSO4·7H2O), anhydrous zinc chloride (ZnCl2), and boric acid (H3BO3). The product was characterized by X-ray diffraction, Fourier-transform infrared and Raman spectroscopy, and thermal gravimetry and differential thermal gravimetry. The effects of reaction time and temperature on product morphology were studied by use of scanning electron microscopy. Results from thermal analysis showed that dehydration occurred in two steps. Thermal dehydration kinetics were investigated by use of the Coats–Redfern and Horowitz–Metzger non-isothermal kinetic methods. In the Coats–Redfern method, activation energies were found to be 225.40 and 570.63 kJ/mol for the first and second steps, respectively. In the Horowitz–Metzger method, activation energies were found to be 254.33 kJ/mol for the first step and 518.22 kJ/mol for the second step.

Thermal dehydration and degradation kinetics of heptylidene chitosan

The thermal dehydration and degradation of chitosan and heptylidene chitosan were studied by differential scanning calorimetry at four different heating rates: 5, 10, 15 and 20 K min−1. The activation energy values of thermal dehydration and degradation of chitosan and heptylidene chitosan were investigated using different isoconversional and maximum rate (peak) methods viz. Kissinger–Akahira–Sunose (KAS), Tang, Starink, Flynn–Wall–Ozawa (FWO) and Bosewell. The variations of activation energy, E α, with conversion function, α, established using these different methods were found to be similar. Compared to the FWO method, the KAS method offers a significant improvement in the accuracy of the E a values. All the maximum rate (peak) methods yielded consistent values of E α for the dehydration and degradation reactions of both chitosan and HEPT-chitosan. From the results, it can be concluded that one can follow the maximum rate (peak) methods to get the value of E α ; however, the complexity of the reaction can be identified only through isoconversional methods.

Combined facile methods of the DSC and origin lab program to study the dehydration kinetics of KMnPO4·H2O

Thermal dehydration kinetics of potassium manganese phosphate monohydrate (KMnPO4·H2O) was studied using alternative procedure, including the combination between DSC data and Origin Lab program. The results revealed that this convenient method is a suitable tool for the determination of reliable kinetic parameters. The peak area at current temperature can be calculated using the Origin Lab program. Consequently, the kinetic parameters by non-isothermal equations can be calculated. The apparent activation energies were found to be 101.26 and 101.45 kJ mol−1 using KAS and iterative methods, respectively. The natural logarithms of pre-exponential factor (lnA) were found to be 12.2775 and 12.4157, respectively based on mechanism function of g(α) = (1−(1 – α)2/3). The experimental enthalpy change of the dehydration process of the studied compound was about 290 J g−1. All detectable peaks from XRD patterns of this compound are indexed as the formula KMnPO4·H2O according to the standard data file PDF#802360. The SEM micrograph exhibits the loose agglomeration phenomenon among the thin plate, which supports the existence of the layered structure compound.

Characterization and thermal dehydration kinetics of highly crystalline mcallisterite, synthesized at low temperatures.

The hydrothermal synthesis of a mcallisterite (Mg2(B6O7(OH)6)2·9(H2O)) mineral at low temperatures was characterized. For this purpose, several reaction temperatures (0–70°C) and reaction times (30–240 min) were studied. Synthesized minerals were subjected to X-ray diffraction (XRD), fourier transform infrared (FT-IR), and Raman spectroscopies and scanning electron microscopy (SEM). Additionally, experimental analyses of boron trioxide (B2O3) content and reaction yields were performed. Furthermore, thermal gravimetry and differential thermal analysis (TG/DTA) were used for the determination of thermal dehydration kinetics. According to the XRD results, mcallisterite, which has a powder diffraction file (pdf) number of “01-070-1902,” was formed under certain reaction parameters. Pure crystalline mcallisterite had diagnostic FT-IR and Raman vibration peaks and according to the SEM analysis, for the minerals which were synthesized at 60°C and 30 min of reaction time, particle size was between 398.30 and 700.06 nm. Its B2O3 content and reaction yield were 50.80 ± 1.12% and 85.80 ± 0.61%, respectively. Finally, average activation energies (conversion values (α) that were selected between 0.1 and 0.6) were calculated as 100.40 kJ/mol and 98.31 kJ/mol according to Ozawa and Kissinger-Akahira-Sunose (KAS) methods, respectively.

Characterization and thermal dehydration kinetics of admontite mineral hydrothermally synthesized from magnesium oxide and boric acid precursor

Magnesium borates are one of the major groups of boron minerals that have high heat and corrosion resistance and high coefficients of elasticity. In this study, magnesium borate minerals are hydrothermally synthesised using boric acid and magnesium oxide and are characterised by various analysis techniques. A drying temperature of 40 °C was used. From the results obtained, admontite mineral is synthesised purely at a reaction temperature of 100 °C and reaction times of both 120 and 240 min. Characterisations of the products are determined with the techniques of X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, differential thermal analysis and thermal gravimetry analysis. Additionally, overall admontite yields were calculated and varied between 89.98 ± 3.05 and 89.07 ± 1.28 %. Moreover, a kinetic study using the Ozawa, Kissenger, and Doyle methods was performed in the stage of decomposition of admontite that had been synthesised at a reaction time of 240 min.

Distinctive features of the formation of geopolymer aluminosilicate materials

The chemical processes underlying the formation of hydroaluminosilicate geopolymer materials under various conditions from various mixtures of amorphous SiO2, metakaolin, sodium hydroxide, and water were studied. The results demonstrate that hardening at elevated temperatures is favorable for partial crystallization of the forming zeolite-like phases, whereas room-temperature hardening leads to the formation of X-ray amorphous phases. According to X-ray microanalysis data, the composition of the aluminosilicate matrix formed during hardening differs markedly from the intended composition. At the same time, the onset temperature for thermal dehydration (about 60–80°C) and hydrolysis kinetics varied little from sample to sample, which allowed us to tentatively determine the composition of the forming hydroaluminosilicate polymer.

Preparation, characterization and thermal dehydration kinetics of titanate nanotubes

Titanate nanotubes were synthesized utilizing the hydrothermal method using titanium dioxide nanoparticles. The experiments were carried out considering the process as a function of reaction temperature, time, NaOH concentration and the acidity of the washing solution. The formation of titanate nanotubes was shown to be affected strongly by variations in any parameter. The optimum conditions for the synthesis of titanate nanotubes were determined to be a reaction temperature of 190 °C, and a reaction time of 12 h, using 10 M NaOH concentration and the washing solution to have a pH of 5.5. In addition, thermogravimetric analysis (TG/DTG) was used to investigate the thermal behaviour and dehydration kinetics of titanate nanotubes. In order to better understand their thermal behaviour, the thermal analysis of bulk hydrogen trititanate was performed. The values of the apparent activation energies of the first and second dehydration stages for titanate nanotubes were 81.44 ± 15.85 and 82.69 ± 7.46 kJ mol−1, respectively. The values of the apparent activation energies of the first, second and third dehydration stages for bulk hydrogen trititanate were 115.93 ± 5.40, 137.58 ± 6.47 and 138.97 ± 8.47 kJ mol−1, respectively.

Thermal Dehydration Kinetic Mechanism of Aluminum Sulfate Hydrates

Thermal dehydration kinetics of aluminum sulfate hydrates was studied with TG/DTA under static open air environment. It was found that the thermal dehydration of the aluminum sulfate hydrates was a two-stage process. The first stage happened in the temperature range from 90 to 300°C with 13 water loss. The second stage happened in the temperature range from 300 to 380 °C with 2 water loss. Activation energy and former factor of each staged were obtained by regression the TG/DTA data with 19 differential and integral functions based on non-isothermal Achar method as well as Coats-Redfern method. The result indicated that the mechanism for the first stage dehydration was the proliferation of three-dimensional, spherical symmetry, 3D, D3, slow-α-t curve, n = 2, reaction is reaction 2. The mechanism of the second stage dehydration was random nucleation and subsequent growth, A3, S-shaped α-t curve, n=1/3, m = 3, reaction is reaction 1/3. Identified that the most likely mechanism of Al2(SO4)3•15H2O dehydration is 2 and 1/3 reactions two process.

Thermal dehydration kinetics of a rare earth hydroxide, Gd(OH)3

AbstractThis paper reports the synthesis, characterization, and dehydration kinetics of a rare earth hydroxide, Gd(OH)3. Uniform rod‐like Gd(OH)3 powder was prepared by a colloidal hydrothermal method. The powder thus obtained dehydrated into its oxide form in a two‐step process, where crystalline GdOOH was obtained as the intermediate phase. Crystal structure study revealed a monoclinic structure for GdOOH, with space group P2/1m and lattice parameters a = 6.0633, b = 3.7107, c = 4.3266, and β = 108.669. The first‐step dehydration follows the F2 mechanism, while the second step follows the F1 model, indicating that both the steps are controlled by nucleation/growth mechanism. The activation energy Ea and frequency factor A are 231±12 kJ/mol and 2.08 × 1018 s−1 for the first step and 496 ± 32 kJ/mol and 7.88 × 1033 s−1 for the second step, respectively. Such high activation energy calculated from the experimental data can be ascribed to the high bonding energy of GdO bond, and the difference in activation energy for the two steps is due to the change in the bond length of hexagonal Gd(OH)3 and monoclinic GdOOH. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 75–81, 2007

The kinetic study of thermal dehydration of oxalic acid dihydrate

The thermal dehydration kinetics of crystalline powders of (COOH)2 · 2 H2O was examined by thermogravimetry both at constant and linearly increasing temperatures. An Avrami-Erofeyev law is found to hold with a possibility that a phase-boundary controlled reaction proceeds simultaneously. This is supported by the particle size effect on the rate constant. The activation energyE for the dehydration is estimated as around 80 kJ mol−1. It is likely that the effects of particle size and temperature onE are compensated by those on the frequency factorA.

ChemInform Abstract: THERMAL DEHYDRATION KINETICS OF DISACCHARIDES

Chemischer InformationsdienstVolume 14, Issue 25 Preparative Organic Chemistry ChemInform Abstract: THERMAL DEHYDRATION KINETICS OF DISACCHARIDES M. D. SCHEER, M. D. SCHEERSearch for more papers by this author M. D. SCHEER, M. D. SCHEERSearch for more papers by this author First published: June 21, 1983 https://doi.org/10.1002/chin.198325116Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue25June 21, 1983 RelatedInformation