Effect of the catalyst MCM-41 on the kinetic of the thermal decomposition of poly(ethylene terephthalate)

The aim of this work is to determine the activation energy for the thermal decomposition of poly(ethylene terephthalate)—PET, in the presence of a MCM-41 mesoporous catalyst. This material was synthesized by the hydrothermal method, using cetyltrimethylammonium as template. The PET sample has been submitted to thermal degradation alone and in presence of MCM-41 catalyst at a concentration of 25% in mass (MCM-41/PET). The degradation process was evaluated by thermogravimetry, at temperature range from 350 to 500 °C, under nitrogen atmosphere, with heating rates of 5, 10 and 25 °C min^?1. From TG, the activation energy, determined using the Flynn–Wall kinetic method, decreased from 231 kJ mol^?1, for the pure polymer (PET), to 195 kJ mol^?1, in the presence of the material (MCM-41/PET), showing the catalyst efficiency for the polymer decomposition process.     

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.     

Thermoanalytical and NMR investigation of NaBH<Subscript>4</Subscript> × 2H<Subscript>2</Subscript>O thermolysis process

This paper describes the thermal investigations and kinetic analysis regarding the solid-state degradation of three compounds used as mental disorder therapeutic agents (antidepressants), namely amitriptyline, desipramine and imipramine. The study was carried according to ICTAC 2000 recommendations, by using three isoconversional methods, namely Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Friedman. The differential method of Friedman indicated multistep degradation, which was later confirmed by the nonparametric kinetic method (NPK). NPK method showed that all three tricyclic antidepressants are degraded by two processes. In terms of apparent activation energies for decomposition, the NPK method indicated 123.4 kJ mol^?1 for imipramine, 112.3 kJ mol^?1 for desipramine and 82.9 kJ mol^?1 for amitriptyline, and the results are in good agreement with the ones suggested by isoconversional methods.     

Dibenzofuran and methyldibenzofuran derivatives: assessment of thermochemical data

Thermochemical data of dibenzofuran, a compound of considerable industrial and environmental significance, obtained from experimental calorimetric and computational techniques are reported in this work. The enthalpy of fusion, (19.4 ± 1.0) kJ mol^?1, at the temperature of fusion, (355.52 ± 0.02) K, was determined by differential scanning calorimetry measurements of dibenzofuran. From the standard (p° = 0.1 MPa) molar enthalpies of formation of crystalline dibenzofuran, (?29.2 ± 3.8) kJ mol^?1, and of sublimation, (84.5 ± 1.0) kJ mol^?1, determined at T = 298.15 K by static bomb combustion calorimetry and by vacuum drop microcalorimetry, respectively, it was possible to calculate the enthalpy of formation of the gaseous compound, (55.0 ± 3.9) kJ mol^?1, at the same temperature. The enthalpy of formation in the gaseous phase was also determined from G3(MP2)//B3LYP calculations. The same computational strategy was employed in the calculation of the standard molar enthalpies of formation, at T = 298.15 K, in the gas-phase, of single methylated derivatives of benzofuran and dibenzofuran.     

Study on thermal decomposition and oxidation kinetics of cation exchange resins using non-isothermal TG analysis

Kinetics of two successive thermal decomposition reaction steps of cationic ion exchange resins and oxidation of the first thermal decomposition residue were investigated using a non-isothermal thermogravimetric analysis. Reaction mechanisms and kinetic parameters for three different reaction steps, which were identified from a FTIR gas analysis, were established from an analysis of TG analysis data using an isoconversional method and a master-plot method. Primary thermal dissociation of SO₃H⁺ from divinylbenzene copolymer was well described by an Avrami–Erofeev type reaction (n = 2, g(α) = [?ln(1 ? α)]^1/2]), and its activation energy was determined to be 46.8 ± 2.8 kJ mol^?1. Thermal decomposition of remaining polymeric materials at temperatures above 400 °C was described by one-dimensional diffusion (g(α) = α ²), and its activation energy was determined to be 49.1 ± 3.1 kJ mol^?1. The oxidation of remaining polymeric materials after thermal dissociation of SO₃H⁺ was described by a phase boundary reaction (contracting volume, g(α) = 1?(1 ? α)^1/3). The activation energy and the order of oxygen power dependency were determined to be 101.3 ± 13.4 and 1.05 ± 0.17 kJ mol^?1, respectively.     

Kinetic and thermodynamic parameters of volatilization of biodiesel from babassu, palm oil and mineral diesel by thermogravimetric analysis (TG)

The boiling point and volatility are important properties for fuels, as it is for quality control of the industry of petroleum diesel and biofuels. In addition, through the volatility is possible to predict properties, such as vapor pressure, density, latent heat, heat of vaporization, viscosity, and surface tension of biodiesel. From thermogravimetry analysis it is possible to find the kinetic parameters (activation energy, pre-exponential factor, and reaction order), of thermally simulated processes, like volatilization. With the kinetic parameters, it is possible to obtain the thermodynamic parameters by mathematical formula. For the kinetic parameters, the minor values of activation energy were found for mineral diesel (E = 49.38 kJ mol^?1), followed by babassu biodiesel (E = 76.37 kJ mol^?1), and palm biodiesel (E = 87.00 kJ mol^?1). Between the two biofuels studied, the babassu biodiesel has the higher minor value of activation energy. The thermodynamics parameters of babassu biodiesel are, ΔS = ?129.12 J mol^?1 K^?1, ΔH = +80.38 kJ mol^?1 and ΔG = +142.74 kJ mol^?1. For palm biodiesel ΔS = ?119.26 J mol^?1 K^?1, ΔH = + 90.53 kJ mol^?1 and ΔG = +141.21 kJ mol^?1, and for diesel ΔS = ?131.3 J mol^?1 K^?1, ΔH = +53.29 kJ mol^?1 and ΔG = +115.13 kJ mol^?1. The kinetic thermal analysis shows that all E, ΔH, and ΔG values are positive and ΔS values are negative, consequently, all thermodynamic parameters indicate non-spontaneous processes of volatilization for all the fuels studied.     

Thermogravimetric analyses revealed the bioenergy potential of <Emphasis Type="Italic">Eulaliopsis binata</Emphasis>

The present study was focused on the thermal degradation of Eulaliopsis binata biomass produced on a salt-affected soil without any fertilizer or pesticide applications. The plant biomass was subjected to thermal degradation experiments at three heating rates, 10, 30 and 50 K min^?1. The kinetic analyses were performed through isoconversional models of Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa, followed by the calculation of thermodynamic parameters of activation. The high heating value was calculated as 15.10 MJ mol^?1. The activation energy values of the grass were shown to be ranging from 118 through 240 kJ mol^?1. Energy difference of enthalpies of activation between the reagent and the activated complex was in accordance with activation energies. Pre-exponential factors indicated the reaction to follow first-order kinetics. Gibbs free energy for the grass was measured to be ranging from 171 to 174 kJ mol^?1. Our data have shown that E. binata biomass offers remarkable potential as a low-cost biomass for bioenergy.     

Thermal study on decomposition of LiBH4 at non-isothermal and non-equilibrium conditions

Thermal decomposition measurements for lithium borohydride (LiBH₄) are performed at non-isothermal and non-equilibrium conditions by means of differential thermal analysis (DTA). A simplified alternative procedure is introduced for evaluating thermodynamic and kinetic parameters simultaneously using a single set of measurements. Rate constant (k) and enthalpy (ΔH = ?102.1 ± 0.7 kJ mol^?1 LiBH₄) are archived. Temperature dependence for activation energy (E _a) is found taking advantage of Guggenheim–Arrhenius method; the mean activation energy is $ \overline{E}_{a} $  93.9 ± 0.9 kJ mol^?1 LiBH₄ in the range of heating rate β 1–50 K min^?1.     

Kinetic parameters for thermal decomposition of hydrazine

The propulsion of most of the operating satellites comprises monopropellant (hydrazine––N₂H₄) or bipropellant (monometilydrazine—MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N₂H₄. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela–Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min^?1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol^?1, lnA = 14.2 ± 0.9 and T _b = 69 °C) and oxygen (E = 64.9 ± 8.6 kJ mol^?1, lnA = 20.7 ± 3.1 and T _b = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F _1/3 model.     

Preparation and Thermal Chemical Property of Complexes of Zinc Nitrate with Trytophan

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Hydrogen sorption–desorption studies on ZrCo–hydrogen system

The ZrCo–H₂ system was investigated in this study owing to its importance as a suitable candidate material for storage, supply, and recovery of hydrogen isotopes. Desorption hydrogen pressure-composition isotherms were generated at six different temperatures in the range of 524–624 K. A van’t Hoff plot was constructed using the plateau pressure data of each pressure-composition isotherms and the thermodynamic parameters were calculated for the hydrogen desorption reaction of ZrCo hydride. The enthalpy and entropy change for the desorption of hydrogen were found to be 83.7 ± 3.9 kJ mol^?1 H₂ and 122 ± 4 J mol^?1 H₂ K^?1, respectively. Hydrogen absorption kinetics of ZrCo–H₂ system was studied at four different temperatures in the range of 544–603 K and the activation energy for the absorption of hydrogen by ZrCo was found to be 120 ± 5 kJ mol^?1 H₂ by fitting kinetic data into suitable kinetic model equation.     

Experimental and computational study of the thermal decomposition of 3-buten-1-ol in m-xylene solution

An experimental study of the thermal decomposition of a β-hydroxy alkene, 3-buten-1-ol, in m-xylene solution, has been carried out at three different temperatures: 553.15, 573.15, and 593.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s^?1) = (27.34 ± 1.24)–(19,328 ± 712) (kJ mol^?1) T ^?1. A computational study has been performed at the MP2/6-31+G(d) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. The Arrhenius equation obtained theoretically, ln k (s^?1) = (28.252 ± 0.025)–(19,738.0 ± 14.4) (kJ mol^?1) T ^?1, agrees very satisfactorily with the experimental one. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis which provides the natural atomic charges and the Wiberg bond indices used to follow the progress of the reaction. The enthalpy of the reaction has been calculated using experimental values taken from literature and theoretic calculations. The agreement between both values is satisfactory.     

Hermetic thermal behaviors and specific heat capacities of bis(aminofurazano)furazan and bis(nitrofurazano)furazan

Thermal behaviors of bis(aminofurazano)furazan (BAFF) and bis(nitrofurazano)furazan (BNFF) were studied by the differential scanning calorimetry (DSC) method with a special hermetic high-pressure crucible and compared to that with a common standard Al crucible. The exothermic decomposition processes of the two compounds were completely revealed. The extrapolated onset temperature, peak temperature and enthalpy of exothermic decomposition at the heating rate of 10 °C min^?1 are 290.2, 313.4 °C and ??2174 J g^?1 for BAFF, and 265.8, 305.0 °C and ??2351 J g^?1 for BNFF, respectively. The apparent activation energies of the decomposition process for the two compounds are 115.7 and 131.7 kJ mol^?1, respectively. The self-accelerating decomposition temperatures and critical temperatures of thermal explosion are 247.5 and 368.7 °C for BAFF, and 249.6 and 268.1 °C for BAFF, respectively. Both BAFF and BNFF present high thermal stability. The specific heat capacities for the two compounds were determined with the micro-DSC method, and the specific heat capacities and molar heat capacities at 298.15 K are 1.0921 J g^?1 K^?1 and 257.9 J mol^?1 K^?1 for BAFF, and 1.0419 J g^?1 K^?1 and 308.5 J mol^?1 K^?1 for BNFF, respectively.     

Synthesis, structure analysis and thermodynamics of [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one)

A novel complex [Ni(H₂O)₄(TO)₂](NO₃)₂·2H₂O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E _a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol^?1, 10^13.80 s^?1; 108.0 kJ mol^?1, 10^23.23 s^?1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ^≠), enthalpy of activation (ΔH ^≠) and the free energy of activation (ΔG ^≠) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being ?1464.55 ± 1.70 kJ mol^?1 by a rotating-bomb calorimeter.     

Kinetics of the thermal decomposition of anhydrous cobalt nitrate by SCRT method

It has been shown the ability of the Sample Controlled Reaction Temperature (SCRT) method for both discriminate the kinetic law and calculate the activation energy of the reaction. This thermal decomposition is best described by a Johnson–Mehl–Avrami kinetic model (with n = 2) with an activation energy of nuclei growth which fall in the range 52–59 kJ mol^?1. The process is not a single-step because the initial rate of decomposition is likely to be limited by nucleation. The results reported here constitute the first attempt to use the new SCRT method to study the kinetic of the thermal decomposition of cobalt nitrate.     

Thermal properties and kinetics of new-generation posterior bulk fill composite cured light-emitting diodes

In this study, the thermal behavior in terms of glass transition (T _g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E _a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min^?1) during DSC. The results show that the Xtrabase composite displayed the highest T _g (120 °C at a 5 °C min^?1 heating rate) and E _a (157.64 kJ mol^?1) values associated with thermal degradation from the main chain of the polymer.     

Reduction Reaction of the Copper(II) Complex Bearing 1,3-Di(pyridine-2-carboxaldimino)propane (pitn) by Decamethylferrocene in Acetonitrile

The reduction reaction of the Cu(II)–pitn complex (pitn = 1,3-di(pyridine-2-carboxaldimino)propane) by decamethylferrocene [Fe(Cp*)₂] was examined in acetonitrile. The observed pseudo-first-order rate constants exhibited saturation kinetics with increasing excess amount of [Fe(Cp*)₂]. Detailed analyses revealed that the reaction is controlled by a structural change prior to the electron transfer step, rather than a conventional bimolecular electron transfer process preceded by ion pair (encounter complex) formation. The rate constant for the structural change was estimated to be 275 ± 13 s^?1 at 298 K (?H* = 33.3 ± 1.0 kJ·mol^?1, ?S* = 86 ± 5 J·mol^?1·K^?1), which is the fastest among gated reactions involving CuN₄ complexes. It was confirmed by EPR measurement and Conflex calculations that the dihedral angle between the two N–N planes is significantly large (40°) in solution whereas it is merely 17.14° in the crystal.     

Thermal decomposition and kinetics studies on the 2,2-dinitropropyl acrylate–styrene copolymer and 2,2-dinitropropyl acrylate–vinyl acetate copolymer

In the present work, kinetics of thermal decomposition of 2,2-dinitropropyl acrylate–styrene copolymer (DNPA/St) and 2,2-dinitropropyl acrylate–vinyl acetate copolymer (DNPA/VAc) was investigated by differential scanning calorimetry (DSC). The influence of the heating rate (5, 10, 15, and 20 °C min^?1) on the DSC behavior of the copolymer was verified. The results showed that, as the heating rate was increased, decomposition temperature of the copolymer was increased. Also, the kinetic parameters such as activation energy and frequency factor of the copolymer were obtained from the DSC data by the isoconversional methods proposed by Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). Average activation energy obtained by KAS and FWO methods for the thermal decomposition reaction of DNPA/St and DNPA/VAc are 157.38 ± 0.27 and 147.67 ± 0.57 kJ mol^?1, respectively. The rate constants for thermal decomposition calculated from the activation parameters showed the structural dependency. The relative stability of two copolymers under 50 °C was in this order: DNPA/St > DNPA/VAc. The results of thermogravimetry (TG) analysis revealed that the main mass changes for DNPA/St and DNPA/VAc occurred in the temperature ranges of 200–270 °C. The DSC-FTIR analysis of DNPA/St indicates that the band intensity of nitro and other groups increased haphazardly from 230 °C due to thermal decomposition.     

Comparative pyrolysis upcycling of polystyrene waste: thermodynamics, kinetics, and product evolution profile

Pyrolysis is one important way to treat polystyrene waste and upcycle it into useful materials. A comparative pyrolysis study of virgin polystyrene (VPS) and two types of commonly used polystyrene products, expanded polystyrene (EPS) and polystyrene container (CPS) was carried out. Various values were found in the thermodynamic study and kinetic study of VPS, EPS, and CPS pyrolysis, suggesting distinct thermal degradation characteristics of these materials. The energy barrier order of the pyrolysis processes was EPS, CPS, VPS, showing activation energy of 230, 219, and 145 kJ mol^?1, respectively. The order of amount of heat absorbed was EPS, CPS, VPS, with enthalpy of 224, 213, and 139 kJ mol^?1, respectively. The reaction favorability order was EPS, CPS, and VPS with Gibbs free energy of 118, 132, and 210 kJ mol^?1, respectively. Thermogravimetric analysis indicated the use of high heating rate would increase the reaction rate and shorten the reaction time. Product evolution profiles showed that VPS and CPS pyrolysis produced mainly aromatics, while EPS pyrolysis produced aromatics at the initial phase of the reaction and aliphatic hydrocarbon at the latter phase. The diverse pyrolysis behaviors of VPS, EPS, and CPS demonstrated that an examination on different polystyrene materials was desired to optimize the pyrolysis conditions and product distribution, and thus benefit the process of valuable materials recovery.     

Physical–chemical characterization of new anti-inflammatory agent (LPSF/GQ-130) and evaluation of its thermal compatibility with pharmaceutical excipients

LPSF/GQ-130 is a drug candidate, according to reports about its significant anti-inflammatory activity and non-toxicity demonstrated in an acute preclinical study. Despite this, knowledge of its physical–chemical properties is insufficient for the development of medicines. Thus, this work aimed to characterize the raw material at its molecular, particle, and agglomerate level as well as evaluate its thermal compatibility to pharmaceutical excipients. Through spectrometric techniques the molecular structure of the substance was confirmed. For thermal analysis its melting (171.3–176.5 °C) and degradation (238.3–297.4 °C) ranges, besides its purity (99.37 %), were determined. The kinetic non-isothermal degradation supplied the order of thermal reaction (0), the activation energy (96.14 kJ mol^?1) and the frequency factor (3.130 × 10^?7 min^?1). The diffraction of X-rays presented well defined signs in the angles 5.5°, 16.3°, and 44.18° 2θ, suggesting crystalline structure. Scanning electronic microscopy exhibited needle morphology. LPSF/GQ-130 presented Type-III isotherm adsorption/desorption, with a superficial area of 81.3529 m² g^?1 and water content calculated at 1 % using the Karl Fisher method. Laser granulometry calculated its granulometry between 11.65 and 13.10 μm, thus it was characterized as a very fine powder. The prototype was classified as insoluble in water (<0.0187 μg mL^?1) and soluble in acetone and acetonitrile, and exhibits instability in basic pH (100 %) and oxidative conditions (30–70 %). In thermal compatibility the excipients PVP K-30, Compritol^® 888 ATO, and MYRJ^® 59 seem to exercise a protective thermal activity for the prototype.