Non-isothermal Thermogravimetric Analysis Research Articles

Crystal structure and thermal decomposition kinetics of 1-(pyridinium-1-yl)propane-(1-methylpiperidinium) bi[bis(trifluoromethanesulfonyl)imide], [PyC3Pi][NTf2

The structure of a room temperature asymmetrical dicationic ionic liquid (ADIL), 1-(pyridinium-1-yl) propane-(1-methylpiperidinium) bi[bis(trifluoromethanesulfonyl)imide] ([PyC3Pi][NTf2]2), was studied by the X-ray diffraction method. Meanwhile, thermal analysis of [PyC3Pi][NTf2]2 was also studied using non-isothermal thermogravimetric analysis (TGA). The title crystal belongs to the triclinic with space group Pī and unit-cell parameters a=0.95217 (8) nm, b=1.05129 (11) nm, c=1.70523 (14) nm, α=89.759 (8)°, β=80.657 (7)°, γ=68.007 (9)°, and F(000)=792. Thermal stability and thermal decomposition kinetics of the title compound were also investigated using TGA under the atmosphere of highly pure nitrogen. Heating curves at different rates were correlated with kinetic equations Friedman and ASTM (also called iso-conversion method). The values of average activation E (kJ·mol−1) and pre-exponential constant lgA are 149.58kJ·mol−1 and 8.83, respectively, which were obtained by the two methods. The kinetic model function, activation energy and pre-exponential constant of this reaction using the multivariate non-linear-regression method were f(α)=(1−α)(1+4.1870α), 151.04kJ·mol−1 and 8.81, respectively, which were basically consistent with iso-conversion methods.

Thermal Decomposition and Kinetic Studies of Solid Riboflavin using Model-Free Methods

The thermal stability and decomposition kinetics of riboflavin were investigated by nonisothermal thermogravimetric analysis (TGA) experiments in an inert atmosphere. For kinetic analysis, riboflavin was heated from room temperature to 800 °C with five different heating rates (5,10,15,20 and 30°C min−1). From the thermal decomposition process, it was found that there are two main stages of pyrolysis. In the DTG thermograms, the temperature peaks at maximum weight loss rate changed with varying heating rate. The kinetic parameters of decomposition including apparent activation energy ( Ea) and ln A (pre-exponential factor) under an inert atmosphere have been evaluated from the model-free isoconversion methods of Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO) and Friedman over the whole temperature domain. It was found that values of Ea and ln A decrease with increasing conversion (α). The reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. The apparent activation energy distributions with conversion calculated by these methods ranged between 15.18 and 236.55 kJ mol−1, and varied over a broad range in a complex manner depending on the heating rate.

Kinetic studies on the reoxidation of beneficiated ilmenite by non-isothermal thermogravimetric analysis

Synthetic rutile is an important titanium feedstock for the production of titanium dioxide pigment and titanium metal. More attention is focussed in recent years on the development of environment friendly processes for the production of synthetic rutile with minimum acidic effluents. CSIR-NIIST, Trivandrum, India, had successfully developed a more environment friendly process for the production of high grade synthetic rutile containing more than 94% TiO2. The process is comprised of metallisation of ilmenite followed by aeration rusting for the production of beneficiated ilmenite and the reoxdiation of beneficiated ilmenite followed by acid leaching. Reoxidation of beneficiated ilmenite plays a major role in rendering the product amenable to acid attack and removal of residual iron. This paper describes in detail the kinetic studies carried out on the reoxidation of beneficiated ilmenite by thermogravimetric technique under non-isothermal conditions. Assuming the oxidation mechanism to be in the form (1 - α)n and considering a contracting spherical model with n = 2/3, the basic equation of non-isothermal reaction was analysed and solved by integral approach. The kinetic parameters such as activation energy, pre-exponential factor and the order of the oxidation reaction were computed from the weight gain data under linear rise in temperature. The paper also discusses the optimisation of reoxidation temperature and residence time for the maximum removal of iron during acid leaching, which in turn results in synthetic rutile of maximum TiO2 content.

A Combined Raman Spectroscopic and Thermogravimetric Analysis Study on Oxidation of Coal with Different Ranks.

Raman spectroscopy and nonisothermal thermogravimetric analysis (TGA) measurements have been reported for different rank coals (lignite, bituminous coal, and anthracite) and the relationship between the measurements was examined. It was found that the Raman spectra parameters can be used to characterize structure changes in the different rank coals, such as the band area ratios based on the curve-fitted results. Higher ranked coal was found to have higher values of I GR/I All and I (G + GR)/I All but lower values of I D/I (G+GR), I DL/I (G+GR), I (S + SL)/I (G+GR), and I (GL+GL')/I (G+GR). The oxidation properties of the coal samples were characterized by the reactivity indexes T ig, T 20%, and T max from TGA data which were found to correlate well with the band area ratios of I GR/I All, I (G + GR)/I All, and I (S + SL)/I (G+GR). Based on these correlations, the Raman band area ratios were found to correlate with the oxidation activity of coal providing additional structural information which can be used to understand the changes in the TGA measurements.

Dependence of Pyrolysis Rate of Coal on Temperature

Pyrolysis process of coal has been researched to define kinetic constants which can be used for design and optimization of different processes of fuel transformation. The article considers anthracite powders and bituminous coal of Krasnogorsky mine with the use of non-isothermal thermogravimetric analysis with mass spectrometry. Spectroscanning microscopy and laser diffraction for definition of sizes and forms of particles distribution has been done. Other parameters – carbon content, ash and volatiles, density and moisture have been defined by standard methods. Energy of activation and pre-exponent with the use of models of Freedman, Starink and distributed activation energy model (DAEM), and also relative deviation of design data from experimental ones have been designed. The results of the analysis have shown the important influence of volatiles content and coal transformation degree on maximum reaction rate. Energy activation values received with the help of DAEM model are higher than with Freedman and Starink models. Process of pyrolysis of bituminous coal has a big rate in comparison with anthracite, and is better described by the above-mentioned models.

Effects of additives on carbon gasification

In this study, the effect of different additives on the kinetics of carbon gasification was studied by nonisothermal thermogravimetric analysis. The results showed that the carbon gasification comprised slow and fast gasification stages. Moreover, the carbon gasification was exothermic and endothermic in the low- and high-temperature regions, respectively. The nonisothermal kinetics of the carbon gasification was studied by the modified Coats-Redfern integration method. In the low-temperature region, the activation energy of the carbon gasification decreased by using B4C and SiO2 and increased by using MgO, Al2O3, and SiC. In the high-temperature region, B4C increased the activation energy, and Al2O3, MgO, SiC, and SiO2 decreased the activation energy.

Green chemical incorporation of silicon into polyoxoanions of molybdenum: characterization, thermal kinetics study and their photocatalytic water splitting activity

Cetylpyridinium silicomolybdate (CSM) nanorods were successfully synthesized by applying green chemistry principles using sodium molybdate and a structure directing cationic surfactant, cetyl pyridinium chloride (CPC) at room temperature. The composition and morphology of the nanorods were established by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) techniques. The thermal decomposition kinetics of CSM nanorods were investigated by a non-isothermal thermogravimetric analyzer at various heating rates. The thermal decomposition of CSM occurred in two stages. The activation energies of the first and second stages of thermal decomposition for all heating rates have been estimated using the iso-conventional methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) and the results are found to be in good agreement with each other. The invariant kinetic parameter (IKP) method and master plot method were also used to evaluate the kinetic parameters and mechanism for the thermal decomposition of CSM. The photocatalytic water oxidation mechanism using the CSM catalyst in the presence of platinum (Pt) co-catalyst enhances the H2 evolution and was found to be 1.946 mmol g−1 h−1.

Effect of γ-irradiation on the hydrolytic stability and thermo-oxidative behavior of bio/inorganic modified urea–formaldehyde resins

In order to minimize emission of formaldehyde from urea–formaldehyde resins (UF) and to improve their thermo-oxidative behavior, the effect of low γ-irradiation on hydrolytic and thermo-oxidative stability of nano-silica modified UF resin, modified UF resin with wood flour (Pinus silvestris L.) as natural filler and modified UF resin with mixture of SiO2/WF fillers were investigated. The hydrolytic stability of modified UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF resins after acid hydrolysis. The studied modified UF resins have been irradiated (50kGy) and effect of γ-irradiation was evaluated on the basis of percentage of liberated formaldehyde before and after irradiation. The minimum percentage (1.23%) of liberated formaldehyde and mass loss of a 25.35% were obtained in wood flour modified UF resin after γ-irradiation which indicate significant improvement in the hydrolytic stability compared to other modified UF resins. The effect of γ-irradiation was evaluated also on the basis of thermo-oxidative behavior of the same modified UF resins before and after irradiation. The thermo-oxidative behavior was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermo-gravimetry (DTG) and differential thermal analysis (DTA) supported by data from IR spectroscopy. After γ-irradiation, the shift of DTA peaks a higher temperature indicates that thermo-oxidative stability of modified UF/SiO2/WF is increase.

Kinetic study of solid waste pyrolysis using distributed activation energy model

The pyrolysis characteristics of municipal solid waste, agricultural residues such as ground nut shell, cotton husk and their blends are investigated using non-isothermal thermogravimetric analysis (TGA) with in a temperature range of 30–900°C at different heating rates of 10°C, 30°C and 50°C/min in inert atmosphere. From the thermograms obtained from TGA, it is observed that the maximum rate of degradation occurred in the second stage of the pyrolysis process for all the solid wastes. The distributed activation energy model (DAEM) is used to study the pyrolysis kinetics of the solid wastes. The kinetic parameters E (activation energy), k0 (frequency factor) are calculated from this model. It is found that the range of activation energies for agricultural residues are lower than the municipal solid waste. The activation energies for the municipal solid waste pyrolysis process drastically decreased with addition of agricultural residues. The proposed DAEM is successfully validated with TGA experimental data.

Kinetic Analysis on Catalytic Co-Gasification of Rubber Seed Shell and High Density Polyethylene Mixtures

In this paper, the catalytic co-gasification of rubber seed shell and high density polyethylene mixtures (0.2:0.8 weight ratio of HDPE:RSS) are investigated using a non-isothermal thermogravimetric analysis (TGA) system in a range of heating rates of 10, 20, 30 and 50 K/min within the temperature range of 323-1173 K. The argon gas is supplied at a flowrate of 100 ml/min and the steam is generated from superheater at 383 K. The steam is injected at flowrate of 300 μL/hour into the TGA system. A commercial nickel powder is used as the catalyst for the gasification process. The thermal decomposition behavior and synergistic effect of the HDPE/RSS mixture are investigated. The activation energy, EA and pre-exponential factor, A are determined based on one step integral method.

The kinetics and mechanism of thermal decomposition of SrCO3 polymorphs

The α→β transformation between orthorhombic (α) and hexagonal (β) polymorphs of strontium carbonate has significant effect on the behavior of SrCO3 during thermal treatment. The kinetics, mechanism and thermodynamics of activated complex in the process of thermal decomposition were investigated by non-isothermal thermogravimetric analysis (TGA) using mechanism-free (Kissinger equation) as well as kinetic function fitting methods. Both techniques as well as the calculation of theoretical activation energy (third law method) show that the transformation of α-SrCO3 to β-SrCO3 reduces the activation energy and changes the mechanism of the process. While thermal decomposition of rhombohedral SrCO3 is limited by the rate of process to the reaction interface (R3: g(α)=1−(1–α)1/3), the process limited by the rate of chemical reaction of 1/3 order (F1/3: 1−(1–α)2/3) was determined for the hexagonal polymorph. The samples before and after thermal treatment were investigated by infrared spectroscopy, scanning electron microscopy and X-ray diffraction analysis.

Evaluation of vapor pressures of 5-Methylresorcinol derivatives by thermogravimetric analysis

Abstract The present study was carried out to evaluate the vapor pressures of various 5-methylresorcinol derivatives using a thermogravimetric analyzer (TGA). In the experiments, 9–12 mg of each 5-methylresorcinol ether or ester was used, which allowed vapor pressures up to 24,500 Pa (on average) to be determined. The error in the measured vapor pressure values is estimated to be below 13.5% at vapor pressures lower than 10,000 Pa, while at values between 10,000 and 24,500 Pa it is below approximately 12%. The quality of the vapor pressure data was evaluated with anthracene, benzoic acid, docosane, hexadecane, nonane, and resorcinol as standard compounds using different calculation methods. The results showed that vapor pressures calculated by the mass transfer equation combined with estimated binary diffusion coefficients gave the most consistent results for these compounds, with errors always smaller than 15% (average absolute deviation 6.4%). These results are also consistent with the accuracies reported in literature for non-isothermal TGA. Therefore, this method could be used for evaluation of preliminary vapor pressure data as it may give more accurate results than group contribution methods.

A synthetic biology approach to characterise cyanobacterial promoters

The present study was carried out to evaluate the vapor pressures of various 5-methylresorcinol derivatives using a thermogravimetric analyzer (TGA). In the experiments, 9–12 mg of each 5-methylresorcinol ether or ester was used, which allowed vapor pressures up to 24,500 Pa (on average) to be determined. The error in the measured vapor pressure values is estimated to be below 13.5% at vapor pressures lower than 10,000 Pa, while at values between 10,000 and 24,500 Pa it is below approximately 12%.The quality of the vapor pressure data was evaluated with anthracene, benzoic acid, docosane, hexadecane, nonane, and resorcinol as standard compounds using different calculation methods. The results showed that vapor pressures calculated by the mass transfer equation combined with estimated binary diffusion coefficients gave the most consistent results for these compounds, with errors always smaller than 15% (average absolute deviation 6.4%). These results are also consistent with the accuracies reported in literature for non-isothermal TGA. Therefore, this method could be used for evaluation of preliminary vapor pressure data as it may give more accurate results than group contribution methods.

Study on the Pyrolysis Kinetics of HCl-Pretreated Soybean Stalk

To study the influences of the acid-washing on the characteristics of soybean stalk pyrolysis , and search the high-efficiency catalyst for biomass pyrolysis, pyrolysis experiments of soybean stalk pretreated by 0.1mol/L HCl acid solution were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The results showed the pyrolysis process of HCl-washed soybean stalk can be separated into four stages (water loss, depolymeri-zation and vitrification, thermal decomposition, and carbonization). At the same heating rate, the maximum pyrolysis rate of HCl-washed is larger than untreated soybean stalk, but the corresponding temperature is higher. All the DTG (differential thermogravimetric) curveas appear a smaller shoulder peak respectively. With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the high-temperature direction, and the maximum pyrolysis rate and its corresponding temperature increase too. HCl-wahsed makes the weight loss rate of the final temperature increase 5% approximately. The value area of activation energy of the main pyrolysis area is 140.19~174.59 kJ/mol calculated by the method of Ozawa. The Šatava method inferred the most possible mechanism function of HCl-wahsed soybean stalk is Zhuralev-Lesakin-Tempelman equation, which is three-dimensional diffusion.

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.

Reactivity during bench-scale combustion of biomass fuels for carbon capture and storage applications

Reactivities of four biomass samples were investigated in four combustion atmospheres using non-isothermal thermogravimetric analysis (TGA) under two heating rates. The chosen combustion atmospheres reflect carbon capture and storage (CCS) applications and include O2 and CO2-enrichment. Application of the Coats–Redfern method assessed changes in reactivity. Reactivity varied due to heating rate: the reactivity of char oxidation was lower at higher heating rates while devolatilisation reactions were less affected. In general, and particularly at the higher heating rate, increasing [O2] increased combustion reactivity. A lesser effect was observed when substituting N2 for CO2 as the comburent; in unenriched conditions this tended to reduce char oxidation reactivity while in O2-enriched conditions the reactivity marginally increased. Combustion in a typical, dry oxyfuel environment (30% O2, 70% CO2) was more reactive than in air in TGA experiments. These biomass results should interest researchers seeking to understand phenomena occurring in larger scale CCS-relevant experiments.

Pyrolysis Kinetics and Characteristics of Wood-Based Materials from Municipal Solid Waste

Wood-based materials from Municipal Solid Waste have the potential of covering a significant part of the future demand on gasification capacities. However, their pyrolysis kinetics and gasification behavior has not yet been fully investigated. This paper describes the pyrolysis characteristics of typing paper and Chinese parasol from municipal solid waste applying the non-isothermal thermogravimetric analysis, the apparent activation energy and the pre-exponential factor were obtained by kinetics analysis at the heating rate of 10/20/40 oC•min-1.

Nanosilica and wood flour-modified urea–formaldehyde composites

In this study, the thermal behavior of modified urea–formaldehyde (UF) resin with nanosilica (nano-SiO2), wood flour (WF), and their mixture of SiO2/WF was investigated. Five modified UF hybrid composite materials with 0.8 F/U ratio with different filler were synthesized using the same procedure. The thermal behavior of materials was studied using nonisothermal thermogravimetric analysis, differential thermal gravimetry (DTG), and differential thermal analysis and supported by data from infrared spectroscopy. The shift of DTG peaks to a high temperature indicates the increase in thermal stability of modified UF resin with hybrid SiO2/WF fillers, which is confirmed by the data obtained from the Fourier transform infrared spectroscopic study. It was estimated that the UF/WF samples based on nano-SiO2 have better thermal stability.

Thermal Degradation Studies of Terpolymer Derived from 2-Aminothiophenol, Hexamethylenediamine, and Formaldehyde

Terpolymer (2-ATPHMDAF-I) has been synthesized by the condensation of 2-aminothiophenol and hexamethylenediamine with formaldehyde in the presence of 2 M hydrochloric acid as a catalyst with 1 : 1 : 2 molar proportion of reacting monomers. The structure of newly synthesized terpolymer has been elucidated and confirmed on the basis of elemental analysis and various spectral techniques, that is, UV-visible, FT-IR, and 1H-NMR spectroscopy. Number average molecular weight (Mn¯) has been determined by conductometric titration in nonaqueous medium. The viscosity measurements in dimethyl sulfoxide (DMSO) have been carried out to ascertain the characteristic functions and constants. The studies have been further extended to nonisothermal thermogravimetric analysis for determination of their mode of decomposition and relative thermal stability. Activation energy Ea, order of reaction (n), and frequency factor (z) were calculated by Friedman, Chang, Sharp-Wentworth and Freeman-Carroll methods. Activation energy calculated by Friedman and Chang methods are in close agreement with each other while the results obtained from Freeman-Carroll and Sharp-Wentworth’s methods are found to be in a similar order.

Degradation of plastics from the ResinKit as a model for the selection of polymers for artworks. Assessment by nonisothermal thermogravimetric analysis and chemiluminometry

Degradation of plastics from the ResinKit as a model for the selection of polymers for artworks. Assessment by nonisothermal thermogravimetric analysis and chemiluminometry