The Thermogravimetric Analyzer (TGA) is a standard state-of-the-art instrument used for investigating char gasification kinetics. However, one major flaw of the TGA is the build-up of a stagnant gas ...region between the empty space of the crucible mouth and the char sample layer, which leads to poor gas-solid contacting. Diffusion is the predominant mechanism for the transport of reactive gas from the crucible mouth to the porous char layer. Therefore, this work aims to present a numerical model for evaluating the kinetic data using a TGA, encapsulating the three diffusion phenomena affecting the reactive gas inside the TGA crucible (i) diffusion of gas between the char layer and crucible mouth, (ii) diffusion of gas within the inter-particle voids of the char layer and (iii) diffusion of the gas within the intra-particle pores of the char particle. The model was first formulated and validated for the non-porous char particles and then extended to the porous particles. The simulation results predicted by the model using the re-evaluated parameters are in good agreement with the experimental results. It was shown that the diffusion of the gas within the inter-particle voids of the char layer in TGA has a significant impact on gasification processes inside TGA sample. In particular, the consideration of diffusional effects within the crucible resulted in an 8.5% increase in the activation energy. A sensitivity analysis showed that the model was highly sensitive to the change in the specific surface area of the char.
•Alternative to common TGA–FTIR/MS techniques for analysing complex mixtures of thermal decomposition products of polymers.•Development of a new technique consisting of thermogravimetry ...(TGA)–solid-phase extraction (SPE)–thermal desorption (TDS)–gas chromatography mass spectrometry (GC–MS).•Ease of handling, unambiguous product identification, good repeatability.•Influence by specific binding of different products.
For analysis of the gaseous thermal decomposition products of polymers, the common techniques are thermogravimetry, combined with Fourier transformed infrared spectroscopy (TGA–FTIR) and mass spectrometry (TGA–MS). These methods offer a simple approach to the decomposition mechanism, especially for small decomposition molecules. Complex spectra of gaseous mixtures are very often hard to identify because of overlapping signals. In this paper a new method is described to adsorb the decomposition products during controlled conditions in TGA on solid-phase extraction (SPE) material: twisters. Subsequently the twisters were analysed with thermal desorption gas chromatography mass spectrometry (TDS–GC–MS), which allows the decomposition products to be separated and identified using an MS library. The thermoplastics polyamide 66 (PA 66) and polybutylene terephthalate (PBT) were used as example polymers. The influence of the sample mass and of the purge gas flow during the decomposition process was investigated in TGA. The advantages and limitations of the method were presented in comparison to the common analysis techniques, TGA–FTIR and TGA–MS.
•Evaluation based on interlaboratory test material (suspended matter w/ and w/o microplastic).•TED-GC/MS is most powerful to determine microplastic in environmental samples.•TGA-FTIR showed high ...robustness in general and good results.•TGA-MS provides PVC determination that is not possible with TED-GC/MS.•MCC is introduced as promising screening tool with 10–20 min measurement time.
Microplastic particles are currently detected in almost all environmental compartments. The results of detection vary widely, as a multitude of very different methods are used with very different requirements for analytical validity.
In this work four thermoanalytical methods are compared and their advantages and limitations are discussed. One of them is thermal extraction-desorption gas chromatography mass spectrometry (TED-GC/MS), an analysis method for microplastic detection that has become established in recent years. In addition, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS) were applied, two methods that are less common in this field but are still used in other research areas. Finally, microscale combustion calorimeter (MCC) was applied, a method not yet used for microplastic detection.
The presented results are taken from a recently published interlaboratory comparison test by Becker et al. (2020). Here a reference material consisting of suspended matter and specified added polymer masses was examined, and only the results of the recoveries were presented. In the present paper, however, the results for the individual polymers are discussed in detail and individual perspectives for all instruments are shown.
It was found that TED-GC/MS is the most suitable method for samples with unknown matrix and unknown, variable kinds and contents of microplastic. TGA-FTIR is a robust method for samples with known matrix and with defined kinds of microplastic. TGA-MS may offer a solution for the detection of PVC particles in the future. MCC can be used as a very fast and simple screening method for the identification of a potential microplastic load of standard polymers in unknown samples.
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•Model-free integral kinetics method and analytical TGA–FTIR were conducted on pyrolysis process of PKS.•The pyrolysis mechanism of PKS was elaborated.•Thermal stability was ...established: lignin>cellulose>xylan.•Detailed compositions in the volatiles of PKS pyrolysis were determinated.•The interaction of biomass three components led to the fluctuation of activation energy in PKS pyrolysis.
Palm kernel shell (PKS) from palm oil production is a potential biomass source for bio-energy production. A fundamental understanding of PKS pyrolysis behavior and kinetics is essential to its efficient thermochemical conversion. The thermal degradation profile in derivative thermogravimetry (DTG) analysis shown two significant mass-loss peaks mainly related to the decomposition of hemicellulose and cellulose respectively. This characteristic differentiated with other biomass (e.g. wheat straw and corn stover) presented just one peak or accompanied with an extra “shoulder” peak (e.g. wheat straw). According to the Fourier transform infrared spectrometry (FTIR) analysis, the prominent volatile components generated by the pyrolysis of PKS were CO2 (2400–2250cm−1 and 586–726cm−1), aldehydes, ketones, organic acids (1900–1650cm−1), and alkanes, phenols (1475–1000cm−1). The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) method at different heating rates. The fluctuation of activation energy can be interpreted as a result of interactive reactions related to cellulose, hemicellulose and lignin degradation, occurred in the pyrolysis process. Based on TGA–FTIR analysis and model free integral kinetics method, the pyrolysis mechanism of PKS was elaborated in this paper.
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•Thermal degradation study of polyethylene terephthalate (PET) form waste soft drink bottles.•Non-isothermal TGA based kinetic analysis for inert and oxygenated environment.•Kinetic ...parameters predicted from isothermal TGA data.•Advance isoconversional and McCallum methods were used to predict the variable activation energy values.
Thermogravimetric analysis (TGA) of polyethylene terephthalate obtained from waste soft drink bottles (PET-SDB) was carried out under inert (nitrogen) as well as reactive (synthetic air) environments to evaluate the degradation behaviour and degradation kinetics. Non-isothermal TGA experiments at heating rates of 5, 10, 20, 40 and 50 °C/min were performed and the kinetic parameters such as activation energy (Eα) and pre-exponential factor (Aα) were determined at various extent of conversions using advance isoconversional (AIC) method. Criados’ master plot technique established F1 (first order) as possible reaction model (fα) for both inert and oxygenated non-isothermal TGA data. Under inert (N2) environment a residue accumulation of around 20% was observed whereas complete conversion of PET-SDB occurred in oxygenated environment. The activation energy values were found in the range of 203–355 kJ/mol and 145–218 kJ/mol for inert and oxygenated environment respectively. Isothermal TGA data at various temperatures were analysed for the estimation of kinetic parameters. In the considered range of conversions, the range of activation energy obtained for multiple isothermal TGA data was found in the range of 196–217 kJ/mol.
•Identification of PT30 resin degradation products by TGA-IR and TGA-MS.•Proposal of a degradation mechanism for PT30 resin in a nitrogen atmosphere.•Identification of the initiation degradation ...reaction based on the results of Density Functional Theory (DFT) calculations which highlight the less energetic network bonds.•Description of each step in the chain scissions of the PT30 resin.•Description of each step in the creation of degradation products.
The non-isothermal thermal degradation of the cured phenolic triazine thermoset resin (PT30) was considered under nitrogen atmosphere. Thermogravimetric analyses (TGA) showed that the degradation mechanism was decomposed in three main steps occurring at 440°C, 550°C, and 720°C. To understand the chemical reactions that happen, TGA experiments were coupled with the analyses of the gaseous products by Fourier transform infrared detection (TGA/FTIR) and by mass spectrometry (TGA/MS). A degradation mechanism is proposed based on these experimental results and on Density Functional Theory (DFT) calculations. It was found that carbon dioxide is the main degradation product generated by the oxygen-carbon chain scissions. In the second step, triazine rings’ rupture led to the formation of cyanide hydrogen and probably cyanic/isocyanic acid. Then, various aromatic compounds are produced from chain scissions and molecules’ recombination. Analyses of these degradation products contributed to proposing assumptions of thermal degradation mechanisms of the PT30 resin.
This research explores the structural effect of phosphoramidates as flame retardants (FRs) for cotton cellulose. Flame retardant (FR) and thermal decomposition actions of phosphate such as triethyl ...phosphate (TEP), primary phosphoramidate such as diethyl phosphoramidate (DEPA) and secondary phosphoramidates such as phosphoramidic acid, N(2-hydroxy ethyl) diethylester (PAHEDE), diethyl ethyl phosphoramidate (DEEP) and diethyl 2-methoxyethylphosphoramidate (DEMEP) on cotton cellulose were investigated. Limiting oxygen index (LOI) of treated cotton cellulose showed that all phosphoramidates exhibited better flame retardant properties as compared to TEP. Secondary phosphoramidate PAHEDE had better flame retardant properties as compared to DEMEP and DEEP which indicate that flame retardancy of secondary phosphoramidates is structure related. Test performed on pyrolysis combustion flow calorimeter (PCFC) for treated cellulose showed higher reduction in heat of combustion for efficient FRs (PAHEDE, DEPA). Evolved gas analysis using thermogravimetric analyzer–Fourier transform infrared spectroscopy (TGA–FTIR) and thermogravimetric analyzer–mass spectrometer (TGA–MS) of treated cellulose showed that phosphoramidates could catalyze the dehydration and char formation of cellulose at a lower temperature. The enhanced flame retardant action of phosphoramidate may be due to the catalytic thermal decomposition of the phosphoramidate structure to produce acidic intermediates which could react with cellulose to alter its thermal decomposition.
The present study focuses on the use of Luffa Cylindrica fibers as a reinforcing agent in a fluoroplastic (PTFE) polymer matrix and TiO2 nanoparticles as a photocatalytic agent with different mass ...fractions (%), for the purpose of the preparation and structural characterization of a new biocomposite material. The granulometry and zeta potential were measured using dynamic light scattering and laser Doppler velocimetry respectively. Structural and vibrational properties of the PTFE/TiO2/LC fibers composites were characterized by micro-Raman spectroscopy in oblique backscattering configuration and FTIR spectroscopy. Lastly, thermal properties were investigated using TGA and DSC. Further, the photocatalytic activity of samples was tested for the degradation of Methylene Blue dye (MB) in aqueous medium.
•Please finds below the highlights of the submitted work:•New biocomposite based on PTFE (75%–65%), TiO2 (5%) and fibers of Luffa Cylindrica (25%–35%).•Biocomposite with 25% of Luffa Cylindrica outperforms others in term of electrostatic stabilization.•Raman-spectra analysis highlights the presence of the anatase and rutile phases of TiO2 in all samples.•TGA and DSC analysis points out that over 30% of LC fibers in the sample is unfavorable regarding thermal degradation.
A review on gasification of biomass Kirubakaran, V.; Sivaramakrishnan, V.; Nalini, R. ...
Renewable & sustainable energy reviews,
2009, 2009-1-00, Letnik:
13, Številka:
1
Journal Article
Recenzirano
Studies on the effect of size, structure, environment, temperature, heating rate, composition of biomass and ash are reviewed. Based on the observations reported so far, auto-gasification of biomass ...by the bio-oxygen and the catalytic ash would be feasible. The auto-gasification may be explained in terms of heterogeneous catalytic reaction. Better understanding of auto-gasification is possible by further studies carrying out on the effect of heating rate on auto-gasification.
A new organic–inorganic compound, bis(4-acetylanilinium) tetrachlorocadmiate, has been synthesized and characterized by single-crystal X-ray diffraction, thermal analysis and dielectric measurements. ...The title compound crystallizes at room temperature in the orthorhombic system (Cmca space group) with the following unit cell parameters: a=19.9803(5)Å, b=15.3829(3)Å, c=13.8168(3)Å and Z=8. Display omitted
The new organic inorganic compound C8H10NO2CdCl4 crystallizes at room temperature in the orthorhombic system (CmCa space group) with the following unit cell parameters: a=19.9803(5)Å, b=15.3829(3)Å, c=13.8168(3)Å and Z=8. The atomic arrangement can be described as an alternation of organic/inorganic layers along the a direction. The organic layer is built up by one type of C8H10NO+ cation and the inorganic layer is built up by isolated and distorted tetrahedral CdCl42− anions. The TGA–DTA curves revealed two endothermic peaks. The first peak may be due to a phase transition, while the second peak corresponds to the decomposition point. Additionally analysis of the dielectric constants ε′ and ε″ versus temperature at several frequencies shows a relaxation process which could be due to disorder in the lattice.
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