TG MS Research Articles

Thermal characterization and kinetic analysis of microfibrillated cellulose/lignosulfonate blends

The water-processable microfibrillated cellulose (MFC) and sodium lignosulfonate (NaLS) system was used for the first time as carbon precursor. After drying and one-step pyrolysis up to 800°C, the resulting bio carbonaceous char can acquire considerable electrical conductivity and porosity, making it a promising electrode material in energy storage devices. The present work characterizes MFC and NaLS separately as well as in blends in terms of morphology (SEM), structure (FTIR) and thermal stability (TG–MS). DTG patterns illustrate that MFC degrades in a narrow temperature range but at high reaction rates, whereas NaLS reacts more steadily in a larger temperature range. The thermal degradation rate of a MFC/NaLS blend differs from an additive weighted thermal degradation rate of each component: MFC and NaLS. The presence of sodium in the blends induced catalytic effects and made MFC decomposition to shift toward lower temperatures. This observation could be kinetically interpreted as a decrease of the MFC thermal degradation activation energies in the composites. The kinetics of MFC/NaLS blends is investigated by both model-free and mode-based methods, with the latter providing more appropriate Arrhenius parameters that allow reproducing the experimental curves.

Heat capacities and thermodynamic properties of Cr-MIL-101

The molar heat capacities of one-three-dimensional metal–organic frameworks (MOFs) Cr3F(H2O)2O(BDC)3 (Cr-MIL-101) were measured by temperature-modulated differential scanning calorimetry over the temperature range from 253 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The fundamental thermodynamic parameters such as entropy and enthalpy relative to 298.15 K were calculated based on the experimentally determined molar heat capacities. The compound was characterized by atomic absorption spectrometer, elemental analysis, powder XRD and FTIR spectrum. Moreover, the thermal decomposition characteristics of Cr-MIL-101 were investigated by thermogravimetry–mass spectrometer (TG–MS). Three stages of mass loss were observed in the TG curve. TG–MS curve indicated that the oxidative degradation products of Cr-MIL-101 are mainly H2O and CO2.

Study on the preheating stage of low rank coals liquefaction: Product distribution, chemical structural change of coal and hydrogen transfer

Preheating stage of direct liquefaction of Yunnan lignite (YN) and Hami sub-bituminous coal (HM) in tetralin at temperature range of 200–350°C was investigated under nitrogen atmosphere. In order to reveal the product characteristics and hydrogen transfer between coal and solvent during preheating process, thermo-gravimetric analyzer coupled with mass spectrometer (TG–MS), X-ray photoelectron spectroscopy (XPS) and gas chromatography coupled with mass spectrometer (GC–MS) were employed. The results show that yields of light products, i.e., oil, gas, and water, increase with raising temperature during the preheating process. YN and HM achieve 51.69% and 44.19% (daf) light products yields at 350°C, respectively. Moreover, oxygen-containing functional groups, such as carboxyl, ethers, and alcohols in raw coal are reduced after preheating. In addition, hydrogen transfer achieves a perceptible extent even at 200°C and the amount of transferred hydrogen increases with raising temperature. A positive dependence of hydrogen transfer on conversion is observed during preheating stage. Comparing the two coal samples, YN obtains higher conversion and hydrogen transfer due to its higher thermal reactivity at this temperature range. However, HM achieves higher oil yield than YN does at 350°C since high hydrogen transfer amount and H/C ratio of raw coal promote the oil yield.

Physicochemical characterisation and investigation of the bonding mechanisms of API-titanate nanotube composites as new drug carrier systems

Titanate nanotube (TNT) has recently been explored as a new carrier material for active pharmaceutical ingredients (API). The aim of the present work was to reveal the physicochemical properties of API-TNT composites, focusing on the interactions between the TNTs and the incorporated APIs. Drugs belonging to different Biopharmaceutical Classification System (BCS) classes were loaded into TNTs: diltiazem hydrochloride (BCS I.), diclofenac sodium (BCS II.), atenolol (BCS III.) and hydrochlorothiazide (BCS IV.).Experimental results demonstrated that it is feasible for spiral cross-sectioned titanate nanotubes to carry drugs and maintain their bioactivity. The structural properties of the composites were characterized by a range of analytical techniques, including FT-IR, DSC, TG–MS, etc. The interactions between APIs and TNTs were identified as electrostatic attractions, mainly dominated by hydrogen bonds. Based on the results, it can be stated that the strength of the association depends on the hydrogen donor strength of the API. The drug release of incorporated APIs was evaluated from compressed tablets and compared to that of pure APIs. Differences noticed in the dissolution profiles due to incorporation showed a correlation with the strength of interactions between the APIs and the TNTs observed in the above analytical studies.

Combustion properties and kinetics of different biomass samples using TG–MS technique

In this research, combustion properties and kinetics of different biomass samples known as poplar wood, hazelnut shell and wheat bran were studied using thermogravimetry–mass spectrometer. Experiments were performed at three different heating rates (10, 20 and 30 °C min−1) under air atmosphere. The reaction regions, peak and burnout temperatures, mass loss, maximum mass loss rate and residue of the biomass samples were determined. It was observed that all the biomass samples studied show similar combustion characteristics. This study was also focused on the main volatile products (H2, O, CO and CO2, etc.) of biomass combustion on the basis of their relative intensities across the temperature range 150–750 °C and on their relevancy, respectively. Activation energy and Arrhenius constant of the biomass samples were calculated using two different iso-conversional methods, known as Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose. It was observed that the activation energy values were in the range of 66.80–68.56 kJ mol−1 for poplar wood, 83.73–93.25 kJ mol−1 for hazelnut shell and 162.17–167.4 kJ mol−1 for wheat bran, respectively. The biomass reactivity is directly related to the light volatile content, whereas combustion of fixed carbon affected the energy release.

Synthesis and properties of barium modified yttrium borate

Samples of Y1-xBaxBO3 with nominal compositions 0≤×≤0.3 have been prepared using coprecipitation method. Phase composition, crystal structure, microstructure and electrical properties were investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). Additionally, Differential Thermal Analysis and Thermogravimetry coupled with Mass Spectrometry (DTA–TG–MS) allowed to propose the mechanism of chemical reactions during synthesis process. Phase composition of the obtained materials depends on the amount of barium dopant and the preparation conditions. The dependence of lattice parameters on Ba content was also found, indicating the incorporation of Ba into the YBO3 lattice. SEM results showed grain growth and formation of microcracks due to Ba doping. The determined electrical properties as a function of temperature and gas atmosphere indicated the possibility of protonic conductivity in the YBO3 – based materials. The influence of Ba on electrical properties has been interpreted basing on the results of XRD and SEM methods.

Study on thermal degradation of cattlehide collagen fibers by simultaneous TG–MS–FTIR

Leather was useful materials since dawn of human history for excellent properties, but thermal degradation mechanism was not very clear yet. In this paper, much progress has been made in elucidating the thermal stability and thermal degradation mechanism by thermoanalytical study in argon. Thermogravimetric analysis simultaneously coupled with mass spectrometry and Fourier transform infrared spectrometry was employed to study the thermal degradation of cattlehide collagen fibers through in-depth analysis of the evolved gas. Thermogravimetry analyses carried out on sample, deprived from any residual catalyst and highlighted a two-step thermal degradation. New evidence demonstrates that the process during temperature range from 373 to 513 K was phase transformation. Photographs of polarizing microscope confirmed the conclusion. The decomposition of cattlehide collagen fibers starts at about 523 K. The cattlehide collagen fibers may undergo the process of melting, oxidation and decomposition. In decomposition, more than three steps take place. The mass spectra and Fourier transform infrared spectrometry stated clearly that double bond of carbon to oxygen, carbon to sulfur and carbon to nitrogen were destroyed firstly because the carbon dioxide, carbon monoxide and ammonia evolved simultaneously. The second peak of carbon monoxide in mass spectra indicated that some organic fragments were decomposed above 1073 K which confirmed that thermal degradation of leather is more than three steps.

TG–MS study on the effect of multi-walled carbon nanotubes and nano-Fe2O3 on thermo-oxidative stability of silicone rubber

In this work, an investigation was focused on how carbon nanotubes and nano-Fe2O3 improved the thermo-oxidative stability of silicone rubber (SR). A series of nanoparticles, including carbon nanotubes (CNTs), Fe2O3 with two different crystalline forms (α-Fe2O3 and γ-Fe2O3), a mixture of CNTs and γ-Fe2O3 (γ-Fe2O3 + CNTs), and γ-Fe2O3-modified CNTs (γ-Fe2O3 − CNTs), were involved in this article. Thermal degradation characteristics of SR samples filled with these nanoparticles were investigated through thermogravimetric analysis equipped with mass spectroscopy system (TG–MS), and the evolutions of prominent volatiles corresponding to different stages of decomposition were recorded. It was discovered that these nanoparticles affected the thermo-oxidative stability of SR in different ways. While CNTs had an effect of delaying every stage of the degradation of silicone rubber, Fe2O3 inhibited the oxidation of the side methyl, in which γ-Fe2O3 had better performance. γ-Fe2O3 − CNTs had the best effect on preventing the side methyl from degradation, which can be seen from the remarkable decreases in methanol, methanoic acid and methane by 58.91, 57.27 and 27.45 %, respectively. This effect was superior to CNTs, γ-Fe2O3 or a mixture of both at the same addition amount. Herein, the reason for the different performance of these nanoparticles, which make a profound contribution to further improvement in thermo-oxidative stability of SR, has been discussed.

Pyrazole-type complexes with Ni(II) and Cu(II)

New nickel(II) and copper(II) coordination compounds were synthesized by the reaction of N-(benzyloxycarbonyl)-1H-pyrazole-1-carboxamidine ligand (HL) with Ni(II) and Cu(II) acetate in methanolic solution. The crystal and molecular structures of the complexes as well as those of the ligand were determined by single-crystal X-ray structure analysis. The octahedral surrounding around the metal centers in the isostructural complexes [ML2(MeOH)2], M = Ni(II), Cu(II), MeOH = methanol, is established by the bidentate coordination of two ligand molecules through the pyrazole nitrogen and the deprotonated nitrogen atom of the carboxamidine group along with the oxygen atoms from two MeOH molecules. Despite that the molecular structure of the complexes was determined by X-ray structure analysis, in the FT-IR spectra of the compounds the characteristic bands for MeOH were missing. By coupled TG–MS measurements, it was found that compounds during the transport and storage exchanged MeOH by water molecules. The amount of the water was calculated on the basis of thermogravimetric data. The antifungal activity of the compounds was tested against fungi Ph. viticola and B. dothidea and compared to that of a commercial fungicide. Depending on the fungi and on the structure, the compounds showed different, but somewhat lower activity than the commercial fungicide.

Excellent performance of TiO2(B) nanotubes in selective transesterification of DMC with phenol derivatives

TiO2(B) nanotubes and anatase TiO2 were synthesized, and the transesterification of dimethyl carbonate (DMC) with phenol and its derivative bisphenol A (BPA) were carried out over them. When reaction was carried out over TiO2(B) nanotube at 150°C, phenol conversion obtained 7.8% and transesterification selectivity reached 99.8%. As reaction temperature increased to 170°C, phenol conversion came up to 54.6% and transesterification selectivity can still maintain a good yield at 99.2%. When bulk BPA reacted with DMC at 150°C, transesterification selectivity and BPA conversion reduced to 92.4% and 3.9%. Raising temperature to 170°C, BPA conversion increased to 43.4%, but transesterification selectivity declined to 90.3%. However, the transesterification of DMC with phenol and BPA took place at 150°C over anatase TiO2, the transesterification selectivity significantly declined to 92.7% and 76.1%, and phenol and BPA conversion only achieved 5.1% and 3.0%. The higher activity of TiO2(B) nanotubes in transesterification was due to its larger surface area, higher pore size and more structure defects. Importantly, in situ DRIFT and TG–MS were used to characterize DMC adsorption, activation and decomposition process over TiO2(B) surface, which provided more information about the mechanism of transesterification and methylation.

Thermal analysis in foundry technology

In this study, a polymer composition of poly(acrylic acid) and dextrin (PAA/D) cross-linked with microwave radiation, belonging to the new BioCo group of environmentally friendly foundry binders, was subjected to thermal analysis (TG–DTG–DSC, TG–MS, TG–IR) in a temperature range of 20–600 °C. A thermal analysis of PAA/D compositions enables the determination of a temperature range at which the composition is not susceptible to thermal degradation and thus does not lose its binding properties. The study showed that the process of thermal degradation of PAA/D is complex and multi-stage (TG–DTG–DSC). Within a temperature range of 20–250 °C, physical and chemical changes take place associated with the evaporation of the water fraction of the solvent (20–100 °C), next with the evaporation of the water hydration and finally with intermolecular dehydration reactions (100–250 °C). Above a temperature of 300 °C, the decomposition of the polymer chains takes places, and thereafter, the intensive degradation of PAA/D occurs together the creation of gaseous substances, primarily low molecular weight inorganic (CO2, H2O, CO) and organic compounds, including methane (TG–IR, TG–MS).

Combustion performance and kinetics of oil shales

ABSTRACTIn this research, combustion performance and kinetics of two Turkish oil shales were investigated using differential scanning calorimetry (DSC), thermogravimetry (TGA/DTG), and thermogravimetry–mass spectrophotometry (TG–MS) techniques at three different heating rates (10, 30, and 50°C/min). The combustion reaction occurred in two different regions and the corresponding mass loss of oil shales was calculated. Activation energies of oil shale samples are calculated using three different methods and the results are discussed from the viewpoint of the origin and grade of the samples.

Kinetic and energy production analysis of pyrolysis of lignocellulosic biomass using a three-parallel Gaussian reaction model

The kinetic and energy productions of pyrolysis of a lignocellulosic biomass were investigated using a three-parallel Gaussian distribution method in this work. The pyrolysis experiment of the pine sawdust was performed using a thermogravimetric–mass spectroscopy (TG–MS) analyzer. A three-parallel Gaussian distributed activation energy model (DAEM)-reaction model was used to describe thermal decomposition behaviors of the three components, hemicellulose, cellulose and lignin. The first, second and third pseudocomponents represent the fractions of hemicellulose, cellulose and lignin, respectively. It was found that the model is capable of predicting the pyrolysis behavior of the pine sawdust. The activation energy distribution peaks for the three pseudo-components were centered at 186.8, 197.5 and 203.9kJmol−1 for the pine sawdust, respectively. The evolution profiles of H2, CH4, CO, and CO2 were well predicted using the three-parallel Gaussian distribution model. In addition, the chemical composition of bio-oil was also obtained by pyrolysis–gas chromatography/mass spectrometry instrument (Py–GC/MS).

An assessment on co-combustion characteristics of Chinese lignite and eucalyptus bark with TG–MS technique

Reactivity of lignite could be potentially improved by adding with biomass such as lowering the gaseous pollutant emissions. The combustion behavior of lignite/eucalyptus bark blends and their individuals were studied by simultaneous TG–MS technique. The influences of heating rates and blending ratios on combustion performances and gaseous pollutant emissions were assessed. The combustion kinetics were also evaluated in conjunction with volatile matter and fixed carbon burning periods. The ignition and comprehensive combustion indices increased with increasing blending ratios or heating rates. Adding the eucalyptus bark to the lignite was an effective way in reducing the CO2, NO2 and SO2 emissions. The dominant mechanisms associated with combustion kinetics of volatile matters and char in the eucalyptus bark and most eucalyptus bark/lignite blends around maximum burning rates were mainly dominated by the three dimension diffusion, while the combustion mechanisms of char in the lignite were mainly described by reaction order models. Blending ratios of 20–40% eucalyptus bark were proposed as optimum values for improving the combustion behavior of the lignite. There were certain synergistic effects between lignite and eucalyptus bark during their co-combustion.

Torrefaction of invasive alien plants: Influence of heating rate and other conversion parameters on mass yield and higher heating value

With the aim of controlling their proliferation, two invasive alien plants, Lantana camara (LC) and Mimosa pigra (MP), both widespread in Africa, were considered for torrefaction for renewable energy applications. Using thermogravimetric analysis, the influence of heating rate (HR: 2.18–19.82°Cmin−1) together with variable temperature and hold time on char yield and HHV (in a bomb calorimeter) were determined. Statistically significant effects of HR on HHV with optima at 10.5°Cmin−1 for LC and 20°Cmin−1 for MP were obtained. Increases of HHV up to 0.8MJkg−1 or energy yield greater than 10%, together with a 3-fold reduction in torrefaction conversion time could be achieved by optimisation of HR. Analysis of the torrefaction volatiles by TG–MS showed that not only hemicelluloses, but also lignin conversion, could influence the optimum HR value.

Study of the effect of mineral matters on the thermal decomposition of Jimsar oil shale using TG–MS

The effect of mineral matters on the thermal decomposition of Jimsar oil shale was investigated through the TG–MS test to raw, carbonate-free, silicate-free and pyrite-free oil shale samples. The pyrolysis experiments were performed at different heating rates (3, 5, 10, 15K/min) up to a temperature of 1000°C. The results show that the mineral matters have no important effect on the pyrolysis reactions of kerogen in Jimsar oil shale, and the activation energy distribution of raw oil shale is almost identical to that of the demineralized oil shale samples. But, removal of minerals has some effect on the secondary reactions of the derived compounds during diffusing out of oil shale particles, consequently influencing the composition of the pyrolysis products. And the MS data shows that pyrites can react with organic matter to form H2S and SO2 at the temperature range of 510 to 650°C.

TG–MS study on the kinetics and mechanism of thermal decomposition of copper ethylamine chromate, a new precursor for copper chromite catalyst

Copper chromite is a well-known burn rate modifier for the combustion of composite solid propellants. In this study, basic copper ethylamine chromate (CEC), a new precursor for copper chromite catalyst, was synthesized by precipitation method. The thermal decomposition of the precursor was followed by thermogravimetry–mass spectroscopy (TG–MS) and X-ray diffraction techniques and compared with that of copper ammonium chromate, a conventional precursor for copper chromite catalyst. TG–MS analysis for the decomposition of CEC revealed that the decomposition starts with the liberation of ethylamine. The change in enthalpy for the decomposition reaction of copper ethylamine chromate was higher than that of copper ammonium chromate due to the oxidation of ethyl group. The reducing atmosphere created by the presence of carbon during the decomposition of CEC produced a mixture of Cu, CuCr2O4, CuCrO2 and CuO, while the oxidizing atmosphere of copper ammonium chromate produced a mixture of CuCr2O4 and CuO. Mechanistic study based on Criado and Coats–Redfern methods showed that CEC follows random nucleation (F1) mechanism as the rate-determining step for the thermal decomposition process.

The influence of polyoxymethylene molar mass on the oxidative thermal degradation of its nanocomposites with hydroxyapatite

In this paper, the influence of mass-average molar mass (M w) of polyoxymethylene (POM) copolymer on the thermooxidative degradation behavior of its nanocomposites with hydroxyapatite (HAp) is reported. POM copolymers’ thermal stability slightly decreases with a decrease in mass-average molar mass. Thermal stability of POM/HAp nanocomposites is lower in comparison with pure POM, and it gets lower with a decrease in mass-average molar mass of POM copolymer. For POM copolymer with the highest molar mass, thermal stability of POM/HAp nanocomposite was ca. 30 °C lower than for pure POM. To get a more in-depth insight into the decomposition process, kinetic analysis of POM/HAp nanocomposite thermal degradation process was performed using Friedman, Ozawa–Flynn–Wall and multiple nonlinear regression methods. The best fit for pristine T2, T3 and T4 copolymers with different molar mass of 100768, 74727 and 68377 g mol−1, respectively, was obtained for one-stage degradation mechanism with autocatalysis, while for T2/10 % HAp and T3/10 % it was parallel reaction model with autocatalysis (Bna) and phase-boundary reaction models (R3). For T4/10 % HAp, the best approximation was found for R2–Bna–D3 reaction model. From hyphenated TG–MS and TG–FTIR thermoanalytical studies, it was found that the main degradation product for POM/HAp nanocomposites is formaldehyde and the amount of other degradation products is lower in comparison with nonmodified POM copolymers.

Dehydrogenation properties of chromium-based ammine borohydrides: CrCl3·nNH3/3LiBH4 (n = 3, 4 and 5)

Three new chromium-based ammine borohydrides were synthesized by ball milling CrCl3·nNH3 (n = 3–5) and LiBH4 in a molar ratio of 1:3. Thermogravimetric analysis–mass spectrometry (TG–MS) measurements showed that the chromium-based ammine borohydrides release H2 in the temperature range of 100–170 °C, concurrent with the evolution of a small amount of NH3 evolution. The dehydrogenation purity increases with decreasing coordination number of ammonia, with the highest dehydrogenation purity (91.8 mol%) achieved for CrCl3·3NH3/3LiBH4. Further improvement on the dehydrogenation of CrCl3·3NH3/3LiBH4 is conducted by the addition of ZnCl2. The 0.5 mol ZnCl2 assisted sample is able to release 7.4 wt.% of hydrogen with a purity of 98.8 mol%.

Thermal treatment process for the recovery of valuable metals from spent lithium-ion batteries

In this paper, a process based on reducing thermal treatment before acid leaching for the recovery of valuable materials from spent lithium-ion batteries is developed. The thermodynamic behavior of the active cathode materials is investigated through analyzing the gases evolved from the thermal treatment with a thermogravimetric–mass spectrometry (TG–MS) instrument. Scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) spectroscopy analyses are also performed on the solid cathode and anode materials to determine their physicochemical changes from the thermal treatment. The results show that the thermal treatment significantly improves the clean separation of the active materials from the current collectors and the complete removal of the binder and carbonaceous conductor. It also alters the molecular structures of, and partially reduces the transition metals in, the active cathode materials, which increases the leaching efficiency of the transition metals in the subsequent leaching step. After thermal treatment, the leaching efficiency of nickel, cobalt and manganese from the active cathode materials has reached over 98%, 99% and 84%, respectively.