TG–DSC analysis of pyrolysis process of two Chinese oil shales

According to the recommendations developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), non-isothermal pyrolysis experiments were carried out to analyze and compare two types of oil shale from the northeast of China using simultaneous differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis at temperatures ranging from 40 to 850 °C. The pyrolysis process of oil shale begins with the evaporation of small molecular substances, then continues by the pyrolysis of kerogen, and finally ends mainly with the complete decomposition of carbonates. In this whole process, almost 36 % of overall pyrolytic heat was used for the pyrolysis of kerogen. When retorting air-dried basis oil shale below 520 °C, a considerable proportion of the heat required will have to be used mainly for the evaporation of small molecular substances below 185 °C. Specific heat capacities of two oil shale semicokes were measured below 500 °C by DSC method, showing that specific heat capacity of semicoke will increase with the increase of the temperature, and carbonization of kerogen can bring about a further positive effect on it. Coats–Redfern method was used to calculate kinetic parameters in three pyrolysis stages.     

Determination of kerogen type by using DSC and TG analysis

The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.     

Dehydration behavior of FGD gypsum by simultaneous TG and DSC analysis

The dehydration behaviors of FGD gypsums from three power plants were investigated at N₂ atmosphere (autogenous and negligible partial pressure of water, P_{\textH 2 \textO} P_{{{\text{H}}_{ 2} {\text{O}}}} ) in non-isothermal and isothermal condition. The dehydration of gypsum proceeded through one step, i.e., CaSO₄·2H₂O → γ-CaSO₄ (γ-anhydrite) or two steps, i.e., CaSO₄·2H₂O → CaSO₄·0.5H₂O (hemihydrate) → γ-CaSO₄ depending on temperature and P_{\textH 2 \textO} P_{{{\text{H}}_{ 2} {\text{O}}}} . The discrepancies of three FGD gypsums on dehydration behavior were very likely due to the different crystalline characteristics (size and habit) and impurities, such as fly ash and limestone. Experimental data of non-isothermal analysis have been fitted with two ‘model-free’ kinetic methods and those of isothermal analysis have been fitted with Avrami and linear equation. The apparent empirical activation energies (E _a) suggest that the transition from gypsum to hemihydrate is mainly controlled by nucleation and growth mechanism, while the transition from gypsum to γ-anhydrite is mostly followed by phase boundary mechanism.     

Thermal analysis study of some transition metal complexes by TG and DSC methods

The thermodynamic and thermal properties of [Cu(L)₂·Cl₂], [Ni(L)₂]·Cl₂, [Co(L)₂·Cl₂]; L=1,2-bis(o-aminophenoxy)ethane (BAFE), complexes have been investigated. The thermal decomposition of the complexes took place in two distinct steps in endothermic reaction up to 700°C. The activation energy E, the entropy change S ^#, enthalpy H change and Gibbs free energy change G ^# were calculated from the results of thermogravimetry analysis (TG) and heat capacity from the results of differential scanning calorimetry (DSC). It was found that the thermal stabilities and activation energies of the complexes follow the order Ni(II)>Cu(II)>Co(II) and E _Co<E _Ni<E _Cu, respectively.This revised version was published online in November 2005 with corrections to the Cover Date.     

Kinetic analysis of consecutive reactions using TG and DSC techniques

A complex mechanism of thermal degradation processes was postulated for the reaction type , and a theoretical analysis of DTG and DSC curves was followed by corresponding mathematical simulation. In this scheme, compoundS represents a volatile product (e.g. gas and/or vapor), which is a necessary assumption in order to explain the differences in results which can arise after the kinetic analysis of DTG and DSC experimental data.Mathematical simulation was performed with different values of the Arrhenius parameter for both reaction rate constants (k ₁, andk ₂) in the range 83.1–291.0 kJ/mol for the activation energy and with corresponding values for the frequency factor (10⁵–10¹⁹ min^–1). The influence of endothermic heat effects (50–200 kJ/mol) in the reactionsAE andRS was also investigated. The calculated rates of mass and heat change (DTG and DSC), for different heating rates, showed that the maximum values of the two curves are reached at different temperatures. The non-uniformity of the DTG and DSC maxima depends on the difference between the values of the reaction rate constants and their temperature sensitivities (E ₁ andE ₂) and also on the heating rate.The theoretical analysis performed demonstrated the possibility of determining the reaction rate parameters (k ₁ andk ₂) in the case of consecutive first-order reactions, by using simultaneous TG and DSC analysis.The proposed theoretical analysis is supported by experimental DTG/DSC data concerning the pyrolysis of oil shale, which were interpreted in terms of consecutive reactions.

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Zusammenfassung Unter Annahme eines komplexen Mechanismus für thermische Abbauprozesse wurde für den Reaktionstyp eine theoretische analyse von DTG- und DSC-Kurven, gefolgt von einer entsprechenden mathematischen Simulation durchgeführt. Hier stellt die VerbindungS ein flüchtiges Produkt dar (lias oder Dampf), was eine notwendige Bedingung zur Erklärung von unterschiedlichen Ergebnissen nach der kinetischen Analyse der experimentellen DTG- und DSC-Daten ist. Bei der mathematischen Simulation wurden unterschiedliche Arrheniusparameterwerte benutzt, für beide Reaktionsgeschwindigkeitskonstanten (k₁ und k₂) in einem Intervall von 83,1–291,0 kJ/mol für die Aktivierungsenergie sowie unter Anwendung entsprechender Frequenzfaktoren (10⁵–10¹⁹ min^–1). Für die ReaktionenA R undR S wurde auch der Einfluß von endothermen Wärmeeffekten (50–200 kJ/mol) untersucht. Die berechneten Geschwindigkeiten für die Veränderung von Masse und Wärme (DTG und DSC) bei verschiedenen Aufheizgeschwindigkeiten zeigen, daß beide Kurven ihr Maximum bei unterschiedlichen Temperaturen erreichen. Die Ungleichmäßigkeit der DTG- und DSC-Maxima basiert auf den unterschiedlichen Werten der Reaktionsgeschwindigkeitskonstanten, deren Temperaturempfindlichkeit (E ₁ undE ₂ und hängt auch von der Aufheizgeschwindigkeit ab. Die durchgeführte theoretische Analyse zeigt, daß es mit Hilfe simultaner DTG- und DSC-Untersuchungen möglich ist, im Falle konsekutiver Reaktionen erster Ordnung die Reaktionsgeschwindigkeitsparameter (k ₁ undk ₂) zu bestimmen. Das vorgeschlagene theoretische Analysenverfahren wird am Beispiel der experimentellen DTG/DSC-Daten der Pyrolyse von Ölschiefer und Anwendung konsekutiver Reaktionen illustriert.

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. S (. ), , . ( _{1 2}) 83,1–291,0 · ^–1 (10⁵–10^{19 –1}). (50–200 ·^–1) AR RS. ( ) , . (E ₁ E ₂), . , ₁, ₂ . / , .

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The authors are greatful for financial support to the KFA International Bureau D-5170 Jülich on the German side, and to the Research Fund of the Belgrade Region Business Association for the Exploration, Production and Exploitation of Oil Shales, Belgrade, and SOUR Jugopetrol, Belgrade on the Yugoslavian side.     

Thermal analyses of home-made zeolite by DSC and TG

Volatile organic compounds (VOCs) and greenhouse gases are the main factors involved in pollution control and global warming. Various treatment methods involving incineration, adsorption, etc., have been employed to reduce VOCs and greenhouse gases concentration in the operating environment and atmosphere. Activated carbon, zeolite, silica gel, and alumina have been broadly used to adsorb pollutants in various industrial applications. Based on the promising effect of adsorption, we analyzed and identified the thermal phenomena of home-made zeolite using various instruments. The endothermic reaction under 100?°C of home-made zeolite was identified as steam adsorption, which is an important discovery. The optimal adsorption temperatures of home-made zeolite have been determined at 200?C550?°C.     

Use of sub-ambient DSC to complement conventional DSC and TG

Several drug substances or excipients are hygroscopic. The uptake or loss of water of such substances is generally difficult to control during processing or storage of drug products. DSC instruments with sub-ambient temperature equipment allow the determination of the amount of freezable water by measuring the corresponding melting enthalpy.The determination of freezable water adds valuable information complementary to TG analysis for understanding the processing and storage of raw materials and drug products. Several substances were tested as is, without treatment, after storage at 92% r.h. and after equilibration with water. The results of these experiments showed that it was possible to demonstrate defined hydrate formation, to determine the upper level of binding of water in amorphous substances and to confirm reversible hydrate formations demonstrated by temperature resolved X-ray diffraction.     

Thermal decomposition of two synthetic glycosides by TG,DSC and simultaneous Py-GC-MS analysis

To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the T _p of GLY-A and GLY-B were 254.6 and 275.7°C. The T _peak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively. Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.     

Thermal analysis of Moroccan phosphates 'Youssoufia' in an oxidative atmosphere by TG and DSC

A non-isothermal experimental study using thermogravimetry (TG) and differential scanning calorimetry (DSC) was conducted for investigation the oxidation reactivity of natural phosphate and its demineralised products. The analyses were carried out in oxygen atmosphere and at different heating rate (5, 10, 20, 30, 50, 60°C min-1) up to 1000°C. The results indicated that the material washed with HCl from the original phosphate, mainly apatite and carbonates of calcium and magnesium, as well as with HCl/HF, silicates minreals, had an inhibition effect during oxidation reactions of organic material. The increase of the heating rate shifted the reactions to higher temperatures. In addition, kinetic parameters were determined by assuming a single first-order kinetic model, using the Coats-Redfern method. The influences of demineralization process of natural phosphate and the heating rate were examined and discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterization by TG/DTG/DSC and FTIR of frying and fish oil residues to obtain biodiesel

Biodiesel is a fuel derived from vegetable oils or wastes. It has a lot of advantages such as less offensive exhaust, more complete combustion, reducing emissions of carbon dioxide and sulfur in addition to generating employment and wealth. This biofuel can be produced through the transesterification reaction of an alcohol with a triglyceride, with the aid of a catalyst, resulting on a biodiesel as main product, glycerol, and other byproducts. The objective of this study is to determine the optimal reaction conditions for transesterification of waste frying oil and fish, varying the reaction time, the amount of catalyst and temperature, to determine which of these variables exert a greater influence on the reaction yield, and characterize biofuels obtained. For a more accurate assessment of the influence of a given variable on the reaction yield, it was performed a statistical experimental design, the full factorial of two levels with three parameters (2³) and three central points, implemented in Statistica 7.0. Regarding the transesterification of waste of the fish oil, the amount of catalyst was the variable that most influenced the reaction yield, the parameters time and temperature had negligible impact on income. Biofuels were also characterized using thermal analysis techniques and FTIR. Most reactions obtained thermogravimetric yield above 90%, a promising result.     

Characterization of monumental carbonate stones by thermal analysis (TG, DTG and DSC)

Thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC), were found to be suitable instrumental techniques for the study of monumental rocks because they need small amounts of sample and provide extensive qualitative and quantitative information. From DTG curves, the calcite/dolomite ratio in the samples as well as the differences between limestones and dolomites can be quantitatively determined. DSC curves are adequate for the identification of the degradation products in the monumental stones since they are usually salts (sometimes hydrates) which present first-order processes under 600°C. This technique makes it possible to carry out quantitative and semiquantitative analysis of the degradation of monumental rocks since it provides data about its mineralogic composition.     

Effect of gemini surfactant additives on pour point depressant of crude oil

Efficiencies of cationic gemini surfactant additives in improving the pour point depressant of crude oil were investigated. The length of alkyl chain is a major factor affecting the improvement of the pour point depression. The adsorption behavior of these gemini surfactants at air/solution and oil/solution interfaces were investigated by measuring the surface tension and interfacial tension as functions of concentration. It is found that there is a good relation between surface properties especially interfacial tension of the gemini surfactants and their efficiency in depressing the pour point. Also, the surface parameters and free energies of micellization and adsorption confirm the decreasing and improving of pour point depression. Crystallization study in crude oil revealed the relationship between the structure and activity of gemini surfactant additives. It is found that the x-ray diffraction patterns of waxes with additives are remarkably different from those without additives. The mechanism of the depressants action has been suggested according the adsorption of each additive. Adsorption of the additive on the surface of the wax particles inhibits their growth and alters the crystal habits through micelle core. Pretreatment of the crude oil with pour point depressants has received the greatest acceptance due to its simplicity and economy.     

Research on thermal decomposition of trinitrophloroglucinol salts by DSC, TG and DVST

The thermal decomposition of the four nitrogen-rich salts of ammonia (NH₄), aminoguanidine (AG), carbohydrazide (CHZ) and 5-aminotetrazo (ATZ) based on trinitrophloroglucinol (H₃TNPG) was investigated using the differential scanning calorimetry (DSC), thermogravity (TG), and dynamic vacuum stability test (DVST). DSC and TG methods research the complete decomposition, while DVST method researches the very early reaction stage. The peak temperatures of DSC curves are consistent with the temperatures of maximum mass loss rates of TG curves. The apparent activation energies of these H₃TNPG-based salts obtained by DSC and DVST have the same regularity, i.e., (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < NH₄(H₂TNPG) < (AG)(H₂TNPG). The thermal stability order is (ATZ)(H₂TNPG)·2H₂O < (CHZ)(HTNPG)·0.5H₂O < (AG)(H₂TNPG) < NH₄(H₂TNPG), which was evaluated by DVST according to the evolved gas amount of thermal decomposition. DVST can monitor the real-time temperature and pressure changes caused by thermal decomposition, dehydration, phase transition and secondary reaction, and also evaluate the thermal stability and kinetics.      

Determination of Ca/NaY zeolite acidity by TG and DSC

The acid properties of the Ca/NaY zeolite were investigated by means ofn-butylamine desorption and thermal decomposition, using both thermogravimetry (TG) and differential scanning calorimetry (DSC). The total acidity of the zeolite was calculated from the TG data, while DSC was used with the Borchardt-Daniels kinetic model to determine the relative acid strength of the catalyst, given in J per acid site. The enthalpies of these processes are proportional to the acid site strength in each specific temperature range.This work was supported by Conselho National de Desenvolvimento Científico e Tecnológico (CNPq). The authors are very grateful to M. L. C. Rodrigues and C. I. Braga, from D. P. Instrumentos Científicos.     

Thermal characterization of dental composites by TG/DTG and DSC

Dental composites can be improved by heat treatment, as a possible way to increase mechanical properties due to additional cure (post-cure). Direct dental composites are essentially similar to the indirect ones, supposing they have the same indication. Therefore, to establish a heat treatment protocol for direct composites, using as indirect (photoactivated by continuous and pulse-delay techniques), a characterization (TG/DTG and DSC) is necessary to determine parameters, such as mass loss by thermal decomposition, heat of reaction and glass transition temperature (T _g). By the results of this study, a heat treatment could be carried out above 160 °C (above T _g, and even higher than the endset exothermic event) and under 180 °C (temperature of significant initial mass loss).     

Catalytic degradation of polyethylene evaluated by TG

HZSM-5 zeolite was screened as catalyst for high density polyethylene degradation at 450C, under nitrogen static atmosphere. Two different samples were studied in this condition: HDPE alone and mixed with HZSM-5. The reactor was connected on line to an HP 5890-II gas Chromatograph. Sample degradation was investigated using a Perkin-Elmer Delta 7 Thermobalance, from room temperature to 800C, with heating rates of 5.0, 10.0 and 20.0C min^–1. From TG curves, the activation energies, calculated using an integral kinetic method, decreased 60.6% in the presence of the zeolite.This work was supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq) and CoordenaÇÃo de Apoio ao Pessoal de Ensino Superior (CAPES).     

TG and DSC studies of filled porous copolymers

A complex approach including thermogravimetry, differential thermal analysis and differential scanning calorimetry was applied to study characteristics of non-filled and filled porous copolymers of divinylbenzene with styrene or some acrylic monomers: di(methacryloyloxymethyl)naphthalene, methacrylic ester of p,p’-dihydroxydiphenylpropane diglycidyl ether, and dimethacrylglycolethylene. High disperse silicas with the grafted methyl and silicon hydride groups in the surface layer were used as fillers. The kinetic parameters of thermal degradation for composites obtained were determined by different methods.     

Coalescence in crude oil emulsions investigated by a light transmission method

Using a strong light source and a sensitive detector the light transmission of crude oil emulsions can be measured. A semi-empirical theory describes how the measured optical density results from the interaction of absorption and scattering. Changes in the scattering can be used to investigate the coalescence effects caused by demulsifiers. The method is of use in testing demulsifier effectiveness.     

Thermal behavior of chitosan/natural rubber latex blends TG and DSC analysis

The thermal behavior of chitosan (CS)/natural rubber latex (NRL) blends has been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). Decomposition behavior of CS changes with the addition of NRL. The effect of blend composition on the amount of residue remaining at various temperatures has been studied. Activation energies of degradation have been calculated using Horowitz-Metzger equation. From the activation energy values, it is found that among the series of the blend compositions, CS₁₅NRL₈₅ exhibits better thermal stability. DSC studies reveals that the CS/NRL blends are thermodynamically incompatible. This is evident from the presence of two glass transitions, corresponding to CS and NRL phases in the blend.