New view on the oxidation mechanisms of crude oil through combined thermal analysis methods

In the previous study, the oxidation behavior of four Chinese crude oils (Oil 1 to 4) in the presence and absence of rock cuttings was investigated by thermogravimetry/derivative thermogravimetry (TG/DTG) techniques and oxidation tube experiments. The present work investigates the thermal behavior of these oils by combining DTG–DTA method. First, we conducted comparative analysis about mass loss rate from DTG curves and endothermic/exothermic phenomenon from DTA curves attempting to clarify the endothermic or exothermic mechanism in crude oil low-temperature oxidation. Finally, we combined the thermal analysis method with low-temperature oil oxidation tube experiment in porous media to ascertain, whether the two methods are consistent in the aspect of low-temperature oxidation mechanism of crude oil by O₂ consumption rate and CO₂ generating rate (carbon bond stripping reaction rate). Results show that crude oils undergo an endothermic oxidation behavior during low-temperature oxidation stage, suggesting the decomposition of hydrocarbon components. Clay can play a catalytic effect on low-temperature oil oxidation. The results of DTG–DTA tests can also better reflect oil oxidation mechanism under real conditions.     

Thermal degradation behaviour of some metal chelate polymer compounds with bis(bidentate) ligand by TG/DTG/DTA

Seven novel divalent transitional metal chelate polymers compounds (commonly known as chelate compounds or metal coordination complexes or polymer complexes) have been characterized by thermogravimetry (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA) methods. Thermal decomposition behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) polymers with terphthaoyl-bis(p-methoxyphenylcarbamide) has been investigated by thermogravimetric analysis (TGA) at heating rate 10 °C min^?1 under nitrogen atmosphere. TG/DTA of chelate compounds were shown to be a stable compound against thermal decomposition which was measured on the basis of final decomposing temperature, but it is observed in some curves that decomposition takes place at low temperature due to the lattice water, which is always placed at outer coordination sphere of the central metal ion. The presence of both lattice and coordinated water were noteworthy investigated in Co(II), Ni(II) and Cu(II) chelate polymer compounds, whereas lattice water found in Zn(II), Cd(II) and Hg(II). However, Mn(II) showed only coordinated water. Thermal stabilities for release of lattice water, coordinated water and organic moiety that occur in sequential decomposition of chelate compounds are explained on the basis of ionic size effect and electronegativity. The processes of thermal degradation taking place in seven chelate polymers were studied comparatively by TG/DTG/DTA curves which indicating the difference in the thermal decomposition. Coats–Redfern integral method is used to determine the kinetic parameters for the successive steps in the decomposition sequence of TG curves. Scanning electron microscope images of some chelate polymers were shown in previous publication revealed that particle sizes of chelate polymers were found to be of nanomaterial level therefore, resulting chelate compounds might be called as nanomaterial.     

Thermal decomposition kinetics of diethyl dithiocarbamate complexes of copper(II) and nickel(II)

Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL₂ and NiL₂ (L^?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL₂, DTG 250–350°, DTA 300–320° and for NiL₂, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

     

Selected thermoanalytical methods and their applications from medicine to construction

There are many thermoanalytical techniques but only several of them such as thermogravimetric analysis (TG), high resolution thermogravimetric analysis (Hi-Res™ TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), calorimetry, differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), evolved gas analysis (EGA), transient thermal analysis (TTA) and thermal conductivity (k) have selected to be discussed in this paper. Simultaneous thermal analysis (STA) is ideal for investigating issues such as the glass transition of modified glasses, binder burnout, dehydration of ceramic materials or decomposition behaviour of inorganic building materials, also with gas analysis. Selected applications of various thermoanalytical techniques from medicine to construction have also been discussed in this paper.     

A Kinetic Study of the Dehydration of VOPO4.2H2O by Thermal Methods

The dehydration of VOPO₄.2H₂O hasbeen studied by thermogravimetric analysis (TGA),differential thermal analysis (DTA) and differentialscanning calorimetry (DSC). From the shift of the DTA,DTG, and DSC peaks, activation energies of thedehydration processes have been calculated based onKissinger's method. The most suitable kinetic modelsfor two-step dehydration have been found.     

Hydrogen reduction of MoO3−Fe mixes studied by stepwise differential isothermal analysis

The method of a stepwise differential isothermal analysis (SDIA) has been designed for studies of reduction processes in metallurgical systems. The basis of the method is in multi-parameter control of reaction rate and its use for monitoring temperature, heating rate, and gas-phase composition. In this study hydrogen reduction of MoO₃ and its mix with 30% Fe have been carried out using the SDIA technique. During the measurements, TG, DTG, DTA, EGA, and temperature control are carried out. Kinetics parameters were determined and possible reduction mechanism was suggested. The SDIA technique is well suited for these studies.     

Characterisation of α-FeOOH Grinding Products Using Simultaneous DTA and TG/DTG Coupled with MS

Effects induced by grinding in synthetic goethite samples were studied. The products of α-FeOOH grinding were characterised by means of DTA, TG/DTG coupled with EGA (Mass spectrometry detection), powder X-ray diffraction analysis, and surface area determination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal analysis of neuroleptic drugs and vitamins

The thermal decomposition of 41 drugs containing acetylsalicylic acid, 5-pyrazolone derivatives, the components stimulating the central nervous system, the Aviomarin, Glutamic acid, and Laxative chocolate tablets, and vitamins has been studied by employing the differential thermal analysis (DTA), thermogravimetry (TG), and differential TG (DTG) techniques. The possibility has been demonstrated to employ the DTA, TG, and DTG curves of their thermal decomposition for the identification of particular dosage forms and for the qualitative and quantitative monitoring of their composition. Based on the stages due to dehydration, decarboxylation, and formation of intermediate decomposition products, the content of the active components was determined in 17 of the drugs. The results of the determinations were in good agreement with those calculated from information supplied by the manufacturers.     

Aluminum Nitride Oxidation by Simultaneous TG and DTA

This work is a study, by simultaneous thermogravimetry (TG) and differential thermal analysis (DTA), of the oxidation of a water resistant aluminum nitride powder which has a special protective coating, and an uncoated AlN powder which has become partially hydrated during its use. The activation energy for oxidation is estimated by the Kissinger and isoconversional methods. In the former method, the temperatures of the oxidation peaks were obtained from DTA and DTG curves. The activation energies for oxidation of the water resistant AlN, obtained by the Kissinger method, are 357±10 kJ mol^–1, 392±12 kJ mol^–1 using respectively DTG and DTA data. For the uncoated AlN, the values are 243±7 and 257±8 kJ mol^–1, respectively. By the isoconversional method, the average values obtained for coated and uncoated samples are, respectively, 323±10 and 224±7 kJ mol^–1. Therefore, the special coating, which protects the aluminum nitride from humidity action, also provides a higher resistance to oxidation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.     

QDTA/T/EGD/GC在线联同技术 Ⅵ.煤的热氧化、燃烧反应过程及其机理的研究

应用QDTA/T/EGD/GC在线联同技术及其装置,测定了四种不同变质程度的煤质之DTA/EGD/GC燃烧特性曲线,从中可提供如下三方面的信息和数据:(1)依据DTA测得的燃烧特性曲线,可取得在氧化、燃烧全过程中各项热特性的表征温度。(2)依据跟踪DTA逸出气成份的浓度变化所测得的EGD曲线,可了解不同煤质在热解、着火和燃烧特性等方面的差异。(3)依据DTA/EGD曲线的演变,可截取各个反应温度下之逸出气,进行在线的GC分析。在上述实验结果的基础上,应用过氧化物学说探讨煤的低温氧化反应机理。     

The application of artificial neural networks for the selection of key thermoanalytical parameters in medicinal plants analysis

In the present study three thermoanalytical methods: differential thermal analysis (DTA), thermogravimetric analysis (TGA), and derivative thermogravimetric analysis (DTG) were used to investigate the thermal behavior of medicinal plant raw materials. In order to describe DTA curve, designation of the onset T(i), and peak T(p), temperatures was required. In TGA the mass losses Delta(m), and in DTG the temperature range of peak DeltaT, peak temperature T(p), and peak height h, were recorded. All parameters were read for three stages of the thermal decomposition of plant samples which resulted in obtaining eighteen thermal variables for each sample. Some similarities in the course of thermal decomposition of the same plant organs were recognized, but complexity of the obtained data made it very difficult to determine if they could differentiate between medicinal plant materials and which of them encode the most valuable information about the studied herbals. In order to confirm the existence of any relations between the chemical composition of medicinal plants and their thermal decomposition and to find out which thermoanalytical variables or decomposition stages can be considered as the most significant in terms of their evaluation, it was decided to apply fully connected feed-forward artificial neural networks (ANN). Two different training algorithms were used to address the problem: back-propagation of error and conjugate gradient descent. To verify the results two-dimensional (2-D) Kohonen self-organizing feature maps (SOFMs) were employed. Two alternative datasets of thirteen key variables discriminating plant samples have been proposed.     

Thermal behaviour studies of procaine and benzocaine

The analysed substances, procaine and benzocaine, are two anaesthetic agents currently being administered in tablet form, also in the topical (cream, gel, balm) and injectable dosage forms. The TG/DTG/DTA curves were obtained in air at different heating rates. For determination of the heat effects, the DTA curves (in μV) were changed with the heat flow curves (in mW), so that the peak area corresponds to an energy in J g^?1 or kJ mol^?1. The non-isothermal experiments are preformed to investigate the thermal degradation process of these active substances, both as a solid and are performed in a dynamic atmosphere of air at different heating rates, by heating from room temperature to 500 °C. The kinetic analysis was performed using the TG data in air for the first step of substance’s decomposition at four heating rates: 7, 10, 12 and 15 °C min^?1. The data were processed according to an appropriate strategy to the following kinetic methods: Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and NPK, to obtain realistic kinetic parameters, even if the decomposition process is a complex one. Thermal analysis was supplemented using Fourier Transform infrared spectroscopy coupled with the TG device to identify the anaesthetics with any products which may have formed (EGA—the evolved gas analysis).     

Preparation and characterization of Cu (II) supported on poly(8‐hydroxyquinoline‐p‐styrene sulphonate) and its application as catalyst for the synthesis of hexahydroquinolines

Cu ( II ) supported on poly(8‐hydroxyquinoline‐p‐styrenesulfonate) (Cu ( II )@PHQSS) was prepared and fully characterized by the different techniques including fourier transform infrared spectroscopy (FT‐IR), ¹H NMR, ¹³C NMR, thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), differential thermal analysis (DTA), scanning electron microscope (SEM) and energy dispersive X‐ray analysis (EDS). Afterward, the Cu ( II )@PHQSS as nanostructured catalyst was used as catalyst for the synthesis of hexahydroquinolines.     

The thermal behaviour of lignins from wasted black pulping liquors

The thermal degradation of lignins separated from black liquor waste from pulping of bagasse and cotton stalks has been investigated. Thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermogravimetry (DTG), between 20 and 1000°C, have been used. Activation energies of treated lignins were calculated. Lignins separated from liquors obtained at low pulping temperature have higher activation energies than high-temperature lignins. The use of anthraquinone (AQ) as an additive for accelerating the pulping process raises the activation energy of the lignin in the black liquors waste.     

Thermal characterization of the poultry fat biodiesel

Chemical composition of oils and fats used in the biodiesel synthesis can influence in processing and storage conditions, due to the presence of unsaturated fatty acids. An important point is the study of the biodiesel thermal stability to evaluate its quality using thermal analysis methods. In this study the thermal stabilities of the poultry fat and of their ethyl (BEF) and methyl (BMF) biodiesels were determined with the use of thermogravimetry (TG/DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC), in different atmospheres. The TG/DTG curves of the poultry fat in synthetic air presented three decomposition steps while only one step was observed in nitrogen (N₂) atmosphere. The DSC results indicated four exothermic enthalpic transitions in synthetic air and an endothermic transitions in N₂ atmosphere attributed to the combustion process and to the volatilization and/or decomposition of the fatty acids, respectively. For both biodiesels the TG/DTG curves in air indicated two mass loss steps. In the DSC curves four exothermic transitions were observed in synthetic air besides an endothermic one in N₂ atmosphere.     

The Thermal Decomposition of Manganese Carbonate Thermogravimetry and Exoemission of Electrons

Results are reported on the thermal decomposition of manganese carbonate, MnCO₃. Thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermoanalysis (DTA) curves were recorded simultaneously and depicted together with the curve of intensity of electron exoemission (EEE). This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of Thermal Behavior of Microwave Induced Graft Copolymerization of Ethylmethacrylate onto Soy Protein Concentrate

Graft copolymerization of ethylmethacrylate (EMA) onto soy protein concentrate (SPC) was carried-out using ascorbic acid/potassium persulphate as redox initiator under microwave radiations. Different reaction parameters like reaction time, solvent amount, initiator ratio, pH and monomer concentration were optimized to get maximum graft yield (78.8%). The graft copolymer formed was characterized by FTIR, XRD, SEM, TGA, DTA and DTG techniques. Graft copolymer showed higher moisture resistance along with increased chemical and thermal stability. TGA, DTA and DTG studies could reveal the distinctive features of graft copolymerization of EMA onto S-S linkages of soy protein concentrate under the influence of microwave irradiations in addition to grafting at peptide linkages, which were further supported by FT-IR studies.     

污水污泥的燃烧特性

通过对几种污泥样品进行热重分析,研究了污泥的燃烧特性,根据燃烧实验所得的热失重曲线,对几种污泥的燃烧过程进行了分析,对实验数据进行处理,采用Ｐｈａｄｎｉｓ法微分法相结合的方法确定了燃烧反应机理并求出了反应动力学常数Ａ和Ｅ。在燃烧的不同阶段,总反应速度控制因素不同。