Thermal kinetics study of light oil oxidation using TG/DTG techniques

In this study, the oxidation behavior of crude oils in the presence and absence of rock cuttings was investigated by thermogravimetry/derivative thermogravimetry (TG/DTG) techniques. Prior to these tests, the composition of cuttings and properties of crude oils were analyzed. Three obvious reaction regions were observed from the TG/DTG curves which are recognized as low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation. The effects of light components (C_7–15), heavy fractions (asphaltene, paraffin, resin), and cutting on oil oxidation behavior were analyzed. Kinetic analysis of crude oils and oil + cutting mixtures was performed by Arrhenius method, and the data were analyzed at last. Results show that high content C_7–15 hydrocarbons can provide negative effect on the LTO behavior of crude oil. On the contrary, the high content unsaturated heavy hydrocarbons including asphaltene, paraffin, and resin are benefit for the oxidation performance. In addition, a shortened FD stage and higher peak temperature in LTO region are observed by addition of cutting. Cutting especially clay in it plays an active role of catalyzing in oil oxidation reaction.     

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.     

马瑞原油在空气和氮气中的热解-氧化性能

低温氧化是注空气采油及原位燃烧采油技术中的重要化学反应,为深入认识原油在有氧环境下复杂热反应过程中的低温氧化特性,我们采用热重/差热分析法(TG/DTA)研究了线性升温和等温条件下马瑞(Merey)原油的热反应行为。 结果表明,Merey原油在空气及线性升温条件下的受热过程分4个阶段:气化段、低温氧化段、热解段和高温氧化段;相邻阶段的物理、化学主导过程的重叠增加了分析原油热反应特征的难度。 升温速率提高,气化段和低温氧化段的终止温度不变;热解段和高温氧化段的终止温度以及热解段的峰温随升温速率的增加而升高。 N₂气与空气下Merey原油的热重/微分热重(TG/DTG)数据对比表明,升温速率越高,空气下的高温氧化段与热解段重叠程度越大,这有利于燃烧但会降低原油采收率。 空气下等温时的TG/DTA结果表明随升温速率增加,升温至300 ℃时的失重率降低,不利于原油轻组分的气化。 反应温度越高,气化过程时间越长,失重分数越大。 Merey原油在低于300℃时低温氧化反应不是主导反应。     

Thermal investigation of heavy crude oil by simultaneous TG–DSC–FTIR and EDXRF

Present study investigates thermal behavior of two heavy crude oils with different °API values by simultaneous thermogravimetry–differential scanning calorimetry–fourier transform infrared spectroscopy (TG–DSC–FTIR), and an evaluation of the chemical element levels present in the oils’ ashes was done by energy dispersive X-ray fluorescence spectrometry. TG and DSC curves were obtained for two samples in nitrogen atmosphere. Among all inorganic components evaluated, the highest concentration in the two oils was SO₃. Thus this study may contribute to a better understanding of the thermal behavior of heavy crude oils and their composition.     

Analysis of the thermal decomposition of commercial vegetable oils in air by simultaneous TG/DTA

This work presents a study of the thermal decomposition of commercial vegetable oils and of some of their thermal properties by termogravimetry (TG), derivative termogravimetry (DTG) and by differential thermal analysis (DTA). Canola, sunflower, corn, olive and soybean oils were studied. A simultaneous SDT 2960 TG/DTA from TA Instruments was used, with a heating rate of 10 K min^-1 from 30 to 700°C. A flow of 100 mL min^-1 of air as the purge gas was used in order to burnout the oils during analysis to estimate their heat of combustion. From the extrapolated decomposition onset temperatures obtained from TG curves, it can be seen that corn oil presents the highest thermal stability (306°C), followed by the sunflower one (304°C). Olive oil presents the lowest one (288°C). The heat of combustion of each oil was estimated from DTA curves, showing the highest value for the olive oil. Except for corn oil, which presents a significantly different thermal decomposition behavior than the other oils, a perfect linear correlation is observed, with negative slope, between the heat of combustion of an oil and its respective extrapolated onset temperature of decomposition in air. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of lignins extracted from different raw materials

The thermal degradation of lignins extracted from bagasse, rice straw, corn stalk and cotton stalk, have been investigated using the techniques of thermogravimetric analysis (TG) and differential thermal analysis (DTA), between room temperature and 600°C. The actual pyrolysis of all samples starts above 200°C and is slow. The results calculated from TG curves indicated that the activation energy, Efor thermal degradation for different lignins lies in the range 7.949–8.087 kJ mol^?1. The DTA of all studied lignins showed an endothermic tendency around 100°C. In the active pyrolysis temperature range, thermal degradation occurred via two exothermic process at about 320 and 480°C, and a large endothermic pyrolysis region between 375 and 450°C. The first exothermic peak represents the main oxidation and decomposition reaction, the endothermic effect represents completion of the decomposition and the final exothermic peak represents charring.     

Thermal behavior of cashew gum by simultaneous TG/DTG/DSC-FT-IR and EDXRF

Cashew gum, an exudate polysaccharide from Anacardium occidentale L., was purified by alcohol precipitation. Thermal behavior of this polysaccharide was investigated by simultaneous TG/DTG/DSC-FT-IR analysis performed under nitrogen and air atmospheres and heating rate of 10 K min^?1. TG/DTG curves under oxidative atmosphere were similar to the curves under N₂ atmosphere until 340 °C, however, it was observed a profile difference due to the presence of two DTG peaks at 430 and 460 °C. DSC results showed endothermic and exothermic events corroborating with TG/DTG curves. The Simultaneous TG/DSC-FTIR analysis revealed that evolved gases from the decomposition of cashew gum sample were CO₂, CO, and groups: O–H, C–H, C=O, C–C, and C–O, in nitrogen and air atmospheres. Energy dispersive X-ray fluorescence analysis from the ash showed that the elements in larger amounts are CaO, MgO, and K₂O.     

Non-Isothermal Pyrolysis and Kinetics of Oil Shales

In this research, non-isothermal pyrolysis behavior and kinetics of three oil shales were studied by thermal analysis methods. All the thermal effects were endothermic and no exothermic region was observed in DSC curves. When oil shales are heated in nitrogen atmosphere in TG/DTG, two different mechanisms causing loss of mass were observed. The region between ambient temperature and 500 K was distillation. The second mechanism was visbreaking and cracking and it was observed between the region 500 and 800 K. Kinetic parameters of all the samples are determined by Coats and Redfern method and the results are discussed with regard to their accuracy and the ease of interpretation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of different clay concentrations on crude oil combustion kinetics by thermogravimetry

The objective of this research was to investigate the effect of different clay composition and concentrations on the thermal behaviour and kinetics of heavy crude oil in limestone matrix by thermogravimetry (TG/DTG). In TG/DTG experiments, three distinct reaction regions were identified in all of the crude oil + limestone mixture known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) respectively. Addition of clay to porous matrix significantly affected the reaction regions. Significant reduction of activation energy due to addition of clay to crude oil indicates the catalytic effect of clay on crude oil combustion.     

Thermochemistry of coal oxidation

Five types of Polish bituminous coal of different grades were analysed using, simultaneously, thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential thermal analysis (DTA) and evolving gas analysis (EGA) to investigate the non-isothermal coal oxidation. The TGA, DTG and DTA curves, together with EGA, provided parameters which characterize the tendency of a given coal towards oxidation. The TGA and EGA parameters can also be used to approximate the specific active surface area of coal in reaction with oxygen. Due to the negative effects of coal oxidation, such as self-oxidation, an inhibitor was proposed and tested by analysis of the above specified thermoanalytical curves and EGA.     

Catalytic effect analysis of metallic additives on light crude oil by TG and DSC tests

This research aimed at the investigation of the effect of different metallic additive on the combustion and kinetic behavior of crude oil. For this purpose, the thermal behavior of the oil-only and oil–metallic salts mixtures were studies by the thermogravimetry (TG)/derivative thermogravimetry and differential scanning calorimetry (DSC) on heating rate at 10 °C min^?1. The result shows that Dagang crude oil exhibited apparent low temperature oxidation (LTO), fuel deposition, and high temperature oxidation processes. With the addition of metallic salts, the LTO process has been shortened and samples added CuSO₄, CrCl₃·6H₂O, and AlCl₃·6H₂O achieved a much lower peak temperature than that of oil. Based on the Arrhenius model, metallic additives were proven to have obvious influence on the combustion activation energy. And, by comprehensive analysis of TG/DSC profile and activation energy, ZnSO₄ exhibited a positive influence on light crude oil combustion during the high pressure air injection process.     

Thermoanalytical study of inner and outer residue of coffee harvest

The better use of agricultural residues is expected, when they are mostly disposed of improperly and it is often burned in the natural environment. This study of the thermal decomposition of residues was performed from the coffee crop for energy purposes and in this case was used thermal analysis techniques for such assessment. The TG/DTG and DSC curves showed that the thermal decomposition occurs in four consecutive events and it is predominantly exothermic. The first mass loss evidenced in TG/DTG curves has an endothermic peak in DSC curve, which it can be associated with the water liberation of the material. This first thermal event also can be related to the liberation of volatile compounds present in the sample, which is also corroborated by the endothermic peak. The other events of mass loss are related with the thermal decomposition of the material. This decomposition has an exothermic behavior, which is positively applied to the main aim of this scientific research: the coffee straw use like biomass energy font. The thermoanalytical techniques were satisfactory in the characterization of this material.     

Thermo-oxidative reactions of Nigerian oil sand bitumen

The thermal behavior of the Nigerian oil sand bitumen in an oxidizing environment was studied using non-isothermal thermogravimetric analysis (TGA) and differential thermal analysis (DTA). This condition can occur during in situ thermal recovery. The kinetics of the reactions was also determined by Arrhenius plot method.Three regions of weight loss corresponding to low-temperature oxidation, fuel deposition and high temperature oxidation were identified. Increasing the heating rate caused a shift in the reaction regions and peak temperatures to higher temperatures. No effect of gas flow rate was observed on the reactions. The oil sands have lower peak temperatures and activation energies compared with their corresponding bitumen extracts, suggesting a catalytic effect of sand on the reactions. The DTA revealed the exothermic nature of the reactions. The exothermicity increased with increasing heating rate.The results of this study showed that the heating rate and the presence of sand have significant effect on the thermo-oxidative reactions of the bitumen.     

Thermal characterization of usnic acid/collagen-based films

The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based (UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer. In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation) did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy (SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film.     

Study of effect of phosphate and uranium ions on the thermal properties of surfactant-modified natural red clay using TG–FTIR–MS techniques

Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay.

     

Thermal analysis of a model bio-membrane

Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited by human skins’ samples, however, they presented different residue and constituents’ content.     

Thermoanalytical study of organs of spontaneous hypertension rats

The thermal behavior of the kidney, heart and liver of spontaneous hypertension rats (SHR) were studied by thermogravimetry (TG) and differential thermal analysis (DTA). SHR are, by far, the most widely used rat model in the study of heart diseases in mammals, because they develop chronic hypertension, which leads to heart failure during their lives. TG curves showed two steps for all samples: at 800°C less residues remained for an SHR kidney (4.0±1.8%) than for an SHR heart (6.9±0.4) and liver samples (7.5±1.9%). It probably happened due to the presence of inorganic substances such as iron, calcium, magnesium, potassium and sodium. DTA curves depicted three endothermic events for kidney (70, 120 and 310°C), heart (85, 250 and 300°C) and liver samples (70, 250 and 310°C), indicating protein denaturation, as well as protein degradation and fat degradation, respectively. TG/DTG/DTA profiles of organs samples showed peculiarities that permit correlation between them. These methods might serve as a simple alternative to investigations over these vital organs.     

Light crude oil combustion in the presence of limestone matrix

In this study the combustion characteristics of crude oils (Karakuę and Beykan) in the presence of a limestone matrix were determined using the thermogravimetry (TG/DTG). Experiments were performed at a heating rate of 10°C min^-1, whereas the air flow rate was kept constant at 10 L h^-1 in the temperature range of 20-900°C. In combustion with air, three distinct reaction regions were identified in all crude oil/limestone mixtures studied known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). The individual activation energies for each reaction region may be attributed to different reaction mechanisms, but they do not give any indication of the contribution of each region to the overall reactivity of the crude oils. Depending on the characteristics, the mean activation energy of samples varied between 50.3 and 55.8 kJ mol^-1. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of metal oxide on light oil combustion

Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) were applied to light crude oil combustion in the presence and absence of metal oxide. In crude oil-limestone mixture, three main transitional stages are detected. These are distillation, low-temperature oxidation (HTO) and high temperature oxidation (HTO) regions respectively. In the case of experiments with Fe(III)-chloride at different amounts, the shape of TG-DTA curve is changed considerably. Kinetic parameters of the samples are determined using ASTM method. Reduction in activation energy is considered to be an indication of the catalytic activity of the additive. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of Pentaclethra macroloba oil

The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing.