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.     

ASTM Kinetics of Oil Shales

Thermal analysis is increasingly being used to obtain kinetic data relating to sample decomposition. In this research differential scanning calorimeter (DSC) was used to determine the combustion kinetics of three (Çan, Himmetoglu and Mengen) oil shale samples by ASTM and Roger &; Morris methods. On DSC curves two reaction regions were observed on oil shale sample studied except Çan oil shale. In DSC experiments higher heating rates resulted in higher reaction temperatures and higher heat of reactions. Distinguishing peaks shifted to higher temperatures with an increase in heating rate. Three different kinetic models (ASTM I-II and Rogers &; Morris) were used to determine the kinetic parameters of the oil shale samples studied. Activation energies were in the range of 131.8-185.3 kJ mol-1 for ASTM methods and 18.5-48.8 kJ mol-1 for Rogers &; Morris method.     

航空润滑油热氧化衰变的高压差示扫描量热法分析

模拟实际使用条件，对ВНИИНП－50－1－4Φ航空润滑油进行热氧化试验，应用高压差示扫描量热法（PDSC）和气相色谱仪（GC）评价抗氧剂N－苯基－α萘胺（NPAN）的热氧化衰变程度；结果发现在50－1－4Φ润滑油热氧化衰变过程中，抗氧剂NPAN质量分数（w）的对数值与PDSC在一定条件下测得的氧化诱导期torr具有良好的线性相关性，表明PDSC是研究润滑油热氧化衰变程度的理想手段。     

Catalytic Effects of Metallic Additives on The Combustion Properties of Crude Oils by Thermal Analysis Techniques

Differential scanning calorimetry (DSC) was applied to crude oil combustion in the presence and absence of metal chlorides. It was observed that in the presence of smaller ratios of metallic additives, the surface reactions were predominant and the catalyst did not affect the reactions much. Three reaction regions were identified as low temperature oxidation (LTO), middle temperature oxidation (MTO) and high temperature oxidation (HTO). Kinetic parameters of the reaction regions were determined with two different methods and the results are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Thermal Degradation of Poly(dimethyl Itaconate-co-4-vinylpyridine)

Copolymers of dimethyl itaconate (DMI) and 4-vinylpyridine (4VP) were synthetized in toluene at 60°C with0.26 mol% of AIBN as initiator. Their compositions were determined by differential refractometry and by differential scanning calorimetry. The 4VP contents of the copolymer samples ranged between 7 and 75 mol%. The reactivity ratios calculated via the Fineman-Ross method were r ₁=0.24 (DMI) and r ₂=0.57 (4VP). The thermal degradations of these copolymers were studied. The results of thermogravimetric measurements indicated that the copolymers degrade at lower temperatures than those of their parent homopolymers. A possible explanation of this anomalous behaviour is the formation of thermally unstable structures during the copolymerisation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of complexes

The iron(II) complex of the Schiff bases trans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn), manganese(II) and vanadyl complexes of the Schiff bases cis- andtrans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn) were prepared and characterized by IR spectroscopy, and elemental analysis. These new complexes were submitted to thermal analysis (TG and DSC) under dynamic air atmosphere. The differences in the decomposition profiles were related to the structure of isomers and decomposition intermediates were characterized according to their X-ray diffraction pattern and by their infrared spectrum. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Analysis Applications In Fossil Fuel Science. Literature survey

In this study, instances where thermal analysis techniques (differential scanning calorimetry, thermogravimetry, differential thermal analysis, etc.) have been applied for fossil fuel characterisation and kinetics are reviewed. The scientific results presented clearly showed that thermal analysis is a well-established technique used in fossil fuel research area. The literature survey showed that thermal methods were important not only theoretically but also from a practical point of view. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal and Structural Behavior of Palm Oil. Influence of Cooling Rate on Fat Crystallization

Summary: The effects of scanning rates (q = −0.5 °C/min to −50 °C/min) on the formation of the different phases occurring at low temperature of a palm oil are investigated by means of calorimetry and optical analysis. It is demonstrated that the cooling rates changed the polymorphism of triacylglycerols (TAGs). The centrifugation is used to separate the two fractions (olein and stearin) of palm oil. We show whereas the rate of centrifugation the separation is not effective. We obtained two fractions, a liquid fraction and a solid fraction which contains some liquid TAGs. It is observed that the solid fraction of palm oil is more sensitive to the effects of the cooling rates. By changing the cooling rate q, it appears threshold behaviour for q = −3 °C/min dividing the data discussion in two parts: for slow cooling rate and for fast cooling rate. At slow cooling rates, TAGs had more time to interact. Contrary at fast cooling rate, TAGs have not the time to be reorganised in more stable conformation. Micrographs revealed that the types of crystals observed were spherolites but some variations in crystal size appeared with the variation of cooling rate.     

DSC and Rheometry Investigations of Crude Oils

Thermal characteristics and rheological behaviour of eight crude oils covered a wide range of fluid composition and properties were studied by differential scanning calorimeter (DSC) and viscometry. Wax appearance temperatures (WAT) of crude oils were determined by DSC and viscometry. Good agreement is obtained between the results. The dynamic viscosity in the Newtonian temperature range of the crude oils (above 30°C) generally obeyed a simple first-order Arrhenius type of temperature dependence. Activation energies of flow in the non-Newtonian range are not uniquely defined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis for the Reaction of Hydroxyethyl Methacrylate/Benzoyl Peroxide/Polymethacrylate Through DSC and Viscosity Changing and Their Resultants as Oil Absorbent

Polymethacrylate was firstly synthesized via suspension polymerization of the monomers including butyl methacrylate (BMA) and hydroxyethyl methacrylate (HEMA) using benzoyl peroxide (BPO) as initiator. Then a mixture was prepared by mixing the synthesized polymethacrylate with the solution of HEMA and BPO and preserved in a sealed container for 24 h. Thereafter, we employed a differential scanning calorimeter (DSC) to monitor the reaction process of HEMA involved in the mixture at a constant heating rate. The viscosity changing with time for the above mixture was also measured by a rotating viscometer at 85°C with N, N-dimethylformamide (DMF) as diluting agent. Finally, the results of DSC test and viscosity test were analyzed for revealing the reaction mechanism of HEMA involved in the above mixture. Based on this analysis, we chose suitable technology parameters for the above-prepared mixture's reactive extrusion. During the reactive extrusion, the polymerization of HEMA was initiated and the generated PHEMA built an interpenetrating polymer network with the synthesized polymethacrylate by H-bonds to make the extruded resultant applicable for oil absorbent. Then the oil-absorptive capacity of the extruded resultant was characterized through oil absorbency, remaining ratio, and gel fraction, and its internal morphology was observed by polarizing microscope and field emission scanning electron microscopy.     

Stability studies on nifedipine tablets using thermogravimetry and differential scanning calorimetry

A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between nifedipine and excipients, or degradation products.     

Effect of Stereoregular Polyelectrolyte on Protein Thermal Stability

Myoglobin was used as a model protein to study the effect of polyelectrolyte on protein thermal stability for solutions. Stereoregular polystyrene sulfonate was used to investigate the effect of chain properties on protein polyion binding affinity. Turbidity measurement indicate stronger binding to protein of atactic polystyrene sulfonate than isotactic polystyrene sulfonate, an effect that might be due to the higher chain flexibility of the atactic form. Differential scanning calorimetry (DSC) and small angle x-ray (SAXS) scattering indicate the presence of the polyelectrolyte has a destabilizing effect on the protein. The results showed that, although the presence of polyelectrolytes has no effect on myoglobin structure at room temperature at pH 7.4, myoglobin stability is reduced as the temperature is elevated. This effect is linked to the binding of the protein to the polylectrolyte. This binding is probably driven by a combination of electrostatic and hydrophobic interactions, the latter of which are enhanced at higher temperatures.     

Changes in Chemical Composition of Flaxseed Oil during Thermal-Induced Oxidation and Resultant Effect on DSC Thermal Properties

To investigate the changes in chemical composition of flaxseed oil during thermal-induced oxidation and the resultant effect on thermal properties, samples with different oxidation levels were obtained by being heated at 180 °C for two hours and four hours. The oxidation degree was evaluated using peroxide value (PV), extinction coefficient at 232 nm and 268 nm (K₂₃₂ and K₂₆₈), and total polar compounds (TPC). Using chromatography, the fatty acid profile and triacylglycerol (TAG) profile were examined. Differential scanning calorimetry (DSC) was used to determine the crystallization and melting profiles. Thermal-induced oxidation of flaxseed oil led to a significant increase (p < 0.05) in PV, K₂₃₂, K₂₆₈, and TPC, but the relative content of linolenic acid (Ln) and LnLnLn reduced dramatically (p < 0.05). TPC derived from lipid degradation affected both crystallization and melting profiles. Statistical correlations showed that the onset temperature (T_on) of the crystallization curve was highly correlated with K₂₃₂, TPC, and the relative content of LnLnLn (p < 0.05), whereas the offset temperature (T_off) of the melting curve was highly correlated with the relative content of most fatty acids (p < 0.05). This finding provides a new way of rapid evaluation of oxidation level and changes of chemical composition for flaxseed oils using DSC.     

Comprehensive Thermal Characteristics of Different Cultivars of Flaxseed Oil (Linum usittatissimum L.)

The aim of this study was to describe the thermal properties of selected cultivars of flaxseed oil by the use of the differential scanning calorimetry (DSC) technique. The crystallization and melting profiles were analyzed depending on different scanning rates (1, 2, 5 °C/min) as well as oxidative induction time (OIT) isothermally at 120 °C and 140 °C, and oxidation onset temperatures (Ton) at 2 and 5 °C/min were measured. The crystallization was manifested as a single peak, differing for a cooling rate of 1 and 2 °C/min. The melting curves were more complex with differences among the cultivars for a heating rate of 1 and 2 °C/min, while for 5 °C/min, the profiles did not differ, which could be utilized in analytics for profiling in order to assess the authenticity of the flaxseed oil. Moreover, it was observed that flaxseed oil was highly susceptible to thermal oxidation, and its stability decreased with increasing temperature and decreasing heating rate. Significant negative linear correlations were found between unsaturated fatty acid content (C18:2, C18:3 n-3) and DSC parameters (OIT, Ton). Principal component analysis (PCA) also established a strong correlation between total oxidation value (TOTOX), peroxide value (PV) and all DSC parameters of thermo-oxidative stability.     

Thermal Characterization of Dolomites

The decomposition behaviour of dolomite samples has been carried out by simultaneous DTA-TG experiments. Dolomite samples could be classified broadly into two categories as regular and iron-bearing dolomites based on DTA decomposition temperatures. The mass% FeO of all the dolomite samples was identified by DTA and the results are confirmed by atomic absorption spectrophotometer experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermoanalytical investigation of blood

The aim of this study is to understand some properties and thermal behavior of blood, giving a possible alternative tool which differs from the traditional blood diagnostic methods, and to improve investigations in hematology and artificial bloods. Wistar rat blood samples (WRBS); SHR rat blood samples (SHRBS) and human blood samples (HBS) were analyzed. TG curves showed two decomposition stages for HBS at around 100 and 230°C (T _onset), while three mass degradation stages for WRBS (70, 110, 270°C) and SHRBS (70, 120, 270°C) could be observed. DSC peaks showed five endotherms for HBS at 65, 82, 194, 201 and 309°C and three endotherms for WRBS at 83, 184 and 313°C.     

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。     

乙酰氧肟酸的热稳定性分析

为预防化工生产、储运和使用中由乙酰氧肟酸(Acetohydroxamic acid, AHA)引发的火灾和爆炸事故, 采用绝热量热法对其热稳定性进行实验研究, 并将加速量热仪(Accelerating Rate Calorimeter, ARC)的测试结果与差示扫描量热仪(Differential Scanning Calorimetry, DSC)的结果进行了比较. ARC绝热测试结果表明, AHA的初始放热温度为352.68 K, 最高放热温度为465.82 K, 最大温升速率和最大温升速率时间分别为8.748 K•min^－1和382.65 min, 单位质量AHA生成气体的最大压力为2.22 MPa•g^－1. 根据ARC绝热测试结果, 采用速率常数法计算了AHA的动力学参数表观活化能和指前因子, 并求出了AHA的某种典型包装的不可逆温度和自加速反应温度. 研究结果表明, AHA的热稳定性较差, 爆炸性较强.     

Thermal Analysis in Propellant Stability Examinations

The thermal analysis of powders and propellants extends the possibilities of study of their chemical stability. Two models of double and triple base powders were analysed by differential scanning calorimetry. Their chemical stabilities were determined by using classical analytical methods. The thermal explosions of the powders were analysed. It was shown that the thermal decompositions of double and triple base powders are controlled by the consumption of nitro-ester stabilizers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal Stability of a Para-Cresol Novolac Resin

The thermal stability of p-cresol novolac resin was studied by means of DSC, X-ray diffraction, thermogravimetry and SEC investigations. After 30 thermal cycles in which the same sample was heated, cooled and heated again, without attainment of the temperature of degradation at any time in the experiment, important structural modifications are observed. At the end of the experiments, the resin, which is initially highly crystalline, exhibits all the characteristics of a semi-crystalline material. This revised version was published online in July 2006 with corrections to the Cover Date.