流动-差热吸附量热系统 Ⅰ. 装置考察与氢型丝光沸石(HM)-苯体系吸附热的测定

本文介绍了一种差热分析(DTA)与色谱联用的吸附量热系统。经特别设计的柱恒温箱把差热与色谱结合起来, 达到了吸附量热所要求的高灵敏度与低噪声。配置了可变宽度的矩形脉冲进样系统。进样与响应的同步性良好。结合 HM-苯体系吸附热的测定, 给出了量热图谱的解析方法。得出了与文献中吸附微量热计接近的结果。利用本系统还可获得吸附平衡的信息。结果表明, 量热与吸附平衡实验数据之间具有良好的一致性。本系统适用于在接近工业反应的动态条件下研究催化剂的吸附性能。     

Thermoanalytical control of paint-shop wastes prior to disposal

The paint-shop wastes under study originated from metallurgical factory painting houses. Displaying a high toxicity and flammability, they are classified as specifically hazardous to the natural environment. Paint-shop wastes can be disposed of in the following ways:

solidification and deposition in sanitary landfills;

storage on a special dumping ground;

incineration.

This paper presents the physicochemical composition and thermal analysis (DTA and TG) of paint-shop wastes and their mixtures with various components. Thermoanalytical measurements were carried out in a dynamic atmosphere of air. Enthalpies were calculated from the peak areas of the DTA curves. Thermoanalytical data were compared with calorimetric results obtained with an oxygen bomb.     

Modeling and thermal analysis of solidification in a low alloy steel

In this study, solidification of a low alloyed steel used for armor material was simulated at various transformation temperatures by the help of thermodynamical calculations using Thermo-Calc software. Differential thermal analysis (DTA) was carried out to determine the critical transformation temperatures for the phases and results were compared with those calculated by Thermo-Calc. It is concluded that the temperatures calculated by Thermo-Calc software are in good agreement with the results obtained from DTA. These results will be very useful to determine the proper austenization temperature having an important effect on the properties of steel serving as an armor material.     

Differential thermal analysis of transitions in finely-divided solids suspended in liquid media

The experimental difficulties associated with differential thermal analysis (DTA) are reviewed. Quantitative work has always required calibration of the equipment, and conventional solid diluents have serious disadvantages. It is shown that calibration is not strictly necessary, given appropriate conditions. Dilute suspensions of polymer crystals in organic liquids provide ideal media for DTA when used as diluent and as reference material. Convection currents are suppressed and the medium can support fine particles of the solid under test, even when the solid has a relatively high specific gravity. The new theory and techniques have been tested experimentally by measuring the heats of fusion of two inorganic salt hydrates. The results are in excellent agreement with literature values. A novel arrangement with a double thermocouple junction is shown to have considerable potentialities as a means of making precise measurements quite simply.     

30 years of research in thermal analysis and calorimetry

The research in thermal analysis and calorimetry, conducted by the author over the period 1964 to 1993, is summarised and concisely reviewed. The major investigations have focussed on thermal analysis studies of coordination compounds, particularly the metal dithiocarbamate complexes. A significant solution calorimetric study of some metal dithiocarbamate complexes has also been undertaken. DSC has been applied to determine the sublimation enthalpies of many metal dithiocarbamate and metal pentane-2,4-dionate complexes and solution calorimetry has been applied to study the thermochemistry of the latter group of complexes. Thermal analysis investigations of several inorganic molten salt systems have been initiated. Thermometric titrimetry has been applied to study metal-macrocyclic ligand systems in aqueous media and particularly those systems of environmental significance. Temperature calibration standards for TMA have been proposed and TMA has been applied to study the mechanical properties of several common inorganic compounds. DTA has been applied to study a wide variety of phenols and has subsequently been applied as an analytical technique to determine the components of solid state phenol mixtures. Thermometric titrimetry has been applied to determine the phenolic content of wines. A comprehensive thermal analysis study of Australian brown coal has been undertaken, involving the DSC determination of coal specific energy, a TG/DTA study of the coal pyrolysis and combustion processes and a TG/DTA and EGA study of the cation catalytic effect on the coal pyrolysis process. Thermal analysis and calorimetric techniques have been extensively publicised and promoted by the publication of specialist reviews, the presentation of symposia review papers and the oral presentation of short courses, particularly in the SE Asian region. This review essentially reveals the diversity of possible application of thermal analysis and calorimetric techniques and the primary significance of thermodynamic data in the fundamental rationalisation of chemical phenomena.     

Ethylenesulfide as a useful agent for incorporation on the biopolymer chitosan in a solvent-free reaction for use in lead and cadmium removal

In this work Chitosan (Ch) was chemically modified with ethylenesulfide (Es) under solvent-free conditions to give (ChEs), displaying a high content of thiol groups due to opening of the three member cyclic reagent. ChEs was used in studies of lead and cadmium adsorption from aqueous solution, using the batchwise method and calorimetric studies were accomplished to those interactions, through the calorimetric titration technique. The obtained results show that the modified Ch, ChEs is a material, that besides presenting the advantages of being a biopolymer, it showed a good adsorption capacity of the lead and cadmium cation metallic, that are extremely poisonous and harmful to the environment. The results of the calorimetric titration showed that the related thermodynamic parameters to those adsorptions shown favorable thermodynamic data.     

Study of thermal behaviour of some edible mushrooms

This paper is aimed to analyse the thermal behaviour in air of edible mushrooms through nonisothermal (TG, DTG, DTA) and calorimetric (Berthelot calorimeter) methods. The studied mushrooms were Pleurotus ostreatus spontaneously grown and from culture and Agaricus bisporus from culture, currently used in alimentation but insufficiently investigated from this point of view. The analysis of TG–DTG–DTA curves has indicated that the degradation mechanism is complex and characteristic to every species and major differences between the cap and the stipe of investigated mushrooms have not been recorded. These species are thermally stable in the range of 30–160 °C. The thermal stability in terms of initial degradation temperature (T _i °C) and the temperature corresponding to the conversion grade (T _α=0.03 °C) indicate that the stipe has a thermal stability close to the cap one and that the cultivated mushrooms are more thermally stable than those spontaneously grown. The obtained results concerning the combustion of the sample using Berthelot calorimeter are in accordance with the TG–DTG–DTA analysis. The residue obtained is a measure of the mineral content and is quantitatively close.     

Thermal investigation of biodiesel blends derived from rapeseed oil

Over the last few years, the production of biodiesel from vegetable oil has significantly increased in Romania due to its obligatory use in the composition of diesel fuel. In this study, biodiesel from rapeseed oil was produced using methanol and a base catalyst. Four samples of biodiesel/diesel blends were prepared for analysis to determine the main thermal decomposition processes and calorimetric events. The thermal profiles were compared to reference diesel. The data obtained on the Thermogravimetry/Differential thermogravimetry and DTA curves show the quality of biodiesel/diesel blends and the possibility that the fuel be used in diesel engines. It was found that biodiesel blends with higher percentage of biodiesel in their compositions were more thermally stable than diesel fuel.     

Application of thermal analysis to mineral synthesis

Differential thermal analysis (DTA) and thermogravimetry (TG) are applied to various fields of mineral science. The present work illustrates the importance of the application of thermal analysis to mineral synthesis, to the determination of the mechanism and optimum temperature of synthesis and the thermal behaviour of minerals and starting materials. Selected examples of applications in this field are given. These include DTA studies of the synthesis of topaz, cryptohalite, wulfenite, perovskite, scheelite and the refractory materials, baddeleyite and corundum. Thermal analysis is proved to be an important and valuable tool in mineral synthesis.     

Thermal degradation of copolymers of styrene and 4-nitrostyrene

The thermal degradation of styrene-4-nitrostyrene copolymers (SNS) has been studied using differential thermal analysis (DTA) and thermogravimetry (TGA) under isothermal and dynamic conditions in dynamic nitrogen. The apparent activation energy of the degradative process was determined following several methods of thermogravimetric analysis. The stability decreases as the nitrostyrene content in the copolymer increases. Fourier-transform infra-red spectroscopy has been used to analyze the degradation products at various degrees of conversion.     

Quantitative DTA under a changed gas atmosphere

The present paper describes a method for experimental determination of the momentary values of the thermal analyser calorimetric sensitivity when the type of gas in the DTA cell is changed.     

DETERMINATION OF DEGREE OF BONDED PHASE AT SILICA,GEL SURFACE USED FOR CHROMOTOGRAPHIC PACKING MATERIALS

Most of the packing materials used for liquid chtomototyraphy takes silica,gel as base The surface cf silica gel is modified by grafting of various functional bond phase to meet the purpose of separation and analysis.In some literatures,only the grafting method and the elemental analysis of bonded phase were reported.No detail quantitative determination has yet been published.This article describes the quantitative determination of material grafted on silica gel prepared by coupling reaction of silica gel with different concentrations of v-glycidoxyproplsiyl(P-GOPS) in water by differential thermal analysis(DTA) thermogravimetry(TG),element analysis(EA) and solution adsorption method.The results obtained are in agreement with those obtained by X-ray photon scat tering(XPS) method     

Thermal and FTIR spectral studies of various proportions of zinc magnesium ammonium sulfate

Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress.     

Thermal and FTIR spectral studies in various proportions of urea thiourea mixed crystal

Mixed crystals of various proportions of urea thiourea were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized using thermogravimetry–differential thermal analysis (TG–DTA) and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two-stage mass loss between 175 and 750 °C. In this temperature range, DTA curves show exothermic peaks supporting the formulated decomposition pattern. The FTIR spectra show the characteristic absorption, vibration frequencies due to urea thiourea. Detailed structural analysis of the compound is under progress.     

Investigation of eutectic transformation of Zn−Al alloy by DTA

The paper discusses the investigation of crystallization of metals and alloys by differential thermal analysis (DTA). It was assumed that this method allows determination of the mechanism and kinetics of volumetric crystallization underiso conditions (e.g. anisothermal) on the basis of the parameters of the equation expressing an integral form of the DTA curve. From DTA, a course of eutectic transformation was determined for a technical Zn?Al alloy containing 4wt% Al. Investigations were carried out under continuous cooling at various rates and the kinetics parameters were determined with the KEKAM equation:-ln(1-x)=kl _n     

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.     

Formation of B-C-N Ceramics Investigated by Emanation Thermal Analysis, TG and DTA

Processes taking place during formation of B-C-N ceramics by thermal treatment of organic precursors were investigated using emanation thermal analysis (ETA), differential thermal analysis (DTA) and thermogravimetry (TG). An additional information about thermal behavior of precursors used for preparation of BC4N, BN and CNx ceramic systems by heating in argon up to 1100°C was obtained. The ETA enabled us to characterize microstructure changes in the samples at in situ conditions of thermal treatment. A good agreement of ETA, TG and DTA results was found. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal hazards related to the use of potassium and sodium methoxides in the biodiesel industry

The introduction of sodium and potassium methoxides in processes leading to biodiesel production has triggered several questions about their stability under actual biofuel manufacturing conditions. In most biodiesel production facilities, basic homogenous catalysis is obtained through the introduction of caustic potash (KOH) or caustic soda (NaOH) in the reactor. In this process, the hydroxides are converted into their corresponding methoxide forms (CH₃OK/Na), which then become the actual catalysts in the reactor. Supplying the actual catalyst directly, instead of the low cost hydroxides, may offer several advantages, but may also introduce new hazards that deserve further characterisation work. From a review of the available literature, it was found that very little was known about the thermal decomposition properties of these methoxides. Therefore, as a starting point, l’Institut National de l’Environnement Industriel et des Risques (France) and the Canadian Explosives Research Laboratory (Canada) have recently undertaken a joint effort to better characterise their thermal behaviour. This was achieved by means of a variety of calorimetric techniques including differential scanning calorimetry, accelerating rate calorimetry and ‘large scale’ thermogravimetry–differential thermal analysis. It was found that these chemicals can become self-reactive close to room temperature under specific physical conditions.     

Application fo pressure DTA (DSC) to thermal hazard evaluation

Any hazard evaluation program should necessarily include assessment of the thermal hazards of a material. To this end, differential thermal methods (DTA and DSC) are commonly employed. The utility of these methods in thermal hazard evaluation can be significantly extended if pressurized atmospheres are also employed. The characterization of volatile chemicals as much as 100°C beyond their atmospheric boiling temperature may be achieved with pressures under 1654 kPa (225 p.s.i.g.). The effective oxygen reactivity is enhanced with a pressurized air atmosphere. Also the confined conditions in a pressurized DTA (DSC) atmosphere produce results which can be used in many instances for the semi-quantative assessment of the pressure—temperature change to be expected in more time-consuming “heating under confinements tests”.     

Some Remarks on the Methodology of Thermal Analysis of Clay Minerals

The influence of certain experimental conditions on the courses of the thermal curves (DTA and DTG) of selected clay minerals was studied. The thickness of the sample layer, the sample mass, the type of sample holder and the parameters of the air atmosphere were varied in thermal analyses of 13 samples of clay minerals. Comparison of the results obtained on different clay samples analysed under different experimental conditions may serve as the basis for the improvement of the thermal analysis methodology applied for the study of clay minerals. This revised version was published online in July 2006 with corrections to the Cover Date.