Use of the Second Derivative of TG Curves for Investigation of the Exchanged Interlayer Cation in Montmorillonite

Various cation-exchanged montmorillonites (Li+, Na+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Ag+, Cd2+, Hg2+, Al3+, Pb2+ and NH4+) were prepared from calcium montmorillonite and their properties were studied by means of X-ray diffraction and thermal analysis. The two methods give information on the cation exchange in the interlayer space only. X-ray diffraction studies at room temperature are mainly suitable for estimation of the exchange of cations of different valencies. At 500°C, when the structure is completely collapsed, the d value of montmorillonite depends on the non-hydrated ionic radius of the interlayer cation, but the measurement interval is limited for fine interpretation. The thermoanalytical method is suitable for a better distinction of different exchangeable cations of higher hydration energy on the basis of the DTG or DDTG curve. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrochemical Investigation of Binding of Heavy Metal Ions to Turkish Lignites

Adsorption and desorption of Cu²⁺, Pb²⁺, Cd²⁺, Ni²⁺ and Zn²⁺ ions on samples of lignites (young brown coal) from three areas in the vicinity of Konya (Anatolia, Turkey) were followed using the polarographic method of analysis. This method enables the determination of free metal ions in suspensions containing both small and colloidal particles of lignite. Effects of pH, nature of the metal ion, and origin of the lignite on its adsorption capacity were followed. Binding is only between 5 and 30% reversible, indicating that ion exchange is not the predominant factor. The role of the size and shape of cavities inside pulverized lignite and of the functional groups inside these cavities was considered.     

Temperature-controlled combustion and kinetics of different rank coal samples

Differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG) has been used to obtain information on the temperature-controlled combustion characteristics of seventeen coals of different origin from Thrace basin of Turkey. Experiments were performed in air atmosphere up to 600°C at a heating rate of 10°C min^-1. The DSC/TG curves clearly demonstrate distinct transitional stages in the entire coal samples studied. Reaction intervals, peak and burn-out temperatures of the coal samples are also determined. Two different kinetic methods known as, Arrhenius and Coats-Redfern, were used to analyze the kinetic data and the results are discussed.     

Combustion curves of some Turkish lignites

In this study, combustion curves of twenty-five Turkish lignites were obtained through use of a differential thermal analyser. 20 mg lignite samples were heated at a constant rate of 10 deg·min^?1 in a 40 cc/min flow of air up to 1073 K and held for 10 minutes at this constant temperature. The combustion curves of the samples are compared and discussed.     

Combustion characteristics of lignite and oil shale samples by thermal analysis techniques

In this research thermal analysis and kinetics of ten lignite's and two oil shale samples of different origin were performed using a TA 2960 thermal analysis system with thermogravimetry (TG/DTG) and differential al analysis (DTA) modules. Experiments were performed with a sample size of ~10 mg, heating rate of 10°C min^-1. Flow rate was kept constant (10 L h^-1) in the temperature range of 20-900°C. Mainly three different reaction regions were observed in most of the samples studied. The first region was due to the evaporation of moisture in the sample. The second region was due to the release of volatile matter and burning of carbon and called as primary reaction region. Third region was due to the decomposition of mineral matter in samples studied. In kinetic calculations, oxidation of lignite and oil shale is described by first-order kinetics. Depending on the characteristics of the samples, the activation energy values are varied and the results are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Catalytic gasification of Pakistani Lakhra and Thar lignite chars in steam gasification

采用热重法在常压与700℃~900℃条件下的水蒸气气化过程,对两种巴基斯坦Lakhra和Thar褐煤半焦进行了单一和混合催化剂(即3%钙和5%钠-黑液单一催化剂及一种3%钙和5%钠-黑液混合催化剂)对碳转化率、气化反应速率常数及活化能、有害污染含硫气体相对量的催化效应研究.两者Lakhra和Thar褐煤半焦经直接气化就可获得高的碳转化率,但采用纸浆黑液催化剂可使气化速率变得很快.含灰高的Thar褐煤半焦在纸浆黑液催化气化过程更易生成一些复杂的硅酸盐,从而导致比含灰低的Lakhra褐煤半焦出现一个更低的转化率.在水蒸气气化过程由半焦和纸浆黑液自身所产生的SO2 和 H2S含硫气体可为存在于纸浆黑液中的Ca盐所捕获而完成脱硫过程,但这一过程在低于900℃时更有效.缩芯模型 (SCM)可较好地用来关联转化率与时间的关系并给出不同温度下的反应速率常数k.基于阿累尼乌斯方程预测了反应活化能Ea 和指前因子A.在纸浆黑液和钙混合催化及纸浆黑液催化剂时,Lakhra褐煤半焦的Ea分别为44.7kJ/mol和 59.6kJ/mol明显小于Thar褐煤半焦的Ea=114.6kJ/mol 和 Ea=100.8kJ/mol,同样也小于无催化剂纯半焦气化时Lakhra褐煤半焦的Ea=161.2kJ/mol和Thar半焦的Ea=124.8kJ/mol.     

Characterisation of Sugar Cane Combustion Particles in the Araraquara Region, Southeast Brazil

Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, São Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world.     

Effect of Different Binders on the Combustion Properties of Lignite. Part II. Effect on kinetics

In this research kinetic analysis of the Tuncbilek lignite and its mixture with different binders (molasses, CMC, sulphide liquor, heavy crude oil, sodium silicate,cornstarch, lime, peridur, bentonite, cement and poly(vinyl-acetate)) were analysed by thermogravimetric (TG/DTG) methods. Two different kinetic models (Arrhenius and Coats–Redfern) were used to determine the activation energies of the samples studied. The concept of weighed mean activation energy was applied to determine the overall reactivity of the samples. It was observed that molasses, CMC, heavy crude oil, peridur, bentonite and poly(acetate) decreased the activation energy of the coal sample, whereas, all other binders increased the activation energy of the coal sample. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modeling of the DTG Curves for Oxidation of a Nanosized Molybdenum Ferrite Coupling Mechanics and Diffusion

From a model for isothermal oxidation kinetics in nanosized ferrite spinels based on a diffusion-induced stress effect, the authors present a modeling of the DTG curves for the oxidation of Fe²⁺ and Mo³⁺ cations on octahedral sites of a molybdenum ferrite. This has been made by considering that the chemical diffusion coefficient is given by the relation , when D _o is a pre-exponential factor, E _a ^′ an activation energy and V _a an activation energy induced by the oxidation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Some Thermal Studies on Pyrotechnic Compositions

Some applications of thermal analysis (TA) and temperature profile analysis (TPA) to the study of a variety of binary pyrotechnic systems are described. Factors that effect the combustion of such fuel/oxidant mixtures are discussed. Trends in burning behaviour and the experimental limitations of the techniques available are identified. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation of the Thermal Properties of a Series of Copper Selenide Cluster Molecules

The thermal properties of a series of the six copper selenide cluster molecules [Cu₂₆Se₁₃(PEt₂R)₁₄] (R = Ph, Et), [Cu₄₄Se₂₂(PEt₂Ph)₁₈], [Cu₇₀Se₃₅(PEt₂R)₂₃] (R = Ph, Et) and [Cu₁₄₀Se₇₀(PEt₃)₃₄] have been investigated along with a characterization of their thermolysis products. For all cluster molecules the phosphine ligand shells are cleaved at temperatures between 60°C and 200°C depending on the experimental conditions (Helium gas flow or vacuum), the type of phosphine ligand and the size of the cluster molecules. The residues of the thermal treatment to 150°C were found to be nanostructured Cu₂Se with crystallite sizes of approximately 12–16 nm which means that the 1–2.5 nm sized cluster cores of the precursor cluster molecules simultaneously grow during this process. A mixture of processes and factors including the strength of the Cu–P bond, the boiling point of the phosphine ligand as well as the thermal stability of the copper selenide clusters against formation of the bulk material determine the shape of the TGA curves. We found some indications in the TGA along with differential scanning calorimetry (DSC), which suggest that the cleavage of the phosphine ligands is probably mostly determined by the tendency of the metastable clusters to form the bulk material meaning their thermodynamic stability and not by the strength of the Cu–P bond. The data for the series of PEt₃ ligated clusters reveal that this stability is dependent on the size of the cluster molecules. Dedicated to Prof. G. Schmid on the occasion of his 70th birthday.     

硫在空气和氧气中燃烧实验的新探究

利用三口烧瓶、打火枪和恒压滴液漏斗等常见的实验仪器设计了一套实验装置,将硫在空气中的燃烧、氧气的制备、硫在氧气中的燃烧以及二氧化硫的吸收处理在一个密闭装置中完成,解决了教材中实验存在的不足。实验改进有利于培养学生的创新能力和环保意识,提高课堂的教学效果。     

Thermogravimetric Investigation of Antioxidant Activity of Selected Compounds in Lipid Oxidation

Uninhibited and inhibited autooxidation of ethyl linoleate(LnEt) in bulk phase initiated by 0.04 M azoisobutyronitrile (AIBN) was investigated by thermogravimetry in isothermal mode at 35, 40 and 50°C. LnEt oxidation was inhibited by:2,6-di-t-butyl-4-methylphenol (BHT), 2-t-butyl-6-methylphenol (BMP),2-hydroxyphenylacetic acid (PAA), 2-hydroxyacetophenone (HAP), α-tocopherol,2,2'-methylene-bis-(4-methyl-6-t-butylphenol) (BIS), caffeic acid andβ-carotene. All investigated compounds showed antioxidant activity measured by induction time, values of rate of oxidation during induction period (R _inh) and values of kinetic chain length ν. At lower temperatures the monohydroxyphenols are more efficient inhibitors than dihydroxyphenols while at 50°C dihydroxyphenols have better antioxidant efficiency. This revised version was published online in July 2006 with corrections to the Cover Date.     

煤液化残渣与褐煤混煤燃烧特性的实验研究

煤液化是提高煤炭资源利用率、减轻燃煤污染的有效途径[1].在煤液化工艺过程中,煤液化残渣的主体是由液化原料煤中未转化的煤有机体、无机矿物质以及外加的液化催化剂组成,是一种高炭、高灰和高硫的物质,在某些工艺中会占到液化原煤总量的30%左右,如此多的残渣量对液化过程的热效率和经济性所产生的影响是不可低估的[2].     

Thermoanalytical Investigation of Formamide Intercalated Kaolinites Under Quasi-isothermal Conditions

The thermal behaviour of fully and partially expanded kaolinites intercalated with formamide has been investigated in nitrogen atmosphere under quasi-isothermal heating conditions at a constant, pre-set decomposition rate of 0.20 mg min^–1 . With this technique it is possible to distinguish between loosely bonded (surface bonded) and strongly bonded (intercalated) formamide. Loosely bonded formamide is liberated in an equilibrium reaction under quasi-isothermal conditions at 118°C, while the strongly bonded (intercalated) portion is lost in an equilibrium, but non-isothermal process between 130 and 200°C. The presence of water in the intercalation solution can influence the amount of adsorbed formamide, but has no effect on the amount of the intercalated reagent. When the kaolinite is fully expanded, the amount of formamide hydrogen bonded to the inner surface of the mineral is 0.25 mol formamide/mol inner surface OH group. While the amount of surface bonded formamide is decreasing with time, no change can be observed in the amount of the intercalated reagent. With this technique the mass loss stages belonging to adsorbed and intercalated formamide can be resolved thereby providing a complex containing only one type of bonded (intercalated) formamide.This revised version was published online in November 2005 with corrections to the Cover Date.     

Recent developments in the application of thermal analysis techniques in fossil fuels

In this review, application of thermal analysis techniques (differential scanning calorimetry, thermogravimetry, differential thermal analysis, etc.) for fossil fuel characterization and kinetics are reviewed between 2001 and 2006. The results presented clearly showed that thermal analysis applications are well-established techniques used in fossil fuel research area.     

Thermochemical Investigation of Some Selected Solvates of Calix[4]resorcinarene

Lipophilic calix[4]resorcinarene derived from lauryl aldehyde forms stable crystalline solvates with a range of organic solvents: acetone, 1,4-dioxane, methylethylvketone, dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, butyronitrile, methanol, 1,2-dimethoxybenzene and acetonitrile. The composition and thermal stability of these solvates was followed by thermogravimetric method, indicating a stoichiometry ranging from 1 to 3 (calixresorcinarene/solvent). The activation energy was evaluated for the selected solvates. Molecular modelling, using Hyperchem 5.0 software, was applied to the selected solvates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Aspects of metallurgical activity in Liguria (Italy) in the middle and late bronze age

Prehistoric metal findings from Liguria are numerous, however, even though there were many metalliferous mines, the metal-working sites have not yet been ascertained.This work discusses results on some metal objects from different archaeological sites in Liguria.The objects examined were: 1) two melting drops 2) an axe, and 3) a knife. The physico-chemical investigation techniques employed were:

污泥水煤浆燃烧和污染排放特性研究

在3.2 MW 卧式炉中对污泥水煤浆和大同烟煤水煤浆进行了对比燃烧实验,分别研究了煤浆的着火、燃烧、结渣及污染物排放特性。结果表明,掺混 10%污泥的水煤浆着火容易,燃烧稳定,炉膛火焰分布均匀,燃烧和结渣特性均优于大同烟煤水煤浆。污泥的添加使水煤浆燃烧烟气中SO₂和NO_x的浓度偏高,实际应用中可通过加入固硫剂等方式缓解。污泥水煤浆在卧式炉中的燃烧状况较理想,为城市污泥资源化利用提供了一条可行的新途径。     

The influence of chemical structure of sulfonamides on the course of their thermal decomposition

The thermal decomposition of several sulfonamides and potassium salts of sulfonamides was investigated. The analyses were performed using a derivatograph in an air atmosphere, sample sizes were from 50 to 200 mg and heating rate from 2.5 to 20 K min^-1. It has been established, that the thermal destruction of studied compounds occurs via three stages with formation of potassium carbonate as a final product of the complete combustion of potassium salts of sulfonamides. The temperature ranges, in which the analyzed compounds undergo thermal transformations were established. For evaluation of the results the principal component analysis (PCA) was applied. By this method the influence of the specific functional groups on the thermal decomposition of sulfonamides and potassium salts of sulfonamides was determined. It has also been recognized, that better discrimination among the analyzed compounds is obtained for the data set of the DTA. This revised version was published online in July 2006 with corrections to the Cover Date.