Evaluation of the combustion behaviour of perhydrous coals by thermal analysis

Summary Perhydrous coals are characterized by a high hydrogen content and exhibit a modified composition and physico-chemical properties in comparison with normal coals. These modifications affect the behaviour of perhydrous coals during pyrolysis and, therefore, may have an influence on the subsequent combustion process. In this work the combustibility behaviour of a series of perhydrous coals was evaluated in order to study the effect of hydrogen enrichment during the thermal treatment of the coals in an oxidant atmosphere. To this end temperature programmed combustion tests for the coals, and air isothermal (500°C) reactivity tests for their chars, were carried out in a thermogravimetric analyser. A clear relationship between the combustion behaviour of the perhydrous coals, and the aromatic to aliphatic hydrogen ratio was found.     

Synthesis and application studies of chitosan acryloylthiourea derivative for the separation of rare earth elements

The adsorption behaviors of lanthanum (III) from an aqueous chloride medium, using Chitosan acryloylthiourea (CATU) derivative, were studied using an equilibrium batch technique. Here, the chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties, and finally would bring new or improved properties. The optimum pH value was defined to be 5.0 at a temperature of 298?K. Kinetic and isotherm experiments were carried out at the optimum pH. It was enough to reach the adsorption equilibrium at 4 hours and the maximum uptake capacity was 2.1?mmol?g^?1 at 25°C. Complexion, ion exchange, and electrostatic interaction were all believed to play a role in lanthanum adsorption on CATU derivative. The equilibrium adsorption data were fitted to a second-order kinetic equation. The Langmuir adsorption isotherm models were used to describe the adsorption process. The proposed method was validated and successfully applied for the determination of lanthanum in certified reference samples and ore sample with satisfactory results. The elution experiment was carried out by 0.05?mol/L CaCl₂ as an eluent.     

CH4 reforming with CO2 for syngas production over La2O3 promoted Ni catalysts supported on mesoporous nanostructured γ-Al2O3

Nanostructured γ-Al₂O₃ with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, N₂ adsorption-desorption, TPR, TPO, TPH, NH₃-TPD and SEM techniques. The BET analysis showed a high surface area of 204 m²·g⁻¹ and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The BET results revealed that addition of lanthanum oxide to aluminum oxide decreased the specific surface area. In addition, TPR results showed that addition of lanthanum oxide increased the reducibility of nickel catalyst. The catalytic evaluation results showed an increase in methane conversion with increasing lanthanum oxide to 3 mol% and further increase in lanthanum content decreased the catalytic activity. TPO analysis revealed that the coke deposition decreased with increasing lanthanum oxide to 3 mol%. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Addition of steam and O₂ to dry reforming feed increased the methane conversion and led to carbon free operation in combined processes.     

微型平板式反应器中甲醇水蒸气重整制氢的研究

研制了一种高效平板式微型制氢反应器,将甲醇重整和催化燃烧集于一体,吸热、放热合理耦合,实现快速启动和制氢过程自热运行;在反应器中进行甲醇水蒸气重整实验,考察了反应器腔内的温度分布,以及温度、空速和水醇比对制氢过程的影响。结果表明,当温度为270℃,空速为870h-1,水醇比为1.3时,甲醇转化率最高为94.85%,重整气组成为74.53%H2、1.76%CO、23.71%CO2;累计运行400h,重整最大产氢量接近6000mL/h,可为便携式燃料电池提供稳定氢源。     

Electrochemical behaviour of lanthanum fluoride in molten fluorides

The electrochemical behaviour of lanthanum fluoride dissolved in molten lithium fluoride and in eutectic mixture LiF-CaF₂ was investigated by cyclic voltammetry and laboratory electrolysis. The cyclic voltammetry experiments were carried out at 900°C and 800°C, respectively, in a graphite crucible (counter electrode). Several types of working electrodes (Mo, W, Ni and Cu) were used. Ni/Ni(II) was used as a reference electrode. Laboratory electrolysis was carried out in the system LiF-CaF₂-LaF₃ at 800°C in galvanostatic (j _c = −0.21 A cm⁻²) and potentiostatic (E = 0.87 V) regimes. In both cases, nickel served as the cathode and graphite as the anode. It was found that no new separate reduction peak occurred on the molybdenum or tungsten electrodes in the investigated systems. When copper or nickel electrodes were used, new peaks corresponding to the reduction of lanthanum(III) to lanthanum metal appeared. This can be explained by the formation of alloys or intermetallic compounds of lanthanum with copper or nickel. X-ray microanalysis showed that lanthanum was electrodeposited together with calcium under formation of intermetallic compounds with the electrode materials in the galvanostatic regime. In the potentiostatic regime, mainly lanthanum was deposited, which enabled its separation.     

Pyrolysis and combustion characteristics of Bio-oil from swine manure

Pyrolysis and combustion characteristics of bio-oil derived from swine manure were investigated using thermogravimetry techniques. Thermogravimetric analysis of the bio-oils were carried out in O₂ and N₂ atmosphere under different heating rates (5–20 °C/min) to a maximum temperature of 900 °C. The results indicate that the combustion processes of bio-oil occurred in three stages, namely the water and the lighter compound evaporation, i.e., the release of the volatile compounds, ignition and burning of the heavier compounds (mainly carbon), and finally decomposition of the carbonate compounds. The effect of heating rate was also studied, and higher heating rates were found to facilitate the combustion process. Different reaction kinetic mechanisms were used to treat TG data, and showed that diffusion models are the best fit for describing the combustion of bio-oil in air. The kinetic parameters of the three stages were determined using Coats–Redfern method. The study provided reliable basic data for the burning of bio-oil.     

Synthesis and Stability of Lanthanum Superhydrides

Recent theoretical calculations predict that megabar pressure stabilizes very hydrogen‐rich simple compounds having new clathrate‐like structures and remarkable electronic properties including room‐temperature superconductivity. X‐ray diffraction and optical studies demonstrate that superhydrides of lanthanum can be synthesized with La atoms in an fcc lattice at 170 GPa upon heating to about 1000 K. The results match the predicted cubic metallic phase of LaH₁₀ having cages of thirty‐two hydrogen atoms surrounding each La atom. Upon decompression, the fcc‐based structure undergoes a rhombohedral distortion of the La sublattice. The superhydride phases consist of an atomic hydrogen sublattice with H?H distances of about 1.1 Å, which are close to predictions for solid atomic metallic hydrogen at these pressures. With stability below 200 GPa, the superhydride is thus the closest analogue to solid atomic metallic hydrogen yet to be synthesized and characterized.     

Kinetic model of the decomposition of a PET fibre cloth in an inert and air environment

The kinetics of the global thermal decomposition of a PET fibre cloth have been studied in three different atmospheres with nitrogen, 20 and 10% oxygen, using thermogravimetric analysis (TGA) between room temperature and 1050 K. Three different heating rates were used at each atmosphere condition. Moreover, several isothermal experiments in nitrogen and 20% oxygen have been carried out. For the pyrolysis of an old PET fibre cloth, the kinetic model comprises three independent reactions. The combustion kinetic model considers that pyrolysis of two fractions of the initial material occurs regardless of the oxygen concentration and then a combustion of the forming char and the third fraction starts. One set of parameters can explain all the isothermal and dynamic experiments at the three different heating rates used.     

Co助剂对甲烷脱氢芳构化反应中Mo/MCM-22催化剂积碳行为的影响

 甲烷在Co-Mo/MCM-22催化剂上进行无氧脱氢芳构化反应的评价结果表明,Co的添加大大提高了Mo/MCM-22催化剂的催化活性和稳定性. 采用程序升温表面加氢反应、程序升温表面二氧化碳反应和热重分析等方法对催化剂表面的积碳物种进行了表征. 结果表明,反应后的催化剂表面主要存在两种积碳物种,H2主要与高温峰对应的积碳发生反应,而CO2对高温峰对应的积碳和低温峰对应的积碳都产生影响. Co的添加对高温峰对应的积碳和低温峰对应的积碳都有明显的抑制作用.     

尺寸可控氢氧化镧纳米棒的水热合成及表征

以硝酸镧为镧源、三乙胺为碱源和络合剂,通过简便的水热法成功合成了大量均一的氢氧化镧纳米棒。详细研究了三乙胺的用量、表面活性剂、反应温度和时间对产物形貌及尺寸的影响。基于实验结果,提出了氢氧化镧纳米棒的形成机理。同时制备了稀土掺杂的氢氧化镧纳米棒。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构和形貌进行了表征分析。     

Influence of Temperature and Concentration of Water on Lanthanum Nitrate Dissolution and Crystallization

The curves of heating and cooling crystalline lanthanum nitrate were registered and numerical differentiation was carried out. The first derivatives of kinetic curves expressed as the temperature function make it possible to carry out comparative studies of dissolution and crystallization. Superposition of relative water concentration scale on the third derivative of heating and cooling curves make the analysis of stoichiometry and mechanism of hydration changes possible in the solid phase and saturated solutions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Combustion study of HTPB–sugar hybrid fuel with gaseous oxygen

In the present investigation, some combustion studies have been carried out with 50 % HTPB + 50 % sugar fuel grain, burning in the gaseous oxygen stream using swirl and showerhead injectors, and the regression rate has been compared. The combustion of fuel grain has been carried out for burning duration of 10 ± 1 s at four different oxidizer injection pressures, viz 1.52, 2.21, 2.76 and 3.24 MPa. The regression rates were found to increase with increasing injection pressure. Use of swirl injector exhibited higher regression rate compared to the showerhead injector. The average regression rate and fuel mass consumption rate in case of swirl injector were found to be higher than that of showerhead injector. The average regression rate for the fuel with swirl injector has been found to be 18.81, 15.11, 17.73 and 20.23 % more than that of shower head injector. The exhaust plume was also found out to be brighter and longer for a swirl injector compared to that of the showerhead injector. The thermal decomposition characteristic of fuel has been determined using differential thermal analysis and thermo gravimetric analysis techniques. The decomposition study was carried out at heating rate of 10 °C min^?1 in an oxygen atmosphere. The exothermic peak indicating that major decomposition takes place at a higher temperature of 483.3 °C. Mass loss have been found using TG analysis. Residual mass of 1.262 % has been obtained in the heating range of 30–500 °C. Heat of combustion of fuel is found to be 6972.41 Cal g^?1.     

Effects of lanthanum addition on Ni-B amorphous alloy catalysts used in anthraquinone hydrogenation

Amorphous Ni-B alloys with or without lanthanum were prepared by KBH₄ reduction, characterized by ICP, BET surface area measurement, XRD, TPD, H₂ chemisorption, etc., and studied in the hydrogenation of anthraquinone. The addition of lanthanum chloride in the preparation procedure leads to the incorporation of lanthanum oxide and the decrease of Ni:B ratio in the Ni-B amorphous alloy. In comparison with Ni-B, the presence of lanthanum oxide in the amorphous alloy lead to higher BET area, higher extents of H₂ chemisorption and desorption, the shift of H₂ desorption peaks to lower temperatures, and higher TOF and reaction rate in the hydrogenation of anthraquinone. The effects of lanthanum were attributed to its dispersion of Ni, leading to much more active centers and the donation of electrons to Ni and therefore activating the adsorbed hydrogen and weakening the binding energy between nickel and hydrogen. As a result, both TOF and the reaction rate in the hydrogenation of anthraquinone were increased with the addition of lanthanum. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermal decomposition behavior of precursors for yttrium aluminum garnet

Precursor powders for yttrium aluminum garnet (YAG) were synthesized by solution combustion reactions (nitrate–glycine reaction with stoichiometric and sub-stoichiometric amount of fuel) and simple decomposition of nitrate solution. The TG-DTA, FTIR and XRD analyses of the precursors and the typical heat-treated samples were carried out to understand the processes occurring at various stages during heating to obtain phase pure YAG. Precursors from all the reactions exhibited dehydration of adsorbed moisture in the temperature range of 30 to 300°C. The precursor from nitrate–glycine reaction with stoichiometric amount of fuel (precursor- A) contained entrapped oxides of carbon (CO and CO₂) and a carbonaceous contaminant. It exhibited burning away of the carbonaceous contaminant and crystallization to pure YAG accompanied by loss of oxides of carbon in the temperature ranges of 400 to 600 and 880 to 1050°C. The precursor from simple decomposition of nitrates (precursor-B) exhibited denitration cum dehydroxylation and crystallization in the temperature ranges of 300 to 600 and 850 to 1050°C. The precursor from nitrate–glycine reaction with sub-stoichiometric amount of fuel (precursor-C) contained entrapped carbon dioxide and exhibited its release during crystallization in the temperature range of 850 to 1050°C. This study established that, in case of metal nitrate–glycine combustion reactions, crystalline YAG formation occurs from an amorphous compound with entrapped oxides of carbon. In case of simple decomposition of metal nitrates, formation of crystalline YAG occurs from an amorphous oxide intermediate.     

Studies on thermal degradation of benzylidene malononitriles

Thermal decomposition studies have been carried out using flash vacuum thermolysis (FVT) to find out the decomposition temperature for benzylidene malononitriles (BMNs) including 2-chlorobenzylidene malononitrile (cs), a widely used riot control agent. The FVT studies have been carried out in a specially designed all glass assembly at various temperatures ranging from 300 to 600°C. A number of rearranged products along with hydrogen cyanide were obtained as major decomposition products. The products were analysed and the structures were confirmed by GC/MS. the thermal behaviour of BMNs has also been investigated by TG under nitrogen atmosphere. These studies show that the pyrotechnic mixture for tear gas munitions should not have burst temperature above 300°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and Structural Characterization of Adduct [La(NO_3)_3·4H_2O]·2(BQEB)

Differentkindsofopenchaincrownethershavebeensynthesizedasthemodelcompoundsofionophoresandtheirinteractionswithsodium,potassiumandrareearthionshavealsobeenstudiedl'z.PanshowedCe(III)yieldedalf1complexwithl,8-bis(8'-quinolyloxy)-3,6-dioxaandtheCe(IIl)ioncoordinatedbothtoetheroxygenandquinolinenitrogenatoms3.TUmInleridentifiedtwolanthanidenitratecomplexeshavingastoichiometryof3:2(3RE:2L)'.InordertostUdythefunctionsofbothquinolineandbenzenering,introducedintothepolyetherchain,a1inearpolyether…     

Thermal Decomposition Kinetics of Lanthanum Complexes of 1,2-(Diimino-4'-Antipyrinyl)ethane

The kinetics and mechanism of the thermal decomposition of perchlorate, nitrate and iodide complexes of lanthanum with the Schiff base 1,2-(diimino-4'-antipyrinyl)ethane (abbreviated as GA) have been studied by TG and DTG techniques. The kinetic parameters like the activation energy, the pre-exponential factor and the entropy of activation were calculated for the major decomposition stages (Stages I and II) using Coats-Redfern equation. The rate controlling process obey ‘Mampel model’ with random nucleation with one nucleus on each particle. The kinetic parameters indicate that the ligands are loosely bound to metal ion and the activated complex formed in the decomposition reaction is more ordered than the reactants. This revised version was published online in July 2006 with corrections to the Cover Date.     

镧在低共熔溶剂中的电沉积研究

以氯化胆碱/尿素低共熔溶剂为介质通过恒电位沉积法成功制备了形状和尺寸均一的橄榄状镧粒子. 采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线能量色散谱（EDX）和X射线光电子能谱（XPS）等技术对所制备的样品进行表征. 同时,研究了沉积电位、温度和时间等因素对样品尺寸、形貌的影响,确定恒电位法制备橄榄状镧粒子的优化工艺条件为沉积电位-1.7 V、温度80 ^oC和沉积时间15 min.     

Principal component analysis of thermal decomposition of magnesium salts used as drugs

Thermal decomposition of magnesium salts of organic acids used in medicine (Mg acetate, Mg valproate, Mg lactate, Mg citrate, Mg hydrogen aspartate, Zn hydrogen aspartate) was analyzed by thermoanalytical, calorimetrical, and computational methods. Thermoanalytical studies were performed with aid of a derivatograph. 50-, 100-, and 200-mg samples were heated in a static air atmosphere at a heating rate of 3, 5, 10, and 15 °C min⁻¹ up to the final temperature of 700–900 °C. By differential thermal analysis (DTA), thermogravimetry (TG), and derivative thermogravimetry (DTG) methods, it has been established that thermal decomposition of the salts under study occurs via two stages. The first stage (dehydratation) was distinctly marked on the thermoanalytical curves. Calorimetrical studies were carried out by using of a heat-flux Mettler Toledo differential scanning calorimetry (DSC) system. Ten milligram samples of compounds under study were heated in the temperature range from 20 to 400 °C at a heating rate of 10 and 20 °C min⁻¹ under an air stream. The studies showed that the values of transitions heats and enthalpies of dehydration for investigated salts varied with the increasing of heating rate. For chemometric evaluation of thermoanalytical results, the principal component analysis (PCA) was applied. This method revealed that points on PC1 versus PC2 diagrams corresponding to the compounds of similar chemical constitution are localized in the similar ranges of the first two PC’s values. This proves that thermal decomposition reflects similarity in the structure of magnesium salts of organic acids.     

Pt-V2O5/HM催化剂积炭机理的TPO研究

Ｐｔ┐Ｖ２Ｏ５／ＨＭ催化剂积炭机理的ＴＰＯ研究蔡炳新（湖南大学化学化工系，长沙４１００１２）周烈华郑小明（杭州大学催化研究所，杭州３１００２８）关键词铂，五氧化二钒，氢型丝光沸石，程序升温氧化酸性载体Ｐｔ系贵金属双功能催化剂表面积炭是导致其催化性能衰...