Thermochemistry on Coordination Behavior of Neodymium Chloride Hydrate with Diethylammonium Diethyldithiocarbamate

The complex of neodymium chloride lower hydrate with diethylammonium diethyldithiocarbamate (D-DDC) was synthesized conveniently in absolute alcohol and dry N2 atmosphere. The title complex was identified as Et2NH2 [ Nd(S2CNEt2)4] by chemical and elemental analyses and the bonding characteristics of which was characterized by IR. The enthalpies of solution of neodymium chloride hydrate and D-DDC in absolute alcohol at 298.15 K and the enthalpies change of liquid-phase reaction of formation for Et2NH2[ Nd (S2CNEt2)4] at different temperatures were determined by microealorimetry. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of liquid-phase reaction of formation were obtained.The enthalpy change of the solid-phase title reaction at 298.15 K was calculated by a thermochemical cycle.     

Measurements of Enthalpy Change of Reaction of Formation, Molar Heat Capacity and Constant-Volume Combustion Energy of Solid Complex Yb（Et2dtc）3（phen）

A ternary solid complex Yb(Et2dtc)3(phen) was obtained from the reaction of hydrous ytterbium chloride with sodium diethyldithiocarbamate (NaEt2dtc), and 1, 10-phenanthroline (o-phen·H2O) in absolute ethanol.The bonding characteristics of the complex were characterized by IR.The result shows Yb3 bands with two sulfur atoms in the Na(Et2dtc)3 and two nitrogen atoms in the o-phen.The enthalpy change of liquid-phase reaction of formation of the complex ΔrHθm (l), was determined as being (-24.838±0.114) kJ·mol-1 at 298.15 K, by an RD-496 Ⅲ type heat conduction microcalormeter.The enthalpy change of the solid-phase reaction of formation of the complex ΔrHθm (s), was calculated as being (108.015±0.479) kJ·mol-1 on the basis of an appropriate thermochemistry cycle.The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature during the liquid-phase reaction.Fundamental parameters, the activation enthalpy, ΔHθ≠, the activation entropy, ΔSθ≠, the activation free energy, ΔGθ≠, the apparent reaction rate constant k, the apparent activation energy E, the pre-exponential constant A, and the reaction order n, were obtained by a combination of the reaction thermodynamic and kinetic equations with the data from the thermokinetic experiments.At the same time, the molar heat capacity of the complex cm, p, was determined to be (86.34±1.74) J·mol-1·K-1 by the same microcalormeter.The constant-volume combustion energy of the complex, ΔcU, was determined to be (-17954.08±8.11) kJ·mol-1 by an RBC-Ⅱ type rotating-bomb calorimeter at 298.15 K.Its standard enthalpy of combustion, ΔcHθm, and standard enthalpy of formation, ΔfHθm, were calculated to be (-17973.29±8.11) kJ·mol-1 and (-770.36±9.02) kJ·mol-1, respectively.     

Nitrogen Desorption in Molten Stainless Steel during Immersion Argon Blowing

The behavior of nitrogen desorption reaction in molten stainless steel for AISI 304 and 316 during immersion argon blowing through an immersed alumina nozzle with 3 mm in I.D. has been investigated by sampling method. Some kinetic parameters such as reaction order, rate constant and apparent activation energy of nitrogen desorption reaction for AISI 304 and 316 have been obtained. Results show that nitrogen desorption reaction from molten stainless steel for AISI 304 and 316 is the second order reaction. The rate constant at 1550 ℃ and 1580 ℃ for AISI 316 is 0.08407%-1·min-1 and 0.82370%-1·min-1, respectively. The rate constant at 1550 ℃ for AISI 304 is 0.4166%-1·min-1. The apparent activation energy Ea of nitrogen desorption reaction for AISI 316 is 2136.47 kJ/mol. This huge value of apparent activation energy verifies that the nitrogen desorption reaction has a complex and multistep reaction mechanism. The rate of nitrogen desorption reaction from molten stainless steel is mixed controlled by the desorption reaction of diatomic molecule nitrogen or of monatomic nitrogen from molten metal at the gas-metal interface and the mass transfer of nitrogen in molten metal. The rate equation of process for nitrogen desorption has been deduced.     

Effects of Particle Size on Nitridation Kinetics of Manganese Powder

Isothermal thermo-gravimetric analysis was applied to investigate the nitridation kinetics of manganese powder with different particle sizes at 800,900 and 1 000℃.The apparent activation energy and nitridation kinetics equations of manganese powder with different particle sizes were obtained from unreacted shrinking core model and Arrhenius formula.It was found that the nitridation mechanism was controlled by interfacial chemical reaction.The apparent activation energy and the apparent rate constant of nitridation reaction were affected by particle sizes.With the decrease of particle size,the apparent activation energy decreased whilst the apparent rate constant increased.It was suggested that the refinement of the manganese powder contributed to the increase of molar surface energy,which accounted for the lower apparent activation energy.     

Thermodynamic optimization and calculation of phase diagrams of YbCl3-MCl （M=Na,K, Rb,Cs）

YbCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated using the CALPHAD （CALculation of PHAse Diagram） technique. The modified quasi-chemical model in the pair-approximation for short-range ordering was used to describe the Gibbs energies of liquid phase in the systems. On the basis of the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized and calculated through an interactive computer-assisted analysis. Furthermore, some reasonable discussions on the thermodynamic parameters for these strong interaction binary systems were carded out. The results showed that the optimized parameters and experimental data are thermodynamically self-consistent.     

MATLAB simulation of preparation of Sm-loaded extractant directly from HEH（EHP）

Computer simulation of the preparation process loading rare earth(RE)directly from acidic extractant and RE chloride was established using MATLAB software.The mechanism of the extraction reaction was assumed,and then an experiment was conducted to confirm the mechanism and the apparent equilibrium constant of the reaction was determined as well.Owing to the involvement of H+ ion in the reaction between acidic extractant and RE chloride,the computer simulation of the process was more complicated than that of the extraction only between different rare earths.In the present work,MATLAB software was therefore introduced to handle the resolution of the complicated processing equation,and the simulation was performed by varying some key parameters including feed composition and phase ratio,etc.Consequently this work presented a simple method to simulate the H+ ion involved countercurrent extraction process of rare earths and also provided the practical references for the relative process designing.     

Kinetics Analysis for the Parallel Reaction of Binary Rare Earth with Tribromoarsenazo

The overall reaction was determined on the basis of the dissociation constant of TBA and the ratio of theligand to the rare earth ion in the complex.The rate law,rate constants and acitivition energies for the reactionof La~(3 ),Gd~(3 )and Ho~(3 )with TBA were studied.It is shown in the study that prerequisites for performingdifferential rate analysis for binary rare earths with TBA are that the pseudo-first-order parallel reactionmechanism should be conformed with,no multinuclear complex would be formed and the co-coloration effectscould be neglected.     

Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50～100℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La203 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.     

Morphology of Oxide Scale and Oxidation Kinetics of Low Carbon Steel

The oxidation kinetics and composition of oxide scales on low carbon steel(SPHC)were studied during isothermal oxidation.Thermogravimetric analyzer(TGA)was used to simulate isothermal oxidation process of SPHC for 240min under air condition,and the temperature range was from 500to 900 ℃.Scanning electron microscope(SEM)was used to observe cross-sectional scale morphology and analyze composition distribution of oxide scales.The morphology of oxide scale was classical three-layer structure.Fe2O3developed as whiskers at the outermost layer,and interlayer was perforated-plate Fe3O4 while innermost layer was pyramidal FeO.From the oxidation curves,the oxidation mass gain per unit area with time was of parabolic relation and oxidation rate slowed down.On the basis of experimental data,the isothermal oxidation kinetics model was derived and oxidation activation energy of SPHC steel was 127.416kJ/mol calculated from kinetics data.     

Study on Kinetics of Natural Rubber Vulcanization by S/La（DiPDP）3

Kinetics of natural rubber （NR） vulcanization by lanthanum O, O＇-diisopropyldithiophosphate [ La（DiPDP）3 ] was studied. La（DiPDP）3 had remarkable accelerating effect on the vulcanization of NR. The rate constant k6 of the reaction that turned polysulphidic cross-links into the modified main chain was higher than that of desulfuration reaction of polysulfidic cross-links （k3 ）. The activation energies （Ea2, Ea3, and Ea6） of the formation, desulfuration, and decomposition of polysulfidic cross-links were 87.57,102.34, and 95.01 kJ · mol^-1, respectively. Activation energy （Eas） of the reaction that turned the cross-link precursors into the modified main chain was 82.67 kJ · mol^-1. It could be concluded that the proportion of polysulphidic cross-links was higher than mono- and di- sulphidic cross-links during induction and curing periods, mono- and di- sulphidic cross-links increased as curing temperature rose. In the temperature range of 140 - 160 ℃, the amounts of polysulphidic cross-links were similar. However, over 160℃, mono- and di- sulphidic cross-links increased rapidly. Moreover, cross-link density of the vulcanizates was determined from the equilibrium-swelling data. A chemical probe detected the concentration of polysulphidic cross-links of vulcanizates. The change trend of the results predicated from equation corresponded to that of the experimental results.     

高铝中钛高炉渣脱硫的动力学机制

 以现场高炉渣化学成分为基准,利用纯化学试剂制备试验渣样,研究了高铝中钛型高炉渣脱硫的动力学过程,确定了其脱硫的动力学参数。结果表明,当反应温度一定时,铁水中硫含量w(［S］)随脱硫反应时间的延长而降低。试验条件下,高铝中钛渣脱硫过程属于二级反应,其限制性环节是硫在熔渣中的扩散。熔渣中硫的传质系数βS随着温度的升高而增大,硫在熔渣中的扩散活化能ED为127.03kJ/mol。     

Na_2O-Al_2O_3-SiO_2-H_2O体系生成水化石榴石的非等温动力学

利用高压DSC(HP-DSC)研究了Na2O-Al2O3-SiO2-H2O体系中生成水化石榴石的反应动力学。采用微分方程法对DSC曲线进行了分析,得到了该反应的动力学参数。结果表明,水化石榴石生成反应的表观活化能为191.17kJ/mol,指前因子为2.767 3s-1,其反应机理为随机成核和随后生长,并符合Mample单行法则。     

A study of the thermal decomposition of BaCO3

In the present work, the decomposition reaction, BaCO₃ (solid) = BaO (solid) + CO₂ (gas), was investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) methods. Both shallow powder beds and densely compacted spheres of the carbonate were employed. In the case of the shallow powder beds, TGA and DTA were carried out simultaneously. The DTA curves showed that BaCO₃ exhibited two phase transformations, the transformation of orthorhombic to hexagonal occurring at 1079 K and that of hexagonal to cubic at 1237 K. The activation energy and the forward reaction rate constant of the decomposition of BaCO₃ were evaluated from the thermogravimetric results of the powder beds. The activation energy of the decomposition was found to be 305(± 14) kJ • mole⁻¹. The experimental results obtained with the compacted spheres were compared with those corresponding to the powder beds. After the initial stages, the formation of liquid due to the eutectic reaction between BaCO₃ and BaO appears to play an important role in the reaction kinetics.     

碳酸锰制备过程中碳酸氢铵的分解速率

研究了在ＭｎＣＯ３制备过程中ＮＨ４ＨＣＯ３的分解速率，用积分法测定出分解反应为一级反应，确定出各温度下的速度常数及活化能。     

硅粉常压直接氮化过程的非催化气固反应模型

以平均粒径2.2μm、纯度99.99%的硅粉为原料,采用纯度99.993%的高纯氮气作为反应气体,在1350和1400℃下进行了氮化时间为10~30 min的氮化实验,得出了不同温度下硅粉转化率随反应时间的变化关系.将硅氮反应看成非催化气固反应,建立了硅颗粒氮化动力学模型.通过对实验数据的拟合,得出两个模型参数:硅氮反应速率常数和氮气在产物层中的扩散系数.假定反应速率常数和扩散系数均满足阿伦尼乌斯公式,求得化学反应激活能和指前因子分别为2.71×104J·mol-1和3.07×10-5m·s-1,扩散激活能和指前因子分别为1.06×105J·mol-1和1.12×10-9m2·s-1.利用本文得出的氮化动力学模型对各温度下不同粒径硅粉的转化曲线进行了预测,预测曲线与文献中的实验数据在趋势上吻合较好.      

铁-高碘酸钾-甲基绿体系阻抑动力学光度法测定铁尾矿中铁

在盐酸-邻苯二甲酸氢钾介质中, 铁(Ⅲ)对高碘酸钾氧化甲基绿的褪色反应有阻抑作用, 且阻抑反应与非阻抑反应在458nm波长处的吸光度差值与铁的质量浓度在一定的范围内呈良好的线性关系, 据此建立了阻抑动力学光度法测定痕量铁的新方法。测定了阻抑褪色反应的动力学参数, 得到阻抑反应的表观活化能E_a=0.85kJ/mol, 反应速率常数K=6.0×10^-4/s。方法的线性范围在20～120μg/L之间, 检出限为8.39μg/L。方法用于本地铁尾矿中铁含量的测定, 测定结果的相对标准偏差为2.4%~3.3%, 标准加入回收率在97%~105%范围。     

Sol-Gel法制备掺Fe莫来石的非等温动力学研究

摘要：为深入了解回转窑结圈的反应动力学机制,结合Sol-Gel法和燃烧法合成了掺杂量（质量分数）为0%、9%、12%和15%Fe的莫来石前驱体。利用DSC、XRD、SEM以及EDS对实验过程的物相转变、微晶变化进行分析,采用非等温动力学模型（KAS、Augis Bennett方程）和GaussAmp拟合方程计算了活化能Ea、Avrami指数n和拟合速率方程f（t）。结果发现,铁的加入会降低莫来石结晶温度,使液相形成温度降低,莫来石纳米晶呈三维扩散长大,晶体由形状良好的等轴球形发展为枝晶状,形成了枝晶互锁结构,对动力学参数进行计算,得Ea为941.49kJ/mol,n为1.46,拟合反应为自催化反应。研究结果表明Fe的加入会促使莫来石反应活化能和液相形成温度降低,导致物料板结,结圈加剧。     

Emission of Polycyclic Aromatic Hydrocarbons on the Combustion of Liquid Crystal Display Components

This study investigated the kinetics and emission factor for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) on the combustion of liquid crystal display components. In addition, chemical characteristics and structure of the liquid crystal sample were also investigated. The evaporation and gas diffusion of liquid crystals occur in the early stage of the combustion process (at <545?K). Continuously, the liquid crystal molecules may be oxidized to form CO2, CO, CH4, C2H6, and PAHs. The activation energy (18.9?Kcal/mol), preexponential constant (1013.9?L/min) and reaction order (3.1) of the combustion of liquid crystal display components were also determined. On the other hand, the analytic results indicated that the emission factor for 16 USEPA priority PAHs in particulate and gas phase is not determined (n.d.)-25.19 and n.d.-31.48?μg/g, respectively. The emission factor is approximately 390 and 1,520 times higher, respectively, than that of waste terephthalic acid and biological sludge combustion. Results of this work suggest that the combustion of liquid crystal display components should emphasize the air pollution control.     

在氯化亚铜溶液中用湿法冶金回收废杂铜

本文就在氯化亚铜溶液中处理回收废杂铜的工艺进行了探讨。对氯盐浸出过程工艺条件的优化进行了研究。并通过浸出反应活化能、反应级数、反应速度常数的测定,探讨了浸出反应的机理