石灰石热分解动力学模型研究

采用TG-DSC方法研究粒径大小为900μm石灰石的热分解过程。根据石灰石热重实验数据,结合Coats-Redfern法,Flynn-Wall-Ozawa法和Kissinger法计算石灰石热分解动力学参数,得到900μm石灰石热分解的活化能E为193.98kJ/mol,指前因子lgA为8.81min-1。根据Malek方法判断石灰石热分解最概然机理函数,得到900μm石灰石热分解属于三维相边界反应模型R3,进一步得到其热分解动力学方程。      

FeS热分解动力学的热分析

FeS诱发含硫油品自燃的事故受到了业界的日益关注.通过在不同升温速率(2,5,8,10,15℃/min)下的热分析实验,应用模型和非模型拟合研究了FeS的热分解动力学机理,结果表明:FeS受热氧化是FeS与氧气物理吸附、化学吸附和化学反应过程,对FeS的模型拟合结果不稳定,可靠性较差;采用等转化率法得到FeS热分解的表观活化能E=(135.81±8.27)kJ/mol;通过Satava-Sestak方程确定了FeS的受热分解符合成核和生长模型函数A2:g(α)=[-ln(1-α)]1/2,其表观活化能E=148.43 kJ/mol,表观指前因子A=3.82×109K/s.     

六水草酸镝热分解过程机理及动力学研究

稀土草酸盐是目前制备稀土氧化物,尤其是制备具有可控粒度的稀土氧化物常用的前驱体,它具有沉淀物晶型好,易于过滤分解等优点.然而,目前稀土草酸盐热分解的动力学研究较少,因此,采用热重-差热分析法,研究六水草酸镝的热分解过程,通过Kissinger、Ozawa和Crane法计算六水草酸镝的分解动力学参数,通过Coats-Redfern法求出反应的机理函数.结果表明:几种方法计算的分解活化能比较接近,六水草酸镝热分解分2步进行,第1步为1级脱水反应,反应机理函数为F1,表观活化能为62.48 kJ/mol,指前因子为1.84×106;第2步也为1级分解反应,反应机理函数为F2,表观活化能为106.42 kJ/mol,指前因子为2.79×107.      

基于非等温热重法的氟化石墨热分解动力学研究

针对氟化石墨热分解动力学机理不确定和动力学预测信息不足的问题,通过测量多组非等温热重曲线,并利用无模型动力学方法分析（CF）_n热分解反应动力学机理.热重曲线显示（CF）_n热分解经历一步失重,产生的平均气相成分为CF_2.95.动力学分析结果表明机理函数随转化率依次变化:α < 0.1,机理函数为JMA方程f（α）=1.5（1-α）[-ln（1-α）]1/3;0.15 < α < 0.3,机理函数为二维Avrami-Erofeyev方程f（α）=2（1-α）[-ln（1-α）]1/2;0.3 < α < 0.8,机理函数为?esták-Berggren方程f（α）=7.5α1.2·（1-α）2;0.85 < α,机理函数为一维Avrami-Erofeyev方程f（α）=（1-α）.推荐的动力学预测参量活化能为264.23±7.82 kJ/mol,指前因子为（8.70±0.21）×1014/s.另外,动力学机理反映出（CF）_n分解过程存在碳核的链生长以及与分支链的相互作用的特征,这可能是反应产物形成非晶态结构碳的重要因素.      

The intrinsic thermal decomposition kinetics of SrCO3 by a nonisothermal technique

The kinetics of the decomposition of SrCO₃ in argon to SrO and CO₂ were studied in the temperature range 1000 to 1350 K. The thermal decomposition was followed simultaneously by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) during linear heating. By using a nonisothermal method, the complete rate expression was determined from a relatively small number of experimental runs. Shallow beds of fine synthetic powder as well as thin flakes of pressed powder were employed to obtain the kinetics of decomposition in the absence of heat- and mass-transfer effects. The thermal decomposition started at about 1000 K. The recommended rate expression for the SrCO₃ decomposition is

Using equations of nonisothermal kinetics for determining the course region of thermal decomposition of copper arsenide

Using the example of processing experimental results from a determination of the degree and rate of decomposition of copper arsenide in vacuum, the application of nonisothermal kinetics to establish the course region of the process is suggested.     

单斜仲钨酸铵快速热分解研究

通过差热分析仪和激光粒度分析仪对单斜仲钨酸铵（APT）在氩气中以9℃／min进行热分解的试验结果分析可以得出：单斜仲钨酸铵（APT）在氩气中以9℃／min进行升温时，在253．3℃时，产物粒度细化的幅度最大；在232．9℃时，产物粒度细化的幅度次之；在297．4℃时，产物粒度粗化的幅度最大；在432．1℃时，产物粒度粗化的幅度次之；在150．2℃和500．0℃时，产物粒度粗化程度不明显。为了得到不同粒度的产物，就可以分阶段性地对单斜仲钨酸铵（APT）进行升温。     

十水草酸镧的热分解及其动力学分析

用热重-差热(TG-DTA)技术,在不同升温速率条件下,研究了十水草酸镧在空气气氛下的热分解过程.分别采用Ozawa-Flynm-Wall法、Kissinger法、Crane法和同步热分析法确定其热分解动力学参数.TG-DTA曲线表明:十水草酸镧分解为四个阶段,前两个阶段为脱水过程,后两个阶段为La_2(C_2O_4)_3的分解过程.实验计算得出四步反应表观活化能E分别为83.92、76.04、136.26、162.61 k J·mol-1左右;指前因子A分别为4.92×10~(10)、6.1×10~7、2.1×10~9、8.46×10~6s-1左右;反应级数n均为1左右,并用Coats-Redfem积分法得出第三步分解机理受F1控制.     

Thermodynamics and kinetics of thermal dissociation of dolomite

The results of investigations into thermodynamic foundations and kinetics of thermal dissociation of dolomites of Ural deposits are presented. Dolomite samples are characteristic of the fraction and coarseness of calcite inclusions, which determines distinctions in their dissociation kinetics. It is established that dolomites dissociate according to the two-stage model limited by the reaction on a three-dimensional surface at the first stage and kinetic equation having the order close to 0.3 and 0.3 at the second stage.     

Manufacture of ferrite powders by thermal decomposition of sulfates

Summary A method has been developed for obtaining magnesium ferrite-chromites by thermal decomposition of sulfates; it is comparatively simple and is universal. The powders obtained give ferrites with satisfactory properties.     

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.     

溶液燃烧-氢还原法制备超细铁粉的水分解反应动力学研究

针对氚化水分解处理需求,采用溶液燃烧-氢还原法制备超细铁粉,采用恒温热重法对不同粒度铁粉及不同比例锆、铑掺杂改性的铁粉进行水分解动力学研究。结果表明:采用溶液燃烧-氢还原法制备的铁粉粒度为纳米级,其水分解反应动力学性能明显优于微米级羰基铁粉和还原铁粉;添加锆元素后铁粉具有明显的抗烧结性能,锆的优化添加量(原子分数,以下同)是10%;10%Zr-Fe粉中添加铑元素后水分解反应速率显著提高,优化添加量是1%。10%Zr-1%Rh共掺杂铁粉具有优良的水分解动力学性能和循环稳定性,这是由于锆以网状ZrO2纳米线的形式包裹铁粉颗粒,阻止其烧结长大;铑分布于颗粒表面,对水分子分解起催化作用。     

The physical chemistry of thermal decomposition of South African chromite minerals

Natural chromite minerals form extended solid solutions with binary spinels of FeCr₂O₄, MgCr₂O₄, FeAl₂O₄, and MgAl₂O₄. The decomposition of natural spinels strongly depends upon the chemical potential imposed in the forms of temperature, pressure, and pH difference in aqueous media (e.g., during natural weathering). In this investigation, we studied the thermal decomposition behavior of South African chromite ores in order to relate the influence of oxygen potential with the likely product phases formed. The decomposition is also a generic step in the understanding of the formation of sodium chromate during soda-ash roasting and the reduction of chromite ores for ferrochrome alloy making. The phase equilibria in South African chromite minerals were investigated by isochronal thermal analysis and isothermal heat treatment of chromite mineral in air, argon, and Ar-5 pct H₂ atmospheres over a temperature range from 473 to 1473 K. The effects of the oxygen partial pressure and temperature on the phase constituents of the heat-treated product are discussed by referring to the results of X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray detector (EDX), and electron probe microanalysis (EPMA). The structure of phases formed and the morphology of phase-separated regions in chromite appear to be strongly dependent on the oxygen partial pressure. The mechanism of the decomposition of complex spinel phases is described under the influence of oxygen partial pressure and temperature.