La(NO3)3和Pr(NO3)3对高岭石脱羟基动力学的影响

采用热重和微商热重(TG/DTA)综合热分析技术在不同升温速率下研究了掺入La(NO₃)₃和Pr(NO₃)₃的高岭石的热分解过程, 利用Coats-Redfern积分法和Achar微分法对热分析实验数据进行动力学计算, 得到了高岭石脱羟基反应过程中的控制机理函数、 活化能和指前因子等动力学参数; 分析了2种稀土掺入对高岭石脱羟基过程动力学参数的影响, 并用Ozawa法对活化能进行了验证. 结果表明, 未掺稀土和掺入Pr(NO₃)₃的高岭石的脱羟基反应过程均受化学反应模型F₃控制, 反应的活化能分别为307.94和282.86 kJ/mol, 指前因子lnA的值分别为47.8980和44.1718; 掺入La(NO₃)₃的高岭石脱羟基反应过程控制机理函数发生改变, 受化学反应模型F₂控制, 反应活化能为196.02 kJ/mol, 指前因子lnA的值为29.5551. 与未掺稀土的高岭石对比, 掺入Pr(NO₃)₃后活化能和指前因子略有降低; 而掺入La(NO₃)₃后则显著降低, 分别降低了36.34%和38.30%. 采用Ozawa法验证得到的活化能与Coats-Redfern积分法和Achar微分法结果一致.     

氧化锌纳米线自组装定向生长动力学研究

研究了以极性高分子(如聚丙烯酰胺)长分子链作为自组装网络, 利用高分子软模板控制ZnO纳米点成核和ZnO纳米线定向生长, 从而使ZnO纳米线在半导体硅衬底上自组装生长的过程; 采用差示扫描量热法(DSC)测试了高分子络合-烧结法制备ZnO纳米线的结晶曲线, 对其结晶动力学进行了研究, 推导出结晶动力学方程为: 1－X_t＝exp(－7.475×10^－2t^1.9); 并利用热重(TG)测试结果, 通过热分解反应, 导出了反应动力学方程: dα/dT＝(3.76×10²³/Φ)e^－21340.8/T(1－α) ^2.8, 从而得到了化学反应速度随时间、浓度和温度变化的关系, 并用结果解释了实验现象.     

吡唑酮型成品红成色剂的照相活性与化学结构之关系

本文合成了七种典型的吡唑酮型成品红成色剂、根据Brand提出彩色显影方程γ=Alogτ+B,测定了这些成色剂的照相活性A。作者论证了在相同显影条件下,A值与吡唑酮型成品红成色剂彩色显影的偶合速度成正比。另外,作者运用SCF-PPP-MO方法计算了吡唑酮型成品红成色剂模型分子中偶合位置上的电子密度、超离域度及定域能等反应参数,发现lnA与电子密度具有较好的线性关系,其关系式为: lnA=15.97Q_r,-18.03 (n=6,r=0.95) 从而得出:彩色显影偶合反应是静电作用控制的。     

H原子和(CH3)2SiH2抽提反应的理论研究

采用UMP2/6-31G(d)理论水平优化了H原子和(CH3)2SiH2抽提反应势能面上的所有驻点,并在此水平基础上进行了内禀反应坐标(IRC)的计算,得到该反应的反应途径(MEP)。应用变分过渡态理论及最小能量途径半经典绝热基态隧道效应校正(MEPSAG)、小曲率半经典绝热基态隧道效应校正(SCSAG)等方法对上述反应进行了动力学研究,期望从理论上提供一套温度范围较宽、精度较高的动力学数据,为阐明反应机理和解释实验结果提供理论依据。     

双(2,3-环氧环戊基)醚与芳香二胺的固化过程

本文用示差扫描量热法(DSC)、动态扭辮分析仪(TBA)对双(2,3-环氧环戊基)醚与芳香二胺的固化过程进行了研究。DSC扫描结果表明固化反应分两个阶段进行,对此两个阶段固化反应的机理进行了讨论。由TBA法测得的凝胶化时间对固化温度倒数作图符合Arrhenius关系式,但较高温度区与低温区的斜率却不相同。这一现象可能与体系在不同温度区所处的状态有关。最后,以实验数据绘出热固化相图,并作了简要讨论。     

碱改性γ-Al_2O_3催化剂上羰基硫的低温水解反应 Ⅰ.催化剂活性及补偿效应

以γ-Al_2O_3为载体,用浸渍法负载碱金属和碱土金属氧化物制备了一系列羰基硫水解催化剂。采用微反-色谱联用装置考察了45—100℃低温区内的活性变化规律。结果表明,催化剂活性与金属氧化物组分及含量有着密切关系。在考察各催化剂在不同温度下水解反应速度常数(K)的变化中,发现指前因子(A)与活化能(E)之间存在着补偿效应,活化能增大时指前因子也随之增大。补偿效应参数(K_0)和能量分布指前因子(1/b)均与负载的金属离子半径(d_m)有关。求得了各催化剂的等动力学温度(T),讨论了羰基硫水解反应中存在补偿效应的原因。     

补偿效应：一条化学/化工动力学基本定律的探讨

补偿效应揭示了Arrhenius方程中反应速率常数k的指数项(-E/RgT)与指前因子(k0)项存在着相互补偿关系。不仅存在于催化与非催化,均相与非均相的反应体系及需要克服能垒的物理过程,而且也存在于生命与非生命、能源、环境与材料等许多领域。本文对补偿效应的定位、理论解释及适用范围进行了探讨,指出其在化学/化工动力学中占有重要位置,不仅是一条定律,而且是与质量作用定律、Arrhenius定律并列的又一条基本定律。本文从统计学角度对补偿效应进行了概率分析,试图对其给出更为广义的理论解释,并指出,均相反应体系和非均相反应体系本质上都是不均匀的。中间络合物生成具有耗散结构特征,在近平衡(准平衡)线性区进行,无序度减小伴随着能量及无序度的同向变化,这是补偿效应存在的根本原因。从而提出了反应速率常数中能量分布、无序度分布的概率因子。其对补偿效应的概率解释与能量指数分布说/焓熵补偿关系说是统一的而非对立的。进而还讨论了自然指数律/自然补偿律,指出补偿效应是自然界存在/运动所遵循的自然律在化学反应领域的具体体现。     

线形低密度聚乙烯／废胶粉热塑弹性体动态硫化性能研究

利用动态硫化法制备了线形低密度聚乙烯(LLDPE)/废胶粉(GTR)热塑弹性体。重点研究了两种交联剂:硫和过氧化二异丙苯(DCP)对共混物性能的影响。加入一定量的苯乙烯-丁二烯-苯乙烯(SBS)共聚物作为增容剂。结果表明,经过DCP动态硫化后的共混物的力学性能比简单共混的共混物有明显的提高,而加入硫磺体系对共混物力学性能影响不大甚至有所下降。通过红外光谱、热分析(DSC)和扫描电镜(SEM)对共混物的热行为和表面形态研究表明,加入DCP交联剂使LLDPE、SBS和胶粉之间发生了交联反应,从而增加了胶粉颗粒与LLDPE间的界面相容性,使其热塑性弹性体的力学性能得以提高。     

含能配位聚合物[Pb(tza)2]n的合成、结构与性能研究

四氮唑乙酸与碳酸铅反应制备得到含能配位聚合物[Pb(tza)₂]_n (Htza＝四氮唑-1H-1-乙酸), 用自然蒸发母液法获得单晶. 运用元素分析和红外光谱对结构进行了表征, X射线单晶衍射结果表明: 该晶体属于单斜晶系, C2/c空间群, a＝1.5370(5) nm, b＝1.0373(3) nm, c＝0.8261(3) nm, β＝119.415(4)°, V＝1.1473(7) nm³, ρ＝2.671 g/cm³, Z＝2. 采用差示扫描量热分析(DSC)和热重-微分热重分析(TG-DTG)研究了该配合物的热分解过程及其非等温反应动力学, 并根据相关标准对配合物进行了感度测试. 结果表明: 该含能配合物具有较好的热稳定性和适当的感度, 分解反应放出大量的热和气体产物, 有望作为含能材料应用于相关领域.     

树枝形大分子/环氧树脂体系固化反应动力学研究

用示差扫描量热仪(DSC)对树枝形大分子PAMAM/双酚-A型环氧树脂体系的固化反应动力学过程进行了分析。通过Kissinger法求得体系固化反应的表观活化能ΔE为59.78kJ/mol,通过Crane法求得体系的固化反应级数n=0.91,并计算出了反应速率常数k和不同升温速率下的频率因子A。根据动态DSC数据确定体系合适的固化反应温度为80~90℃,后固化温度为140℃。     

The appearance of a compensation effect in the thermal decomposition of manganese(II) carbonates, prepared in the presence of other metal ions

In this study, a compensation effect is observed for the thermal decomposition of manganese(II) carbonates, prepared in the presence of Al³⁺ and Na⁺ ions. This compensation effect is described by the equation log A = aE + b, and the parameters are showm to be a = 0.1 and b = −2.9. The mechanism of decomposition was found to follow first order kinetics.

Both A, the pre-exponential function, and E, the energy of activation, depended on the concentration and type of metal ion present in the carbonate preparation, and on the experimental method used to obtain Arrhenius parameters. In the rising temperature experiments, more than one Arrhenius plot was obtained over different temperature ranges.     

Thermal decomposition of poly(1,4-dioxan-2-one)

To evaluate the feasibility of poly(1,4-dioxan-2-one) (PPDO) as a feed stock recycling material, the pyrolysis kinetics of PPDO were investigated. The pyrolysis of PPDO exclusively resulted in the distillation of 1,4-dioxan-2-one (PDO). From thermogravimetric measurements conducted at different heating rates, the kinetic parameters of the pyrolysis: activation energy, E_a=127 kJ mol⁻¹; order of reaction, n=0; and pre-exponential factor, A=2.3×10⁹ s⁻¹, were estimated by plural analytical methods. The estimates show that the decomposition of PPDO proceeds by unzipping depolymerization as main reaction and random degradation process with lower E_a and A values. Equivalent isothermal degradation curves calculated from the thermogravimetric curves were supported by experimental isothermal degradation data. The calculation that PPDO is converted smoothly into PDO at 270°C agrees with the reported ceiling temperature of PPDO.     

Erfahrungen mit vier Softwarepaketen für Kinetische Auswertungen in der Thermischen Analyse

Four computer programs as well as one demo-version for non-linear evaluation of kinetic data in thermal analysis and calorimetry, were presented. The multi-task program TA-kin meets all mathematical requirements for solving the numerical assignments. It is shown that the so-called compensation effect is due to the mathematical structure of the Arrhenius equation. Several applications of TA-kin to a lot of DSC- and TG-measurements and isoperibolic batch experiments as well as adiabatic semi batch experiments realized by precision calorimetry have been discussed.     

Kinetics study of geopolymerization of fly ash using isothermal conduction calorimetry

Isothermal conduction calorimetry has been used to study the reaction kinetics of early geopolymerization of fly ash. Fly ash particles were subjected to react with NaOH solution in 2:1 ratio at isothermal temperatures of 34, 39, 45, 52, and 60 °C. The reaction kinetic parameters such as activation energy, rate of reaction, and pre-exponential function were calculated using the rate of heat evolution data. It is observed that the geopolymerization reaction followed a nucleation and growth mechanism. The activation energy obtained from an Arrhenius plot was around ~100 kJ mol^?1.     

Kinetics of isothermal thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene blends

The thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene blends of different compositions was investigated by means of isothermal thermogravimetry in flowing atmosphere of synthetic air at temperatures 240–270 °C. The main degradation processes are dehydrochlorination of PVC and CPE. For calculation of the apparent activation energy and apparent pre-exponential factor two kinetic methods were used: isoconversional method and Prout–Tompkins method. True compensation dependency between Arrhenius parameters, obtained using Prout–Tompkins model, was found. Calculated kinetic parameters of isothermal thermooxidative degradation are close to those from non-isothermal degradation and confirm the assumption of the main degradation process in PVC/CPE blends.     

乙酰氧肟酸的热稳定性分析

为预防化工生产、储运和使用中由乙酰氧肟酸(Acetohydroxamic acid, AHA)引发的火灾和爆炸事故, 采用绝热量热法对其热稳定性进行实验研究, 并将加速量热仪(Accelerating Rate Calorimeter, ARC)的测试结果与差示扫描量热仪(Differential Scanning Calorimetry, DSC)的结果进行了比较. ARC绝热测试结果表明, AHA的初始放热温度为352.68 K, 最高放热温度为465.82 K, 最大温升速率和最大温升速率时间分别为8.748 K•min^－1和382.65 min, 单位质量AHA生成气体的最大压力为2.22 MPa•g^－1. 根据ARC绝热测试结果, 采用速率常数法计算了AHA的动力学参数表观活化能和指前因子, 并求出了AHA的某种典型包装的不可逆温度和自加速反应温度. 研究结果表明, AHA的热稳定性较差, 爆炸性较强.     

Influence of molecular weight on the thermal decomposition of hydroxyl terminated polybutadiene

Thermogravimetric analysis of hydroxyl terminated polybutadiene (HTPB) and its fractions of different molecular weights separated by preparative GPC shows two major stages of weight loss of different nature in a nitrogen atmosphere. The first stage is primarily depolymerisation, cyclisation and crosslinking of molecules and the second stage is mainly the decomposition of the residue from the first stage. The kinetic parameters, viz. activation energy E and pre-exponential factor A using four different non-isothermal integral equations show a systematic increase with increase in molecular weight for the first stage, whereas for the second stage, the effect of molecular weight on E and A values is not prominent. The increase in E and A values for the first stage is attributed to the formation of greater number of cyclised and crosslinked products from molecules of higher dimensions. Quantitative correlations between the kinetic constants and the molecular weight parameters were derived for the first stage as a quadratic curve following the equation: E or ln A = K₁ − K₂/M (where K₁ and K₂ are empirical constants whose values are different for the different molecular weight averages, viz. M_n, M_w and M_z and for the different equations).     

Thermal analysis of Na2CO3 · H2O crystals

Monohydrated sodium carbonate crystals have been grown by slow evaporation of its aqueous solution maintained at 40 ± 1°C. The thermal dehydration of this crystal has been studied by dynamic and isothermal TG measurements. It is observed from dynamic TG that the single molecule of water of crystallization is lost in two steps of 0.3 mole and 0.7 mole at temperatures 426 ± 5 and 454 ± 5 K, respectively. From isothermal and dynamic TG measurements, the kinetic parameters E and Z are calculated using different known forms of the function F(). It is observed that consistency of E and Z values in isothermal and dynamic TG measurements for the two dehydration steps gives the correct function F() = −[log(1-)]^0.5. The activation energies for this function for the two dehydration steps are ≈6 and ≈9 kcal mole⁻¹, respectively.