热分析量热仪主要包括动态、等温、恒温及绝热四种操作模式。很多学者基于动态及等温模式的测试结果,采用Arrhenius速率常数进行动力学计算,进而发现了所谓的“动力学补偿效应”。为了解绝热模式下是否也存在动力学补偿效应,分别采用绝热加速量热法(ARC)及动态差示扫描量热法(DSC)研究了过氧化二异丙苯(DCP)、40%(质量分数,下同)DCP溶液、葡萄糖、45%葡萄糖溶液的热分解特性,在此基础上基于Arrhenius公式计算了对应的表观活化能E和指前因子A,并对计算结果进行了分析。结果表明:绝热模式下,不同质量的同种样品及其溶液的最佳动力学参数,或者同一组数据采用不同的反应级数获得的lnA和E之间均存在明显的线性关系。此外,尽管由动态DSC数据计算获得的E和lnA普遍小于绝热模式的结果,但两种模式下获得的lnA和E之间仍然存在动力学补偿效应。由此可以推断,具有相同或类似反应机理的反应,虽然实验模式不同,但其E和lnA之间存在明显的动力学补偿效应。 Thermal analysis calorimeters can be used with different temperature control modes. Dynamic, isothermal, isoperibolic, and adiabatic modes are commonly used. A kinetic compensation effect was discovered when the kinetic parameters were calculated using the Arrhenius equation, based on dynamic and isothermal data. To determine whether the kinetic compensation effect existed in adiabatic mode, accelerating rate calorimetry (ARC) and differential scanning calorimetry (DSC) were used to obtain thermal decomposition curves of dicumyl peroxide (DCP), 40%(w) DCP in ethylbenzene, glucose, and 45% (w) glucose in water. The apparent activation energies (E) and pre-exponential factors (A) were calculated based on the Arrhenius rate constant. An obvious kinetic compensation effect was observed in a plot of lnA vs E for a given sample at different concentrations or for the same set of ARC data analyzed with different reaction orders n. Although the calculated lnA and E values using the dynamic differential scanning calorimetry data were usually lower than those using the adiabatic ARC data, a significant kinetic compensation effect existed between the two sets of results. This result suggested that the kinetic compensation effect existed between the activation energy and pre-exponential factor in reactions with the same or similar reaction mechanisms, regardless of the temperature control mode
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