【作者】 唐万军；

【导师】 汪存信；

【作者基本信息】 武汉大学 ， 物理化学， 2004， 博士

【摘要】 热分析动力学对于诸多领域的研究工作有着重要的意义。利用热分析动力学基本理论与方法，推导出了新的温度积分的近似公式，提出了新的热分解反应最可几动力学判定方法，以氨基酸热解反应为研究对象，采用热分析动力学理论研究了氨基酸热解反应动力学。完成的工作如下： 一、温度积分近似公式的研究： 1．在区间15≤u≤55，即1／55≤x≤1／15，采用Simpson积分法分别计算各个u所对应的integral from n=0 to x(e^-1/xdx)和integral from n=0 to x(xe^-1/xdx)的数值，建立了integral from n=0 to x(xe^（-1）/xdx)/integral from n=0 to x(e^（-1）/xdx-x)的线性关系，在该线性关系与温度积分的分步积分一级展开式的基础上推导出了温度积分近似表达式Ⅰ P（u）=(e^-u)/（u²）1/（1.00198882+1.87391198/u） 对温度积分近似表达式Ⅰ与其它近似公式数值计算的结果进行了比较。结果表明新的温度积分公式简单、精确、可靠，完全可用于线性非等温热分析动力学数据处理。 2．在区间20≤u≤60，采用数值计算法进行了分步线性拟合，即dln P（u）／du对1/u和（ln P（u）-cln u）对u。这两步拟合显示了良好的线性相关，通过拟合直线的斜率与截距得到了近似式ln P（u）=a+bu+cln u的系数a、b、c的值，从而推导了温度积分近似表达式Ⅱ-ln P（u）=0.37771216+1.89467112ln u+1.00145007u 对温度积分近似表达式Ⅱ与其它同类近似公式数值计算的结果进行了比较。结果表明采用新方法推导出的温度积分近似表达式Ⅱ的精确度得到了显著提高，具有简单和可靠好等优点，完全可用于线性非等温热分析动力学数据处理。 3．引入了普遍温度积分函数的概念，对普遍温度积分函数分步积分展开，首次得到了普遍温度积分函数的近似表达式Ⅰ integral from n=u to ∞(exp（-u）/u^m+2du)=exp（-u）u^-m-2/[1+（m+2）/u]采用数值计算和数值分析法相结合，推导了普遍温度积分函数的近似表达式Ⅱ integral from n=u to ∞(exp（-u）/u^m+2du)=exp（-u）/u^m+2[1+（m+2）（0.00099441+0.93695606/u）] 对普遍温度积分函数近似表达式Ⅰ和Ⅱ的精确度和可靠性进行了数值分析。结果表明在不同的m取值时，近似表达式Ⅰ和Ⅱ都具有较高的近似精确度。两式相比，近似表达式Ⅰ形式简单，近似表达式Ⅱ近似精确度更高。二、主曲线法判定最可几动力学模型函数研究:1.在温度积分近似表达式I和n的基础上，提出了用等转化率法和主曲线法求算热分解动力学三因子的步骤。即首先采用等转化率法求算在不同转化率下的活化能的数值，通过活化能和转化率关系对反应是否遵循单一机理进行判断，然后比较实验曲线和理论曲线，确定动力学模型的类别，最后求算出动力学模型函数的指数和动力学指前因子，从而得到完整的动力学三因子。2.采用TGA和Dsc联用技术研究了偏钒酸按热分解过程。在惰性气氛中，偏钒酸钱经历两个中间物分解生成五氧化二钒。采用上述步骤对热分解三阶段的反应动力学机理进行判定结果表明三阶段的热分解反应都遵循单一的动力学机理，都能用随机成核与核随后生长模型来进行描述，并且得到了热解反应三阶段各自完整的动力学三因子。3.采用TGA技术研究了水合草酸钙脱水反应，采用上述步骤研究了水合草酸钙脱水反应的动力学三因子。水合草酸钙脱水反应的活化能的数值几乎不随转化率变化，在转化率范围a=0.2一0.8，其平均值为（99.02土2.61）kJ，mof一‘，反应遵循单一动力学机理。采用主曲线法判定反应动力学过程为扩散控制机理，凡类动力学模型函数的动力学指数n=2.3，指前因子A=2.42 xl夕s一’。4.合成并表征了超细水合草酸锌，采用上述步骤研究了水合草酸锌热分解生成氧化锌反应的动力学三因子。在转化率范围a=0.2一0.8，其平均值为（198.99士3.36）幻，mol”，反应可以用单一的动力学机理描述，其动力学模型函数为Am，得到的动力学指数m=1.62和指前因子的对数值为31.22。三、氨基酸热解历程与热解动力学研究:1.采用热重法研究了丙氨酸、撷氨酸、亮氨酸、异亮氨酸和脯氨酸等脂肪链氨基酸以及半肤氨酸、肤氨酸和甲琉氨酸等含硫氨基酸的热解反应，各氨基酸的热重曲线均为一个台阶。采用上述步骤研究了热解反应的动力学三因子的结果表明，脂肪链氨基酸（脯氨酸除外）的热解反应遵循单一的扩散控制动力学机理，脯氨酸的热解反应遵循简单级数动力学机理，含硫氨基酸的热解反应可以用JMA动力学模型函数进行描述。2.采用热重法与IR法研究了甘氨酸，苯丙氨酸、酪氨酸和色氨酸等芳环侧链氨基酸，精氨酸、赖氨酸和组氨酸等碱性氨基酸，丝氨酸和苏氨酸等轻基侧链氨基酸，天门冬氨酸和谷氨酸等酸性氨基酸，以及天门冬酞胺和谷氨酸胺等酞胺侧链氨基酸等热解反应历程。除了谷氨酸热解时发生谷氨酸分子内酞化成五元环的焦谷氨酸外，这些氨基酸最先可能发生的反应是氨基酸的盐键破裂，氨基和梭基脱水酞化，两个分子缩聚成二氢毗嗦二酮，二氢毗嚓二酮在高温下可以进一步脱氢脱水生成毗嗦类化合物或发生其它发生的热解反应。采用上述步骤研究表明，甘氨酸、色氨酸、丝氨酸、组氨酸和?更多还原

【Abstract】 Thermal kinetic analytics play a very important role in many fields. In this thesis, we put forward the approximate formulae of temperature integral and suggested a procedure to determine the most possible kinetic model function based on the principle of thermal kinetic analysis. And various amino acids were subjected to pyrolysis and their pyrolytic mechanism and kinetics were studied. What we have done is shown below:I. Study on the approximate formulae for temperature integral1. Simpson’s procedure is used to evaluate numerical integral values of and forvarious u at interval of 1 in the range of The linear dependence of on x has been established. Combining this linear dependence andintegration-by-parts, the approximate formula I was proposed, which can be put in the formThe validity of this equation has been tested with data from numerical calculating. Compared with several published approximate formulae, this new one is much superior, to all other approximations and is the most suited solution for the evaluation of kinetic parameters from linear-heating TG experiments.2. Numerical procedure is used to evaluate the linear dependence of d lnP(u)/du on 1/wand the lineardependence of (In P(u)-cln u) on u in the range of 20 < u < 60. Good linear relationships of these two dependences have been established. Also, the coefficients a, b and c of lnP(u) = a+bu + c\nu have been obtained from the slopes and the intercepts. Finally, the approximate formula II was proposed, which can be put in the form-In P(u) = 0.37771216 + 1.89467112 ln i +1.00 145007uCompared with several published approximate formulae in the similar form, the accuracy of the approximate formula II is improved observably. It is evident that the new one is valid and easily used in the field of linear-heating TG experiments data analysis.3. The concept of generalized temperature integral function was introduced. The approximate formulae I for the generalized temperature integral function was proposed for the first time by using part-integration, which can be put in the formAlso, the approximate formulae II for the generalized temperature integral function was deduced by using numerical calculation and numerical analysis.The validities and the accuracies of the formulae I and II were analyzed. Results show that both the formulae I and II were accurate, valid, and easily used for different values of m. In both the formulae, the formulae I is simpler in the style while the formulae II is more accurate.II. Determining the most possible kinetic model function by using the master plots method1. A procedure was proposed to evaluate kinetic triplet based on the formulae I and II. This procedure involves the isoconversional method and the master plot method. That is, the activation energies at various conversions were evaluated by using model-free methods and the observed independence of activation energies on the conversions is always a clear indication that the reaction under investigation proceed as a single-step reaction, then the master plots method is used to determine the most possible class of kinetic models conforms to the reaction, finally the kinetic exponent and the pre-exponent are estimated, consequently, full kinetic triplet are proposed.2. The calcination of ammonium metavanadate was investigated using simultaneous TGA-DSC techniques. Two intermediates proceed before Ammonium metavanadate produces vanadium pentoxide. Kinetic analysis of the calcination of ammonium metavanadate were carried out by using the above procedure. Results show that each steps is subjected to a single kinetic process and can be described by using the random nucleation and nuclei growth kinetic model. The kinetic triplets for each steps were obtained eventually.3. TGA technique was applied to investigate the thermal dehydration of hydrated calcium oxalate. Also, the kinetic triplets of this process were studied. The activation energies hardly varied with the conversion and the averaged value of acti更多还原