硝酸胍热分解特性及其动力学分析

采用5、10、15、20K/min的不同线性升温速率，研究硝酸胍（GN）的热分解过程，通过Flynn-Wall-Ozawa （FWO）法、Kissinger Akahira and Sunose （KAS）法和Coats-Redfern （CR）法进行热动力学分析，并利用热力学理论求解相关热安全性参数。结果表明，硝酸胍在450~700K的温度范围内呈一步失重，热重法（TG）的平均外推起始温度为580.28K；当转化率为0.1~0.9时，FWO法和KAS法得到的平均表观活化能分别为140.43kJ/mol和137.82kJ/mol，自燃倾向等级为Ⅰ级；CR法表明Avrami-Erofeev （A2）为硝酸胍的最适机理函数模型；在310~370K的温度范围内，硝酸胍的比热容随温度的升高而逐渐增大，平均值为3.148J/（g·K）；自加速分解温度（T_SADT）和自发火温度（T_be0）分别为530.15K和548.10K；活化熵（ΔS^≠）和活化焓（ΔH^≠）随升温速率的增大而减小，活化自由能（ΔG^≠）和反应速率常数随升温速率的增大而增大。

Thermal decomposition characteristics and thermokinetics of guanidine nitrate

The thermal decomposition of guanidine nitrate (GN) has been studied at different linear heating rates of 5, 10, 15 and 20K/min. The thermokinetics of GN was analysed by the Flynn-Wall-Ozawa (FWO) method, the Kissinger-Akahira-Sunose (KAS) method and the Coats-Redfern (CR) method. The thermal safety parameters were extracted using thermodynamic theory. The results showed that GN displayed a one-step weight loss in the temperature range 450-700 K, and the average extrapolated onset temperature in thermogravimetry (TG) is 580.28 K. The average activation energies obtained using the FWO and KAS methods are 140.43 kJ/mol and 137.82 kJ/mol, respectively, when the conversion rates are 0.1-0.9, and the level of spontaneous combustion tendency is grade Ⅰ. The CR method showed that Avrami-Erofeev (A2) is the optimal mechanistic function model for GN. The specific heat capacity of GN increases gradually with increasing temperature when the temperature is in the range 310-370 K, and the average value is 3.148 J/(g·K). The self-accelerating decomposition temperature (T_SADT) and the spontaneous ignition temperature (T_be0) are 530.15 K and 548.10 K, respectively. The activation entropy (ΔS^≠) and activation enthalpy (ΔH^≠) decrease as the heating rate increases, while activation free energy (ΔG^≠) and reaction rate constant increase as the heating rate increases.