N-硝基吡唑合成过程中的热安全性

Thermal Safety in the Synthesis Reaction of N-nitropyrazole

为解决N-硝基吡唑安全生产问题,利用反应量热仪EaysmaxHFCal测定N-硝基吡唑合成过程中的放热速率、传热系数、比热容等热力学数据,结果表明:加料过程中平均放热速率为6.72 W,保温过程中平均放热速率为0.11 W,理论绝热温升为111.19℃。采用绝热加速量热仪ARC测定硝化液的热稳定性,结果表明:硝化液绝热分解分为3个阶段,后两个阶段为其主要热分解阶段。主要的热分解在78.8℃开始,整体绝热分解过程较为缓慢。计算了第2段热分解过程的活化能及指前因子,分别为118.81 kJ/mol、6.94×1013 s-1。反应液到达最大反应速率用时24 h所对应的温度为48.11℃,通过冷却失效情形法,确定其危险度等级为2级,反应过程的热危险较低,不需要采取特殊措施。

To solve the safety production problem of n-nitropyrazole,EasymaxHFCal was used to measure the heat release rate,heat transfer coefficient,specific heat capacity,and other thermodynamic data in the synthesis process of N-nitropyrazole.The result shows that the average heat release rate of nitration reaction in feeding was 6.72 W and in the finish period was 0.11 W.The theoretical adiabatic temperature rise was 111.19℃.The thermal decomposition behavior of the nitrate solution in the reaction process was studied by ARC(accelerating rate calorimeter).Based on the experiment result,the adiabatic decomposition can be divided into three stages and the last two stages are the main thermal decomposition.The adiabatic decomposition of n-nitropyrazole is slow with the initial decomposition temperature began at 78.8℃.The activation energy and pre-exponential factor of thermal decomposition in the second stage were calculated,which are 118.81 kJ/mol and 6.94×1013 s-1,respectively.The temperature corresponding to the reaction of the reaction solution to reach the maximum thermal decomposition rate of 24 h was 48.11℃.The risk level was determined as level 2 by the cooling failure situation method.Therefore,the thermal runway risk of this reaction is low,no special measures are required for this reaction.