基于TG-MS联用的烟碱盐热失重及产物释放特性研究

Study on thermogravimetric characteristics and product release behavior of nicotine salts based on thermogravimetric-mass spectrometry(TG-MS)

【目的】考察不同种类烟碱盐的热稳定性差异。【方法】采用TG-MS联用技术分析不同烟碱盐的热失重特性及产物释放规律,并基于Coats-Redfern法获得各烟碱盐热分解过程的动力学模型及热动力学参数。【结果】(1)试验选定的6种烟碱盐热失重特征参数差异明显,磷酸烟碱盐热分解呈现两阶段的失重过程,最大失重速率最低,热分解温度区间最宽,具有最低的CPI为0.12×10^(-3)%/(min×℃^(2)),热稳定性最佳;其余5种烟碱盐均呈现单一的失重阶段,T_(max)在150.3℃~204.9℃之间;各样品的失重过程均发生吸热现象。(2)磷酸烟碱盐、苯甲酸烟碱盐及草酸烟碱盐-1:1的反应活化能及指前因子较低,热分解反应活性小,热稳定性高。(3)有机酸类型及酸与烟碱的摩尔比是影响烟碱盐稳定性及热释放行为的关键因素。

In order to investigate the difference in thermal stability of different kinds of nicotine salts,TG-MS technique was used to analyze the thermogravimetric characteristics and product release behavior of different nicotine salts.Moreover,the kinetic models and thermodynamic parameters of the each nicotine salt during thermal decomposition process were obtained based on Coats-Redfern method.The results showed that:(1)There were significant differences in the thermogravimetric characteristic parameters among the selected six nicotine salts.The thermal decomposition of Nic.phosphate presented a two-stage weight loss process,which was characterized with the lowest maximum weight loss rate,the widest thermal decomposition temperature range and the lowest CPI(0.12×10^(-3)%/(min×℃^(2))),indicating the best thermal stability.The other five nicotine salts presented a single weight loss stage,and the Tmax was in the range of 150.3-204.9℃.Endothermic phenomena occurred in the weight loss process of each sample.(2)The activation energy and pre-exponential factor of Nic.phosphate,Nic.benzoate and Nic.oxalate-1:1 were relatively low,their thermal decomposition reactivity was low,so their thermal stability was high.(3)The type of organic acid and the acid-to-nicotine molar ratio were the key factors affecting the stability and thermal release behavior of nicotine.