不同烟碱盐的热失重特性及动力学分析

Thermal pyrolysis characteristics and kinetic study of different nicotine salts

烟碱盐合成及应用是新型烟草制品配方开发中的关注热点,烟碱盐的热稳定性直接影响烟碱释放和烟草制品的感官质量。本文利用热重分析技术分别考察了氮气和空气气氛下六种烟碱盐的热稳定性,分析了不同烟碱盐热失重特性差异,并基于单一升温速率的Coats-Redfern法获得了不同烟碱盐的热失重动力学模型及参数。结果表明:(1)各烟碱盐的热失重行为差异明显,热稳定性表现各异。草酸烟碱盐和没食子酸烟碱盐的起始分解温度及完全分解温度均相对较高;同时最大失重速率也相对较大,半峰宽较窄,热分解过程较为剧烈。磷酸烟碱盐最大失重速率最低,半峰宽最宽,热分解过程最为缓和,在热解温度为450℃时的失重率约为60%。(2)六种烟碱盐热分解动力学的最适反应机理模型不一,动力学参数也存在一定的差异,两种气氛下活化能值分别介于40.76~160.19和52.27~392.11 kJ·mol^(-1)之间,指前因子范围为6.26×10^(3)~6.78×10^(17)和2.76×10^(3)~4.54×10^(41) min^(-1)。其中草酸烟碱盐和没食子酸烟碱盐活化能明显高于其他烟碱盐,且指前因子较大;而磷酸烟碱盐反应活化能及指前因子均较低。

The synthesis and application of nicotine salt is a focus of attention in the development of new tobacco products.The thermal stability of nicotine salt directly affects the release of nicotine and the sensory quality of tobacco products.In this study,thermogravimetric analysis technology was used to investigate the thermal stability of six nicotine salts in nitrogen and air atmosphere.At the same time,the differences in thermal decomposition characteristics of different nicotine salts were analyzed.Based on the Coats-Redfern method,the thermal weight loss kinetics model and parameters of different nicotine salts were obtained.The results show that:(1)The thermal weight loss behavior and the stability of the nicotine salts is obviously different.The initial decomposition temperatures of nicotine oxalate and nicotine gallate are higher,indicating a better thermal stability.At the same time,the maximum weight loss rate is relatively large,the half-peak width is narrow,and the thermal decomposition process is more intense.The maximum weight loss rate of nicotine phosphate is the lowest,while the half-peak width is the widest,indicating a slowest thermal decomposition process.The weight loss rate is about 60%when the pyrolysis temperature reached to 450 ℃.(2)The optimal reaction mechanism models for the thermal decomposition kinetics of the six nicotine salts are different,and the kinetic parameters also have certain differences.Under the two atmospheres,the activation energy value is 40.76~160.19 and 52.27~392.11 kJ·mol^(-1) ,and the pre-referred factor is in the range of 6.26× 10^(3)~6.78×10^(17) and 2.76×10^(3)~4.54×10^(41) min^(-1) .Among them,the activation energy of nicotine oxalate and nicotine gallate are significantly higher than other nicotine salts,and the pre-digital factor was larger;while the activation energy of nicotine phosphate and the pre-digital factor were both lower.