采用变温法研究直链淀粉/水杨酸包合物脱包反应动力学

Kinetic study on dissociation of amylose/salicylic acid compound using non-isothermal method

采用密封控温技术制备直链淀粉/水杨酸包合物,通过红外光谱及粉末X-射线衍射验证包合物的形成。从脱包率与时间的关系入手,采用变温法,结合非线性最小二乘法解析脱包反应的动力学参数。红外光谱及粉末X-射线衍射验证了直链淀粉/水杨酸包合物的形成,水杨酸以分子状态存在于直链淀粉的螺旋结构中形成了分子包合物。脱包反应为一级反应。当升温速率为5和10℃·h-1时,采用变温法求得脱包反应的活化能(Ea)分别为21.71和22.41kJ·mol-1,频率因子(lnA)分别为9.32和10.08;而恒温法中脱包反应的Ea为22.17kJ·mol-1,lnA为9.26。表明两种方法求得的动力学参数Ea和lnA具有一致性。本文所采用的变温法能够快速准确地确定脱包反应的动力学参数,可用于包合物稳定性的研究。

The inclusion compound of amylose and salicylic acid（SA） was prepared by a sealed temperature control method,and the formation of the inclusion compound was confirmed by IR spectrum and powder X-ray diffraction.The kinetic parameters of dissociation of amylose/SA compound were studied by the non-isothermal method which was defined as a relationship between the dissociation ratio and time.The values of activation energy（Ea） and frequency factors（lnA） were calculated by a nonlinear least-square method.In this study,the formation of the inclusion compound of amylose/SA was confirmed by IR spectrum powder X-ray diffraction.SA existed in a molecule form in the spiral stouction of amylose.The dissociation of amylose/SA compound was attributed to first order reaction.The values of Ea calculated by the nor-isothermal method were 21.71 and 22.41 kJ·mol-1 at heating rate 5 and 10℃·h-1,respectively.The corresponding isothermal method value of Ea was 22.17 kJ·mol-1;the calculated lnA values were 9.32 and 10.08 at heating rate 5 and 10℃·h-1,respectively.The corresponding isothermal method lnA value was 9.26.The results were in good agreement with Ea values and lnA values by isothermal method.These results indicated that the non-isothermal method described in this study could be adequately used for the stability study of inclusion compound and was a rapid and accurate method for the determination of kinetic parameters.