阿司匹林的热解机理及热动力学研究

在用热重法研究了阿司匹林的热稳定性实验的基础上,通过量子化学方法(ab initio DFT)计算了阿司匹林分子的键级,据此计算结果提出了阿司匹林的热解机理,按此机理得到的理论计算值与实验结果一致;运用Freeman-Carroll、Kissinger和Ozawa三种方法分别计算了阿司匹林的热解动力学参数:活化能(E)、反应级数(n)和指前因子(A),其热解动力学方程为: dα/dt=4.74×1011[exp(－(100.34±5.18)×103/RT)](1－α)2.8±0.3;用差示扫描量热法测定的该物质的熔点、摩尔熔化焓和摩尔熔化熵分别为(409.19 ± 0.22) K、(29.17 ± 0.41) kJ•mol-1和(71.09±1.06) J•mol-1•K-1.

Studies on Thermal Decomposition Mechanism and Kinetics of Aspirin

The mechanism of thermal decomposition of aspirin was studied by both thermogravimetry and Mayer bond orders calculated by Cerius2 software. The parameters of thermal decomposition kinetics for aspirin, such as activation energy (E), reaction order (n) and frequency factor (A) were obtained by thermogravimetry. The kinetic equation of thermal decomposition of aspirin is expressed as: dα/dt=4.74×1011[exp－(100.34±5.18)×103/RT]](1－α)2.8±0.3Melting point, molar enthalpy and entropy of fusion of aspirin were examined to be (409.19±0.22) K, (29.17±0.41) kJ•mol-1 and (71.09±1.06) J•mol-1•K-1, respectively, by means of DSC with a rising temperature program. The results obtained show that theoretical mass-loss derived from Mayer bond orders of aspirin is in very good agreement with that obtained from thermogravimetry experiment.