热分析法与分子模拟技术研究芦丁的热降解机理及其分解动力学

Study on Thermal Decomposition Mechanism and Kinetics of Rutin by Thermal Analysis and Molecular Simulation

利用热重-微分热重技术测得芦丁在氮气气氛中不同升温速率β下的热分解曲线,使用Achar法、Coats-Redfern法、Kissinger法和Ozawa法4种方法同时进行动力学分析,根据第一步热分解的表观活化能Eα和指前因子A计算推断芦丁在不同温度下的贮存期。研究表明,随着升温速率的提高,芦丁的热分解温度逐渐升高;芦丁三步热分解的机理依次是随机成核与随后生长控制、三维扩散控制、随机成核与随后生长控制,分别对应的函数是Avrami-Erofeev方程、Z.-L.-T.方程和Avrami-Erofeev方程;经Gaussian模拟和热重数据结合分析,芦丁在第一步分解时,失去3个O原子;第二步分解时失去10个O原子;第三步分解时失去烷烃分子链和1个苯环。根据第一步热分解的表观活化能Eα和指前因子A推断,在室温25℃下,芦丁的贮存期为1.5～2年。

The thermal decomposing curves of turin in different heating speeds were obtained under dynamic conditions in nitrogen atmosphere, using non-isothermal thermogravimetric and derivative thermogravimetry methods（TG -DTG）. Four thermal analysis kinetic methods, e.g. Achar, Coats - Redfern, Kissinger and Ozawa method were used to speculate the probable mechanisms of thermal de- composing reaction and the kinetic parameters. The shelflives of turin at sevral different temperatures were calculated by the kinetic parameters of first stage. With increase of the heating rate, the ther- mal decomposing tempreture of rutin rose. The most probable kinetic mechanisms of the three-stage thermal decomposition were nucleation and growth, three-dimensional diffusion, nucleation and growth, which correspond to Avrami - Erofeev Equation, Z. -L. -T. Equation and Avrami - Erofeev Equation, respectively. In accordance with the data of TG and Gaussian simulation, one molecule of rutin lost three oxygen atoms at the first stage of decomposition and lost ten oxygen atoms at the second stage while paraffins and one benzene ring were lost at the third stage. The shelflives of rutin at room temperature were about 1.5 -2 years based on the apparent activation energy（Eα ） and pre-exponen- tial factor（A） of the first stage.