盐酸石蒜碱的热降解机理及其分解动力学研究

Thermal Decomposition Mechanism and Kinetics of Lycorine Hydrochloride

利用热重-微分热重技术测得盐酸石蒜碱在氮气气氛中的热分解曲线,协同使用Achar法和Coats-Redfern法两种方法同时进行动力学处理,根据热分解的表观活化能(Ea)和指前因子(A)计算推断石蒜碱的贮存期。盐酸石蒜碱晶体在154.9～233.9℃失去一分子H2O和一分子HCl转为石蒜碱,第二步分解(233.9～309.2℃)和第三步分解前半部分(α0.2-0.7,309.2～407.9℃)的机理都是化学反应控制,对应的函数名称是反应级数方程,反应级数n=2;第三步分解后半部分(α0.8-1.0,407.9～467.5℃)时为随机成核和随后生长控制机制,符合Avrami-Erofeev方程。经Gaussian模拟和热重数据结合分析,晶体在第二步分解时,失去1分子CO2;第三步分解分两个阶段完成,首先失去1分子CO2和1分子NH3,然后再释放出一分子的CH4;根据第二步热分解的表观活化能(Ea)和指前因子(A)推断,在室温25℃下,石蒜碱的贮存期为3 a。

Thermal decomposing curves of lycorine hydrochloride were obtained in the nitrogen atmosphere by thermogravimetry and differential thermogravimetry techniques. Two thermal analysis kinetic methods of Aehar and Coats-Redfern were used to speculate the probable mechanism of thermal decomposing reaction and the kinetic parameters. The shelflife of lycorine at room temperature was calculated by the kinetic parameters of the thermal decomposition. Before 233.9℃, one molecule of the crystal- line powder had lost 1 molecule H20 and 1 molecule HC1. The most probable kinetic mechanisms of the second-stage and third- stage （α0.2-0.7 ） thermal decomposition were all chemical reactions. The corresponding mechanisms follow Reaction Order while the third-stage （α0.8-1：0 ） thermal decomposition was Nucleation and growth, corresponding with Avrami-Erofeev Equation. In ac- cordance with the data of TG and Gaussian simulation, one molecule of the crystalline powder lost 1 molecule CO2 at the second- stage weightlessness and lost another 1 molecule CO2 and 1 molecule NH3 at α0.2-0.7 of the third stage while a molecule CH4 was lost at α0.8 -1.0 of the third stage. The storage time of lycorine at room temperature was about 3 years.