奎宁的热解机理、动力学及贮存期研究

Thermal decomposition mechanism,kinetics and shelflife of quinine

利用热重-红外联用技术测得奎宁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(E_a)和指前因子(A)计算推断奎宁的贮存期。奎宁晶体在219.93～389.93℃发生了第一步分解,先后释放了醇类、CO、CO_2、醚类、胺类等物质,反应机理为化学反应控制,对应的函数名称是反应级数方程,反应级数n=2;第二步分解(389.93～800℃)是由于残余分子骨架中苯并吡啶环的深度裂解碳化,过程较为缓慢,形成了CO_2、H_2O、NH_3等气体。经红外光谱解析和热重数据结合分析,晶体在第一步分解时又先后分为两个阶段,首先是苯并吡啶环上与两个氧原子相连的化学键断裂,其次是支链上的其它原子化学键相继发生断裂并裂解;根据第一步热分解的表观活化能(E_a)和指前因子(A)推断,在室温25℃下,奎宁的贮存期为4～5年。

Thermal decomposition curves of quinine were measured by thermo-gravimetric and Fourier-transform infrared spectroscopy coupled technology,and the experimental data of TG were synergistically processed by Achar method and Coats-Redfern method to infer the thermal decomposition mechanism and the kinetics parameters (apparent activation energy E a and pre-exponential factor A ),which were also used to calculate the shelflife of quinine.Based on TG data and FT-IR spectra analysis,thermal decomposition of the first stage started from 219.93 ℃ to 389.93 ℃,chemical bonds between oxygen atoms and quinolone ring cracked and released ROH,CO,CO 2,R-O-R,R-NH 2,etc.,which was followed by Chemical Reaction mechanism and corresponding with Reaction Order equation (the order of reaction n = 2).At the second stage,residual molecular skeleton (quinolone ring) was thermally cracked deeply from 389.93 ℃ to 800 ℃ and the gases such as CO 2,H 2O and NH 3 were released.According to the kinetic parameters of thermolysis at the first stage,the shelflives of quinine were inferred,which were 4-5 years at room temperature (25 ℃).