头孢地嗪钠的热分解机理及动力学

Mechanism and Kinetics of Thermal Decomposition of Cefodizime Disodium

关键词:  头孢地嗪钠  量子化学  热分析  机理  热重法  差示扫描量热法

Key words:  cefodizime disodium  quantum chemistry  thermoanalysis  mechanism  thermogravimetry  differential scanning calorimetry

摘要:

目的 测定头孢地嗪钠(CDZ)的热性质，研究CDZ的热分解机理、热分解动力学和CDZ的热稳定性。方法 采用热重法(TG) 和差示扫描量热法(DSC)测定CDZ在氮气氛和空气氛中的热分解过程，测定CDZ及其在热分解过程中不同阶段残存物的红外光谱，运用量子化学GAMESS软件计算CDZ分子的键级，根据不同升温速率下的热重曲线计算CDZ热分解反应的动力学参数，采用Dakin方程计算CDZ在各种温度下的预期寿命。结果 CDZ的热分解过程是多阶段过程。在氮气氛中热分解表观活化能 Ea=173.9 kJ·mol-1，指前因子 A=1.175×1017 min-1；在空气氛中热分解表观活化能 Ea=172.3 kJ·mol-1，指前因子 A=2.692×1017 min-1。结论 CDZ在常温下有很好的热稳定性。

Abstract:

OBJECTIVE To probe into the thermal property，the mechanism of the thermal decomposition and the prospective lifetime of cefodizime disodium (CDZ). METHODS The thermal decomposition of CDZ was measured by thermogravimetry (TG) and differential scanning calorimetry(DSC)，the IR spectra of CDZ and its remainders from thermal decomposition at various temperatures were determined, the molecular bond orders were calculated by GAMESS method of quantum chemistry, the kinetics parameters of thermal decomposition of STVD were obtained by thermogravimetry and the prospective lifetime of CDZ at different temperature was speculated by Dakin equation. RESULTS The results indicated that the thermal decomposition of CDZ was a multi-stages process. The kinetic parameters, such as activation energy Ea=173.9 kJ·mol-1, pre-exponential factor A =1.175×1017 min-1 in N2, and Ea =172.3 kJ·mol-1, A =2.692×1017 min-1 in air，were obtained. CONCLUSION The thermal property of CDZ is quite stable in the routine temperature.