关键词:

热分解, 非等温动力学, 六氨氯化镁, 热重分析

Abstract:

Thermal decomposition and non-isothermal kinetic evaluation of magnesium chloride hexammoniate (MgCl₂·6NH₃) were studied with thermogravimetric analysis (TGA).The decomposition mechanism of MgCl₂·6NH₃ was investigated at five heating rates of 4, 7, 10, 13 and 16 K·min^-1 with an air flow of 50 ml·min^-1.The results showed that the thermal decomposition of MgCl₂·6NH₃ was divided into three stages.A globally optimized iterative iso-conversion method was proposed to calculate the activation energy of thermal decomposition.The calculated activation energies of MgCl₂·6NH₃ at each thermal decomposition stage were 51.38, 64.70 and 73.55 kJ·mol^-1 respectively.The most probable decomposition mechanism functions and pre-exponential factors corresponding to each stage of thermal decomposition of MgCl₂·6NH₃ were derived.The thermal decomposition of MgCl₂·6NH₃ at the first stage belonged to the phase boundary reaction (n=1/4), and the corresponding pre-exponential factor (A) was 3.281×10⁵ s^-1 .The thermal decomposition mechanism of MgCl₂·6NH₃ at the second stage belonged to the nucleation and growth mechanism (n=1.8), and A was 5.624×10⁶ s^-1.The thermal decomposition mechanism of MgCl₂·6NH₃ at the third stage belonged to the chemical reaction mechanism (n=1.5), and A was 5.862×10⁵ s^-1.

Key words:

热分解, 非等温动力学, 六氨氯化镁, 热重分析