Abstract
The thermal decomposition mechanism and process of MgCl2·6H2O·1,4-C4H8O2 were studied using thermogravimetric–mass spectrometry analysis for non-isothermal decomposition, and mechanical convection drying for isothermal decomposition. The pyrolysis products were analysed using chemical analysis, GC measurement, and X-ray powder diffraction. The results showed that there were four stages in the non-isothermal decomposition of MgCl2·6H2O·1,4-C4H8O2 from 25°C to 250°C. The first stage should be the decomposition of 1,4-C4H8O2 in the MgCl2·6H2O·1,4-C4H8O2 adduct, the second and third stages turned out to be the elimination of crystal water, while the fourth stage included the elimination of water and HCl. The kinetic analysis of the thermal decomposition process was performed using the Coats–Redfern method and the Malek method. Results showed that the first two stages obeyed the 2-dimensional phase boundary mechanism (model R2) and the 3-dimensional phase boundary mechanism (model R3), respectively, while the last two ones followed the nucleation and nuclei growth (A1) kinetics. The isothermal decomposition process for 48h from 60°C up to 140°C could be divided into three groups: Below 60°C, there was no decomposition of MgCl2·6H2O·1,4-C4H8O2; for the temperature range from 70°C up to 100°C, the main decomposition product was MgCl2·4H2O; while for the temperature range of 110°C to 140°C, the main products were a mixture of MgCl2·4H2O and MgCl2·2H2O. The temperature of 100°C was chosen for further industrial MgCl2·6H2O·1,4-C4H8O2 decomposition study due to low energy consumption and tiny amount of by-products. This study provides a valuable theoretical basis for industrializing the MgCl2·6H2O·1,4-C4H8O2 decomposition process.
Published Version
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