Thermal Stability Determination of Propylene Glycol Sodium Alginate and Ammonium Sulfate with Calorimetry Technology

Propylene Glycol Alginate Sodium Sulfate (PSS) is widely produced and used in medicine as a marine drug for treating hyperlipidemia. During the sulfonation synthesis of PSS, the sulfona-tion of chlorosulfonic acid is exothermic. At high temperatures, the process can easily produce a large amount of ammonium sulfate. Ammonium sulfate adheres to PSS in crystal and participates in the sulfonation reaction. In this study, the sulfonation process of commercial PSS was reproduced in the laboratory using chlorosulfonic acid and formamide. We used differential scanning calorimetry and thermogravimetric analyzer to examine the thermal stability of PSS, and we used both differential and integral conversional methods to determine the appropriate thermokinetic models for this substance. We also established an autocatalytic model to study the conversion limit time and the maximum rate time of this substance. After calculation, the activation energy of this substance is no more than 60 kJ/mol, and it has other exothermic performances at different heating rates. The results help to optimize the sulfonation process of PSS and analyze the thermal risk of PSS with ammonium sulfate.