Exploring the thermal behavior of phosphorus pentachloride (PCl5): A kinetic analysis using differential scanning calorimetry

Abstract

Phosphorus pentachloride (PCl₅) plays an important role in the chemical industry of pharmaceuticals, agrochemicals, and, more recently, the manufacture of electrolytes for energy storage systems. In this study, its thermokinetic behavior was analyzed for the first time using differential scanning calorimetry (DSC) under a nitrogen atmosphere. Kinetic parameters were determined using complementary methods, such as Friedman isoconversional analysis, Kissinger method, combined kinetic analysis, and nonlinear regression optimization. The findings suggest that PCl₅ sublimates at significantly lower temperatures than previously reported, starting at room temperature with a single endothermic event. The apparent activation energy obtained was 70.65 ± 0.04 kJ/mol, with a pre-exponential factor of $\text{ln}\left(A/s^{-1}\right)$ = 17.65 ± 0.06. The process follows a surface geometric contraction (R2) kinetic model, which well correlated with a sublimation process. This sublimation process was indirectly corroborated by XRD characterization of the recondensed gas. This obtained kinetic model can aid in optimizing PCl₅ storage, transportation, and handling, contributing to safer and more efficient industrial processes.