A novel and easy way to improve the thermal stability of insoluble sulfur by curing process

GRAPHICAL ABSTRACT

ABSTRACT

The influence of the curing atmosphere on the thermal stability of insoluble sulfur has been systematically studied. The effect of oxygen concentration, which was the preferred atmosphere, on the thermal stability of insoluble sulfur was further investigated. In addition, the thermodynamic characteristics of insoluble sulfur in various gaseous atmospheres were conducted by differential scanning calorimetry (DSC), and the thermal degradation activation energy was calculated using the Ozawa method and the Kissinger method. The results showed that in air atmosphere, the thermal stability was higher than in nitrogen and oxygen, but it was a little lower than in mixtures of nitrogen–oxygen atmosphere. In nitrogen–oxygen mixed gas atmosphere, the thermal stability could be improved efficiently at approximately less than 80% oxygen concentration; otherwise, the presence of more than 80% oxygen concentration could lead to the decrease of thermal stability, which indicated that the optimum curing atmosphere for improving thermal stability was obtained to be an atmosphere of oxygen (80%) and nitrogen (20%). The DSC analysis results showed the maximum thermal degradation activation energy was found in the stream of 80% oxygen and 20% nitrogen, which exactly consisted with the curing atmosphere experiment results.

KEYWORDS:

• Insoluble sulfur
• thermal stability
• curing atmosphere
• DSC

Funding

The authors would like to thank the financial support for this study from SINOPEC (No.LQJS1109QT0005).