Effects of bitumen component on wax crystallization characteristic by the thermodynamic model

Abstract

To analyze the effect of bitumen component on wax crystallization characteristic, this study obtained the Paraffinic, Naphthenic and Aromatic (PNA) distribution of two samples with high wax contents (AAM-1 and AAC-1) by Gas Chromatography (GC) test, and form the thermodynamic model. The results indicate that the content of crystalline wax with large carbon number is higher than the original distribution of wax in bitumen, as the temperature decreases the main composition of crystalline wax in AAM-1 will change from C20-C38 to C13-C19, and the even smaller components will begin to crystallize at 15 °C. As for AAC-1, the decrease in temperature will only affect the crystalline wax components of C16-C25, which could be due to the paraffinic distribution or aromatic content based on the PNA distribution. To determine the internal factors affecting wax crystallization, bitumen with different component compositions were designed, finding that wax will be easier to crystallize from bitumen with more large carbon number paraffinic. While the crystalline wax content is nearly the same at −20 °C, as the aromatic content increases, the decrease in WPT is close to linear. This suggests that the shape and crystal morphology of the wax crystals may have changed, based on the crystal growth and nucleation theory of wax, thereby inhibiting the crystallization of wax.

Keywords

• Bitumen
• Wax crystallization
• Bitumen component
• Variable Temperature-Fourier Transform Infrared Spectroscopy (VT-FTIR)
• Thermal dynamic model