Research on azeotropic breaking extraction technology for High-Value chemicals from wash oil

In response to the challenge of achieving high-purity separation within a mixture containing acenaphthene, dibenzofuran, fluorene, and biphenyl in coal tar wash oil fractions, the azeotropic behavior of this mixture was investigated through phase equilibrium experiments to elucidate the azeotropic system. Once the azeotropic system was identified, attention shifted to intermolecular forces, and simulation calculations utilizing the Lennard-Jones potential energy function were employed to reveal the mechanism underlying high-purity separation in the azeotropic system. Building upon this foundation, the feasibility of solvent crystallization was explored as a means to break the azeotrope and achieve high-purity separation. This involved a thorough analysis of the intermolecular interactions between the crystallization solvent and the mixture system. Ethanol, methanol, and pentanol were chosen as potential solvents for conducting solvent crystallization experiments. Results demonstrate that ethanol performs admirably within the solvent crystallization method, exhibiting a high degree of crystallization selectivity for acenaphthene. On the other hand, pentanol demonstrates advantages in the separation and crystallization for removing biphenyl. Using ethanol as the solvent for crystallization, the acenaphthene content can be refined to 99.17%, while the biphenyl content can be reduced to a mere 0.002%. These findings underscore the effectiveness of ethanol as a solvent in effectively addressing the azeotropic challenge arising from the coexistence of biphenyl and acenaphthene, ultimately achieving an efficient separation of the targeted substances. Considering both crystallization selectivity and yield, ethanol emerges as the most suitable crystallization solvent for this intricate multi-component system. This study presents a practical solution for the efficient separation of acenaphthene, dibenzofuran, fluorene, and biphenyl—all of which constitute azeotropic systems within the heavy distillate fraction of wash oil.