Separation of Aromatic Hydrocarbons from Straight-Run Naphtha by Bimetallic Halides

The separation of aromatic hydrocarbons from straight-run naphtha is crucial for the optimal utilization of naphtha resources in the petrochemical industry. Bimetallic halides exhibit excellent performance in aromatic separation from straight-run naphtha. Therefore, it is highly significant to investigate the complexation mechanism and aromatic separation mechanism for bimetallic halide selection and further separation performance enhancement. In this study, CuAlCl4 and Sn(AlCl4)2 were used in the separation of aromatics from naphtha and exhibited excellent performance. The complexation mechanism of bimetallic halide-aromatic complexes was elucidated by XAFS, FT-IR, and density functional theory. The results unveiled that bimetallic halides could coordinate with only one aromatic ring. The geometric structures, bonding characteristics, and weak interaction between bimetallic halides and hydrocarbons were analyzed by a series of wavefunction analysis methods. The results indicated that there was π complexation between bimetallic halides and aromatics, in which s and d orbitals of Cu(I) ion and s and p orbitals of Sn(II) ion played an important role. Meanwhile, there was weak hydrogen bonding interaction between bimetallic halides and aliphatic hydrocarbons. The directional complexation between bimetallic halides and aromatics was the essential reason for aromatic separation.