Research on the Effect of the Solvent Structure and Group on Separation of 1‑Hexene, Benzene, and Thiophene

Recent studies have investigated the separation of olefins from fluid catalytic cracking naphtha by solvent treatment to produce motor gasoline. This study explored the effect of the structure and group of six solvents on the separation of the 1-hexene–benzene and 1-hexene–thiophene systems. Solvents with a chain structure, such as N-methyl diethanolamine (MDEA) and tetraethylene glycol, showed satisfactory separation performance for olefins but poor performance for benzene and thiophene. This result can be ascribed to the weak polarity of the chain structure for the low solubility of benzene and thiophene. By contrast, solvents with a ring structure separated 1-hexene by enhancing the solubility of the mixture for the solvent, especially the dissolution of benzene and thiophene. The selective dissolution of benzene and thiophene by the solvent containing a ring structure was generally greater than that by the solvent containing a chain structure. At the highest 1-hexene content, the solubility of N-methyl diethanolamine for benzene and thiophene was higher than 11, whereas that of MDEA with the chain structure was only 7. The highly electronegative sulfoxide group improved the selectivity for olefins. The selectivity θ of 1-hexene by sulfolane and dimethyl sulfoxide in separating 1-hexene from benzene or thiophene was about 2–14 times that of alcohol amine solvents. Therefore, the ring structure primarily enhanced the processing capacity of the solvents in the separation of the olefins–aromatics/sulfide system, whereas the sulfoxide group improved the selectivity of the solvents in the separation of olefins.