三苯抽提蒸馏过程中溶剂-烃类分子的相互作用

 采用红外光谱、核磁共振、分子模拟等方法，探讨了溶剂-芳烃-非芳烃在三苯(苯、甲苯、二甲苯)抽提蒸馏过程中的分子相互作用，发现溶剂与烃类分子的相互作用能与其宏观选择性存在相关性。结果表明：非芳烃能够打破芳烃分子间的共轭体系，并与芳烃形成较强的色散力；环丁砜与芳烃之间相互作用更强，其诱导效应及空间位阻对共轭π键的破坏更显著。三者共存时，芳环的环面及C=C键振动更加剧烈。通过模拟纯环丁砜、苯、乙基环己烷(ECH)分子对的稳定形态和质心距离，并结合苯-环丁砜-ECH混合体系模型的几何优化，提出了在抽提蒸馏塔釜物料可能的微观形态。由于存在溶剂的“极性包围圈”，非芳烃很难靠近芳烃并与之形成较强的相互作用，进而可通过精馏实现二者的分离。建立了溶剂宏观选择性与溶剂-芳烃、溶剂-非芳烃相互作用能之差的定量关系(αECH-BZ=1.246ΔE-0.375)，据此可为新溶剂初步筛选、复配或分子设计提供参考。

Solvent-Hydrocarbon Molecular Interaction in BTX Extractive Distillation Process

Infrared spectrum, nuclear magnetic resonance and molecular simulation were used to investigate molecular interaction of solvent-aromatics-non-aromatics in benzene-toluene-xylene (BTX) extractive distillation process. In addition, a qualitative relationship between interaction energy of solvent-hydrocarbon molecules and solvent selectivity was also established. Experimental results showed that non-aromatics can disrupt the conjugation system between aromatic molecules and form strong dispersion force with them. Especially, the interaction between sulfolane and aromatic hydrocarbons is very strong, and thus can significantly disrupt conjugated π bonds due to induction and steric hindrance effects. When the three compounds coexist, the vibration of benzene ring and C=C bond is more intensive. Through simulating the stablest conformation of benzene, ethylcyclone (ECH), sulfolane molecule pairs and centroid distance as well as geometric optimization of benzene-sulfolane-ECH system, a possible micro-form of molecules at the bottom of extractive distillation column was proposed. Due to the formation of “polar envelope” by the solvent, it is difficult for non-aromatics to get close to aromatics to form strong interactions with them, and make the separation of the two possible through distillation. Quantitative relationship between solvent selectivity and interaction energy difference of solvent-aromatics and solvent-non-aromatics was established (αECH-BZ=1.246ΔE-0.375). This can provide guidance for new solvent selection and formulation or molecular design.