Department of Chemistry, Iowa State University, Ames, IA, 50011, USA; Ames National Laboratory-U.S. Department of Energy, Ames, IA, 50011, USA.
Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL, 35487, USA.
J Chromatogr A. 2024 Oct 25;1735:465306. doi: 10.1016/j.chroma.2024.465306. Epub 2024 Aug 24.
Copper(I) ions (Cu) are used in olefin separations due to their olefin complexing ability and low cost, but their instability in the presence of water and gases limits their widespread use. Ionic liquids (ILs) have emerged as stabilizers of Cu ions and prevent their degradation, providing high olefin separation efficiency. There is limited understanding into the role that polymeric ionic liquids (PILs), which possess similar structural characteristics to ILs, have on Cu ion-olefin interactions. Moreover, copper ions with diverse oxidation states, including Cu and Cu ions, have been rarely employed for olefin separations. In this study, gas chromatography (GC) is used to investigate the interaction strength of olefins to stationary phases composed of the 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([CMIM][NTf]) IL and the poly(1-hexyl-3-vinylimidazolium [NTf]) (poly([CVIM][NTf])) PIL containing monovalent and divalent copper salts (i.e., [Cu][NTf] and [Cu]2[NTf]). The chromatographic retention of alkenes, alkynes, dienes, and aromatic compounds was examined. Incorporation of the [Cu]2[NTf] salt into a stationary phase comprised of poly(dimethylsiloxane) resulted in strong retention of olefins, while its addition to the [CMIM][NTf] IL and poly([CVIM][NTf]) PIL allowed for the interaction strength to be modulated. Olefins exhibited greater affinities toward IL and PIL stationary phases containing the [Cu]2[NTf] salt compared to those with the [Cu][NTf] salt. Elimination of water from both copper salts was observed to be an important factor in promoting olefin interactions, as evidenced by increased olefin retention upon exposure of the stationary phases to high temperatures. To evaluate the long-term thermal stability of the stationary phase, chromatographic retention of probes was measured on the [Cu]2[NTf]/[CMIM][NTf] IL stationary phase after its exposure to helium at a temperature of 110 °C.
铜（I）离子（Cu）由于其烯烃配位能力和低成本而用于烯烃分离，但由于其在水和气体存在下的不稳定性，限制了其广泛应用。离子液体（ILs）已成为稳定铜离子的稳定剂，并防止其降解，提供高烯烃分离效率。对于具有与 ILs 相似结构特征的聚合离子液体（PILs）在铜离子-烯烃相互作用中的作用，人们的理解有限。此外，具有不同氧化态的铜离子，包括 Cu 和 Cu 离子，很少用于烯烃分离。在这项研究中，气相色谱（GC）用于研究由 1-己基-3-甲基咪唑双[(三氟甲基)磺酰基]亚胺([CMIM][NTf])IL 和含有单价和二价铜盐（即[Cu][NTf]和[Cu]2[NTf]）的聚(1-己基-3-乙烯基咪唑[NTf])（poly([CVIM][NTf]）PIL 组成的固定相与烯烃的相互作用强度。研究了烯烃、炔烃、二烯烃和芳烃的色谱保留。将[Cu]2[NTf]盐掺入由聚二甲基硅氧烷组成的固定相中导致烯烃的强保留，而将其添加到[CMIM][NTf]IL 和 poly([CVIM][NTf])PIL 中允许调节相互作用强度。与含有[Cu][NTf]盐的 IL 和 PIL 固定相相比，烯烃对含有[Cu]2[NTf]盐的 IL 和 PIL 固定相表现出更大的亲和力。从两种铜盐中去除水被观察到是促进烯烃相互作用的一个重要因素，这可以通过在固定相暴露于高温时增加烯烃保留来证明。为了评估固定相的长期热稳定性，在 110°C 的温度下用氦气暴露后，测量了探针在[Cu]2[NTf]/[CMIM][NTf]IL 固定相上的色谱保留。
