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大量实验表明,离子液体基于其良好的物理化学性质,可以在温和的条件下有效地将芳香烃从其与脂肪烃的混合物中分离出来,并表现出较高的选择性和溶质分配系数。本文应用密度泛函理论(DFT)探究1-丁基-3-甲基咪唑四氯化铁([BMIM][[FeCl_4])离子液体与正辛烷/对二甲苯分子间的相互作用,同时以[BMIM]Cl离子液体与溶剂相互作用作为对照。从计算结果可以看出,[BMIM][[FeCl_4]和[BMIM]Cl离子液体均能够有效地分离正辛烷和对二甲苯混合物。离子液体阳离子和阴离子之间存在的多重氢键,对离子对、离子液体-溶剂复合物的稳定性起决定性作用。其中,由于咪唑环上C2位置具有较强的路易斯酸性,因此C2-H···Cl具有最强的氢键作用。由于Cl-被[[FeCl_4]~-取代时,电荷被分散,导致[BMIM][[FeCl_4]~-正辛烷/对二甲苯的相互作用弱于[BMIM]Cl-正辛烷/对二甲苯。
Numerous experiments show that based on their good physicochemical properties, ionic liquids can effectively separate aromatics from their mixtures with aliphatic hydrocarbons under mild conditions and exhibit high selectivity and solute partition coefficient. In this paper, the interaction between 1-butyl-3-methylimidazolium tetrachloride ([BMIM] [[FeCl 4]) and n-octane / p-xylene molecules was investigated by using density functional theory The interaction of [BMIM] Cl ionic liquids with solvents was used as a control. It can be seen from the calculation results that both [BMIM] [[FeCl_4] and [BMIM] Cl ionic liquids can effectively separate n-octane and p-xylene mixtures. The multiple hydrogen bonds existing between the cation and the anion of the ionic liquid play a decisive role in the stability of the ion pair and the ionic liquid-solvent complex. Among them, C2-H ··· Cl has the strongest hydrogen bond due to strong Lewis acidity at the C2 position of the imidazole ring. The charge is dispersed as Cl- is replaced by [[FeCl 4] ~ -, resulting in weaker interaction of [BMIM] [[FeCl 4] ~ -noctane / p-xylene than [BMIM] Cl -n-octane / Toluene.