铝铜双金属离子液体在1-己烯/正己烷分离中的应用

doi:10.11949/0438-1157.20241074

摘要/Abstract

摘要：

石脑油中烯烃/烷烃的分离是石油化工过程原料优化和产品精制的需求，液液萃取是烯烃/烷烃分离的重要途径。以1-己烯/正己烷为模型化合物，探讨了铝铜双金属离子液体选择性萃取烯烃的可行性。结果表明，铝铜双金属离子液体对1-己烯/正己烷具有较好的分离性能，在剂油质量比为2、萃取温度10℃的条件下，1-己烯萃取选择性为6.33，优于常规咪唑型离子液体和传统有机溶剂。此外，铝铜双金属离子液体具有良好的重复使用性能。通过同步辐射X射线吸收精细结构光谱（XAFS）和密度泛函理论（DFT）揭示了双金属离子液体阴离子结构。利用量子化学计算手段对离子液体与1-己烯、正己烷相互作用进行计算分析，解释了双金属离子液体选择性分离1-己烯的原理。

关键词: 萃取, 离子液体, 1-己烯, 正己烷, 分离

Abstract:

The separation of olefin/alkane in naphtha is the requirement of feedstock optimization and product purification in petrochemical processes, and liquid-liquid extraction is an important olefin/alkane separation method. This study investigated the feasibility of bimetallic ionic liquids for highly selective extraction of olefins using 1-hexene/n-hexane as a model hydrocarbon mixture. The results showed that the aluminum-copper bimetallic ionic liquid had good separation performance for 1-hexene/n-hexane. Under the conditions of a solvent-oil mass ratio of 2 and an extraction temperature of 10℃, the 1-hexene extraction selectivity is 6.33, which is better than conventional imidazole-type ionic liquids and traditional organic solvents. The aluminum-copper bimetallic ionic liquid had good reusability. The anionic structure of the bimetallic ionic liquid was revealed by synchrotron X-ray absorption fine structure spectroscopy (XAFS) and density functional theory (DFT). The interaction of the ionic liquid with 1-hexene and n-hexane was further analyzed by using quantum chemistry software to explain the selective separation of 1-hexene by the bimetallic ionic liquid.

Key words: extraction, ionic liquids, 1-hexene, n-hexane, separation

中图分类号:

TQ 028

崔家馨, 殷梦凡, 郑涛, 刘晗, 张睿, 刘植昌, 刘海燕, 徐春明, 孟祥海. 铝铜双金属离子液体在1-己烯/正己烷分离中的应用[J]. 化工学报, 2025, 76(2): 686-694.

Jiaxin CUI, Mengfan YIN, Tao ZHENG, Han LIU, Rui ZHANG, Zhichang LIU, Haiyan LIU, Chunming XU, Xianghai MENG. Application of aluminum-copper bimetallic ionic liquids in 1-hexene/n-hexane separation[J]. CIESC Journal, 2025, 76(2): 686-694.

图/表 14

表1 萃取剂的烯烃分离性能

Table 1 Olefin separation performance of extractants

萃取剂	S	D	PI
N-甲酰基吗啉	2.12	0.046	0.10
N-甲基吡咯烷酮	1.31	0.301	0.39
乙二醇	2.25	0.028	0.06
[Bmim]Cl-1.0FeCl₃	2.40	0.041	0.10
[Bmim]Cl-1.0AlCl₃	2.39	0.036	0.09
[Bmim]Cl-1.0CuCl [Bmim]Cl-1.5CuCl [Bmim]Cl-2.0CuCl	2.96 4.39 6.41	0.034 0.034 0.039	0.10 0.15 0.25
[Bmim]NTf₂	1.82	0.142	0.26
[Bmim]BF₄	2.45	0.032	0.08
[Bmim]PF₆	2.53	0.042	0.11
[Bmim]Cl-1.0AlCl₃+[Bmim]Cl-2.0CuCl	3.24	0.040	0.13
[Bmim]Cl-0.6AlCl₃-1.0CuCl	6.33	0.073	0.46

图1 金属型离子液体红外光谱图

Fig.1 Infrared spectrum of metal-type ionic liquid

图2 铝铜双金属离子液体的XAFS分析

Fig.2 XAFS analysis of aluminum-copper bimetallic ionic liquid

表2 Cu K-edge XAFS的曲线拟合参数

Table 2 Curve-fit parameters for Cu K-edge XAFS

Path	N	R/Å	σ²/Å²
Cu—Cl	2.00	2.21	0.013
Cu—Al	1.45	2.93	0.024

图3 [AlCuCl5]-的可能生成路径

Fig.3 Possible formation pathways of [AlCuCl5]-

图4 配位金属含量对分离选择性和萃取性能指数的影响

Fig.4 Effect of the content of coordination metals on the separation selectivity and extraction performance index

图5 温度对1-己烯和正己烷的分离选择性和萃取性能指数的影响

Fig.5 Influence of temperature on the separation selectivity and extraction performance index of the extraction

图6 剂油质量比对分离选择性和萃取性能指数的影响

Fig.6 Influence of the mass ratio of solvent to feed on the separation selectivity and extraction performance index of the extraction

图7 双金属离子液体对不同原料配比的1-己烯/正己烷的分离效果

Fig.7 Separation effect of 1-hexene/n-hexane in bimetallic ionic liquids with different raw material ratios

图8 双金属离子液体重复使用能

Fig.8 Bimetallic ionic liquid reusability

图9 新鲜离子液体和回收5次后离子液体的红外光谱图

Fig.9 FTIR spectra of fresh bimetallic ionic liquid and the bimetallic ionic liquid after recycling 5 times

表3 离子液体与1-己烯/正己烷之间的结合能比较

Table 3 Comparison of binding energies of ionic liquids with 1-hexene and n-hexane

离子液体+1-己烯/正己烷	ΔE/(kJ/mol)
[Bmim][CuCl₂]+1-己烯	-89.79
[Bmim][CuAlCl₅]+1-己烯	-138.08
[Bmim][CuCl₂]+正己烷	-24.89
[Bmim][CuAlCl₅]+正己烷	-19.99

图10 [Bmim][AlCuCl5]、[Bmim][AlCuCl5]-1-己烯及[Bmim][AlCuCl5]-正己烷的AIM分析（球体代表原子；N：蓝色；H：白色；C：青色；Cl：绿色；Cu：橙色；Al：粉色）

Fig.10 The AIM analysis for [Bmim][AlCuCl5], [Bmim][AlCuCl5]-1-hexene and [Bmim][AlCuCl5]-n-hexane (spheres represent the atoms; N: blue; H: white; C: cyan; Cl: green; Cu: orange; Al: pink)

表4 BCPs拓扑性质

Table 4 Topological properties of BCPs

体系	BCP	原子标签	ρ(BCP)	∇²ρ(BCP)
[Bmim][AlCuCl₅]	1	C—H…Cl	0.0046	0.0159	0.0009
	2	C—H…Cl	0.0072	0.0241	0.0012
	3	C—H…Cl	0.0077	0.0257	0.0013
	4	C—H…Cl	0.0045	0.0135	0.0007
	5	C—H…Cl	0.0041	0.0142	0.0008
	6	C—H…Cl	0.0174	0.0532	0.0019
	7	C…Cl	0.0082	0.0279	0.0013
	8	C—H…Cl	0.0131	0.0397	0.0017
[Bmim][AlCuCl₅]-1-己烯	9	Cu…Cl	0.0783	0.2614	0.0238
	10	C—H…Cl	0.0110	0.0328	0.0015
	11	C—H…Cl	0.0217	0.0631	0.0015
	12	C…Cl	0.0065	0.0239	0.0013
	13	C…Cl	0.0036	0.0122	0.0008
	14	C…Cl	0.0050	0.0168	0.0009
	15	C—H…Cl	0.0068	0.0209	0.0010
	16	C—H…Cl	0.0068	0.0232	0.0012
	17	C—H…Cl	0.0077	0.0259	0.0013
	18	Cu…C	0.0831	0.2393	-0.0257
	19	Cu…Cl	0.0463	0.1723	-0.0061
	20	Cu…Cl	0.0155	0.0433	-0.0001
	21	C—H…Cl	0.0075	0.0268	0.0014
	22	C—H…Cl	0.0047	0.0152	0.0008
	23	C—H…Cl	0.0027	0.0097	0.0006
[Bmim][AlCuCl₅]-正己烷	24	C—H…Cl	0.0052	0.0156	0.0008
	25	C—H…Cl	0.0064	0.0190	0.0009
	26	Cu…H	0.0134	0.0337	-0.0004
	27	Cu…Cl	0.0145	0.0354	-0.0003
	28	C—H…Cl	0.0034	0.0110	0.0006
	29	C—H…Cl	0.0176	0.0538	0.0019
	30	C—H…Cl	0.0124	0.0376	0.0016
	31	C—H…Cl	0.0049	0.0168	0.0010
	32	C—H…Cl	0.0076	0.0257	0.0013
	33	C—H…Cl	0.0041	0.0148	0.0009
	34	C—N…Cl	0.0077	0.0269	0.0013
	35	C—H…Cl	0.0038	0.0116	0.0006
	36	C—H…Cl	0.0041	0.0143	0.0009

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