Solubility of light alkanes and alkenes in ionic liquids

doi:10.11949/0438-1157.20200735

Abstract

Abstract:

The solubility of light hydrocarbons in a variety of ionic liquids was studied, and it was found that ionic liquids containing Cu(Ⅰ) had higher solubility for hydrocarbons and alkene/alkane solubility selectivity, and Et₃NHCl-2.1CuCl ionic liquid was preferred. The effects of temperature and pressure on the solubility of light hydrocarbons were investigated for the selected ionic liquid. It was found that low temperature and high pressure were favorable for the dissolution of light hydrocarbons, and the alkene/alkane solubility selectivity decreased with the increase of temperature and pressure. The alkene/alkane solubility selectivity was above 8.3 at the temperature of 30℃ and the pressure of 0.2 MPa. The initial dissolution rate of hydrocarbons in ionic liquid was large, but it decreased rapidly with prolonging time, and the dissolution rate of alkenes was higher than that of alkanes at the same conditions. The alkene/alkane separation selectivity increased with decreasing content of alkenes in the mixture of alkenes and alkanes. Light hydrocarbons dissolved in ionic liquids could be desorbed by means of increasing temperature, restoring the dissolution capability of ionic liquids to hydrocarbons. Alkanes were easier to be desorbed than alkenes, and small-molecule hydrocarbons were easier to be desorbed than large-molecule hydrocarbons. The desorption percentage exceeded 92% under optimal conditions. Ionic liquid had a good reusable performance in the absorption and separation of light alkanes and alkenes. The solubility only decreased by less than 5% when it was reused five times, and the alkane/alkane solubility selectivity was basically not affected by reusing times. Software Gaussian 09 was used to study the interaction between anions of ionic liquids and light alkanes and alkanes, and the solubility difference of light alkenes and alkanes in different ionic liquids was well explained.

Key words: ionic liquid, alkane, alkene, solubility, absorption, desorption

摘要：

研究了多种离子液体对小分子烃类的溶解性能，发现含有Cu(Ⅰ)的离子液体对烃类具有较高的溶解度和烯烃/烷烃溶解选择性，优选出了Et₃NHCl-2.1CuCl离子液体。考察了温度和压力对小分子烃类溶解性能的影响规律，发现低温和高压有利烃类的溶解，烯烃/烷烃溶解选择性随温度和压力的升高而减小；在30℃和0.2 MPa的条件下，烯烃/烷烃溶解选择性均在8.3以上。烃类在离子液体中的初始溶解速率较大，但随时间的延长快速降低，相同条件下烯烃的溶解速率高于烷烃的溶解速率。烯烃/烷烃分离选择性随混合气中烯烃含量的减小而增大。升温可以解吸出离子液体中的烃类，烷烃比烯烃容易解吸，优化条件下的解吸率可达92%以上。离子液体对小分子烷烃和烯烃的吸收分离具有良好的重复使用性能。利用Gaussian 09软件对离子液体的阴离子与烯烃、烷烃的作用进行了计算分析，解释了烯烃和烷烃在不同离子液体中溶解性能差异的原因。

关键词: 离子液体, 烷烃, 烯烃, 溶解, 吸收, 解吸

CLC Number:

TE 624

Rui ZHANG, Shuyuan DONG, Luo WU, Zhichang LIU, Chunming XU, Haiyan LIU, Xianghai MENG. Solubility of light alkanes and alkenes in ionic liquids[J]. CIESC Journal, 2020, 71(10): 4674-4687.

张睿, 董淑媛, 伍洛, 刘植昌, 徐春明, 刘海燕, 孟祥海. 小分子烷烃与烯烃在离子液体中的溶解性能[J]. 化工学报, 2020, 71(10): 4674-4687.

Figures/Tables 19

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离子液体	乙烯溶解度/ (mol/mol)	乙烷溶解度/ (mol/mol)	乙烯/乙烷选择性
Et₃NHCl-0.6AlCl₃	0.0280	0.0200	1.40
Et₃NHCl-0.6FeCl₂	0.0235	0.0190	1.23
Et₃NHCl-0.6FeCl₃	0.0231	0.0192	1.20
Et₃NHCl-0.6CuCl	0.0396	0.0168	2.36
[BMIM]Cl-0.6AlCl₃	0.0241	0.0186	1.30
[BMIM]Cl-0.6CuCl	0.0291	0.0132	2.21
Et₃NHCl-1.0AlCl₃	0.0284	0.0203	1.40
Et₃NHCl-1.0FeCl₂	0.0290	0.0205	1.42
Et₃NHCl-1.0FeCl₃	0.0281	0.0208	1.35
Et₃NHCl-1.0CuCl	0.0404	0.0165	2.45
[BMIM]Cl-1.0CuCl	0.0300	0.0132	2.28
[BMIM][BF₄]	0.0177	0.0142	1.25

离子液体	乙烯溶解度/ (mol/mol)	乙烷溶解度/ (mol/mol)	乙烯/乙烷选择性
Et₃NHCl-0.6AlCl₃	0.0280	0.0200	1.40
Et₃NHCl-0.6FeCl₂	0.0235	0.0190	1.23
Et₃NHCl-0.6FeCl₃	0.0231	0.0192	1.20
Et₃NHCl-0.6CuCl	0.0396	0.0168	2.36
[BMIM]Cl-0.6AlCl₃	0.0241	0.0186	1.30
[BMIM]Cl-0.6CuCl	0.0291	0.0132	2.21
Et₃NHCl-1.0AlCl₃	0.0284	0.0203	1.40
Et₃NHCl-1.0FeCl₂	0.0290	0.0205	1.42
Et₃NHCl-1.0FeCl₃	0.0281	0.0208	1.35
Et₃NHCl-1.0CuCl	0.0404	0.0165	2.45
[BMIM]Cl-1.0CuCl	0.0300	0.0132	2.28
[BMIM][BF₄]	0.0177	0.0142	1.25

离子液体	乙烯溶解度/ (mol/mol)	乙烷溶解度/ (mol/mol)	乙烯/乙烷选择性
Et₃NHCl-1.0CuCl	0.0050	0.0033	1.52
Me₃NHCl-1.0CuCl	0.0048	0.0031	1.56
Et₂NH₂Cl-1.0CuCl	0.0044	0.0032	1.38
Me₂NH₂Cl-1.0CuCl	0.0034	0.0025	1.36
EtNH₃Cl-1.0CuCl	0.0025	0.0022	1.14

离子液体	乙烯溶解度/ (mol/mol)	乙烷溶解度/ (mol/mol)	乙烯/乙烷选择性
Et₃NHCl-1.0CuCl	0.0050	0.0033	1.52
Me₃NHCl-1.0CuCl	0.0048	0.0031	1.56
Et₂NH₂Cl-1.0CuCl	0.0044	0.0032	1.38
Me₂NH₂Cl-1.0CuCl	0.0034	0.0025	1.36
EtNH₃Cl-1.0CuCl	0.0025	0.0022	1.14

离子液体	乙烯溶解度/ (mol/mol)	乙烷溶解度/ (mol/mol)	乙烯/ 乙烷选择性
Et₃NHCl-1.0CuCl	0.0404	0.0165	2.45
Et₃NHCl-1.3CuCl	0.0465	0.0159	2.92
Et₃NHCl-1.5CuCl	0.0503	0.0154	3.26
Et₃NHCl-1.7CuCl	0.0624	0.0109	5.70
Et₃NHCl-2.0CuCl	0.0866	0.0102	8.47
Et₃NHCl-2.1CuCl	0.0872	0.0099	8.78
Et₃NHCl-2.2CuCl	0.0872	0.0099	8.81
Et₃NHCl-2.4CuCl	0.0873	0.0100	8.71