title: Novel Guanidinium-Based Ionic Liquids for Highly Efficient SO2 Capture.
abstract: The application of ionic liquids (ILs) for acidic gas absorption has long been an interesting and challenging issue. In this work, the ethyl sulfate ([C2OSO3](-)) anion has been introduced into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs, namely 2-ethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([C2(2)(C1)2(C1)2(3)gu][C2OSO3]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3]). The ethyl sulfate ILs, together with 2-ethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([C2(2)(C1)2(C1)2(3)gu][NTf2]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([(C2)2(2)(C1)2(C1)2(3)gu][NTf2]), are employed to evaluate the SO2 absorption and desorption performance. The recyclable ethyl sulfate ILs demonstrate high absorption capacities of SO2. At a low pressure of 0.1 bar and at 20 °C, 0.71 and 1.08 mol SO2 per mole of IL can be captured by [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3], respectively. The absorption enthalpy for SO2 absorption with [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3] are -3.98 and -3.43 kcal mol(-1), respectively. While those by [C2(2)(C1)2(C1)2(3)gu][NTf2] and [(C2)2(2)(C1)2(C1)2(3)gu][NTf2] turn out to be only 0.17 and 0.24 mol SO2 per mole of IL under the same conditions. It can be concluded that the guanidinium ethyl sulfate ILs show good performance for SO2 capture. Quantum chemistry calculations reveal nonbonded weak interactions between the ILs and SO2. The anionic moieties of the ILs play an important role in SO2 capture on the basis of the consistently experimental and computational results.
authors.affiliation: †Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Xiaoxing
authors.initials: X
authors.lastname: Lu
authors.affiliation: †Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.affiliation: †Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Jianzhou
authors.initials: J
authors.lastname: Wu
authors.affiliation: †Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Guo
authors.affiliation: ‡Department of Applied Chemistry, Zhejiang Gongshang University, Hangzhou 310018, PR China.
authors.forename: Hujun
authors.initials: H
authors.lastname: Xie
authors.affiliation: †Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Fang
mesh_terms: D000393:Air Pollutants / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D003198:Computer Simulation; D005740:Gases / Q000737:chemistry; D019791:Guanidine / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011789:Quantum Theory; D013458:Sulfur Dioxide / Q000737:chemistry*; D013463:Sulfuric Acid Esters / Q000737:chemistry; D013696:Temperature
chemical_list: D000393:Air Pollutants; D000838:Anions; D005740:Gases; D052578:Ionic Liquids; D013463:Sulfuric Acid Esters; D013458:Sulfur Dioxide; D019791:Guanidine; C011612:diethyl sulfate