Structure and SO₂ Absorption Properties of Guanidinium-Based Dicarboxylic Acid Ionic Liquids

Abstract

A new series of functionalized ionic liquids (ILs) with 1,1,3,3-tetramethylguanidine ([TMG]+) cations as well as dicarboxylic acid anions {[−OOC–(CH2–CH2) n –COO–], where n = 1, 3, and 5} was synthesized, and their SO2 absorption properties were investigated. A high SO2 absorption capacity of the prepared ILs was achieved. The molar ratios of SO2 to [TMG]­[succinic acid] {([TMG]­[SUC]) (n = 1)}, [TMG]­[suberic acid] {([TMG]­[SUB]) (n = 3)}, and [TMG]­[dodecanedioic acid] {([TMG]­[DOD]) (n = 5)} were 4.76, 5.96, and 5.96, respectively. The evidence of spectroscopic measurements and quantum chemical calculations confirmed that SO2 could interact with the carboxyl and adjacent methylene groups on the anion as well as the amino group on the cation. The SO2 absorption capacity of these ILs was strongly influenced by their asymmetry and space resistance. The high symmetry and large steric hindrance could reduce the SO2 absorption capacity of ILs.

Specific Heat Capacity of Non-Functional and Functional Ionic Liquids during the Absorption of SO2

“…The syntheses of ILs in this experiment follow methods reported in literature. − For example, [TMG]­[Lac] was prepared by mixing 1,1,3,3-tetramethylguanidine and lactic acid in a 1:1 molar ratio in an ice-water bath, after which the mixture was stirred for 5 h. The water in the synthesized ILs was removed using rotary evaporators, followed by N 2 bubbling at 80 °C for 24 h. The methods for synthesizing 1,1,3,3-tetramethylguanidinium suberate ([TMG]­[SUB]), 1,1,3,3-tetramethylguanidinium dodecanedioate ([TMG]­[DOD]), and [TMG]­[BF 4 ] were the same as those reported in the literature. − Karl-Fischer moisture titration was used to determine the moisture contents of functional ILs. The moisture contents of the synthesized ILs were less than 3%.…”

Protic ionic liquids with low viscosity for efficient and reversible capture of carbon dioxide

“…For example, Alcantara et al (2018) (Reddy et al, 2015;Porwal et al, 2016;Singh et al, 2017). In recent years, TMG-based PILs were applied in acid gases absorption due to low viscosity, simple synthetic routes and excellent absorption performance (Jin et al, 2011;Meng et al, 2018 (Jessop et al, 2012). Recently, a novel method for CO 2 capture by tunable anionfunctionalized PILs based on the single-site interaction between the CO 2 and electronegative nitrogen or oxygen atom was reported, it was shown that CO 2 absorption capacity can be easily tuned by the IL basicity (Wang et al, 2011).…”

Recent Advances in Ionic Liquid-Mediated SO2 Capture

“…[DOD] (Scheme 4), and their corresponding SO 2 solubility is 3.0, 8.74, 5.96, 4.76, and 5.96 mol of SO 2 per mol of ILs at 25 °C, respectively. 44,45 Anions of the ILs, as the main factor, greatly influence the solubility of SO 2 . In these , the increased chain length in the anion enlarges the asymmetry of ILs and decreases the space resistance, avoiding SO 2 crowding in the interstice and causing the hydrogen atom of methylene to interact with SO 2 easily.…”