Highly efficient and reversible absorption of SO₂ by hydroxyl ammonium ionic liquids at low partial pressure

Abstract

BLACKGROUND The control of sulfur dioxide (SO2) emissions is vital for the treatment of flue gases of combustion. The wet flue gas desulfurization process using limestone‐gypsum is now used widely, due to its high efficiency and reliability. However, it has the disadvantages of high cost and production of hazardous by‐products. Ionic liquids are new green organic solvents that can absorb acidic gases selectively. Hydroxyl ammonium ionic liquids with different anions were synthesized by neutralization and used to separate SO2 from simulated flue gas at low partial pressure of SO2. RESULTS The absorption capacities of SO2 using ionic liquids were 1.02 mol/mol, 1.19 mol/mol, and 3.34 mol/mol for [TEOA][AC], [TEOA][LA] and [TEOA][CA], respectively, at the SO2 partial pressure of 4 kPa. Viscosity of ionic liquid affected the absorption process. A longer time was required to attain absorption equilibrium in the case of [TEOA][CA]. Low temperatures favoured absorption because the process was exothermic. Water in flue gas accumulated in the ionic liquids, causing a reduction in absorption of SO2. A mixture containing different ionic liquids could decrease the viscosity and achieve optimal absorption capacities. The ionic liquids could be recycled and regenerated by desorption at high temperature. A reduction of ≈2% in absorption capacities was found after four cycles of regeneration. Analysis of the absorption mechanism indicated that nitrogen atoms in the cationic part of ionic liquid molecules were the predominant site for combined chemical and physical absorption processes. CONCLUSION Hydroxyl ammonium ionic liquids exhibited excellent potential for absorption of SO2 at low partial pressure by combined chemical and physical absorption processes. © 2019 Society of Chemical Industry

Dual‐functionalized protic ionic liquids for efficient absorption of NH3 through synergistically physicochemical interaction

“…In recent years, ionic liquids (ILs) have been demonstrated to be promising media for the recovery of CO 2 , hydrogen sulfide (H 2 S), sulfur dioxide (SO 2 ) and NH 3 owing to their negligible volatility, excellent thermal stability, remarkable solubility and structure designability. Compared to the water scrubbing method, the goals of no waste water discharge, lower energy consumption and high purity NH 3 recovery can be achieved by using ILs.…”

Synthesis of Guanidinium-Based Poly(ionic liquids) with Nonporosity for Highly Efficient SO2 Capture from Flue Gas

“…These results confirm that the fragments of guanidinium ILs and ammonium ILs were formed and existed in these three poly­(ionic liquids). In addition, in the bromide region (Figure b), the binding energies at around 67 and 68 eV were attributed to Br 3d 5/2 and Br 3d 3/2 , respectively. , It is worth noting that the binding energy of Br 3d in P­([allyl-TMG]­Br-DVB) was found to be slightly lower than in the cases of P­([allyl-HMTA]­Br-DVB) and P­([allyl-DABCO]­Br-DVB). The monomer guanidinium IL in P­([allyl-TMG]­Br-DVB) may have an electron-donating effect on the bromide ion, and thereby enhance the electron density of Br – , resulting in the relatively low binding energy of Br 3d in P­([allyl-TMG]­Br-DVB).…”

“…In addition, in the bromide region (Figure 4b), the binding energies at around 67 and 68 eV were attributed to Br 3d 5/2 and Br 3d 3/2 , respectively. 19,22 It is worth noting that the binding energy of Br 3d in P([allyl-TMG]Br-DVB) was found to be slightly lower than in the cases of P( showed a better SO 2 affinity and resulted in a higher SO 2 uptake capacity. Moreover, the effect of adsorption temperature on the performance of P([allyl-TMG]Br-DVB) was also studied (Figure S6, Supporting Information).…”

“…Recently, ionic liquids (ILs) have been popularly considered as novel and efficient solvents for gas absorption because of their excellent ability for selective molecular recognition. , So far, a lot of ILs have been reported and used for efficient capture of SO 2 and CO. − For example, Xing et al prepared a kind of nonporous imidazolium-based poly­(ionic liquid) xerogel, which showed large SO 2 adsorption capacity (7.78 mmol g –1 ) and high selectivity of SO 2 /CO 2 (up to 614) via a swelling mechanism but excluded the adsorption of CO 2 and N 2 . However, such nonporous poly­(ionic liquids) need a complex preparation process involving microfluidic technology and photopolymerization, and the column breakthrough performance is also not satisfied entirely.…”

Theoretical investigation of metal oxides for SO2 capture through first‐principles calculations

“…Ionic liquids for wet FGD have also been utilized to capture the acid gas (e.g., SO 2 ) from flue gas 10 . Qi et al 11 found that hydroxyl ammonium ionic liquids show outstanding SO 2 absorption at low SO 2 partial pressures. Liu et al 12 experimentally suggested that caprolactam‐based eutectic ionic liquids can be promising absorbents for capturing SO 2 at T = 30–70°C and P = 1 atm.…”