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Highly efficient and reversible absorption of SO 2 by hydroxyl ammonium ionic liquids at low partial pressure
Author(s) -
Qi Yanfei,
Hu Xiude,
Liu Yongzhuo,
Sun Deshuai,
Li Runhao,
Zhu Hongtang
Publication year - 2019
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.6143
Subject(s) - ionic liquid , chemistry , absorption (acoustics) , flue gas , flue gas desulfurization , inorganic chemistry , partial pressure , ionic bonding , organic chemistry , ion , materials science , catalysis , oxygen , composite material
BLACKGROUND The control of sulfur dioxide (SO 2 ) 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 SO 2 from simulated flue gas at low partial pressure of SO 2 . RESULTS The absorption capacities of SO 2 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 SO 2 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 SO 2 . 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 SO 2 at low partial pressure by combined chemical and physical absorption processes. © 2019 Society of Chemical Industry