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Novel SO2 Phase-Change Absorbent: Mixture of N,N‑Dimethylaniline and Liquid Paraffin

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journal contribution
posted on 24.08.2018 by Muyuan Chai, Wenbo Zhao, Genming Li, Shengchao Xu, Qingming Jia, Yuan Chen
In order to avoid the high energy consumption in SO2 capture with aqueous amine absorbents, a liquid–liquid SO2 phase-change absorbent (SPCA) was developed in the present work using N,N-dimethylaniline (DMA) as absorbent, and high-boiling liquid paraffin was used as solvent to adjust the boiling point of the solution. The homogeneous solution would form two immiscible liquid phases after SO2 bubbling, only the SO2-rich phase needed to be desorbed, which could effectively reduce the energy consumption. Different from the liquid–solid phase-change absorbents developed in our previous work, the liquid–liquid phase-change absorbent avoid their shortcomings such as difficulties in separation of absorption products. The absorption product of SPCA was proved to be a charge-transfer complex DMA·SO2 by NMR and FTIR characterization, and the phase-change mechanism was attributed to the polarity variation between DMA and DMA·SO2. The viscosities of SPCAs was lower than 11.65 mPa·s, and the viscosity of SO2-rich phase was 3.9 mPa·s at 30 °C. The mass absorption capacity was found to be 0.89 g SO2/g DMA at 1 atm and 20 °C by ignoring liquid paraffin. The SPCA exhibited extremely high mass selectivity of SO2/CO2 with the value of 351. In addition, it was found that water had no effect on the structure of the absorption product and the SO2 capacity of SPCA. SPCA could be completely regenerated in 50 min at 80 °C. All the results showed that the SPCAs composed of DMA/liquid paraffin have a good application prospect.