Conventional removal of SO₂ yields a large amount of waste salts or requires significant energy for regeneration of the absorbent. Phase-change capture has been considered a possible method to solve these problems since only the absorption product needs to be disposed for recovery and the solvent could be reused directly. In the present work, the phase-change absorption behavior of 1,3,5-trimethylpyrazole, 2-methylimidazole, 1-methylimidazole, and 1,2-dimethylimidazole has been investigated in organic solvent. Among these absorbents, only 1,2-dimethylimidazole exhibited an obvious phase-change performance in solvents three glycol dimethyl ether, propylene carbonate, and dimethylacetamide but not in butanol. The composition and structure of the absorption product were not related to the type of solvent but affected by the air. 1,2-Dimethylimidazole reacted with SO₂ to form a charge-transfer complex, which converted to pyrosulfite (C₅H₉N₂)₂S₂O₅ in the presence of water. The absorption product was further oxidized to dithionate (C₅H₉N₂)₂S₂O₆ by oxygen from the air. Once the filtrate, which was created from the separation process of the phase-change product and solvent, was exposed to air for several days, another type of oxidative product (C₅H₉N₂)₂SO₄ was discovered.

中文翻译：

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在水和氧气存在下咪唑在有机溶剂中对SO ₂的相变吸收和吸收产物的转化

常规去除SO ₂产生大量的废盐或需要大量的能量来再生吸收剂。相变捕获已被认为是解决这些问题的一种可能方法，因为仅需要处置吸收产物进行回收，并且溶剂可以直接重复使用。在目前的工作中，已经研究了在有机溶剂中1,3,5-三甲基吡唑，2-甲基咪唑，1-甲基咪唑和1,2-二甲基咪唑的相变吸收行为。在这些吸收剂中，只有1,2-二甲基咪唑在溶剂三乙二醇二甲醚，碳酸亚丙酯和二甲基乙酰胺中表现出明显的相变性能，而在丁醇中则没有。吸收产物的组成和结构与溶剂的类型无关，但受空气影响。1,2-二甲基咪唑与SO反应₂形成电荷转移络合物，在水存在下将其转化为焦亚硫酸盐（C ₅ H ₉ N ₂）₂ S ₂ O ₅。吸收产物被来自空气中的氧气进一步氧化成二硫氰酸盐（C ₅ H ₉ N ₂）₂ S ₂ O ₆。一旦将由相变产物和溶剂的分离过程产生的滤液暴露于空气中数天，便会产生另一种氧化产物（C ₅ H ₉ N ₂）₂ SO _4。 被发现。