Hydrolysis of Sulfur Dioxide in Small Clusters of Sulfuric Acid: Mechanistic and Kinetic Study

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• 作者：Jingjing Liu ; Sheng Fang ; Zhixiu Wang ; Wencai Yi ; Fu-Ming Tao ; Jing-yao Liu
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：November 17, 2015
• 年：2015
• 卷：49
• 期：22
• 页码：13112-13120
• 全文大小：603K
• ISSN：1520-5851

文摘

The deposition and hydrolysis reaction of SO₂ + H₂O in small clusters of sulfuric acid and water are studied by theoretical calculations of the molecular clusters SO₂鈥?H₂SO₄)_n鈥?H₂O)_m (m = 1,2; n = 1,2). Sulfuric acid exhibits a dramatic catalytic effect on the hydrolysis reaction of SO₂ as it lowers the energy barrier by over 20 kcal/mol. The reaction with monohydrated sulfuric acid (SO₂ + H₂O + H₂SO₄ 鈥?H₂O) has the lowest energy barrier of 3.83 kcal/mol, in which the cluster H₂SO₄鈥?H₂O)₂ forms initially at the entrance channel. The energy barriers for the three hydrolysis reactions are in the order SO₂ + (H₂SO₄)鈥揌₂O > SO₂ + (H₂SO₄)₂鈥揌₂O > SO₂ + H₂SO₄鈥揌₂O. Furthermore, sulfurous acid is more strongly bonded to the hydrated sulfuric acid (or dimer) clusters than the corresponding reactant (monohydrated SO₂). Consequently, sulfuric acid promotes the hydrolysis of SO₂ both kinetically and thermodynamically. Kinetics simulations have been performed to study the importance of these reactions in the reduction of atmospheric SO₂. The results will give a new insight on how the pre-existing aerosols catalyze the hydrolysis of SO₂, leading to the formation and growth of new particles.