氢气还原二氧化硫机理分析

采用DFT方法对氢气还原SO₂过程的微观反应机理进行了研究。计算结果表明:氢气能以氢自由基（路径一）、氢分子（路径二）两种形式参与反应,对SO₂进行还原。氢气以氢自由基形式参与反应时,氢气分子均裂产生氢自由基的过程中需要586.80 KJ/mol的能量,是反应路径一的速控步骤,一旦氢自由基形成,后续反应的能垒低于反应路径二中氢气以分子形式参与反应的能垒;而氢气以氢分子形式参与反应时,各步反应的能垒大致在（40～150）KJ/mol范围内,均可以在较缓和的条件下发生。可以认为,在有可降低氢气解离形成氢自由基难度的催化剂存在时,氢气有可能以氢自由基形式为主参与反应,对SO₂进行还原,而在纯粹热反应条件下,氢气更有可能以氢分子形式还原SO₂。在小型连续管式反应器中,对氢气还原SO₂进行实验研究,实验结果支持模拟得出的结论,即在无催化剂条件下,氢气可以氢分子形式参与还原SO₂的反应。

Mechanism analysis of hydrogen reacting with sulfur dioxide

The mechanism of hydrogen reduction reaction of SCV was studied by DFT method.The calculation results show that the hydrogen participated the reaction in the forms of hydrogen radical（paths 1）,hydrogen molecule（path 2）,responding to SO₂ for reduction.Hydrogen to hydrogen radical forms involved in response,the hydrogen gas molecules are split and generate hydrogen free radical process that needed 586.80 KJ/mol’s energy,is the reaction of speed control steps of path 1,once the hydrogen radical was formed,the energy barrier of subsequent reactions are lower than that of path 2.When the hydrogen participating in the form of molecular hydrogen,it can be in relatively mild conditions occur.And the energy of each step reaction can be roughly in the range of（40～150）KJ/mol.In conclusion,with catalyst which can reduce the difficulties of hydrogen disintegrating to the form of hydrogen radical,hydrogen is possible for hydrogen radical forms mainly involved in response,for reduction of SO₂,and under the condition of flavoring substances in pure hydrogen,more likely to molecular form SO₂ reduction.In the small continuous tubular reactor of hydrogen reduction in SO₂ experiment research,the experimental results support the conclusion of the simulation,that in no catalyst conditions,molecular hydrogen can participate in the form of SO₂ reduction reaction.