Science in China Series B: Chemistry

, Volume 44, Issue 3, pp 283–293 | Cite as

Investigation on the mechanism and applications of the reaction Cl2+2HBr=2HCl+Br2

  • Heming Xiao
  • Zunyao Wang
  • Jijun Xiao
  • Zhaoxu Chen


The mechanism of reaction Cl2+2HBr=2HCl+Br2 has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl2+HBr→HCl+BrCl and BrCl+HBr→HCl+Br2 is smaller than the dissociation energy of Cl2, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br2 from HBr. Gaseous Cl2 directly reacts with HBr gas, which produces gaseous mixtures containing Br2, and liquid Br2 and HCl are obtained by cooling the mixtures and further separated by absorption with CCl4. The recovery percentage of Br2 is more than 96%, and the Cl2 remaining in liquid Br2 is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory.


chlorine bromine hydride bromine density functional theory reaction mechanism recycling process 


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Copyright information

© Science in China Press 2001

Authors and Affiliations

  • Heming Xiao
    • 1
  • Zunyao Wang
    • 1
    • 2
  • Jijun Xiao
    • 1
  • Zhaoxu Chen
    • 1
  1. 1.Department of ChemistryNanjing University of Science and TechnologyNanjingChina
  2. 2.Department of Chemical EngineeringYancheng Institute of TechnologyYanchengChina

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