Because chlorine residues, which originate from HAuCl4, enhance the aggregation of gold particles during the preparation processes of gold-supported catalysts, chlorine removal via hydrogen is used to prepare highly dispersed Au catalysts by the impregnation method. However, details of this phenomenon have yet to be investigated. Herein DFT calculations are performed for HCl elimination reactions from HAunCl model clusters (n = 1-6). The calculation results reveal that the activation energies of these model reactions have odd-even oscillations and increase as the Au cluster size increases. (C) 2013 Elsevier B.V. All rights reserved.