In this work, we checked the influences of the silica-supported copper (II) chloride substance composition on the oxychlorination of CO to phosgene. The effects of the content of copper (II) chloride, the ratio of copper to potassium, the different kinds of promoters, like sodium chloride, potassium chloride and caesium chloride, and the surface area of silica gel were systematically investigated. The lower surface area of the support can contribute to the formation of phosgene while the higher surface area of the support can lead to a rather low yield of phosgene. The reaction activity of silica-supported copper (II) chloride substance increases with the content of copper chloride (within 30 wt.%). However, in order to avoid the agglomeration of the substance, the content of copper chloride should be less than 30 wt.%. The optimized molar ratio of CuCl2 to KCl is 5:1. Of all three promoters, NaCl, KCl and CsCl, CsCl or KCl can function better than NaCl due to the stronger Lewis basicity. The molten phase can remarkably improve the contact of CuCl2 and CO. On the whole, the lower-surface-area support, the higher content of CuCl2 and the promoter CsCl or KCl are prefered in the oxychlorination of CO. (C) 2009 Elsevier B.V. All rights reserved.