The oxidative carbonylation of ethanol for diethyl carbonate synthesis offers prospects for a "green chemistry" replacement of phosgene used for polymer production and other processes. Effects of a potassium promoter on the CuCl2-PdCl2-NaOH/AC catalyst for diethyl carbonate synthesis were evaluated. The catalytic activity was improved significantly when KCl was added to the catalyst while other promoters only had little influence on the catalytic performance. Further investigations on the KCl promoter indicated that the conversion of ethanol reaches over 30% while the selectivity is around 95%. The optimal molar ratio of the reactant (CO:O-2:C2H5OH) is around 10:1:4. Analysis by X-ray diffraction and XPS showed that copper chloride hydroxides (Cu(OH)Cl) is formed when KCl is added to the catalyst and is beneficial for the catalytic activity for the oxidative carbonylation of ethanol. The great improvement on the catalytic performance of the catalyst CuCl2-PdCl2-KCl-NaOH/AC is attributed to the efficient electronic transfer between PdCl2 and Cu(OH)Cl. (C) 2004 Elsevier B.V. All rights reserved.