CO catalytic synthesis of diethyl carbonate in vapor phase had been studied in a continuous flow system and a fixed-bed reactor at atmospheric pressure. PdCl2-CuCl2/AC (activated carbon) catalyst exhibited better catalytic activity compared with other Wacker-type catalyst systems using SiO2, alpha-Al2O3 and hexagonal mesoporous silica (HMS) as the carriers. The catalytic activity of the catalyst could be effectively improved by chemical pretreatment with H-2. The suitable Pd content was 2.0 wt.% considering both factors of DEC production and DEC selectivity, and an optimum Pd/Cu mole ratio existed for catalytic activity, which was 1/2. The study also revealed that CH3OH was an excellent solvent for PdCl2-CuCl2/AC catalyst preparation. (c) 2006 Elsevier Ltd. All rights reserved.