The Cu-based methanol synthesis catalyst was modified with Mn to improve its activity and stability for dimethyl ether (DME) synthesis from syngas in slurry phase. Mn was added by impregnating co-precipitated CuZnAl catalyst with aqueous solution of manganese nitrate (Mn/CuZnAl) or co-precipitation of the nitrates of Cu, Zn, Al and Mn (CuZnAlMn). The catalyst characterizations by H-2-TPD and XRD showed that CuO in CuZnAlMn catalyst was easily reduced, and Cu particles were well dispersed. XRD results indicated that the eutectic CuZn existed only over CuZnAlMn catalyst, and the promoter MnO did not appear over both of Mn/CuZnAl and CuZnAlMn catalysts. In DME synthesis reaction, it was found that Mn-modified CuZnAl catalyst have high activity and good stability. The proper content of Al and Zn can enhance the DME yield., (c) 2005 Elsevier B.V. All rights reserved.