Molybdenum carbides, beta-Mo2C and alpha-MoC1-x, promoted by K2CO3 were studied as catalysts for CO hydrogenation reactions at T = 573 K, P = 8.0 MPa, GHSV = 2000 h(-1), H-2/CO = 1.0. Unpromoted molybdenum carbides produced mainly light hydrocarbons under these conditions. Addition of K2CO3 as a promoter, however, both beta-Mo2C and alpha-MoC1-x resulted in remarkable selectivity shift from hydrocarbons to alcohols. Moreover, the promoter of potassium enhanced the ability of chain propagation of beta-Mo2C and alpha-MoC1-X, with higher selectivity to C2+OH. Meanwhile, the investigation of the loadings of K2CO3 in beta-Mo2C and alpha-MoC1-x revealed that the maximum of yield of alcohol was obtained at K/Mo (molar ratio) of 0.2 and 0.1, respectively. On K/beta-Mo2C catalysts, the distribution of hydrocarbons obeyed traditional linear A-S-F plot, while alcohols gave a unique linear A-S-F distribution with remarkable deviation of methanol compared with that of on beta-Mo2C catalyst. However, there was no significant difference between alpha-MoC1-x and K/alpha-MoC1-x catalysts about the distributions of alcohols and hydrocarbons; they both have similar linear A-S-F plots. Thus, the potassium promoter played a different role over beta-Mo2C and alpha-MoC1-x catalysts upon the catalytic performance of mixed alcohols synthesis. (c) 2006 Elsevier Ltd. All rights reserved.