Performances of mixed alcohols synthesis over potassium promoted molybdenum carbides

Molybdenum carbides, β-Mo2C and α-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, H2/CO = 1.0. Unpromoted molybdenum carbides produced mainly light hydrocarbons under these conditions. Addition of K2CO3 as a promoter, however, both β-Mo2C and α-MoC1−X resulted in remarkable selectivity shift from hydrocarbons to alcohols. Moreover, the promoter of potassium enhanced the ability of chain propagation of β-Mo2C and α-MoC1−X with higher selectivity to C2+OH. Meanwhile, the investigation of the loadings of K2CO3 in β-Mo2C and α-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/β-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 β-Mo2C catalyst. However, there was no significant difference between α-MoC1−X and K/α-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 β-Mo2C and α-MoC1−X catalysts upon the catalytic performance of mixed alcohols synthesis.