XPS study of potassium-promoted molybdenum carbides for mixed alcohols synthesis via CO hydrogenation

The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both, beta-Mo(2)C and alpha-MoC(1-x) pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied XPS results revealed that the content of surface Mo and as valence distribution between beta-Mo(2)C and alpha-MoC(1-x), were quite different Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over beta-Mo(2)C Potassium had strong electronic effect on beta-Mo(2)C, which led to a higher Mo(4+) content On the contrary, potassium had little electronic effect on alpha-MoC(1-x), and K-Mo interaction was weak Therefore. Mo(0) and Mo(2+) became the dominant species on the catalyst surface. and the Mo(4+) content showed almost no increase as the pretreatment temperature enhanced In terms of catalytic performance of molybdenum carbides, the increase in Mo(0) most likely explained the increase in hydrocarbon selectivity, yet Mo(4+) might be responsible for the alcohols synthesis