Potassium promotion effects in carbon nanotube supported molybdenum sulfide catalysts for carbon monoxide hydrogenation

•MoO2 and mixed K-Mo oxides present in the calcined catalysts.•Sulfidation of oxide phases leads to MoS2 and K-Mo sulfides.•Difficult sulfidation of MoO2 species.•Olefins, paraffins, alcohols and higher hydrocarbons produced on mixed K-Mo sulfides.•Moderate basicity essential for olefin and alcohol synthesis.

The paper focuses on the effect of potassium promotion on the structure and catalytic performance of carbon nanotube supported molybdenum sulfide catalysts for carbon monoxide hydrogenation. A combination of characterization techniques showed the presence of MoO2 and mixed K-Mo oxides in the calcined catalysts. The sulfidation of oxide phases leads to MoS2 and K-Mo sulfides. MoO2 showed somewhat lower extent of sulfidation compared to other molybdenum oxide species. MoS2 was principally responsible for CH4 production, while lighter olefins, paraffins, alcohols and higher hydrocarbons were produced on the mixed K-Mo sulfides. The catalyst basicity seems to be one of the important factors controlling the reaction selectivity; moderate basicity is essential for higher rates of olefin and alcohol synthesis.

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