Co-decorated carbon nanotubes as a promoter of Co–Mo–K oxide catalyst for synthesis of higher alcohols from syngas Original Research Article

A metal cobalt-decorated multi-walled carbon nanotube (MWCNT)-promoted Co–Mo–K oxide-based catalyst was developed, with excellent performance for the selective formation of C2–9-alcohols from syngas. Under reaction condition of 5.0 MPa and 593 K, the space–time-yield of C2–9-alcohols reached 628 mg/(g h) over the Co1Mo1K0.05–12%(4.2% Co/MWCNT) catalyst. The addition of a minor amount of the Co-decorated MWCNTs into the Co1Mo1K0.05 host catalyst caused little change in the apparent activation energy for the higher alcohol synthesis (HAS), but led to an increase of surface concentration of the two kinds of catalytically active species, CoO(OH)/Co3O4 and Mo4+, both closely associated with the alcohol generation. Addition of 5% CO2 in the feed gas at properly elevated reaction temperature (593 K) could further enhance the surface concentration of those active Mo and Co species. An excellent adsorption performance of the Co-decorated MWCNTs as promoter for H2 would be conducive to generating a surface micro-environment with a high concentration of H-adspecies on the functioning catalyst, thus increasing the rate of surface hydrogenation reactions in the HAS. In addition, high concentration of H-adspecies on the catalyst would, through synergistic action with the CO2 in the feed gas, greatly inhibit the water–gas-shift side-reaction. All these factors contribute to an increase in the yield of alcohols.