Preparation and characterization of carbon nanotube-promoted Co–Cu catalyst for higher alcohol synthesis from syngas

A cobalt–copper catalyst promoted by “herringbone-type” multiwalled carbon nanotubes (CNTs) was developed. This catalyst displayed excellent performance for higher alcohol synthesis (HAS) from syngas, with the (C2–8-alc. + DME)-STY reached 760 mg/(g·h) under the reaction conditions of 5.0 MPa and 573 K, which was 1.78 times that of the CNT-free host, Co3Cu1. The addition of a minor amount of the CNTs to the Co3Cu1 host did not cause a marked change in apparent activation energy for the HAS, but led to an increase at the surface of the catalyst of the concentration of catalytically active Co-species, CoO(OH), a kind of surface Co-species related closely to the selective formation of the higher alcohols. Excellent adsorption performance of this kind of CNTs for H2 generated 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. Moreover, synergistic action of the high surface-concentration H-adspecies with CO2 in the feed-gas led to a greater inhibition for the WGS side-reaction. All these factors contribute considerably to an increase in the yield of alcohols.