Co–Co2C and Co–Co2C/AC Catalysts for Hydroformylation of 1-Hexene under Low Pressure: Experimental and Theoretical Studies

Unsupported Co–Co2C catalyst and active carbon supported Co–Co2C (Co–Co2C/AC) catalysts were prepared and have been first proven to be highly active for 1-hexene hydroformylation under low pressure (P = 3.0 MPa and T = 453 K). It is found that the catalytic performances over the Co–Co2C and Co–Co2C/AC catalysts were strongly dependent on the ratio of Co2C to Co. Highly catalytic performances were achieved with the XRD intensity ratio of Co2C to Co ranging from 0.7 to 1.2. Co–Co2C/AC catalyst with carburization for 20 h has a highly catalytic stability for 1-hexene hydroformylation with a time stream of 140 h, indicating that no dissolved cobalt carbonyl species were formed and thus led to no cobalt elusion during hydroformylation under reaction conditions. Density functional theory (DFT) calculations have been conducted to understand the nature of the catalytic performance. We found that the interface between Co and Co2C plays a significant role in ethylene hydroformylation. Metallic Co sites are used for olefin adsorption and activation to form surface carbonaceous species, while Co2C sites, for CO molecular adsorption, activation, and insertion. Our results have provided a strategy for designing highly active bifunctional non-noble metal catalysts.