Incorporation of Highly Dispersed Cobalt Nanoparticles into the Ordered Mesoporous Carbon for CO Hydrogenation

Highly dispersed cobalt nanoparticles were incorporated into the ordered mesoporous carbon (OMC) via the ultrasonically assisted vacuum-pressure impregnation (UAVI) for CO hydrogenation. The as-synthesized samples were subjected to the characterization of N-2 physisorption, HAADF-STEM, XRD, XPS, magnetic measurement, H-2 chemisorption and Co-59 zero field spin-echo NMR. It is found that the cobalt particles are exclusively distributed into the channels of OMC and the rigid frameworks significantly bridle the growth of active species to obtain ultrafine cobalt particles with size less than 4 nm. The highly dispersed cobalt nanoparticles perform superior catalytic performances during the CO hydrogenation as compared to the catalyst prepared by the conventional impregnation. The observed stability of novel catalysts outperforms the conventional one during the 96 h evaluation on stream due to the confinement effect to the sintering and conglomeration of active species. On the other hand, a typical structural sensitivity is also observed for the highly dispersed catalysts and the coordinative-unsaturated disordered stacking of cobalt atoms renders higher efficiency to improve CO turnover frequency. Besides, a high selectivity to mixed alcohols is also obtained for the highly dispersed catalysts and the yields of methane and methanol decrease gradually with increasing the particle size. Unfortunately, the highly dispersed particles also display a relatively high selectivity to CO2.