Lignin-Based Fabrication of Co@C Core-Shell Nanoparticles as Efficient Catalyst for Selective Fischer-Tropsch Synthesis of C_(5+) Compounds

摘要

Novel Co@C core-shell nanoparticles were prepared by a straightforward low-temperature carbonization process. The industrially available lignin was used as a low-cost biorenewable carbon source for the first time. The products were characterized by X-ray diffraction, energy-dispersive X-ray spectrometry, transmission electron microscopy, nitrogen adsorption-desorption, and Raman spectrum. The results showed that the synthesized Co@C catalysts had a well-defined core-shell structure with a moderate degree of graphitization, and the metal Co nanoparticles with the sizes of 20-150 nm were wrapped by several layers of graphitic carbon. This unique core-shell structure is useful in a Fischer-Tropsch reaction since it can provide high adsorption space and the graphite carbon layer defects are beneficial for H2 dissociative adsorption. Furthermore, the shell of graphitic carbon layers could restrict the aggregation of the cobalt nanoparticles during the activation and reaction processes. Fischer-Tropsch synthesis results showed that the Co@C core-shell catalysts had a high catalytic performance with the highest C_(5+) selectivity up to 56.8%, which is much higher compared with the traditional Co/AC catalyst (46.2%).