Ultrasound-assisted preparation of a highly active and selective Co-B amorphous alloy catalyst in uniform spherical nanoparticles

摘要

Uniform spherical Co-B amorphous alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)_6~(2+) with BH_4~- in aqueous solution,and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time.During liquid-phase cinnamalde-hyde (CMA) hydrogenation,the as-prepared Co-B catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH_4~-.The higher activity can be attributed to both the higher dispersion of Co active sites (S_(Co)) and the higher intrinsic activity (R ).The higher selectivity can be attributed to both the uniform Co-B amorphous alloy particles and the strong electronic interaction between Co and B,which enhances the competitive adsorption of C=O group against C=C group in the CMA molecule.Meanwhile,the stronger adsorption for hydrogen on Co active sites was more favorable for C=O hydrogenation in comparison with the C=C hydrogenation.