Abstract:

Highly dispersed Co catalysts supported on SiO₂ were prepared in the presence of ethylene glycol(EG)by co-impregnation and tested in the vapor-phase hydrogenolysis of ethyl lactate to 1,2-propanediol.Thesynthesis parameters of Co metal loading,ratio of EG to cobalt nitrate,type of alcohol and calcinationtemperature,which influenced the physical properties of the Co₃O₄ nanoparticles,were investigated throughthe use of X-ray diffraction(XRD).It revealed that the ratio of EG to cobalt nitrate and the type of alcoholsignificantly affected the particle size of Co₃O₄ supported on SiO₂.During co-impregnation with EG,the interactionbetween Co²⁺ and the SiO₂ support was strongly enhanced,resulting in the high dispersion of cobalt speciesand the decrease of Co₃O₄ particle size from 16 nm to below 5 nm;the significantly enhanced cobalt dispersionwas associated with the formation of amorphous cobalt silicate.Meanwhile the conversion of ethyl lactate wasgreatly improved to 98.6% from 69.5%,with 98.0% selectivity of 1,2-propanediol over 10%(w,mass fraction)Co/SiO₂ catalysts under the given reaction conditions(2.5 MPa and 160 ℃).The obtained catalysts were characterized by X- ray diffraction(XRD),transmission electron microscopy(TEM),X- ray photoelectronspectroscopy(XPS),N₂ adsorption-desorption measurements,and H₂ temperature-programmed reduction(H₂-TPR)methods.

Key words: Co/SiO₂, Co-impregnation, Ethyl lactate hydrogenation, 1,2-Propanediol, Ethylene glycol