Preparation of Highly Dispersed Co/SiO2 Catalyst Using Ethylene Glycol and Its Application in Vapor-Phase Hydrogenolysis of Ethyl Lactate to 1,2-Propanediol

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. The synthesis parameters of Co metal loading, ratio of EG to cobalt nitrate, type of alcohol and calcination temperature, which influenced the physical properties of the Co3O4 nanoparticles, were investigated through the use of X-ray diffraction (XRD). It revealed that the ratio of EG to cobalt nitrate and the type of alcohol significantly affected the particle size of Co3O4 supported on SiO2. During co-impregnation with EG, the interaction between Co2+ and the SiO2 support was strongly enhanced, resulting in the high dispersion of cobalt species and the decrease of Co3O4 particle size from 16 nm to below 5 nm; the significantly enhanced cobalt dispersion was associated with the formation of amorphous cobalt silicate. Meanwhile the conversion of ethyl lactate was greatly 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 degrees C). The obtained catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N-2 adsorption-desorption measurements, and H-2 temperature-programmed reduction (H-2-TPR) methods