Abstract: Ni₂P/SiO₂ and Ni/SiO₂ catalysts were prepared for the hydrogenolysis of glycerol, and their structural properties were characterized by N₂ sorption, X-ray diffraction, X-ray fluorescence, CO chemisorption, H₂ temperature-programmed desorption, and NH₃ temperature-programmed desorption. It was found that Ni₂P/SiO₂ had a similar density of exposed Ni sites as Ni/SiO₂, while Ni₂P/SiO₂ had much larger amount of acid sites and surface hydrogen species than Ni/SiO₂. Ni₂P/SiO₂ was more active than Ni/SiO₂ in the hydrogenolysis of glycerol. This is attributed to the synergism between acid and metal sites on Ni₂P/SiO₂. Glycerol was mainly converted to 1,2-propanediol over Ni₂P/SiO₂, while it was mostly converted to not only 1,2-propanediol but also ethylene glycol and ethanol over Ni/SiO₂. The formation of ethylene glycol and ethanol on Ni/SiO₂ is attributed to the C–C bond cleavage catalyzed by metallic Ni rather than weak acidity. In addition, temperature and H₂ pressure increase did not promote the formation of ethylene glycol and ethanol on Ni₂P/SiO₂. Instead they mainly promoted the further conversion of 1,2-propanediol to form 1-propanol. Thus, Ni₂P/SiO₂ was more active for the cleavage of C–O bonds and less active for the cleavage of C–C bonds than Ni/SiO₂. We suggest that the higher activity of Ni₂P/SiO₂ for the cleavage of C–O bonds can be ascribed to its acidity, while its lower activity for the cleavage of C–C bonds may be mainly related to its electronic and geometrical properties.

Key words: glycerol hydrogenolysis, nickel phosphide, nickel, acidity, electronic and geometrical properties