Glucose hydrogenation over Ni-B/SiO2 amorphous alloy catalyst and the promoting effect of metal dopants

The Ni-B/SiO2 amorphous catalyst was prepared by chemical reduction with KBH4 aqueous solution. The amorphous structure was verified by XRD, EXAFS, and DSC. During the liquid phase glucose hydrogenation, the as-prepared Ni-B/SiO2 amorphous catalyst exhibited much higher activity than other Ni-based catalysts, such as the corresponding crystallized Ni-B/SiO2 catalyst, the Ni/SiO2 catalyst obtained by H-2 reduction, and even the commercial Raney Ni catalyst. This was interpreted in terms of both the structural effect and the electronic effect. Effects of the preparation conditions on the activity of the Ni-B/SiO2 amorphous catalyst were investigated which revealed that the maximum activity was achieved by using the 40-60 mesh SiO2 support and calcining the catalyst precursor at 473 K for 2 h. Appropriate concentration of Cr-, Mo-, and W-promoters could further enhance its activity since the presence of these promoters in the low-valent state could act as Lewis adsorption sites which favored the adsorption and polarization of the carbonyl group (C=O) in the glucose molecule. However, large concentration of the promoters led to a decrease in the activity since too many Ni active sites were covered by these oxides. (C) 2002 Elsevier Science B.V All rights reserved.