Liquid phase glucose hydrogenation over Cr-promoted Ru–B amorphous alloy catalysts

The undoped Ru–B and Cr-doped Ru–B(Ru–Cr–B) amorphous alloy catalysts in the form of ultrafine particles were prepared by chemical reduction with borohydride in aqueous solution. During the liquid phase glucose hydrogenation, the Ru–B amorphous alloy exhibited much higher activity than Ni– or Co–B amorphous catalysts, Raney Ni, and other Ru-based catalysts including the metallic Ru powders and the crystallized Ru–B alloy. In the presence of the Cr-dopant, the specific activity of the Ru–Cr–B amorphous alloy catalysts per gram of Ru (RHm) first increased and then decreased with the increase of the Cr-content, showing that the Cr-dopant had both the positive and negative effects on the activity of the Ru–B amorphous alloy. The optimum Cr-content (molar ratio between Cr and Cr+Ru) was determined as 3.3%. The positive effect of the Cr-dopant could be attributed to the formation of Cr2O3, resulting in the higher surface area owing to its dispersing effect. The negative effect of the Cr-dopant was mainly attributed to its effect on the intrinsic activity per square meter of catalyst (RHS). A possible explanation was the electronic interaction between the Ru atom and the Cr2O3, making Ru less electron-enriched in comparison with that in the undoped Ru–B amorphous alloy. Such less electron-enriched Ru active sites were favorable for the glucose adsorption but unfavorable for the competitive adsorption of hydrogen. Thus, the activity decreased because the glucose hydrogenation was first-order with respect to the hydrogen, but zero-order with respect to the glucose. [Copyright &y& Elsevier]