A Ce-promoted Ni–B amorphous alloy catalyst (Ni–Ce–B) for liquid-phase furfural hydrogenation to furfural alcohol

A Ce-doped Ni–B amorphous catalyst (Ni–Ce–B) was prepared by chemical reduction of mixed NiCl2 and CeSO4 with KBH4 in aqueous solution. During liquid-phase hydrogenation of furfural (FFR), all the as-prepared Ni–Ce–B amorphous catalyst exhibited excellent selectivity to furfural alcohol (FFA) owing to the unique amorphous structure and the electronic interaction between the metallic Ni and the alloying B. With the increase of the Ce dopant, the activity first increased and then decreased. The optimum Ce/(Ce+Ni) molar ratio (XCe) was determined as 1.28%. The X-ray photoelectron spectroscopy (XPS) spectra revealed that most of the Ce species in the Ni–Ce–B sample were present in the form of Ce2O3. On one hand, the Ce2O3 might serve as a support for the Ni–B amorphous alloy particles, resulting in the higher surface areas (SBET). On the other hand, the Ce2O3 might serve as a Lewis acid which could strongly adsorb and further polarize the CO group in the FFR molecule. These two factors could successfully account for the promoting effect of the Ce dopant on the hydrogenation activity of the Ni–B amorphous alloy. Very high content of the Ce dopant (XCe>1.28%) resulted in the decrease of the hydrogenation activity because too many Ni active sites were covered by Ce2O3 species. Treatment of the Ni–Ce–B catalyst at high temperature also caused a decrease in activity due to the transformation from the amorphous structure to the crystalline structure and the loss of the surface area.