부산대학교 도서관

Unsupported and silica-supported amorphous metal-boron materials (Ni-B, Mo-O-B, and Ni-Mo-O-B) were prepared by NaBH{sub 4} reduction of aqueous or impregnated metal salts. The resulting materials were characterized by a range of techniques, including conventional and time-resolved X-ray diffraction. The latter technique was used to determine the onset of crystallization of the amorphous materials during annealing in He flow and to identify the phases formed. Annealing of unsupported Ni-B resulted in the crystallization of predominantly Ni{sub 3}B, followed by Ni metal, whereas Ni-B/SiO{sub 2} formed Ni and then NiO. There was no evidence for crystallization of B-containing phases for Mo-O-B or Mo-O-B/SiO{sub 2} on annealing; instead, the predominant phase formed was MoO{sub 2}. In general, the phases formed for Ni-Mo-O-B and Ni-Mo-O-B/SiO2 were consistent with those formed in the monometallic materials, but at higher annealing temperatures. Catalysts prepared by sulfiding Ni-B/SiO{sub 2} and Ni-Mo-O-B/SiO{sub 2} materials had significantly higher thiophene HDS activities than conventionally prepared sulfided Ni/SiO2 and Ni-Mo/SiO{sub 2} catalysts, whereas a sulfided Mo-O-B/SiO{sub 2} catalyst had a dramatically lower HDS activity than a sulfided Mo/SiO{sub 2} catalyst.