Structural characterization of W-Ni-Al2O3 catalysts

A series of W/Ni/Al2O3 catalysts was prepared by coprecipitation of nickel and aluminum and impregnation of tungsten. The samples were characterized b y XRD, XPS and XAS techniques. XRD measurements detected two phases: NiO as the main phase and NiAl2O4 in lower amount; no phase containing tungsten w as detected. XPS measurements indicated the presence of Al2O3, NiAl2O4, and Al-2 (WO4)(3) phases on the catalyst surfaces. The XANES spectra of cataly sts were rather similar for all of the samples. According to the EXAFS resu lts, at the short range level, tungsten does not form any bound with Ni ato ms. The nickel first coordination shell in the catalysts containing tungste n is similar to that encountered in COP 1 catalyst without tungsten. The lo wer Ni-Ni coordination number observed for all catalysts, when compared to the NiO phase, can be attributed to the nickel-aluminum interaction.