Investigation of surface site of Ni species on NiMo/[Al.sub.2][O.sub.3] hydrodesulfurization catalyst sulfided at high-pressure by means of DRIFTS combined with low-temperature NO adsorption

A high-pressure DRIFT chamber for low temperature NO adsorption was newly constructed, and used to probe surface sites of the Ni-Mo-S phase on NiMo/[Al.sub.2][O.sub.3] catalysts sulfided at high-pressure (1.1 MPa, 673 K). A sharp IR band was evolved at 1,765 [cm.sup.-1] after NO adsorption at 186-199 K, whereas this band was not observed after NO adsorption at ambient temperature. The band at 1,765 [cm.sup.-1] was observed neither in the spectra of Mo/[Al.sub.2][O.sub.3], Ni/[Al.sub.2][O.sub.3] nor their physical mixture even after NO adsorption at 186-199 K, suggesting that this band results from adsorption of nitrosyl species on the Ni-Mo-S phase.