To obtain direct evidence of the formation of the Ni-Mo-S phase on NiMo/Al(2)O(3) catalysts under high-pressure hydrodesulfurization conditions, a high-pressure EXAFS chamber has been constructed and used to investigate the coordination structure of Ni and Mo species on the catalysts sulfided at high pressure. The high-pressure chamber was designed to have a low dead volume and was equipped with polybenzimidazole X-ray windows. Ni K-edge k(3)chi(k) spectra with high signal-to-noise ratio were obtained using this high-pressure chamber for the NiMo/Al(2)O(3) catalyst sulfided at 613 K and 1.1 MPa over a wide k range (39.5-146 nm(-1)). The formation of Ni-Mo and Mo-Ni coordination shells was successfully proved by Ni and Mo K-edge EXAFS measurement using this chamber. Interatomic distances of these coordination shells were almost identical to those calculated from Ni K-edge EXAFS of NiMo/C catalysts sulfided at atmospheric pressure. These results support the hypothesis that the Ni-Mo-S phase is formed on the Al(2)O(3)-supported NiMo catalyst sulfided under high-pressure hydrodesulfurization conditions.

A highly sensitive and quantitative analysis was performed using a poly(dimethylsiloxane) (PDMS) microwell array in a scanning electrochemical microscopy setup. A microelectrode with a relatively large seal radius was used to cover the top of the cylindrical PDMS microwell (96 pL). The voltammogram for 4 mM ferrocyanide resulted in a charge value of 38 nC, suggesting that almost 100% of the reductant in the microwell was converted to the oxidation current. When genetically modified yeast cells were entrapped in the microwell, the accumulation of p-aminophenol (PAP) produced by expressing beta-galactosidase (betaGAL) was successfully observed.

Ni species on the spent NiMo catalyst from ultra-deep hydrodesulfurization of gas oil in a commercial plant were studied by Ni K-edge EXAFS and TEM measurement without contact of the catalysts with air. The Ni-Mo coordination shell related to the Ni-Mo-S phase was observed in the spent catalyst by quasi in situ Ni K-edge EXAFS measurement with a newly constructed high-pressure chamber. The coordination number of this shell was almost identical to that obtained by in situ Ni K-edge EXAFS measurement of the fresh catalyst sulfided at 1.1 MPa. On the other hand, large agglomerates of Ni(3)S(2) were observed only in the spent catalyst by quasi in situ TEM/EDX measurement. MoS(2)-like slabs were sintered slightly on the spent catalyst, where they were destacked to form monolayer slabs. These results suggest that the Ni-Mo-S phase is preserved on the spent catalyst and Ni(3)S(2) agglomerates are formed by sintering of Ni(3)S(2) species originally present on the fresh catalyst.

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 2 O 3 catalysts sulfided at high-pressure (1.1 MPa, 673 K). A sharp IR band was evolved at 1,765 cm -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 -1 was observed neither in the spectra of Mo/Al 2 O 3 , Ni/Al 2 O 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.

No abstract