Characterization and Catalytic Activity of WNiMo/Al₂O₃ Catalyst for Hydrodenitrogenation of Pyridine

Abstract

Various transition-metal catalysts supported on γ-alumina were prepared and applied for the hydrodenitrogenation (HDN) of pyridine. The NiMo/Al 2 O 3 catalyst showed higher activity than the Mo/Al 2 O 3 catalyst. On the basis of the results of reaction experiments and measurements of IR and TPR, the enhancement in the HDN activity with nickel addition could be attributed more to the improvement in the reducibility of molybdenum than to the effect of Bro ¨nsted acid site. Tungsten impregnated on the NiMo/Al 2 O 3 catalyst as a secondary promoter enhanced the catalytic activity. From the results of various characterization analyses, the positive evidences supporting the HDN activity promotion were obtained. These are the formation of more Bro ¨nsted acid sites (FT-IR), the enhanced reducibility of Mo (TPR), the increase of octahedrally coordinated Mo 6+ species (DRS), and the creation of more anion vacancy sites (ESR and NO adsorption). Apparently, all of these features are combined to give the promotional effect of tungsten in the NiMo/Al 2 O 3 catalyst for the HDN activity.

Catalytic Synthesis of Methanethiol from Carbon Disulfide and Hydrogen Over Sulfided KMo/Al2O3 Catalysts

“…As can be seen from Fig. 2a [5,23], this suggests that more than one type of Lewis acid sites exist on the surface of cAl 2 O 3 . When potassium and molybdenum were incorporated into the alumina support, the intensity of all the bands for Lewis acid sites was distinctly weakened, which most probably because that K 2 CO 3 is alkaline and it can reduce acidity by neutralizing some Lewis acid sites on the surface of the catalysts.…”

Preparation and Characterization of CeO2-MoO3/TiO2 Catalysts for Selective Catalytic Reduction of NO with NH3

“…According to the XPS results, the ratios of Ce 3+ /Ce 4+ were different in various samples. It has been reported that Mo 6+ species can be present in both tetrahedral and octahedral coordination (Park et al, 1997). Therefore, it can be inferred that the difference in H 2 consumption for various samples was likely to correlate with the formation of subtly different surface structure of Ce and Mo oxide species, resulting from different catalyst preparation methods.…”

Preparation and catalytic activity of K4Zr5O12 for the oxidation of soot from vehicle engine emissions

“…And a catalyst which is active for soot oxidation is usually attached to lower the soot ignition temperature [11][12][13]. Owing to the high price of the current choice of Pt catalyst, many attempts have been made to develop Pt-free catalysts which include perovskite-type oxides, spinel type oxides, alkaline or heavy metal oxides, mixtures of halides with vanadates or molybdates and so on [14][15][16][17][18][19][20][21][22][23][24].…”