Promotion of sulfidized W/Al2O3 systems by the decomposition of chemisorbed nickel carbonyl
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The state of tungsten in sulfidized samples of W/Al2O3 with various tungsten contents was studied by x-ray photolectron spectroscopy (XPS) and IR spectroscopy. It was shown that both tungsten in the composition of a WS2-like structure and tungsten in a state with the highest valence +VI are present simultaneously on the surface of the support. The fraction of WS2 depends on the tungsten content. It was then shown that nickel carbonyl is chemisorbed mainly on the tungsten disulfide. In this way a high “degree of promotion” is obtained in the deposited tungsten disulfide. The small promoting effect (low specific activity calculated per gram-atom of metal) for the samples with a low tungsten content is explained by the decrease in the fraction of WS2 and of the “active” nickel associated with it.
Key wordsHydrodesulfurization catalysts sulfide catalysts deposited sulfides chemisorption of nickel carbonyl
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