Niobium-Containing Lindqvist Isopolyanions [NbxW6-xO19](2+x)- Used as Precursors for Hydrodesulfurization Catalysts with Isomerization Properties

Lindqvist isopolyanions [NbxW6–xO19](2+x)– (x = 0–4 and 6) were prepared and their spectroscopic and thermal properties were determined by Raman and IR spectroscopy as well as TGA/DSC. The structure of the [NbW5O19]3– anion obtained as single crystal was determined. Ni‐promoted alumina‐supported hydrodesulfurization (HDS) catalysts were prepared from the best soluble NbW polyoxometalates. In the calcined catalysts, better dispersion of the metallic species is observed when using NbW isopolyanions instead of the conventional ammonium metatungstate. The presence of niobium was expected to introduce acidity leading to isomerization property in classical NiW HDS catalysts. In HDS reaction conditions (under hydrogen pressure and sulfided environment) the cyclohexane isomerization into methylcyclopentane activity of niobium‐based catalysts was found up to 5 times superior to that of conventional NiW catalyst, showing the beneficial effect of niobium for this reaction. [NbxW6–xO19](2+x)– Lindqvist type isopolyanions were synthesized and characterized to prepared NbWNi‐based alumina‐supported hydrodesulfurization catalysts. Nb‐containing catalysts showed improved CC6 isomerization properties under HDS conditions (H2 pressure and H2S presence) compared to those of a reference NiW catalyst related to the acid properties induced by niobium.