Niobium‐Based Nickel–Tungsten Hydrotreatment Catalysts with Enhanced Isomerization Properties

Abstract

Alumina‐supported NiW catalysts doped with Nb were prepared with different W contents and different Ni/W ratios. Studies of the sulfide state by TEM and X‐ray photoelectron spectroscopy (XPS) demonstrated the influence of Nb on the sulfidation of W and Ni. The catalytic performance of the solids was evaluated in toluene hydrogenation and cyclohexane isomerization and was compared to that of Nb‐free catalysts. The presence of Nb resulted in a decrease of the hydrogenation activity at low W content and low Ni/W ratio, in agreement with XPS and TEM characterizations. However, increasing the W content and the Ni/W ratio increased the hydrogenation activity. Regardless of the W and Ni content, cyclohexane conversion was significantly improved by the presence of Nb. The most efficient catalyst of the series, with a W content of 15 wt % WO3 and a Ni/W ratio of 0.9, showed slightly higher activity for hydrogenation than that of a Nb‐free NiW catalyst. Also, the isomerization activity was greatly enhanced, demonstrating the potential of these Nb‐based catalyst formulations.

Cesium salts of niobo-tungstate isopolyanions with intermediate group V–group VI character

“…17 This compositional series of Linqvist-type Nb/W isopolyanions, [Nb x W 6Àx O 19 ] (2+x)À (x = 1-4), was originally prepared 40 years ago by Dabbabi et al from the reactions of K 8 [Nb 6 O 19 ] and sodium tungstate in aqueous media under pH control and in the presence of H 2 O 2 . 18 The original report did not include crystallographic analysis of the structures and just [NbW 5 O 19 ] 3À (as the TMA + /K + , 19 and the TBA + salt 20 ), [Nb 2 W 4 O 19 ] 4À , 21 and a hybrid derivative of the latter 22 have been structurally characterized so far. These highly symmetric clusters with mixed metal site occupancies present significant disorder, rendering proper structure interpretation challenging, but Cs + may provide the advantage of orienting the clusters by preferred coordination to the more basic niobium-bonded oxo-ligands.…”

Nanomaterials for sustainable hydrogen production by (photo)electrolysis

“…The final particle size of WC1-x in the composite is decided by the size of intermediate WO3 nanoparticle. In an inert atmosphere, ammonia metatungstate decomposed to WO3 at 250-380℃ [152,153] , thus an additional calcination step at 300℃, 350℃ or 400℃ for 30min was conducted before ramp up to 600℃, and then follow the typical calcination protocol. The samples are denoted as WC1-x/C-300, WC1-x/C-350 and WC1-x/C-400 respectively.…”