Mo-Ni-0 powders

Jovic VD, Jovic BM, Lacnjevac U, Brankovic G, Bernik S, Recnik A (2010) An attempt to predict the mechanism of Mo-Ni-0 powders electrodeposition from the results of their TEM analysis. Electrochim Acta 55 4188-4193... 

Fig. 8.25 (a) Polarization curves in chloride-containing electrolytes for different Ni/Mo ratios (marked in the figure), (b) Polarization curve for powder electrodeposition and hydrogen evolution (hot), polarization curve for hydrogen evolution (in), and polarization curve for powder electro-deposition after subtraction of the current density for hydrogen evolution (iMo.Ni o)- Inset current efficiency for Mo-Ni-0 powder electrodeposition as a function of potential (Reprinted from Ref. [1] with kind permission from Springer)... 

Fig. 5.45 Typical agglomerates for the Mo-Ni-0 powders electrodeposited at the Ni/Mo = 1/0.5 (Reprinted from [121] with the permission of Elsevier.)...

The Mo-Ni-O powders were electrodeposited from two supporting electrolytes, as in the case of Co-Ni system 1 M NHjCl-fO. M NH4OH and 1 M (NH4)2S04 -f 0.7 M NH4OH, with the pH of the solutions being 9.0. 

It should be emphasized here that, except our recent papers [121-123], there are no papers in the literature concerning electrodeposition of Mo-Ni alloy powders (actually powders of the system Mo-Ni-0) and their characterization. 

The TEM analysis was performed on two Mo-Ni-O powders Ni-rich (Ni/Mo = 1/0.3) and Mo-rich (Ni/Mo = 1/3) powders. The common characteristic of both powders is the presence of amorphous and crystalline particles. 

Impregnation of the monoliths with the metals (NiMo) was done in a glass setup device especially designed for the treatment of monoliths in liquid phase, where the liquid is forced by internal recycling through the channels of the monolith. Two monoliths were placed in this device in 200 ml of solution. The impregnation solution to use w as determined by the tests of the powder catalysts. The preparation procedure that provided the best results with the powder catalysts was used (this aspect will be discussed in sect. 4). Several concentrations of metaLs were tested (IM Mo and 0.5M Ni, 0.5M Mo and... 

Fig. 5.61 (a) TEM image of the amorphous Mo-Ni-O particle detected in the powder electrodeposited at the Ni/Mo ratio 1/0.3. (b) SAED pattern recorded from this area (a) shows predominantly amorphous material (am) with weak reflections corresponding to MoNi4 nanocrystals (xl). (c) High magnification of amorphous Mo-Ni-O particle with MoNt4 nanocrystals (Reprinted from [123] with the permission of Elsevier.)... 

To promote the activity and selectivity of Raney nickel catalysts, alloying of the starting Ni-Al alloy with metal was often used. For instance, Montgomery (ref. 4) prepared catalysts by activating ternary alloy powders of Al (58 wt %)-Ni (37-42 wt %) - M (0.5 wt %) where M = Co, Cr, Cu, Fe and Mo. All promoted catalysts tested were more active than the reference catalyst, in hydrogenation of butyronitrile. Molybdenum was the most effective promoter. With Cr or Ti, hydrogenation of isophtalonitrile on Raney nickel occurred at lower optimum temperature than with non activated nickel (ref. 5). It was shown that addition of Ti or Co to Raney nickel suppressed the formation of secondary amine (ref. 6). 

Copper in contact mass plays the role of a catalyst. Pure copper is obtained by the electrolysis of copper sulfate. For direct synthesis, we use the copper of two brands, Mo and Mi with 99.95-99.9% of Cu. The total impurity content (Bi, Sb, As, Fe, Ni, Pb, etc.) should not exceed 0.05-0.1%. To ensure high activity of contact mass, it is necessary to use copper powders with complex surfaces. Good results in direct synthesis are also obtained when using fine copper prepared by the mechanical spraying of copper powder or deposition of copper from copper salts. 

Figure 8 Nitrogen Conversion (wt %) Versus Time on Stream (hours) - open and closed circles are for 3.2 mm extrudates and 0,6 mm powder particles. Both catalysts were Ni-Mo on alumina promoted with F.

With the decrease of the Ni/Mo ratio (1/1), cauliflower-type agglomerates. Fig. 8.28a, b, characterized with spherical edges (Fig. 8.28c) and the presence of cracks, were obtained. Their size is much higher than that of the powder particles electrodeposited at the 1/0.5 ratio, varying in the range of about 50-500 pm. In the case of Ni/Mo ratio of 1/3 (Fig. 8.28d), flat and thin parts of the powder. 

The morphology of powder particles electrodeposited from electrolytes with different Ni/Mo ion concentration ratios (1/0.3, 1/1, and 1/3) is shown in Figs. 8.29, 8.30, and 8.31. For the Ni/Mo ratio, 1/0.3 typical spongy particles were detected... 

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