Nickel distribution

It has been observed that solid oxide fuel cell voltage losses are dominated by ohmic polarization and that the most significant contribution to the ohmic polarization is the interfacial resistance between the anode and the electrolyte (23). This interfacial resistance is dependent on nickel distribution in the anode. A process has been developed, PMSS (pyrolysis of metallic soap slurry), where NiO particles are surrounded by thin films or fine precipitates of yttria stabilized zirconia (YSZ) to improve nickel dispersion to strengthen adhesion of the anode to the YSZ electrolyte. This may help relieve the mismatch in thermal expansion between the anode and the electrolyte. 

Under FCCU operating conditions, almost 100% of the metal contaminants in the feed (such as nickel, vanadium, iron and copper porphyrins) are decomposed and deposited on the catalyst (2). The most harmful of these contaminants are vanadium and nickel. The deleterious effect of the deposited vanadium on catalyst performance and the manner in which vanadium is deposited on the cracking catalyst differ from those of nickel. The effect of vanadium on the catalyst performance is primarily a decrease in catalyst activity while the major effect of nickel is a selectivity change reflected in increased coke and gas yields (3). Recent laboratory studies (3-6) show that nickel distributes homogeneously over the catalyst surface while vanadium preferentially deposits on and reacts destructively with the zeolite. A mechanism for vanadium poisoning involving volatile vanadic acid as the... 

Ciccarelli RB, Wetterhahn KE. 1982. Nickel distribution and DNA lesions induced in rat tissues by the carcinogen nickel carbonate. Cancer Res 42 3544-3549. 

Vanadium and Nickel Distribution Factors in Residuum Hydroprocessing Catalysts"- ... 

Catalyst Average pore diameter (relative scale) Vanadium distribution factor Nickel distribution factor ... 

Figure 9.5 Copper and nickel distribution among BCR sequentially extracted fractions in Sudbury soils around the Copper Cliff smelter. (HOAc = acetic acid-extractable red = reducible oxi = oxidisable res = residual) (from Adamo ft a ., 1996).

Table V further shows that vanadium and nickel distributions in fractions closely follow the pattern of Type II nitrogen or Type II sulfur 82%, 17.4%, and 0.6% of the vanadium originally present in the residue are found later in, respectively, asphaltenes, resins, and oils (obtained through C5 precipitation).

Figure 3. Nickel distribution in the lower part of the lithologic sequence including underclay, the Kinneman Creek lignite, and directly overlying clay and mudstone.

In the example shown here, the distribution of active elements (Co, Mo) and that of the deposited metals (Ni, V) arc of particular interest. This profile shows a strong interaction between Co and Mo (the signals follow each other and run counter to that of Al, the tracer clement from the matrix). The metals arc distributed at the surface for vanadium and at the core for nickel. Distribution coefficients can be defined to characterise these profiles and facilitate comparison between catalysts. 

The initial coking also has some interesting indicators for metals distribution in the catalyst, as can be illustrated using data reported by Tamm et al [20]. They found that nickel distribution in pellets at the inlet and the outlet of the reactor passed through a maximum across the fractional radius of the pellet. Near the inlet, the maximum deposition was some distance inside the pellet, as opposed to vanadium which was deposited predominantly at or near the external surface. Similar observations have been observed by others [21, 22]. 

Figure 2 shows vanadium and nickel distribution for the spent NiMo/Al203 and C0M0/AI2O3 catalysts of the unsulfided and presulfided test runs. For the unsulfided catalysts, both Ni and V are observed to be more highly concentrated on the outer edges of the pellet. 

Figure 2. Vanadium and nickel distribution profile across pellets of the spent catalysts of test runs RO1-R04. The y-axis is the relative concentration of metal.

Nickel distribution throughout the catalytic filter disc... 

Figure 5. The EDXA nickel distribution map of the same sample area shown in Figure 4. Zeolites... 

Loading procedures of metal to the alumina-washcoated cordierite monoliths was studied by using nickel as the metal. It was concluded that simple adsorption method using aqueous solutions of nickel acetate or nitrate leads to unsatisfactory distribution of nickel on the monolith. Homogeneous nickel distribution on the washcoated alumina layer can be achieved by using the deposition precipitation method developed by Geus and his coworkers [10]. 

Figure 6.2 Scanning eleclron microscopy images of a Ni-YSZ cermet with elemental resolution, showing (a) nickel distribution, (b) overall cermet morphology, and (c) zirconia structural skeleton / 6 /.

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