Nickel nitrate, decomposition

FIGURE 28 Metal concentration profiles along the length of a monolith for deposition precipitation by use of urea decomposition with nickel nitrate on a cordierite monolith. Metal deposited on a 25-cm-long, 1-cm-diameter, 400 cpsi monolith. Profiles were determined by X-ray fluorescence spectroscopy of finely ground 2.5-cm long sections of the monolith. 

The results of Hightower and White s work02 confirm those of the earlier workers. With a nickel catalyst prepared by the decomposition of nickel nitrate on porcelain in a current of hydrogen, these workers obtained the following results from single slow passes of the gas mixture over the catalyst at 350° C. ... 

X-ray data and IR-vlbrational spectra (Table 1) show that the crystallinity of the samples is preserved after the removal of the template (samples 1-3) and after the decomposition of nickel nitrate (sample 4). The X-ray powder diffraction patterns exhibit only a negligible decrease in the intensity of some reflections. The ratio of the peak intensities at 26=12.9 and 14.9 degrees Varies after calcination, as already described [11], The preliminary thermal treatment in hydrogen (Table 1,Sample 2a) also leads to no substantial changes in the crystalline structure. 

Sulfur-free catalyst is generally obtained by treating nickel nitrate with alkali carbonate, hydroxide, or hydrogen carbonate. The alkali salts formed during the precipitation must be removed so far as possible from the product. The nickel hydroxide or basic carbonate is then reduced, without prior conversion into the oxide. Nickel oxide is usually prepared by decomposition of nickel acetate or nitrate. 

A broad band with an absorption maximum at 4.54-A.56 // is observed during the decomposition of nickel nitrate when the sample is being prepared. In order to be sure that the 4.56-// band observed during the oxidation of CO was due to a species containing carbon, C 0 was used in an oxidation reaction. This shifted the 4.56-// band to 4.70 // and is proof that carbon is present in the species producing this band. It now appears that the broad band near 4.56 // which is observed during the nitrate decomposition is due to a structure similar to that postulated for the oxidation intermediate, with the exception that it contains nitrogen instead of carbon, Ni----O—— —N O. 

KAL/PUR] Kalinichenko, I. I., Purtov, A. 1., The thermal decomposition of nickel nitrate hexahydrate, Russ. J. Inorg. Chem., 11, (1966), 891-893. Cited on page 198. 

The incipient wetness catalyst was prepared with an aqueous solution of Ni(N03)2.6 H2O added slowly to the support (Silica Ketjen 77, 270 m g" ). The solution concentration was adjusted to obtain catalysts with ca. 10% nickel content. The precipitation-deposition catalyst was prepared by precipitating nickel from an aqueous solution of nickel nitrate slurried with the support. The precipitation was produced by a slow and homogeneous change in the pH induced by urea thermal decomposition. 

Fig. 2.3 Mass intensity signals of Ni species for the thermal decomposition of a nickel nitrate sample containing 0.5 fig Ni (a) NiO+, (b) Ni(N03)J, and (c) Ni+. The experimental conditions are indicated in Table 2.1. (Reprinted from [12], with permission.)...

Deposition precipitation [10,11] was later used to deposit nickel onto the alumina-washcoated monolith blocks. It was found that the method as described by [10] using aqueous solution of nickel nitrate and urea was suitable to obtain a homogeneous deposition of nickel on the washcoated alumina layer of monolith. However, due to the slow rate of urea decomposition under heating a long reaction time, typically, at least S h, is necessary. The equation is as follows ... 

Ni particles are formed in nano-size by the decomposition of nickel nitrate solution. Some unique interface properties are reported when the particle sizes are in nano-level (Lopez-Esteban et al., 2006). Toughness, as shown in Figure 7.6a, remains nearly constant for nano-composites while it decreases significantly in the case of micro-composites. Hardness as a function of Ni contents presented in Figure 7.6b also behaves quite differently. In micro-level (1-2 p.m), a linear softening with increasing nickel content is observed, which corresponds to the rule of the mixture. However, in nano-size (10-100 nm), the hardness is at its highest with the Ni content at... 

Transition metal nitrate hydrates are industrially favored precursors for the preparation of supported metal (oxide) catalysts because of their high solubility and facile nitrate removal. The final phase and particle size depend on the experimental conditions, as reported for both supported and unsupported metal nitrates [1-3]. Several authors report that decreasing the water partial pressure during the decomposition of unsupported nickel nitrate hexahydrate, via vacuum or a high gas flow, increases the final NiO surface area [3, 4], The low water partial pressure results in dehydration of the nickel nitrate hydrate to anhydrous nickel nitrate followed by decomposition to NiO. Decomposition at higher particle pressures, however, occitrred through the formation of intermediate nickel hydroxynitrates prior to decomposition to NiO. Thus, NiO obtained via intermediate nickel hydroxynitrate species showed a poorer siuface area (1 m /g) compared to NiO obtained via anhydrous nickel nitrate species (10 mVg) [4]. 

TG/DTG experiments were performed in Mettler Toledo TGA/SDTA851e thermo-gravimetry to understand decomposition process of nickel nitrate and the removal temperature of carbon template. The nickel nitrate impregnated carbon was placed in the atmosphere of 80% Ar and 20% O2 and heated at 5 °C/min to the final temperature... 

There have been many instances of examination of the effect of additive product on the initiation of nucleation and growth processes. In early work on the dehydration of crystalline hydrates, reaction was initiated on all surfaces by rubbing with the anhydrous material [400]. An interesting application of the opposite effect was used by Franklin and Flanagan [62] to inhibit reaction at selected crystal faces of uranyl nitrate hexa-hydrate by coating with an impermeable material. In other reactions, the product does not so readily interact with reactant surfaces, e.g. nickel metal (having oxidized boundaries) does not detectably catalyze the decomposition of nickel formate [222],... 

Ephraim and Bolle 3 find that the stability of the ammines of general formula [M(NII3) ]R2 depends not only on the central atom but also on the anion. These influences oppose one another, and the stability of the whole molecule is therefore the resultant of the two influences consequently, very little parallelism may appear between analogous compounds. For instance, the temperatures of decomposition of the hexanunino-salts of nickel decrease in the order perchlorate, iodide, bromide, chlorate, nitrate, chloride, sulphate whilst in the ease of the liexammino-salts of zinc, the order for decreasing stability is iodide, bromide, chloride, perchlorate, sulphate, nitrate, chlorate. 

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