Cobalt-phosphate

A current area of interest is the use of AB cements as devices for the controlled release of biologically active species (Allen et al, 1984). AB cements can be formulated to be degradable and to release bioactive elements when placed in appropriate environments. These elements can be incorporated into the cement matrix as either the cation or the anion cement former. Special copper/cobalt phosphates/selenates have been prepared which, when placed as boluses in the rumens of cattle and sheep, have the ability to decompose and release the essential trace elements copper, cobalt and selenium in a sustained fashion over many months (Chapter 6). Although practical examples are confined to phosphate cements, others are known which are based on a variety of anions polyacrylate (Chapter 5), oxychlorides and oxysulphates (Chapter 7) and a variety of organic chelating anions (Chapter 9). The number of cements available for this purpose is very great. 

Bu, X., Feng, P and Stucky, G.D. (1997) Science, 278 (5346), 2080-2085 Feng, P Bu, X., and Stucky, G.D. (1997) Hydrothermal syntheses and structural characterization of zeolite analogue compounds based on cobalt phosphate. Nature, 388, 735-741 Feng, P Bu, X., Gier, T.E., and Stucky, G.D. (1998) Amine-directed syntheses and crystal structures of phosphate-based zeolite analogs. Microp. Mesoporous Mater., 23 (3-4), 221-229. 

Bu, X., Gier, T.E., Feng, P., and Stucky, G.D. (1998) Cobalt phosphate based zeolite structures with the edingtonite framework topology. Chem. Mater., 10, 2546-2551. 

Fig. 6.1.4 DTA curve for the cobalt phosphate particles shown in Figure 6.1.2.

Fig. 6.1.5 TEM pictures of the cobalt phosphate particles calcined in air at different temperatures. (A) Original particles prepared under the conditions given in Figure 6.1.2 (B) 300°C (C) 500°C and (D) 600°C.

Spherical particles of various metal phosphate particles can be prepared by precipitation using urea as a homogeneous precipitation agent. Surface-active agents, such as SDS and CTAC, are effective in preparation of uniform-size spherical particles. The formed spherical particles are amorphous and contain OH- and H20, except cobalt phosphate particles with layered structure. These panicles are agglomerates of primary particles, and have pores of different sizes ranging from ultramicropore to mesopore. 

Kanan MW, Yano J, Surendranath Y, Dinca M, Yachandra VK, Nocera DG. Structure and valency of a cobalt-phosphate water oxidation catalyst determined by in situ X-ray spectroscopy. J Am Chem Soc. 2010 132(39) 13692 701. 

In addition to the above one-dimensional structures, a strip-like cobalt phosphate structure has been isolated. The strip consists of two corner-shared chains fused together forming the architecture shown in Fig. 7.5a-c [18]. The one-dimensional linear chains are connected via a three-coordinated oxygen atom, giving rise to such an arrangement. This type of structure could be a key intermediate in the formation of framework solids from the basic one-dimensional chains. 

Figure 7.5. The formation of a strip-Mks, cobalt phosphate (c) by the fusion of two corner-shared four-membered rings (a and b).

Figure 7.9. A layered cobalt phosphate. Note that the zig-zag ladders are connected by two phosphate groups forming 12-membered apertures within the layer (Rao et al. [18]).

Tri-cobalt Dipbosphide, Co3P2, is formed as a black precipitate on reducing cobalt phosphate with a eurrent of hydrogen and by the action of hydrogen phosphide on cobalt chloride.4... 

Table 45 Preparations Cobalt Phosphate, Phosphate Ester, Phosphonate and Phosphite Complexes...

Table 46 Structures Cobalt Phosphate, Phosphonate, Phosphite, ADP and ATP Complexes... 

Zazhigalov et al. (209) investigated cobalt-doped vanadium phosphate catalysts prepared by coprecipitation and impregnation methods. The performance of catalysts prepared by both methods was improved as a consequence of the promotion. The cobalt is thought to have been present as cobalt phosphate, which is considered to stabilize excess phosphorus at the surface, which has previously been foimd to be an important characteristic of active catalysts. 

It is known that non-aqueous synthesis has been effectively applied in the preparation of various metal phosphates, including amine-containing aluminum, gallium, indium, zinc and cobalt phosphates with three-dimensional open-framework structures [17-24]. Moreover, phosphates with a layered or chain structure can been crystallized from non-aqueous media [25, 26]. Since the fluoride ions mineralizer was introduced into the synthesis of zirconium phosphates, several zirconium phosphate fluorides with novel structures have also been developed. 

A patent (726) has described the preparation of 2methyl-pyrazine by reaction with ammonia and air at 350° over a catalyst containing vanadium pentoxide and potassium sulfate a series of cyanomethylpyrazines has been prepared from the corresponding methylpyrazines by reaction with sodium amide in liquid ammonia followed by Af-methyl-A -phenylcyanamide in dioxane (644). 2-Hydroxyiminomethylpyrazine has been prepared from 2-methylpyrazine, sodium amide, and liquid ammonia with butyl nitrite (727, 728), and 2-hydroxy-iminomethyl-3,6-dimethyI-5-pentylpyrazine similarly from 2,3,5-trimethyl-6-pentylpyrazine (648). Nitrones (28) have been prepared from 23-and 2,5-dimethyl-and tetramethylpyrazine through the substituted methylpyridinium (perchlorates) (27) by reaction with p-nitroso-A, fV-dimethylaniline (729). Dehydrogenation of ethylpyrazine at 600° over a calcium cobaltous phosphate catalyst gives 2-vinyl-pyrazine (658). 

Derivation By heating alumina with (1) cobaltous oxide, or a material yielding this oxide on calcination (2) cobalt phosphate (3) cobalt arsenate. Greenish shades may be made by incorporating zinc oxide. 

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