Rare earth nitrates

Decomposition of the rare earth nitrates proceeded [821] through the intermediate formation of oxysalts of the form MON03 and E values were low Nd(N03)3, 33 kJ mole 1, 663-703 K Dy(N03)3, 23 kJ mole 1, 583—633 K Yb(N03)3, 46 kJ mole 1, 563—598 K. Thermogravimetric curves showed that the formation of anhydrous salts was possible, in contrast to observations by Wendlandt and Bear [826]. In a similar study [827] of the reaction of Pr(N03)3 at 558—758 K, the intermediate formation of a nitrite is postulated during decomposition to a non-stoichiometric residual oxide, Pr0li83 (the actual composition depends on temperature). 

Lanthanum also may be separated from aqueous solutions of rare-earth nitrates by liquid-hquid extraction using a suitable water-immiscible organic hquid such as tributyl phosphate or another complexing agent dissolved in it. 

Solvating agents have the ability to solvate the hydrogen ion. TBP is the most useful since it extracts rare earths nitrates (Figure 16). 

The solution chemistry of the rare earth vanadates has received considerable attention [359,360]. It has been found that when ammonium metavanadate solution is added to rare earth nitrate solutions, an increase in acidity results with the formation of the orthovanadates (eq. 35). However, when the solutions are mixed in the opposite order the pH of the medium remains unchanged and precipitates of metavanadates the (eq. 36) are produced. 

The third-power TBP dependence has been verified by Peppard et al. [55, 56] for lower Z rare earths and toluene diluent, and for Y and Ce by Scargill and his coworkers [57—59]. However, there is a lack of direct evidence for the third-power nitrate dependence. In a nitrate medium with TBP, using a countercurrent system Weaver, Kappel-mann and Topp [60] were able to prepare 95 per cent pure Gd in kilogram quantities. Additional equilibrium data on rare earth nitrate-TBP system has recently appeared [61]. 

Few workers [288, 290] have determined the stability constants of rare earth-nitrate complexes. The stability constants for the MX2+ species of several rare earths are compared in Table 19. It will be noticed from the table that the k values for the species MX2+ show a definite increase in the light rare earth region reaching the highest value at europium and then slowly decreasing. 

Table 19. Stability constants for the MX2+ species of severed rare earth nitrate [288 complexes (p = 1.0 at 22° C)...

The M—O stretching frequency for the anhydrous rare earth nitrates is found to occur [297a] between 237 and 265 cm-1. In the case of Eu(N0s)3 this particular frequency occurs at 239 cm-1. 

The metavanadates crystallize from aqueous solution as MV3O9 4H2O. If, however, solutions of ammonium metavanadate and rare earth nitrate are mixed with an equal volume of alcohol at a pH value depending on the ion (shown below) hexavanadates of the composition M VbOitJs 48H2O are obtained. 

The solvent extraction of rare-earth nitrates into solutions of TBP has been used commercially for the production of high-purity oxides of yttrium, lanthanum, praseodymium and neodymium from various mineral concentrates,39 as well as for the recovery of mixed rare-earth oxides as a byproduct in the manufacture of phosphoric acid from apatite ores.272 273 In both instances, extraction is carried out from concentrated nitrate solutions, and the loaded organic phases are stripped with water. The rare-earth metals are precipitated from the strip liquors in the form of hydroxides or oxalates, both of which can be calcined to the oxides. Since the distribution coefficients (D) for adjacent rare earths are closely similar, mixer—settler assemblies with 50 or more stages operated under conditions of total reflux are necessary to yield products of adequate purity.39... 

These samples were prepared by impregnation of La203, of surface 2.0 m2 g 1, with rare earth nitrate solution of concentration sufficient to give approximately the same nominal surface concentration of the paramagnetic species as occurs in the self-supported oxide. Moderate differences in preparative treatment caused changes of 2 to 3 fold in ka, but no significant change in AkH except as described later. 

Nitration of phenols. Phenols can be nitrated in a two-phase system (ether-water) by NaN03(l equiv.) and HC1 (excess) in the presence of a catalytic amount of several rare earth nitrates in yields generally > 80%. The o/p ratio can be controlled to some extent by change in the acidity, but ort/io-nitration generally predominates. Aromatic hydrocarbons are not nitrated under these conditions. 

Copper (I) iodide, 6 3 Crystallization, apparatus for, of tetrachloro (diethylene)di-platinum(II), 5 213 fractional, of magnesium rare earth nitrates, 2 52, 53 of rate earth bromates, 2 62... 

Magnesium cerium(III) nitrate, 3Mg(N03)2-2Ce(N03)3-24H20, separation of praseodymium from lanthanum by, 2 57 Magnesium chloride, anhydrous, 1 29 5 154n. 6 9 Magnesium cyclopentadienide, 6 11 Magnesium rare earth nitrates,... 

Although many early studies on the solvent extraction of rare earth chloride into alcohols, ether, ketone, rare earth thiocyanates into butanol, rare earth nitrates into n-hexanol were done, extraction of rare earth nitrates by tri-n-butyl phosphate (TBP) proved to be the most promising system. The general step of extraction is ... 

Han et al. (2008) reported the s)mthesis of heavy lanthanide sesqui-oxide (R2O3, R = Y, Dy, Ho, Er) nanobelts by thermolysis of solid rare earth nitrate hydrates in a dodecylamine/l-octadecene mixed solvent system. The nitrate hydrates showed poor solubility in the mixed solvent, and the heat-transport differences between the liquid and the solid assisted in separation of the nucleation and growth processes. 

Rare earth nitrates can be prepared using nitric acid to react with a corresponding oxide, hydroxide, carbonate or metal. These nitrates dissolve easily in polar solvents such as water, alcohols, esters or nitriles. They are unstable to heat as the decomposition temperature for the nitrates of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium are 510,480, 780,450, 505, 830, and 750 °C, respectively. 

Rare earth nitrates usually have the formula RE(N03 )3 nU20 where n = 6 for the lighter rare earth nitrates (lanthanum to neodymium) and n = 5 for the heavier rare earth nitrate (europium to lutetium) and this is caused by lanthanide contraction. 

Structure In rare earth nitrates, the nitrate groups usually have one of the coordination modes shown in Figure 1.26 when coordinated to the central ions. 

The synthesis is in two steps (i) the neutralization of R-COOH with a base, such as ammonia, NaOH, or KOH (Equation 3.2) and (ii) the reaction of the resulting solution with the rare earth salts (Equation 3.3). The most commonly used salts are rare earth nitrates, chlorides, and perchlorates, largely because of their good solubility in water or in the polar solvents (THE, MeOH, EtOH, MeCN, DME, and DMSO). The synthesis can be accomplished under either ambient conditions or by solvothermal synthesis. 

Junk, P.C., Kepert, C.J., Wei-Min, L., Skelton, B.W., and White W.A. (1999) Structural systematics of rare earth complexes. XIII. ( Maximally ) hydrated (heavy) rare earth nitrates. Australian Journal of Chemistry, 52 (6), 497-505. 

By using the template directed cyclization between 2,6-pyridinedicarbaldehyde and ethyl-diamine in the presence of rare earth nitrate salts, a series of corresponding complexes... 

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