Thorium carboxylates

Thorium carbides, 24 761, 4 689—690 Thorium carbonate, 24 765 Thorium carboxylates, 24 768-769 Thorium chlorides, 24 762-763 Thorium complexes allyl, 24 773... 

Oxygen-Gontaining Organics. Neutral and anionic oxygen-containing organic molecules form complexes with thorium. Recent work has focused on alkoxides (72), aryloxides, and carboxylates however, complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates are also well known. 

CycHzation with loss of one carboxyl takes place in the presence of metal oxides, notably barium and thorium. Thus adipic acid yields cyclopentanone, carbon dioxide, and water (Dieckmaim reaction). 

Carboxylic acids can be converted to symmetrical ketones by pyrolysis in the presence of thorium oxide. In a mixed reaction, formic acid and another acid heated... 

Although not part of soil, lichens, by virtue of their solubilising action on rocks, contribute to the elemental enrichment of soil. Several studies have identified lichen acids as complexing agents for the iron and aluminium of rocks (95, 96). An examination of the various structures indicates that the basic structure responsible for the chelation is the carboxylic acid group with an orthophenolic group. Grodzinskii (97) has found lichens to be intense accumulators of elements in the uranium-radium, actinouranium and thorium orders. 

Carboxylic acids can be converted to symmetrical ketones by pyrolysis in the presence of thorium oxide. In a mixed reaction, formic acid and another acid heated over thorium oxide give aldehydes. Mixed alkyl aryl ketones have been prepared by heating mixtures of ferrous salts.1717 When the R group is large, the methyl ester rather than the acid can be decarb-methoxylated over thorium oxide to give the symmetrical ketone. 

As an addition compound was reported to be formed193 between thorium salicylate and an undissociated salicylic acid molecule, addition of neutral donors to salicylic acid or other carboxylic acids may give regions of synergism and antagonism with tetravalent ions also, as with U(VI). No study however has been reported on this. 

A number of investigations on the synergistic effect of a second extractant, such as amines and oximes, on the extraction of metal carboxylates have been carried out. The utilized synergists include 8-hydroxyquinoline-2-aldoxime for Zr(IV) and Hf(IV) (122,123), various amines (25), Lix 63 (27) and nonylphenol (28) for Cu(II), dialkylphos-phoric acids for Hf(IV) (44), rhodamine B for Be(IE) (102), trioctylphos-phine oxide for U(VI) (69, 77), p-alkylphenol for Cs(I) (1), collidine for Zr(IV) and Sc(IEI) (62), and nonchelating oximes for Ni(II) and Co(II) (103). Mareva et al. (77) have successfully utilized a salicylic acid-trioctylphosphine oxide mixture for the separation of uranium from rare earths, thorium, zirconium, and iron. 

The old method of heating the calcium salts of formic and a second carboxylic acid for aldehyde formation has been modified by the use of a catalytic decomposition technique. By this scheme, the acid vapors are passed over thorium oxide, titanium oxide, or magnesium oxide at 300° or the acids are heated under pressure at 260° in the presence of titanium dioxide. In the latter procedure, non-volatile acids can be used. With aliphatic acids over titanium oxide, reaction occurs only when more than seven carbon atoms are present, the yields increasing with increase in the molecular weight (78-90%). Aromatic-acids having halo and phenolic groups are converted in high yields to aldehydes, e.g., salicylaldehyde (92%) and p-chlorobenzaldehyde (8S>%). Preparation of a thorium oxide catalyst has been described (cf. method 186). 

Fundamental studies have been reported using the cationic liquid ion exchanger di(2-ethylhexyl) phosphoric acid in the extraction of uranium from wet-process phosphoric acid (H34), yttrium from nitric acid solution (Hll), nickel and zinc from a waste phsophate solution (P9), samarium, neodymium, and cerium from their chloride solutions (12), aluminum, cobalt, chromium, copper, iron, nickel, molybdenum, selenium, thorium, titanium, yttrium, and zinc (Lll), and in the formation of iron and rare earth di(2-ethylhexyl) phosphoric acid polymers (H12). Other cationic liquid ion exchangers that have been used include naphthenic acid, an inexpensive carboxylic acid to separate copper from nickel (F4), di-alkyl phosphate to recover vanadium from carnotite type uranium ores (M42), and tributyl phosphate to separate rare earths (B24). 

The complexation of thorium(IV) and plutoniumflV) with a tetrahydroxamate ligand based on the cyclohexane-1,2-diyldinitrilotetraacetate complexon, with hydroxamate instead of carboxylate groups has been reported. The speciation appears to be pH dependent. Up to pH 9 the complexes... 

The kinetics of the decomposition [17] of thorium tetraformate to ThOj can be described by the Prout-Tompkins equation with = 150 kJ mol" from 498 to 553 K. The autocatalytic process was ascribed to participation of the oxide in breakdown of the carboxyl groups at the reaction interface to yield ThOj, formaldehyde and carbon dioxide as the primary products of reaction. The volatile products could, however, react further on the surface of the active solid to yield a number of secondary products amongst which the following gases were identified Hj, CO, HjO, CHjOH, HCOOCHj, HCOOH and (CHj). Addition of nickel formate to the reactant not only accelerated decomposition but also influenced the composition of the gases evolved, yielding predominantly CO, COj and H2 (which are the main products of nickel formate decomposition). 

TAAHA, and TTHA each have six carboxylic acid groups, TTHA is better able to encapsulate the metal ion and removes much more thorium from rats than does TAAHA94). As with EDTA, the complete phosphorylation of DTPA decreases its ability to remove plutonium90). 

A method used in industry for ketonization of aliphatic acids is to pass the carboxylic acid vapors at about 300° over calcium, barium, or thorium oxide catalysts, and this is in principle also a calcium salt distillation. 

The bimolecular ketonization of short-chain carboxylic acids is known to be catalysed by oxides of cerium and thorium, supported on titanium oxides [5]. The present work shows that erionite-offretite zeolites are potential alternative catalysts. 

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