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Transition metal extraction

Kislik V and Eyal A. Mechanisms of titanium(IV) and some other transition metals extraction by organophosphoric acids. In Logsdail DH and Slater Ml Eds. Proceedings of ISEC 93, London, July 1993. Elsevier Applied Science for SCI 1993 3 1353-1361. [Pg.401]

Impregnated Resins for Transition Metal Extraction Separation... [Pg.301]

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... [Pg.219]

Hafnium metal is analy2ed for impurities using analytical techniques used for 2irconium (19,21,22). Carbon and sulfur in hafnium are measured by combustion, followed by chromatographic or in measurement of the carbon and sulfur oxides (19). Chromatographic measurement of Hberated hydrogen follows the hot vacuum extraction or fusion of hafnium with a transition metal in an inert atmosphere (23,24). [Pg.443]

Thiocyanates are rather stable to air, oxidation, and dilute nitric acid. Of considerable practical importance are the reactions of thiocyanate with metal cations. Silver, mercury, lead, and cuprous thiocyanates precipitate. Many metals form complexes. The deep red complex of ferric iron with thiocyanate, [Fe(SCN)g] , is an effective iadicator for either ion. Various metal thiocyanate complexes with transition metals can be extracted iato organic solvents. [Pg.151]

Transition metal catalysis in liquid/liquid biphasic systems principally requires sufficient solubility and immobilization of the catalysts in the IL phase relative to the extraction phase. Solubilization of metal ions in ILs can be separated into processes, involving the dissolution of simple metal salts (often through coordination with anions from the ionic liquid) and the dissolution of metal coordination complexes, in which the metal coordination sphere remains intact. [Pg.70]

Since no special ligand design is usually required to dissolve transition metal complexes in ionic liquids, the application of ionic ligands can be an extremely useful tool with which to immobilize the catalyst in the ionic medium. In applications in which the ionic catalyst layer is intensively extracted with a non-miscible solvent (i.e., under the conditions of biphasic catalysis or during product recovery by extraction) it is important to ensure that the amount of catalyst washed from the ionic liquid is extremely low. Full immobilization of the (often quite expensive) transition metal catalyst, combined with the possibility of recycling it, is usually a crucial criterion for the large-scale use of homogeneous catalysis (for more details see Section 5.3.5). [Pg.214]

Apart from the activation of a biphasic reaction by extraction of catalyst poisons as described above, an ionic liquid solvent can activate homogeneously dissolved transition metal complexes by chemical interaction. [Pg.220]

Obviously, there are many good reasons to study ionic liquids as alternative solvents in transition metal-catalyzed reactions. Besides the engineering advantage of their nonvolatile natures, the investigation of new biphasic reactions with an ionic catalyst phase is of special interest. The possibility of adjusting solubility properties by different cation/anion combinations permits systematic optimization of the biphasic reaction (with regard, for example, to product selectivity). Attractive options to improve selectivity in multiphase reactions derive from the preferential solubility of only one reactant in the catalyst solvent or from the in situ extraction of reaction intermediates from the catalyst layer. Moreover, the application of an ionic liquid catalyst layer permits a biphasic reaction mode in many cases where this would not be possible with water or polar organic solvents (due to incompatibility with the catalyst or problems with substrate solubility, for example). [Pg.252]

Yosida et al. [41] found that p-t< rr-butylcalix[6]ar-ene can extract Cu from the alkaline-ammonia solution to the organic solvent. Nagasaki and Shinkai [42] described the synthesis of carboxyl, derivatives of calix-[n]arenes ( = 4 and 6) and their selective extraction capacity of transition metal cations from aqueous phase to the organic phase. Gutsche and Nam [43] have synthesized various substituted calix[n]arenes and examined the complexes of the p-bromo benzene sulfonate of p-(2-aminoethyl)calix[4]arene with Ni, Cu , Co-, and Fe. ... [Pg.342]

Based on the above results they have concluded that the ligand groups circularly arranged on the lower rim of the calixarene cavity construct a novel cyclic metal receptor for selective extraction of transition metal cations. Results suggest that the fine tuning in molecular... [Pg.344]

Recently, Deligoz and Yilmaz [51] prepared three polymeric calix[4]arenes, which were synthesized by reacting chloromethylated polystyrene with 25,26,27-tribenzoyloxy-28-hydroxy calix[4]arene (2a, 3a) and po-lyacryloyl chloride with 25,26,27,28-tetraacetoxy ca-lix[4]arene (4a). After alkaline hydrolysis of the polymers, they were utilized for selective extraction of transition metal cations from aqueous phase to organic phase. [Pg.345]

Deligoz and Yilmaz [52] reported that the selective liquid-liquid extraction of various alkali and transition metal cations from the aqueous phase to the organic phase as carried out by using p-tert-h iy calix[4]arene (1), p-tert-b x. y calix[6]arene (2), tetra-ethyl-p-tm-butylcalix[4]arene-tetra-acetate (3), tetra-methyl-p-/< /-/-butyl calix[4]arene-tetraketone (4), calix[n]arenes ( = 4 and 6) bearing oxime groups on the lower rim (5 and 6) and a polymeric calix(4]arene (8). It was found that compounds 5 and 6 showed selectivity towards Ag, Hg, Hg, Cu, and Cr and the order of the ex-tractability was Hg > Hg > Ag > Cu > Cr. The polymeric calix[4]arene (8) was selective for Ag, Hg, and Hg , unlike its monomeric analog. [Pg.347]

Transition metal oxides or their combinations with metal oxides from the lower row 5 a elements were found to be effective catalysts for the oxidation of propene to acrolein. Examples of commercially used catalysts are supported CuO (used in the Shell process) and Bi203/Mo03 (used in the Sohio process). In both processes, the reaction is carried out at temperature and pressure ranges of 300-360°C and 1-2 atmospheres. In the Sohio process, a mixture of propylene, air, and steam is introduced to the reactor. The hot effluent is quenched to cool the product mixture and to remove the gases. Acrylic acid, a by-product from the oxidation reaction, is separated in a stripping tower where the acrolein-acetaldehyde mixture enters as an overhead stream. Acrolein is then separated from acetaldehyde in a solvent extraction tower. Finally, acrolein is distilled and the solvent recycled. [Pg.215]

This review focuses on the structural stability of transition metal oxides to lithium insertion/extraction rather than on their electrochemical performance. The reader should refer to cited publications to access relevant electrochemical data. Because of the vast number of papers on lithium metal oxides that have been published since the 1970s, only a selected list of references has been provided. [Pg.295]

Kinetic observations for decomposition of some representative transition metal sulphides are summarized in Table 13. Several instances of an advancing interface [contracting volume, eqn. (7), n = 3] rate process have been identified and the rate may be diminished by the presence of sulphur. Diffusion control is, however, believed to be important in the reactions of two lower sulphides (Ni0.9sS. [687] and Cu1-8S [688]). These solids have attracted particular interest since both are commercially valuable ores and pyrolysis constitutes one possible initial step in metal extraction. [Pg.156]

A series of Be-Pt intermetallic compounds arc prepared during the electrodeposition of Be on Pt from a solution of BeCl2 in an equimol NaCl-KCl mixture at 710°C. X-Ray diffraction of the electrode surface shows the presence of BePt, BcjPt. Electrolytic methods are also used to extract single crystals of Be,V from alloys prepared by arc melting Be and the transition metal in the proportion 15 1. [Pg.471]


See other pages where Transition metal extraction is mentioned: [Pg.151]    [Pg.7199]    [Pg.43]    [Pg.49]    [Pg.151]    [Pg.7199]    [Pg.43]    [Pg.49]    [Pg.199]    [Pg.252]    [Pg.75]    [Pg.56]    [Pg.122]    [Pg.62]    [Pg.48]    [Pg.70]    [Pg.72]    [Pg.220]    [Pg.293]    [Pg.294]    [Pg.294]    [Pg.317]    [Pg.121]    [Pg.179]    [Pg.911]    [Pg.206]    [Pg.349]    [Pg.285]    [Pg.12]   
See also in sourсe #XX -- [ Pg.324 , Pg.325 , Pg.326 , Pg.327 ]




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Metals extraction

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