Platinum family metals preparation

3 Platinum family metals preparation. The platinum metals (with gold and silver) are commonly found together, and a number of schemes are in current use for their separation. Platinum metals not only are extracted from ores but, due to their high value, are also recovered from a wide range of industrial residues such as Pt, Rh gauze catalysts, defective components from glass industries, etc. 

The first step in the preparation of Pt-group metals is the dissolution of the raw materials (primary deposits, ores, metal scraps, supported catalysts, etc.). According to the characteristics of their content in the different mixed noble metals, different dissolution methods are used. Typical processes are dissolution in 

Several methods are employed for the purification of the single platinum metal salts, for instance re-crystallization of Na2[Pt(Cl)6] with oxidative hydrolysis of the impurities of Pd, Rh, Ir, etc. which together with base-heavy metals are removed as insoluble hydroxides. Generally the metals are obtained, initially as sponge or powder, by conversion of their salts through thermal decomposition or by reduction of aqueous solutions of the ammonium-chloro complexes. Os which has been oxidized to the volatile 0s04 and Ru have to be reduced by H2. 

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An interesting, peculiar laboratory preparative reaction may finally be mentioned. This is based on the very high stability of the intermetallic compounds of actinides (and lanthanides) with the platinum family metals. The combined reduction capability of Pt with H2 (coupled reduction, see 6.7.2 fi) can be used to obtain, from its oxide, the platinide of the actinide metal. The An-Pt intermetallic compound can then be decomposed by heating in vacuum and the actinide can be obtained by distillation. 

It is clear, therefore, that we need to investigate alternative lean NOx catalysts. One such family of catalysts comprises the platinum group metals supported on metal oxides. Promising results from such systems have already appeared in the literature [5]. Here we restrict our attention to a series of Pt/MOs catalysts of various loadings and prepared from various R precursors. 

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