Platinum group metals reduction

Precious Meta.1 Ca.ta.lysts, Precious metals are deposited throughout the TWC-activated coating layer. Rhodium plays an important role ia the reduction of NO, and is combiaed with platinum and/or palladium for the oxidation of HC and CO. Only a small amount of these expensive materials is used (31) (see Platinum-GROUP metals). The metals are dispersed on the high surface area particles as precious metal solutions, and then reduced to small metal crystals by various techniques. Catalytic reactions occur on the precious metal surfaces. Whereas metal within the crystal caimot directly participate ia the catalytic process, it can play a role when surface metal oxides are influenced through strong metal to support reactions (SMSI) (32,33). Some exhaust gas reactions, for instance the oxidation of alkanes, require larger Pt crystals than other reactions, such as the oxidation of CO (34). 

The hydrogen reduction of the metal halides, described in Sec. 1.2, is generally the favored reaction for metal deposition but is not suitable for the platinum-group metals since the volatilization and decomposition temperatures of their halides are too close to provide efficient vapor transport. 1 1 For that reason, the decomposition of the carbonyl halide is preferred. The exception is palladium which is much more readily deposited by hydrogen reduction than by the carbonyl-halide decomposition. 

Catalytic Reductive Alkylation of Aromatic and Alkyl Amines and Diamines over Sulfided and Unsulfided Platinum Group Metals... 

Secondary amines synthesized by catalytic reductive alkylation of primary amines are used in a variety of fine and specialty chemical indnstries. For example, derivatives of cyclohexylamine are used as corrosion inhibitors, N-(l,3-dimethylbntyl)-N -phenyl-p-phenylenediamine (6-PPD) is nsed as an anti-oxidant in rabber indnstiy, several dialkylated diamines are used in the coatings indnstiy, while they are nsed in the pharmacentical industry as pharmacophores (1-7). Harold Greenfield and co-workers have examined the ability of platinum group metals (PGM), base metals, and their snlfides to catalyze rednctive alkylation of primary and secotrdary amines (8-11). They found that different catalysts are optimal for the... 

Burch, R., Breen, J.P. and Meunier, F.C. (2002) A review of the selective reduction of NO, with hydrocarbons under lean-burn conditions with non-zeolitic oxides and platinum group metal catalysts, Appl. Catal. B, 39, 283. 

Nitric acid synthesis, platinum-group metal catalysts in, 19 621 Nitric acid wet spinning process, 11 189 Nitric oxide (NO), 13 791-792. See also Nitrogen oxides (NOJ affinity for ruthenium, 19 638—639 air pollutant, 1 789, 796 cardioprotection role, 5 188 catalyst poison, 5 257t chemistry of, 13 443—444 control of, 26 691—692 effect on ozone depletion, 17 785 mechanism of action in muscle cells, 5 109, 112-113 oxidation of, 17 181 in photochemical smog, 1 789, 790 reduction with catalytic aerogels, l 763t, 764... 

Coupled reduction with platinum group metals. Very pure metals of the alkaline earth, lanthanide and actinide series can be prepared from their oxides (or fluorides) by coupled reduction by pure hydrogen in presence of platinum group metals (see 6.7.2.2). 

Preparation of base metals by coupled reduction with platinum group metals. Very pure metals of the alkaline- earth, lanthanide and actinide series can be prepared from their oxides (or fluorides) through coupled reduction by pure hydrogen in presence of platinum group metals. According to a precursory paper on this subject (Berndt et al. 1974), the preparation scheme of Li, Ca, Sr, Ba, Am and Cf was described. As an example, Ca can be obtained by synthesis of a Pt compound, followed by its vacuum decomposition and recovery by distillation of the more volatile base metal ... 

Ruthenium was the last of the six platinum group metals to be isolated, and was discovered in Kazan (now capital of the Tatarstan Republic, Russian Federation) by Karl Karlovich Klaus (1796-1864) in 1844. The original papers were published in Russian journals which are difficult to obtain now, but were published in Western Europe in 1845 [1,2] with a summary in English [3]. Klaus made the metal by reduction of RuOj with H3 and named it Ruthenium in honour of his native land (Ruthenia, Latin for Russia) there are short biographies of him [4, 5],... 

The most usual synthetic routes to the derivatives of platinum group metals are the exchange reactions of the complexes containing halide ligands with alkali metal alkoxides (method 5), alcoholysis of the same kind derivatives (usually by phenols, method 4), alcoholysis of hydroxide complexes (method 3), and redox reactions — reduction of chlorides or 0s04 in alcohol media (method 7) (Table 12.25). 

Although there are some differences in the literature concerning the relative activities of the platinum group metals for this reaction, the most likely sequence is Rh > Pd > Pt.9 Over AU/AI2O3, the reduction of nitric oxide in the absence of oxygen occurs as low as 323 K, producing nitrous oxide ... 

The problem of ordering platinum group metals for the relative rate of reduction of various functions in competition is, with few exceptions, unsolved. A generalized solution would do much to aid in the proper choice of metal for selective reduction of bifunctional compounds. 

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