Platinum rhodium and

Some metals used as metallic coatings are considered nontoxic, such as aluminum, magnesium, iron, tin, indium, molybdenum, tungsten, titanium, tantalum, niobium, bismuth, and the precious metals such as gold, platinum, rhodium, and palladium. However, some of the most important poUutants are metallic contaminants of these metals. Metals that can be bioconcentrated to harmful levels, especially in predators at the top of the food chain, such as mercury, cadmium, and lead are especially problematic. Other metals such as silver, copper, nickel, zinc, and chromium in the hexavalent oxidation state are highly toxic to aquatic Hfe (37,57—60). 

High Temperature Properties. There are marked differences in the abihty of PGMs to resist high temperature oxidation. Many technological appHcations, particularly in the form of platinum-based alloys, arise from the resistance of platinum, rhodium, and iridium to oxidation at high temperatures. Osmium and mthenium are not used in oxidation-resistant appHcations owing to the formation of volatile oxides. High temperature oxidation behavior is summarized in Table 4. 

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

The above generalities apply particularly to palladium. Hydrogenation over platinum or rhodium are far less sensitive to the influence of steric crowding. Reduction of 1-t-butylnaphthalene over platinum, rhodium, and palladium resulted in values of /ci//c2 of 0.42, 0.71, and 0.024, respectively. Also, unlike mononuclear aromatics, palladium reduces substituted naphthalenes at substantially higher rates than does either platinum or rhodium. For example, the rate constants, k x 10 in mol sec" g catalyst", in acetic acid at 50 C and 1 atm, were (for 1,8-diisopropylnaphthalene) Pd (142), Pt(l8.4), and Rh(7.1)(25). 

Both amine oxides related to pyridines and aliphatic amine oxides (/25) are easily reduced, the former the more so. Pyridine N-oxide has been reduced over palladium, platinum, rhodium, and ruthenium. The most active was rhodium, but it was nonselective, reducing the ring as well. Palladium is usually the preferred catalyst for this type of reduction and is used by most workers 16,23,84 158) platinum is also effective 100,166,169). Katritzky and Monrol - ) examined carefully the selectivity of reduction over palladium of a... 

Compared with platinum, rhodium and iridium, palladium has much less resistance to chemical attack. Its theoretical corrosion diagram is depicted in Fig. 6.5, from which it may be seen that the metal is stable in the presence... 

The trend in CVD metallization is toward greater use of copper, and the refractory metals and their silicides in multilayered metallization designs, typically consisting of metal-silicide contacts, refractory-metal barriers, and copper or an aluminum alloy as the principal interconnect metal. Other metals deposited by CVD such as chromium, molybdenum, platinum, rhodium, and ruthenium are also actively considered for use as conductors. 

LEED patterns at 0 = 1 /4, but was identified at lower coverages in islands surrounded by mobile sulfur atoms at platinum, rhodium and rhenium surfaces. Sautet and co-workers42 have analysed the statistical correlations between the intensities of sulfur features in p(2 x 2) islands on rhenium surfaces and also of streaks in areas between islands, which they attribute to sulfur atoms diffusing under the tip (Figure 10.12). 

Palladium gave the highest activity of all the platinum group metals evaluated platinum, rhodium and ruthenium exhibited very poor activity. The choice of support was also demonstrated to be very important the activated carbon supported Pd catalyst showed a nearly fourfold increase in activity than did Pd supported on alumina. 

Several mechanistic investigations concerning the hydrogenation of pyruvate derivatives (ethyl or methyl esters) were performed with platinum, rhodium and... 

Transition metals and their compounds are used as catalysts. Catalysts you may already know are Iron In the Haber process (Industrial production of ammonia) platinum in the Ostwald process (Industrial production of nitric acid) and platinum, rhodium and palladium In catalytic converters. 

Ruthenium is derived from platinum metal ores. Method of production depends on the type of ore. However, the extraction processes are simdar to those of other nohle metals (see Platinum, Rhodium and Iridium). Ruthenium, like Rhodium, may he obtained from accumulated anode sludges in electrolytic refining of nickel or copper from certain types of ores. Also, residues from refining nickel by Mond carbonyl process contain ruthenium and other precious metals at very low concentrations. The extraction processes are very lengthy, involving smelting with suitable fluxes and acid treatments. 

Garcia JRV, Goto T (2003) Chemical vapor deposition of iridium, platinum, rhodium and palladium. Materials Transactions 44(9), 1717-1728... 

Transition metal catalyzed reactions are becoming commonplace in synthetic chemistry. Heterogeneous or homogeneous catalysts containing valuable metals such as palladium, platinum, rhodium and ruthenium are frequently used in the manufacture of active pharmaceutical ingredients (API).[1] The use of such catalysts can lead to metal contamination of the product. The amount of precious... 

It has been suggested (162) that there exists only negligible 7r-backbonding in [AuCl(CO>], and a number of displacement reactions have been described (162, 163). Vibrational and NMR spectroscopic studies have been made of this complex (164), and the results have been compared with those for carbonyl complexes of palladium, platinum, rhodium, and iridium. 

M. Moldovan, M. M. Gsmez, M. A. Palacios, Determination of platinum, rhodium and palladium in car exhaust fumes, J. Anal. Atom. Spectrom., 8 (1999), 1163D1169. 

Rylander and Rakoncza compared the rates of hydrogenation of pyridine V-oxide over 5% palladium-, platinum-, rhodium-, and ruthenium-on-carbon in methanol, water, and acetic acid.224 Rhodium was always the most active, although the pyridine ring was hydrogenated concomitantly with the reduction of the V-oxide group. 

Over platinum metals such as platinum, rhodium, and ruthenium, aromatic compounds can be hydrogenated even at room temperature and a low hydrogen pressure. Adams and Marshall hydrogenated various aromatic hydrocarbons with use of the Adams platinum oxide in acetic acid at 25-30°C and 0.2-0.3 MPa H2, although often a long reaction time was required.6 Examples are shown in eqs. 11.5 and 11.6. 

Grishina T. M., Mestcheryakova E. V., Hydrogen adsorption on platinum, rhodium and their alloys at different temperatures. J. Phys. Chem. 60 (1986) pp. 1510-1513 (in Russian). 

Okay. These are the reactions we want to happen, and they do happen somewhat as the byproducts of the engine leave the exhaust. The problem is that they don t happen all that quickly, leaving bad stuff heading out into the atmosphere. That s why we use catalysts that lower the activation energies for these reactions and help them proceed at a rapid rate. A catalytic converter is inserted in the exhaust system of a car so that it receives the bad stuff after it s left the engine. The catalytic converter contains a ceramic core coated with very expensive metals—platinum, rhodium, and palladium—and has two sections. The first section deals with nitrogen oxide and nitric oxide. 

A tellurium-containing borane without carbon atoms in the Te — B cage was obtained from B10H14 and sodium polytelluride. The telluraborane BioHjjTe was used for the preparation of cobalt, iron, platinum, rhodium, and iridium complexes, in which the TeBioHjo moiety served as the ligand. 

The deposition of platinum, rhodium and ruthenium acetylacetonates on titania takes place by reaction with the surface hydroxy groups to give a supported complex. Thermal decomposition of these supported complexes in vacuum gave highly dispersed titania supported metal catalysts having metal particles about 2 nm in diameter. ... 

The application of confocal Raman microscopy to surface Raman has led to some promising results for transition-metal surfaces that yield weak or negligible field enhancement. High-performance CCD detection provided high SNR, and the confocal sampling reduced the background from the solution or gas over the surface (22, 23). Metals such as platinum, rhodium, and ruthenium... 

Thus, it was assumed that the formation of acetaldehyde observed by the Consortium is based on eq. (2), and it was found to occur almost stoichio-metrically [1,6]. Other palladium salts, such as the sulfate, nitrate, acetate, etc., react similarly even salts of other noble metals such as platinum, rhodium, and ruthenium give acetaldehyde in the same way but at a distinctly reduced rate. 

Supported platinum, rhodium, and ruthenium complex catalysts have been used extensively in the reaction of trisubstituted silanes with acetylene in the gas phase, predominantly in a continuous-flow apparatus. Formation of a polymer layer on the surface after immobilization of the platinum complex has protected the catalyst against leaching in long-term hydrosilylation tests [91]. 

Wilke, T., Gao, X., Takoudis, C.G., and Weaver, M.J. (1991) Surface-enhanced Raman spectroscopy as a probe of adsorption at transition metal-high-pressure gas interfaces NO, CO, and oxygen on platinum-, rhodium-, and ruthenium-coated gold. Langmuir, 7, 714-721. 

For calorimetry performed at medium and high temperatures, thermocouples are used most frequently. For example, they are made of iron and constantan for medium temperatures or of platinum, rhodium, and iridium for high temperatures. Very frequently, a number of thermocouples linked in series in order to obtain a voltage measurable with sufficient precision, are used. 

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