Platinum monoxide

Development of methods related to DFT that can treat this situation accurately is an active area of research where considerable progress is being made. Two representative examples of this kind of work are P. Rinke, A. Qteish, J. Neugebauer, and M. Scheffler, Exciting Prospects for Solids Exact Exchange Based Functional Meet Quasiparticle Energy Calculations, Phys. Stat. Sol. 245 (2008), 929, and J. Uddin, J. E. Peralta, and G. E. Scuseria, Density Functional Theory Study of Bulk Platinum Monoxide, Phys. Rev. B, 71 (2005), 155112. 

Platinum monoxide is used to prepare platinum-based catalysts. 

Platinum monoxide is prepared by thermal decomposition of platinum(ll) hydroxide, Pt(OH)2, under careful heating. 

Platinum monoxide may be obtained as a black precipitate when an alkali hydroxide is added to an aqueous solution of potassium tetrachloroplati-nate(II) (potassium chloroplatinate), K2PtCl4. 

Platinum Dichloride Platinum Dioxide Platinum Hexafluoride Platinum Monoxide Platinum Tetrachloride Plutonium Polonium Potassium Potassium Acetate Potassium Bicarbonate Potassium Bisulfide Potassium Borohydride Potassium Bromate Potassium Bromide Potassium Carbonate... 

For platinum compounds, the nitric/perchloric acid digestion mixture used in NIOSH procedure S-191 was replaced with aqua regia to solubilize platinum metal. Platinum dioxide was solubilized by first heating the compound to >380°C to convert the Pt02 to the aqua regia-soluble forms of platinum metal and platinum monoxide. 

Platinous Oxide, Platinum Monoxide, PtO, is produced2 in the anhydrous condition in the form of superficial blackening when platinum, either in the form of sponge or of thin foil, is heated m dry oxygen at about 450° 0., the product containing as much as 43 per cent, of oxide. 

Hydrated Platinum Monoxide, Pt0.2H20, is obtained in a more or less impure condition by the addition of warm potassium hydroxide solution to platinous chloride.4 The pure hydrated oxide, however, may be obtained8 by boiling a solution of potassium chlor-platinite with the calculated amount of sodium hydroxide solution. The hydrated oxide separates out as a dark precipitate, which is readily oxidised by exposure to air, so that it is necessary to wash and dry it in an atmosphere of carbon dioxide. It retains its combined water very tenaciously, and cannot be completely dehydrated without partial decomposition. 

The freshly precipitated oxide is soluble in concentrated hydrochloric acid and in sulphurous acid. Concentrated nitric and sulphuric acids also effect its solution, but the dilute acids are practically without action. After drying in an exsiccator, however, hydrated platinum monoxide is insoluble in concentrated sulphuric or nitric acid. It dissolves, however, in concentrated hydrochloric acid. 

Carbonyl Platinum Monoxide, PtO.CO, is presumably obtained when the hydrochloric acid solution of the carbonyl platinum dichloride is stirred into an acidified solution of ammonium acetate.1 The liquid becomes violet in colour, and then deposits a bluish black, flocculent precipitate of what is presumably the carbonyl monoxide. 

PGM catalyst technology can also be appHed to the control of emissions from stationary internal combustion engines and gas turbines. Catalysts have been designed to treat carbon monoxide, unbumed hydrocarbons, and nitrogen oxides in the exhaust, which arise as a result of incomplete combustion. To reduce or prevent the formation of NO in the first place, catalytic combustion technology based on platinum or palladium has been developed, which is particularly suitable for appHcation in gas turbines. Environmental legislation enacted in many parts of the world has promoted, and is expected to continue to promote, the use of PGMs in these appHcations. 

Oxidation. Carbon monoxide can be oxidized without a catalyst or at a controlled rate with a catalyst (eq. 4) (26). Carbon monoxide oxidation proceeds explosively if the gases are mixed stoichiometticaHy and then ignited. Surface burning will continue at temperatures above 1173 K, but the reaction is slow below 923 K without a catalyst. HopcaUte, a mixture of manganese and copper oxides, catalyzes carbon monoxide oxidation at room temperature it was used in gas masks during World War I to destroy low levels of carbon monoxide. Catalysts prepared from platinum and palladium are particularly effective for carbon monoxide oxidation at 323 K and at space velocities of 50 to 10, 000 h . Such catalysts are used in catalytic converters on automobiles (27) (see Exhaust CONTHOL, automotive). 

In one patent (31), a filtered, heated mixture of air, methane, and ammonia ia a volume ratio of 5 1 1 was passed over a 90% platinum—10% rhodium gauze catalyst at 200 kPa (2 atm). The unreacted ammonia was absorbed from the off-gas ia a phosphate solution that was subsequently stripped and refined to 90% ammonia—10% water and recycled to the converter. The yield of hydrogen cyanide from ammonia was about 80%. On the basis of these data, the converter off-gas mol % composition can be estimated nitrogen, 49.9% water, 21.7% hydrogen, 13.5% hydrogen cyanide, 8.1% carbon monoxide, 3.7% carbon dioxide, 0.2% methane, 0.6% and ammonia, 2.3%. 

Transition-metal organometallic catalysts in solution are more effective for hydrogenation than are metals such as platinum. They are used for reactions of carbon monoxide with olefins (hydroformyla-tion) and for some ohgomerizations. They are sometimes immobihzed on polymer supports with phosphine groups. 

Being acidic, fluorocarbon ionomers can tolerate carbon dioxide in the mel and air streams PEFCs, therefore, are compatible with hydrocarbon fuels. However, the platinum catalysts on the fuel and air elec trodes are extremely sensitive to carbon monoxide only a few parts per million are acceptable. Catalysts that are tolerant to carbon monoxide are being explored. Typical polarization curves for PEFCs are shown in Fig. 27-64. 

Copper or glass-lined equipment for carbonyl in the presence of carbon monoxide Most common metals for dry gas. For moist gas use 18 8 stainless steel, PTFE Any common metal Most common metals for dry gas. For moist gas use 18 8 stainless steel Nickel and Monel are preferred. Steel, copper and glass are acceptable at ordinary temperatures Steel for dry gas otherwise use 18 8 stainless steel Nickel, Monel and Inconel. For moist gas tantalum is suitable Most common metals Cast iron and stainless steel <120°C, steel <175°C, Inconel, nickel and platinum <400°C Most common metals... 

H. P. Kaukonen, R. M. Nieminen. Computer simulations studies of the catalytic oxidation of carbon monoxide on platinum metals. J Chem Phys 97 4380- 386, 1989. 

Examples of perfluoroalkyl iodide addition to the triple bond include free radical addition of perfluoropropyl iodide to 1 -heptyne [28] (equation 21), thermal and free radical-initiated addition of lodoperfluoroalkanesulfonyl fluorides to acetylene [29] (equation 22), thermal addition of perfluoropropyl iodide to hexa-fluoro 2 butyne [30] (equation 23), and palladium-catalyzed addition of per-fluorobutyl iodide to phenylacetylene [31] (equation 24) The E isomers predominate in these reactions Photochemical addition of tnfluoromethyl iodide to vinylacetylene gives predominantly the 1 4 adduct by addition to the double bond [32] Platinum catalyzed addition of perfluorooctyl iodide to l-hexyne in the presence of potassium carbonate, carbon monoxide, and ethanol gives ethyl () per fluorooctyl-a-butylpropenoate [JJ] (equation 25)... 

Perhaps the most familiar example of heterogeneous catalysis is the series of reactions that occur in the catalytic converter of an automobile (Figure 11.12). Typically this device contains 1 to 3 g of platinum metal mixed with rhodium. The platinum catalyzes the oxidation of carbon monoxide and unburned hydrocarbons such as benzene, C6H6 ... 

Using a platinum catalyst, this reaction can now be carried out at temperatures as low as 40°C. The hydrogen used must be very pure traces of carbon monoxide can poison the catalyst. 

The most successful class of active ingredient for both oxidation and reduction is that of the noble metals silver, gold, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum and palladium readily oxidize carbon monoxide, all the hydrocarbons except methane, and the partially oxygenated organic compounds such as aldehydes and alcohols. Under reducing conditions, platinum can convert NO to N2 and to NH3. Platinum and palladium are used in small quantities as promoters for less active base metal oxide catalysts. Platinum is also a candidate for simultaneous oxidation and reduction when the oxidant/re-ductant ratio is within 1% of stoichiometry. The other four elements of the platinum family are in short supply. Ruthenium produces the least NH3 concentration in NO reduction in comparison with other catalysts, but it forms volatile toxic oxides. 

A sophisticated quantitative analysis of experimental data was performed by Voltz et al. (96). Their experiment was performed over commercially available platinum catalysts on pellets and monoliths, with temperatures and gaseous compositions simulating exhaust gases. They found that carbon monoxide, propylene, and nitric oxide all exhibit strong poisoning effects on all kinetic rates. Their data can be fitted by equations of the form ... 

Fig. 18. Inhibition effect of carbon monoxide on carbon monoxide conversion at 400°F over platinum. 100 ppm CaH8> 4.5% 02, 100 ppm NO.

Figure 2.2. Thermal desorption spectra of carbon monoxide, measured mass spectrometically at mass 28 (atomic units, a.u.), on a platinum (100) surface upon which potassium has been pre-adsorbed to a surface coverage of 0K.7 Reprinted with permission from Elsevier Science.

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