Platinum automobile catalysts

Miscellaneous. Chloroplatinic acid is used in the production of automobile catalysts. Platino-type prints based on reduction of Pt(II) to Pt(0) by a photosensitive reducing agent such as iron(III) oxalate are used in art photography (261,262). Infrared imaging devices based on a platinum siLicide detector have been developed (263). 

The main use of rhodium is with platinum in catalysts for oxidation of automobile exhaust emissions. In the chemical industry, it is used in catalysts for the manufacture of ethanoic acid, in hydroformylation of alkenes and the synthesis of nitric acid from ammonia. Many applications of iridium rely on... 

The main uses of palladium [13] are in the electronics and electrical industries, in circuitry and in dental alloys. It finds many catalytic applications in industry, as well as in diffusion cells for the synthesis of hydrogen, and in automobile catalysts. Jewellery and three way auto-catalysts are the principal uses of platinum, which fulfils a wide range of roles in the chemical industry. 

Becker DA (1995) Resolution of discrepant analytical data in the certification of platinum in two automobile catalyst SRMs. Fresenius J Anal Chem 352 224-226. 

Particularly, the formation of C02 by the oxidation of CO over platinum metal catalysts is the reaction that has been studied most extensively in the past years and whose elementary steps appear to be best understood. This reaction is an important process in automobile catalytic converters [92] and its mechanism proceeds as follows [129] ... 

E. Helmers, Elements accompanying platinum emitted from automobile catalysts, Chemosphere, 33 (1996), 883 D 885. 

Helmers, E., Mergel, N. Platinum and rhodium in a polluted environment smdying the emissions of automobile catalysts with emphasis on the application of cathodic-stripping voltammetry (CSV) rhodium analysis. Fresenius J. Anal. Chem. 362, 522-528 (1998)... 

Catalytic converters help break down pollutants that result from gasoline combustion and are required in automobiles in the United States. Most catalytic converters contain a platinum-rhodimn catalyst that coats the extensive surface of a honeycomb structure in the converter. Why would having the catalyst spread out over a large surface area be useful ... 

CEPLACA (2001) Assessment of environmental contamination risk by platinum, rhodium and palladium from automobile catalyst (CEPLACA, ENV4-CT97-0518). Final report. 

Therefore preparation of non-contaminated and well defined particulate material, which resemble Pd particles emitted from automobile catalysts into the environment and which are available in higher standardized quantities, is very reasonable. A comparable approach for platinum was made by Ruehle et al. (1997) focussing on traffic related platinum emissions, but for palladium appropriate material was not yet available. Synthesis of the Pd particles was performed by chemical reduction of Pd° to Pd° in aqueous solutions similar to a method first described by Mucalo et al. (1991). Optimization of this method yielded in a simple, fast and very reproducible preparation method for appropriate Pd nanoparticles with a narrow size distribution. Three types of Pd particles—Pd... 

Palacios MA, Gomez M, Moldovan M, Gomez B (2000) Assessment of environmental contamination risk by Pt, Rh, and Pd from automobile catalyst. Microchem J 67 105-113 Ravindra K, Bencs L, Van Grieken R (2004) Platinum group elements in the environment and their health risk. Sci Total Environ 318 1 3... 

Suies B, Zimmermaim S, Messerschmidt J, von Bohlen A, Alt F (2001) First report on the uptake of automobile catalyst emitted palladium by European eels (Anguilla anguilla) following experimental exposure to road dust. Environ Pollut 113 341-345 Vaughan GT, Elorence TM (1992) Platinum in the human diet, blood, hair and excreta. Sci Total Environ 111 47-58... 

Platinum metals are eventually coming into the focus with the continuing progress of their use in automobile catalysts with potential tendencies for environmental and biological accumulation. " " " This concerns predominantly Pt, Pd and Rh, whereas the remaining elements are used in much minor extent. Available... 

In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. Much interest exists in using platinum as a catalyst in fuel cells and in antipollution devices for automobiles. 

Black nickel oxide is used as an oxygen donor in three-way catalysts containing rhodium, platinum, and palladium (143). Three-way catalysts, used in automobiles, oxidize hydrocarbons and CO, and reduce NO The donor quaUty, ie, the abiUty to provide oxygen for the oxidation, results from the capabihty of nickel oxide to chemisorb oxygen (see Exhaust control, automotive). 

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). 

This reaction takes place similarly in automobile exhaust converters, although the metals in these catalysts are platinum and rhodium, among other components, and other reactions occur. 

Two classes of metals have been examined for potential use as catalytic materials for automobile exhaust control. These consist of some of the transitional base metal series, for instance, cobalt, copper, chromium, nickel, manganese, and vanadium and the precious metal series consisting of platinum [7440-06-4], Pt palladium [7440-05-3], Pd rhodium [7440-16-6], Rh iridium, [7439-88-5], Ir and mthenium [7440-18-8], Ru. Specific catalyst activities are shown in Table 3. 

Platinum compounds Hydrosilation cross-linking of silicone polymers Hydrogenation, isomerization and hydroformylation of alkenes Automobile exhaust catalyst Sensitization dermatitis... 

Automobile catalytic converter. Catalytic converters contain a "three-way" catalyst designed to convart CO to CO2, unbumed hydrocarbons to CO2 and H2O. and NO to N2. The activa components of the catalysts are the precious metals platinum and rhodium palladium is sometimes used as well. 

Serious research in catalytic reduction of automotive exhaust was begun in 1949 by Eugene Houdry, who developed mufflers for fork lift trucks used in confined spaces such as mines and warehouses (18). One of the supports used was the monolith—porcelain rods covered with films of alumina, on which platinum was deposited. California enacted laws in 1959 and 1960 on air quality and motor vehicle emission standards, which would be operative when at least two devices were developed that could meet the requirements. This gave the impetus for a greater effort in automotive catalysis research (19). Catalyst developments and fleet tests involved the partnership of catalyst manufacturers and muffler manufacturers. Three of these teams were certified by the California Motor Vehicle Pollution Control Board in 1964-65 American Cyanamid and Walker, W. R. Grace and Norris-Thermador, and Universal Oil Products and Arvin. At the same time, Detroit announced that engine modifications by lean carburation and secondary air injection enabled them to meet the California standard without the use of catalysts. This then delayed the use of catalysts in automobiles. 

For the noble metals used in oxidation, the loading is about 0.1 oz per car, with calls for a million ounces per year. The current world production rates of platinum, palladium, and rhodium are 1.9, 1.6, and 0.076 million ounces respectively the current U,S. demand for platinum, palladium, rhodium, and ruthenium are 0.52, 0.72, 0.045, and 0.017 million ounces respectively (72, 73). The supply problem would double if NO reduction requires an equal amount of noble metal. Pollution conscious Japan has adopted a set of automobile emission rules that are the same as the U.S., and Western Europe may follow this creates a demand for new car catalysts approaching the U.S. total. The bulk of world production and potential new mines are in the Soviet Union and South Africa. The importation of these metals, assuming the current price of platinum at 155/oz and palladium at 78/oz, would pose a balance of payment problem. The recovery of platinum contained in spent catalysts delivered to the door of precious metal refiners should be above 95% the value of platinum in spent catalysts is greater than the value of lead in old batteries, and should provide a sufficient incentive for scavengers. 

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