Automobiles palladium

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). 

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. 

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. 

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. 

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. 

By far the most important use of the platinum metals is for catalysis. The largest single use is in automobile catalytic converters. Platinum is the principal catalyst, but catalytic converters also contain rhodium and palladium. These elements also catalyze a wide variety of reactions in the chemical and petroleum industry. For example, platinum metal is the catalyst for ammonia oxidation in the production of nitric acid, as described in Pt gauze, 1200 K... 

The development of new technology for extraction and recycling of palladium has been stimulated by its increasing use in automobile catalysts, which now consume ca. 55% of world production. A range of options for extraction from acidic media and for separation from other PGMs is possible because Pd11 is relatively substitution-labile. This allows cationic exchange, e.g.,... 

Catalytic converters are basically smog control devices on newer automobiles. Catalytic converters have an oxidation catalyst that oxidizes CO and hydrocarbons to CO2 and H2O. It may also have a reduction catalyst that reduces NO to N2. The catalysts involved with these processes are generally platinum or palladium metal operating at relatively high temperature. 

When rhodium is combined with platinum and palladium, the elements together form the internal metals of automobile catalytic converters, which convert hot unburned hydrocarbon exhaust gases to less harmful CO and H O. Similar alloys are used to manufacture high-temperature products such as electric coils for metal refining furnaces and high-temperature spark plugs. 

In an automobile s catalytic converter, CO and hydrocarbons present in the exhaust gases are oxidized. Unfortunately the effectiveness of these units decreases with use. The phenomenon was studied by Summers and Hegedus in /. Catalysis, 51, 185 (1978) by means of an accelerated aging test on a palladium impregnated porous pellet packed bed converter. From the reported data on hydrocarbon conversion shown below, develop an expression to represent the deactivation rate of this catalyst. 

One of the most important apphcations of palladium is to catalyze hydrogenation, dehydrogenation, and petroleum cracking. Such reactions are widely employed in organic syntheses and petroleum refining. Palladium and platinum are installed in catalytic converters in automobiles to cut down the emission of unsaturated hydrocarbon gasses. 

Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable abdity to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald s process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control. 

Oxidation of CO in automobile exhaust Platinum or palladium on alumina... 

These porous solids obviously have very high surface areas, and they lend themselves naturally to service in catalysis. Palladium catalysts supported on alumina aerogels have been used successfully to remove CO and NO from automobile exhausts,13 and a V205/Ti02 aerogel is itself a catalyst for the selective reduction of NO to N2 and water by gaseous ammonia.14... 

A catalytic converter reduces the pollution caused by automobile exhaust by converting such harmful combustion products as NO, CO, and hydrocarbons to harmless N2, 02, and COz. The catalyst is typically platinum, Pt, palladium, Pd, or rhodium, Rd. 

Palladium, as with other members of the platinum group, exhibits catalytic activity for various reactions. One of its best known uses is in conjunction with other platinum metals in the catalytic converters of present-day automobiles. 

Automobile and Hydrocarbon Emissions. The oxidation of carbon monoxide and hydrocarbons is catalyzed by platinum/palladium/rhodium on alumina. If catalyst poisons such as lead and phosphorus are not present, the major problems become initiation of oxidation at low temperature, thermal stability at high temperature, resistance to thermal schock, and a high external surface area catalyst configuration. 

E. Helmers, H. Schwarzer, M. Schuster, Comparison of palladium and platinum in environmental matrices palladium pollution by automobile emission , Environ. Sci. Pollut. Res., 5 (1998), 44D50. 

J. Begerow, L. Dunemann, Internal platinum and palladium exposure of the general population with emphasis on the exposure from automobile exhaust and dental restorative alloys, in F. Zereini, F. Alt (eds), Anthropogenic Platinum-group Element emissions. Their Impact on Man and Environment, Springer, Berlin, 2000, pp. 227 D 236. 

S. Zimmermann, A. von Bohlen, J. Messerschmidt, B. Sures, Accumulation of the precious metals platinum, palladium and rhodium from automobile catalytic converters in Paratenuisentis ambiguus as compared with its E>sh host, Anguilla Anguilla, J. Helminthol., 79(1) (2005), 85 D89. 

Concern about air pollution has led to extensive investigations of catalysts for automobile exhausts. Elements such as lead (a potential poison), palladium and platinum can be determined after dissolution of the catalyst in acids such as aqua regia. Janouskova et al. [55] reported a detection limit of 0.8 ng for platinum in a catalyst using graphite furnace atomisation and 265.9nm. 

The market for gas cleaning is dominated by applications in automobiles and power plants, but it is interesting that in many more fields monoliths are applied, mainly because of their low-pressure drops. Emission control by monoliths is performed in several industrial plants, for example, phthalic anhydride plants (Siidchemie Envicat). A good example in the transport sector is the abatement of ozone that is present in the air fed to the cabins of airplanes. Palladium on ceramic monoliths appears to function well (142). 

Palladium has two primary uses as a catalyst and in making jewelry and specialized alloys. A catalyst is a substance used to speed up a chemical reaction without undergoing any change itself. Palladium catalysts are used in breaking down petroleum to make high quality gasoline and other products. It is also used in the production of some essential chemicals, such as sulfuric acid (H2SO4), which is used in paper and fabric production. The catalytic converters used in automobiles today may also contain a palladium catalyst. A catalytic converter is a device added to a car s exhaust system. It helps the fuel used in the car burn more efficiently. 

In a fuel cell, each electrode is a hollow chamber of porous carbon walls that allow contact between the inner chamber and the electrolyte surrounding it. The walls of the chamber also contain catalysts, such as powdered platinum or palladium, which speed up the reactions. These catalysts are similar to those in an automobile s catalytic converter, which you read about in Chapter 17. The following oxidation half-reaction takes place at the anode. 

FIGURE 18.16 (a) The arrangement of a catalytic converter used to reduce automobile pollution, (b) Cutaway views of several catalytic converters showing different structures for organizing metal catalysts, platinum, palladium, and rhodium on different substrates and supports. A steel-alloy heating element raises the temperature to 400 C in seconds, activating the catalysts and reducing the pollution emitted in the first minutes after the car is started. 

One of the most widely known examples of catalyst poisoning is taken from the automobile industry. Though tetra-ethyl lead has been removed from essentially all gasoline in North America, the ban on leaded gasoline is not worldwide, and leaded and unleaded gasoline is available in many countries. Catalytic converters, which contain precious metals like platinum, palladium, and rhodium, are used to both reduce NO c and oxidize CO and unburned hydrocarbons. Lead irreversibly destroys the catalytic ability of the converter. Concentrations of lead in leaded gasoline are nominally 150mg/L. 

Catalytic converters in automobile exhaust systems were developed to remove some of the carbon monoxide and unburned hydrocarbons from automobile exhaust. A catalyst is any substance that speeds a chemical reaction without being permanendy altered itself Some of the transition metals, such as platinum, palladium, iridium, and rhodium,... 

A.N. Anthemidis, D.G. Themelis, J.A. Stratis, Stopped-flow injection liquid-liquid extraction spectrophotometric determination of palladium in airborne particulate matter and automobile catalysts, Talanta 54 (2001) 37. 

Palladium Airborne particulate matter, automobile catalysts Chloroform UV-Vis 0.007 mg L 1 C-FIA with zone stopping membrane for phase separation [475]... 

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