Automobile catalytic converters

We consider next perhaps the bet understood catalyzed reaction the oxidation of CO over group VIII metal catalysts. The reaction is an important environmental one since it involves the conversion of CO to CO2 in automobile catalytic converters. The mechanism is straightforward ... 

K. C. Taglot, Automobile Catalytic Converters, Sptinger-Verlag, New York, 1984. 

Beginning with the 1975 U.S. automobiles, catalytic converters were added to nearly all models to meet the more restrictive emission standards. Since the lead used in gasoline is a poison to the catalyst used in the converter, a scheduled introduction of unleaded gasoline was also required. The U.S. petroleum industry simultaneously introduced unleaded gasoline into the marketplace. 

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. 

Steady state models of the automobile catalytic converter have been reported in the literature 138), but only a dynamic model can do justice to the demands of an urban car. The central importance of the transient thermal behavior of the reactor was pointed out by Vardi and Biller, who made a model of the pellet bed without chemical reactions as a onedimensional continuum 139). The gas and the solid are assumed to have different temperatures, with heat transfer between the phases. The equations of heat balance are ... 

Heterogeneous catalysts are the active ingredients in automobile catalytic converters. When combustion occurs in an automobile engine, side reactions generate small amounts of undesired products. Some carbon atoms end up as poisonous CO rather than CO2. Another reaction that takes place at the high temperatures and pressures in automobile engines is the conversion of N2 to NO. Furthermore, the combustion process fails to bum all the hydrocarbons. Hydrocarbons, CO, and NO all are undesirable pollutants that can be removed from exhaust gases... 

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... 

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. 

A heterogeneous catalyst is in a different phase or state of matter than the reactants. Most commonly, the catalyst is a solid and the reactants are liquids or gases. These catalysts provide a surface for the reaction. The reactant on the surface is more reactive than the free molecule. Many times these homogeneous catalysts are finely divided metals. Chemists use an iron catalyst in the Haber process, which converts nitrogen and hydrogen gases into ammonia. The automobile catalytic converter is another example. 

True/False. An automobile catalytic converter is an example of a heterogeneous catalyst. 

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. 

Lanthanum is used for electronic instruments, as a rocket fuel, as a reducing agent, and in automobile catalytic converters. 

The compound cerium oxide (either Ce Oj or CeO ) is used to coat the inside of ovens because it was discovered that food cannot stick to oven walls that are coated with cerium oxide. Cerium compounds are used as electrodes in high-intensity lamps and film projectors used by the motion picture industry. Cerium is also used in the manufacturing and polishing of high-refraction lenses for cameras and telescopes and in the manufacture of incandescent lantern mantles. It additionally acts as a chemical reagent, a misch metal, and a chemical catalyst. Cerium halides are an important component of the textile and photographic industries, as an additive to other metals, and in automobile catalytic converters. Cerium is also used as an alloy to make special steel for jet engines, solid-state instruments, and rocket propellants. 

The cordierite extruded monoliths, having 400 square cellsAn, were similar to those used in automobile catalytic converters. However, instead of using an alumina washcoat as in the catalytic converter, these catalyst supports were loaded directly with 12 to 14 wt.% Pt in the same manner as the foam monoliths. Because these extruded monoliths consist of several straight, parallel channels, the flow in these monoliths is laminar (with entrance effects) at the flow rates studied. 

Catalysts are of enormous importance, both in the chemical industry and in living organisms. Nearly all industrial processes for the manufacture of essential chemicals use catalysts to favor formation of specific products and to lower reaction temperatures, thus reducing energy costs. In environmental chemistry, catalysts such as nitric oxide play a role in the formation of air pollutants, while other catalysts, such as platinum in automobile catalytic converters, are potent weapons in the battle to control air pollution. 

Another important application of heterogeneous catalysts is in automobile catalytic converters. Despite much work on engine design and fuel composition, automotive exhaust emissions contain air pollutants such as unburned hydrocarbons (CxHy), carbon monoxide, and nitric oxide. Carbon monoxide results from incomplete combustion of hydrocarbon fuels, and nitric oxide is produced when atmospheric nitrogen and oxygen combine at the high temperatures present in an... 

PROBLEM 13.22 A platinum catalyst is used in automobile catalytic converters to hasten the oxidation of carbon monoxide ... 

The transition metals iron and copper have been known since antiquity and have played an important role in the development of civilization. Iron, the main constituent of steel, is still important as a structural material. Worldwide production of steel amounts to some 800 million tons per year. In newer technologies, other transition elements are useful. For example, the strong, lightweight metal titanium is a major component in modern jet aircraft. Transition metals are also used as heterogeneous catalysts in automobile catalytic converters and in the industrial synthesis of essential chemicals such as sulfuric acid, nitric acid, and ammonia. 

This reaction is a very important process in automobile catalytic converters. 

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] ... 

FIG. 19-18 Monolith catalysts (a) Schematic of an automobile catalytic converter for the three-way removal of CO, hydrocarbons, and NO, (b) Schematic of a diesel trap. (Figs. 7.10 and 9 6 in Heck, Farrauto, and Gulati, Catalytic Air Pollution Control Commercial Technology, Wiley-Interscience, 2002.)... 

Schafer, J., and Puchelt, H. (1998). Platinum-group-metals (PGM) emitted from automobile catalytic converters and their distribution in roadside soils. J. Geochem. Explor. 64, 307—314. 

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. 

A billion cars and coimting, himdreds of millions of them with catalytic converters—this application is a landmark success of catalytic science and technology. Automobile catalytic converters are mostly monoliths— like ceramic honeycombs with porous catalyst layers on their inner wall surfaces. These monoliths are the most widely used structured reactors, the topic addressed by Moulijn, Kreutzer, Nijhuis, and Kapteijn. In contrast to the classical reactors containing discrete particles of catalyst and characterized by random and chaotic behavior, structured reactors are characterized by regular structures and predictable laminar flow. Structured reactors can be designed in full detail up to the local surroimdings of the... 

Supported rhodium is used in many catalytic processes, and rhodium is an active component in the automobile catalytic converter (rhodium catalyzes the reduction of NO to N2, as well as the oxidization of CO to CO2) (1), which explains the large number of investigations of adsorption under UHV (e.g., references cited in Reference (403)). As rhodium surfaces are able to dissociate CO (373-375), CO adsorption may be accompanied by CO dissociation. CO dissociation on rhodium is... 

K. C. Taylor, Automobile catalytic converters. In Catalysis Science and Technologyy Vol. 5 (J.R. Anderson and M. Boudait, eds.). Springer-Verlag, Berlin, 1984. 

K.C. Taylor. Automobile Catalytic Converters. Springer-Verlag, Berlin, 1984, pp. 24-25. 

K C Taylor. Automobile catalytic converters. Catalysis—Science and Technology (J R Anderson and M Boudart, Eds ), Sponger Verlag, Berlin, 1984, p 119... 

Platinum and its alloys are used in jewelry, dentistry, the chemical industry, and the electrical industry. Most automobile catalytic converters contain platinum. Certain platinum compounds that have the cis configuration and can combine with DNA are useful therapeutic agents for many cancers that do not respond readily to conventional chemotherapy (especially testicular, ovarian, bladder, prostate, and thyroid cancers). Testicular cancer, which was once always fatal, now responds to platinum-containing drugs. 

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