Automobile Emission Control Catalysts

Cooper, B. J., Renny, L. V., and White, R. J., Lead Poisoning of Automobile Emission Control Catalysts—Influence of Emission System and Catalyst Design Characteristics on the Poisoning Mechanism, Am. Chem. Soc.. Symp. Automot. Catal., Chicago Meet., 1975. 

Rhodium compounds are somewhat toxic and have been used in oncological chemotherapy, but they are less effective than platinum complexes. The expense and rarity of rhodium means that it is rarely a significant pollution hazard, particularly as it is of low inherent toxicity. The occupational exposure limit to dust is lmgm and the LD50 for oral ingestion is 200mgkg for several species. At these levels, rhodium and its compounds exhibit weak carcinogenicity and adverse reproductive effects have been observed. Nevertheless, rhodium dust and water-soluble rhodium compounds are now found at roadsides as a result of erosion of automobile emission control catalysts. 

The trends in the automobile emission standards for the USA and Eitrope since 1966 are given in Table 11.7. Compliance with the standards set has been made possible by the use of automobile emission control catalysts. These were first used in the US during 1975 and in Europe from 1993. As a resirlt of continuous improvement to design and manufacture, the catalysts have been able to conform with the increasing severity of the regulations. 

Catalyst in fuel cells and automobile emission control. 

While the discovery of the catalytic properties of zeolites was driven by the desire to improve industrial prcKessing, the development of emission control catalysts was necessitated by governmental fiat. The first requirement was for 90+% removal of CO and of hydrocarbons, a goal which could not be met by oxidation with base metal oxides. To achieve the required spedfications during automobile operations, it was necessary to develop supported platinum catalysts. Originally the support was alumina in pellet form. Later platinum on cordierite was used in honeycomb form, containing 200-400 square channels per square inch. 

Recently there has been a growing emphasis on the use of transient methods to study the mechanism and kinetics of catalytic reactions (16, 17, 18). These transient studies gained new impetus with the introduction of computer-controlled catalytic converters for automobile emission control (19) in this large-scale catalytic process the composition of the feedstream is oscillated as a result of a feedback control scheme, and the frequency response characteristics of the catalyst appear to play an important role (20). Preliminary studies (e.g., 15) indicate that the transient response of these catalysts is dominated by the relaxation of surface events, and thus it is necessary to use fast-response, surface-sensitive techniques in order to understand the catalyst s behavior under transient conditions. 

AECC - Automobile Emissions Control by Catalyst, Avenue de Tervueren 13 A, 1040 Brussels, Belgium... 

Searles Robert Automobile Emissions Control by Catalyst Belgium... 

DEVELOPMENT OF A COPPER CHROMITE CATALYST FOR CARBON MONOXIDE AUTOMOBILE EMISSION CONTROL... 

Development of a Copper Chromite Catalyst for Carbon Monoxide Automobile Emission Control",... 

Tn the development of oxidative automotive emission control catalysts for use in the 1975 model year, certain requirements were recognized from the beginning. The catalyst had to be physically rugged and capable of withstanding both the mechanical and thermal abuse to which it would be subjected in an automobile driven by average drivers on real roads. The catalyst had to exhibit high levels of activity so that the catalytic units would be of reasonable size. The catalyst had to be stable for at least 50,000 miles and capable of withstanding chemical abuse from the exhausts of the various fuels to which it would be subjected. 

But on a long term basis a major increase of the amount of Pd used in automobile converters might change the price situation completely. Indeed, presently only 9 % of the Pd available to the market is used in automotive emission control catalysts. In case of Pt this share is about 45 %, whereas the world supply of Pt and Pd is in the same order of magnitude, see Figure 2. 

Kummer, J.T. Catalysts for automobile emission control. Prog. Energy Combust. Sci. 1980, 6, 177-199. 

Process Industries Furnaces used for the fabrication of spark plug insulators, catalyst supports for automobile emission control systems, dinnerware, magnetic ceramics, and electrical ceramics are lined with ceramics. Ceramic high-temperature furnace linings and thermal insulation are used in petroleum and chemical processing, cement production, heat treatments, and paper production. 

Emission Control Technologies. The California low emission vehicle (LEV) standards has spawned iavestigations iato new technologies and methods for further reducing automobile exhaust emissions. The target is to reduce emissions, especially HC emissions, which occur during the two minutes after a vehicle has been started (53). It is estimated that 70 to 80% of nonmethane HCs that escape conversion by the catalytic converter do so during this time before the catalyst is fully functional. 

A catalytic oxidation system may cost 150 per car, but the catalyst cost is estimated to be 30, less than 1% of the cost of an automobile (2). In a few years, the gross sale of automotive catalysts in dollars may exceed the combined sale of catalysts to the chemical and petroleum industries (3). On the other hand, if the emission laws are relaxed or if the automotive engineers succeed in developing a more economical and reliable non-catalytic solution to emission control, automotive catalysis may turn out to be a short boom. Automotive catalysis is still in its infancy, with tremendous potential for improvement. The innovations of catalytic scientists and engineers in the future will determine whether catalysis is the long term solution to automotive emissions. 

The catalyst companies were encouraged to resume their research activities in automotive catalysis in the late 1960 s as further tightening of automotive emissions standards became imminent, and it appeared that mere engine modifications might be inadequate to meet the new standards. A systems approach was first used upon the formation of the Inter-Industry Emission Control Program by the Ford Motor Company and the Mobil Oil Corporation in 1967, which was joined by a number of oil companies in the U.S. and a number of automobile companies in Italy, Japan, and Western Germany. 

Examples of multi-disciplinary innovation can also be found in the field of environmental catalysis such as a newly developed catalyst system for exhaust emission control in lean burn automobiles. Japanese workers [17] have successfully merged the disciplines of catalysis, adsorption and process control to develop a so-called NOx-Storage-Reduction (NSR) lean burn emission control system. This NSR catalyst employs barium oxide as an adsorbent which stores NOx as a nitrate under lean burn conditions. The adsorbent is regenerated in a very short fuel rich cycle during which the released NOx is reduced to nitrogen over a conventional three-way catalyst. A process control system ensures for the correct cycle times and minimizes the effect on motor performance. 

Belton, D. N. and Taylor, K. C. (1999) Automobile exhaust emission control by catalysts , Curr. Opin. Solid State. Mater. Sci., 4, 97. 

Since 1962 rare earths have been used to stabilize zeolite cracking catalysts for the petroleum industry (1, 2. Until recently this application to catalysis has been the only commercially significant one. Currently, however, a number of new applications of potential commercial significance are appearing. One of the most important of these is the use of cerium in catalysts for automobile exhaust emission control. We will emphasize this application in our review without neglecting other applications. 

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