Exhaust automotive emission control

Automotive Emission Control Catalysts. Air pollution (qv) problems caused by automotive exhaust emissions have been met in part by automotive emission control catalysts (autocatalysts) containing PGMs. In the United States, all new cars have been requited to have autocatalyst systems since 1975. In 1995, systems were available for control of emissions from both petrol and diesel vehicles (see Exhaust control, automotive). 

Mehrdad Ahmadinejad, Maya R. Desai, Timothy C. Watling and Andrew P.E. York, Simulation of Automotive Emission Control Systems Anke Giithenke, Daniel Chatterjee, Michel Weibel, Bemd Krutzsch, Petr Koci, Milos Marek, Isabella Nova and Enrico Tronconi, Current Status of Modeling Lean Exhaust Gas Aftertreatment Catalysts... 

FIGURE 3.2 Block diagrams of two automotive emission control configurations, (a) Thermal reactor plus EGR. (b) Catalytic exhaust purification. 

Riegel, J., Neumann, H. and Wiedenmann, H.-M. (2002) Exhaust gas sensors for automotive emission control. Solid State Ionics, 152—153, 783-800. 

Since 1975, CATALYSIS has been the only practical way for automotive manufacturers to meet the severe regulation of exhaust gas emission in JAPAN and in the U.S. Similar measures will be applied in Europe in the near future. For numerous economic and technical reasons, automotive emission control catalysts are supported catalysts. This means that the active phase is dispersed on the surface of a catalytically almost inert material. That material is the subject of this investigation. 

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. 

Griffing, M. E., Maler, A. R., Borland, J. E., and Decker, R. R., Applying a New Method for Measuring Benzo(a)pyrene in Vehicle Exhaust to the Study of Fuel Factors, presented at the Symposium on Current Approaches to Automotive Emission Control, American Chemical Society, Los Angeles, CA, March 31, 1971. 

Aromatic Aldehydes and Phenols in the Exhaust from Leaded and Unleaded Fuels," Symposium on Current Approaches to Automotive Emission Control, American Chemical Society,... 

PPS, 40% glass fibre reinforced Automotive head lamps, petrol, oil and hydraulic fluid resistant parts, exhaust gas emissions, control valves, pumps, precision mechanical parts Terminal blocks, connectors, electric motor housings, boxes for electronic components High heat applications High chemical resistance applications... 

Valve plates, pistons, rotors Bearings, washers, piston rings, seals, impellers Pump housings, valves, high-stress structures Automotive head lamps under bonnet parts exposed to oil, petrol, and hydraulic fluids pumps valves precision mechanical parts Automotive head lamps, petrol, oil, hydraulic fluid—resistant parts, exhaust gas, emission control valves, pumps, precision mechanical parts... 

Although perovskite oxides have been proposed as potential TWCs for automotive emissions control, most of the studies up to now are focusing on model reactions, such as those described previously, and only few studies have been devoted on automotive emissions control under simulated or real exhaust conditions. Table 25.6 summarizes such efforts. 

Control of NO emissions from nitric acid and nitration operations is usually achieved by NO2 reduction to N2 and water using natural gas in a catalytic decomposer (123—126) (see Exhaust control, industrial). NO from nitric acid/nitration operations is also controlled by absorption in water to regenerate nitric acid. Modeling of such absorbers and the complexities of the NO —HNO —H2O system have been discussed (127). Other novel control methods have also been investigated (128—129). Vehicular emission control is treated elsewhere (see Exhaust control, automotive). 

Emission Control Catalysts. An appHcation of growing importance for cerium is as one of the catalyticaHy active components used to remove pollutants from vehicle (autoexhaust) emissions (36). The active form of cerium is the oxide that can be formed in situ by calciaation of a soluble salt such as nitrate or by deposition of slurried oxide (see Exhaust control, automotive). 

Motor vehicle emissions catalysis for, 24 57-125 see also Exhaust gases, automotive Federal control requirements, 24 60, 61 MP2 method, 42 135 MS, see Multiple scattering MSD... 

Recent emission control system development in the automotive industry has been directed mainly towards the use of three-way or dual bed catalytic converters, This type of converter system not only oxidizes the hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas but will also reduce the nitrous oxides (NO ). An integral part of this type of system is the exhaust oxygen sensor which is used to provide feedback for closed loop control of the air-fuel ratio. This is necessary since this type of catalytic converter system operates efficiently only when the composition of the exhaust gas is very near the stoichiometric point. 

Pt-Rh/AROs catalysts are widely used in automotive-exhaust emission control. In these systems, Pt is generally used for the oxidation of CO and hydrocarbons and Rh is active for the reduction of nitric oxide to N2. HRTEM and AEM show two discrete particle morphologies and Pt-Rh alloy particles (Lakis et al 1995). EM studies aimed at understanding the factors leading to deactivation, surface segregation of one metal over the other and SMSI are limited. There are great opportunities for EM studies, in particular, of surface enrichment, and defects and dislocations in the complex alloy catalysts as sites for SMSI. 

One of the major uses of activated carbon is in the recovery of solvents from industrial process effluents. Dry cleaning, paints, adhesives, polymer manufacturing, and printing are some examples. Since, as a result of the highly volatile character of many solvents, they cannot be emitted directly into the atmosphere. Typical solvents recovered by active carbon are acetone, benzene, ethanol, ethyl ether, pentane, methylene chloride, tetrahydrofuran, toluene, xylene, chlorinated hydrocarbons, and other aromatic compounds [78], Besides, automotive emissions make a large contribution to urban and global air pollution. Some VOCs and other air contaminants are emitted by automobiles through the exhaust system and also by the fuel system, and activated carbons are used to control these emissions [77,78],... 

A major engineering textbook from 1998, which should contain just about everything one needs to know about Diesel emissions, is entitled Handbook of Air Pollution from Internal Combustion Engines with the subtitle Pollutant Formation and Control. The book is co-authored by a dozen of the world s leading experts on automotive emissions. It should be an excellent source of information on precisely how one might kill people with Diesel exhaust. But in the entire 550 page book, which is rather typical of all other hooks one can find on this subject, there was only one sentence relevant to our subject.65... 

Exhaust gas catalysts has been widely used since the laimching of the 1970 Clean Air Act in the USA and especially after the introduction of stricter regulations in 1981. At present, one of the fastest growing areas of catalyst-based technology is automotive pollution control. All gasoline-fuelled vehicles sold in the USA, Japan and in the European Community must be equipped with exhaust aftertreatment in order to meet the emission standards. Oxidation catalysts for heavy-duty vehicles have only been used for a short period, but following the tightening emission standards there will be an increased demand for such systems. 

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