Emission standards, automobile exhaust

Recent automobile exhaust emissions standards are summarized in Table III, and a review of the catalytic systems designed to meet these standards has recently appeared (26). Catalytic converters have been used as a part of emission control systems since 1975. One approach has been to use a dual bed catalytic converter where the reduction of NO to N2 occurs over the first bed, and excess O2 is provided to the second bed to oxidize the CO and hydrocarbons more completely. Typically, the exhaust contains compounds listed in Table IV plus some poisons containing Pb, P, S etc, (27). The catalytic system must reduce concentrations of CO, hydrocarbon and NOx to legally acceptable levels. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

In the United States, federal regulations require automobile manufacturers to certify that vehicles are ia compliance with exhaust emission standards when tested under specific test procedures. 

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. 

Congress attempted to correct that deficiency and other air pollution problems in a series of amendments to the 1963 act passed in 1965, 1966, 1967, and 1969. The 1965 amendments, for example, authorized the secretary of health, education and welfare to establish nationwide standards for automobile exhaust emissions. This legislation and later amendments also authorized the surgeon general to study the effects of air pollutants on human health, expanded local air quality programs, set compliance deadlines for meeting new air quality standards, established air quality control regions (AQCRs), and authorized research on low emission fuels and more fuel-efficient automobiles. 

Association des Constructeurs Europeens d Automobiles (ACEA), Future Exhaust Emission Standards of Passenger Cars, AE/71/91/VE/ACEA/2, Brussels, 1991. 

The US Clean Air Act (CAA) of 1970 required that automobile exhaust emissions be regulated to meet new environmental standards. From 1975 all new models were to be fitted with catalytic combustion converters to reduce levels of carbon monoxide and unbumt hydrocarbons in the exhaust. This led to the phase-out of lead additives in gasoline between 1973 and 1996. To compensate for the loss of octane rating of the gasoline more reformate and alkylate needed to be added. Octane catalysts were also developed for FCC units and the aromat-... 

Shape-selective reactions have been extensively studied since zeohtes were first used in catalytic crackers during 1967" and Mobil has introduced several octane-boosting processes since 1968. ° Gasoline composition and octane number were reviewed when the Clean Air Act was passed in 1970. This mandated the phased removal of tetraethyl lead from gasoline as catalytic converters (see Chapter 11) were introduced to treat automobile exhaust gas. Octane boosting was the first in a series of measures that led to reformulated gasoline and improved exhaust emissions standards. 

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. 

C05-0080. California s automobile emission standards require that exhaust gases contain less than 220 parts per million hydrocarbons and less than 1.2% CO (both of these values are in moles per mole of air). At standard atmospheric pressure, what are the partial pressures, in torr and in atmospheres, that correspond to these values ... 

Another typical example of the use of the katherometer in the analysis of gas mixtures is afforded by the separation of the components of the Scott gas mixture 237. This is a standard mixture which consists of a mixture of oxygen, carbon monoxide, methane, and carbon dioxide in an excess of nitrogen. The sample is a typical mixture of gases that are liable to be found in automobile exhaust fumes and is used to test emission analyzing equipment and gas analyses apparatus. An example of such a separation carried out on a proprietary packing at 25°C is shown in figure 5. 

Automobiles are the primary source of air pollution in many parts of the world. The Clean Air Act was enacted in 1968 to address the issue of smog and other forms of pollution caused by automobile exhaust. This act has been amended to set new, more restrictive emission-control standards for automobiles driven in the United States. Table 2 lists the standards for pollutants in exhaust set in 1996 by the U.S. Environmental Protection Agency. 

Photochemical smog also contains unbumed hydrocarbons and carbon monoxide, both of which come from the exhaust of automobile engines. These pollutants can be reduced or eliminated from the atmosphere in a variety of ways. Cleaner running engines and catalytic converters greatly reduce NO and hydrocarbon levels. Strict federal tailpipe emission standards are encouraging automobile manufacturers to develop new cars that are powered by electricity or alternative fuels such as natural gas. 

The absorption of infrared radiation (1 to 1,000 micrometers, or 0.0000394 to 0.0394 inches) causes bonds in molecules to vibrate. A bond in the molecule must undergo a change in the dipole moment when the infrared radiation is absorbed. The stiffer the bond, the more energy is required to cause the bond to stretch. Therefore the frequency required to cause C-N, C=N, and C N bonds to stretch increases from left to right. Often the infrared spectrum is considered to be a fingerprint of the molecule. Matching a sample s spectrum with a standard spectrum can positively identify the sample. This technique is used to measure emissions in automobile exhaust. 

The Clean Air Act Amendments of 1970, which followed the original Clean Air Act of 1967, set national air quality standards for six criteria air pollutants NOx, SOx, ozone, carbon monoxide (CO), particulates and lead. The result was the removal of lead from gasoline and the installation of emission control technologies, including baghouse filters for particulate control, wet and dry scrubbers for SOx control and automobile exhaust catalysts for controlling hydrocarbons (HC), CO and NOx. As a consequence, lead emissions have been dramatically reduced, SOx emissions are being controlled, and automobile CO, HC and NOx emissions have decreased by nearly a factor of 10 (over uncontrolled emissions). In spite of these dramatic improvements, in 1989 approximately 130 million people in the U.S. lived in 96 areas which did not meet air quality standards either in ozone, in carbon monoxide, or in both [2]. 

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