Automobiles pollution control

R. Impens, in A. Crucq and A. Frennet, eds.. Catalysis and Automobile Pollution Control, Elsevier, Amsterdam, the Netherlands, 1987, pp 11—30. 

J. Dettling, Z. Hu, Y. Lui, R. Smaling, C. Wan, and A. Punke, in Proceedings of CAPoCg, Third International Congress on Catalyst and Automobile Pollution Control, Brussels, Belgium, April 20—22, 1994. 

Air Pollution Control Device Meehanism or equipment that eleans emissions generated by a source (e.g., an incinerator, industrial smokestack or an automobile exhaust system) by removing pollutants that would otherwise be released to the atmosphere. 

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. 

With the advance of three-way catalysis for pollution control, used mainly in automobile catalytic conversion but also for the purification of gas exhausts from stationary sources, a need has arisen to develop a basic understanding of the reactions associated with the reduction of nitrogen oxides on transition metal catalytic surfaces [1,2]. That conversion is typically carried out by using rhodium-based catalysts [3], which makes the process quite expensive. Consequently, extensive effort has been placed on trying to minimize the amount of the metal needed and/or to replace it with an alternatively cheaper and more durable active phase. However, there is still ample room for improvement in this direction. By building a molecular-level picture of theprocesses involved,... 

Research dating back to the mid 1950 s has shown that volatile orgamc compounds (VOC s) photochemically react m the atmosphere and contribute to the formation of ground level ozone, a precursor to smog [1]. Medical studies have shown that human exposure to ozone can result in eye and smus tract irritation, and can lead to respiratory related illnesses [2]. Due to the unique and severe smog problems that affected many cities in the state of California, studies of the causes of ah pollution were initiated m the 1950 s [3]. Based on its findings, California formed the Motor Vehicle Pollution Control Board m 1960 to regulate pollution from automobiles. 

Clean Air Act (CAA) was first passed in 1955 as the Air Pollution Control, Research and Technical Assistance Act and amended in 1963 to become the CAA. A more significant statute was passed in 1970 and amended in 1977 and 1990. It provides EPA authority to regulate air pollutants from a wide variety of sources including automobiles, electric power plants, chemical plants, and other industrial sources. 

The oxidation of CO by Oj over group VIII metal catalysts has been the subject of a large body of ultrahigh vacuum surface science and high pressure catalysis work due to its importance in pollution control. Currently, the removal of CO as CO2 from automobile exhaust is accomplished by catalytic converters which employ a supported Pt, Pd, and Rh catalyst. The importance of CO oxidation has led to numerous recent studies of the kinetics of this reaction on supported metal catalysts and transient kinetic studies on polycrystalline foils , which have sought to identify and quantify the parameters of the elementary mechanistic steps in CO oxidation. 

Doyle, G. J., and J. L. Jones. Automobile exhaust-gas aerosols A review of studies conducted at Stanford Research Institute. J. Air Pollut. Control Assoc. 13 365-367, 387, 1%3. 

National Academy of Scknces. National Academy of gineering. Coordinating Committee on Air Quality Studies. Air Quality and Automobile Emission Control. Vol. 2. Health Effects of Air Pollutants. U.S. Senate Committee Print Serial No. 93-24. Washington, D.C. U.S. Government Printing Office, 1974. 511 pp. 

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. 

One place this problem has become especially severe is the nation s national park system. Visitors to national parks have found their enjoyment of the natural scenery compromised by poor air quality that leaves famous and noteworthy features only barely visible. For this reason, one section of the 1977 Amendments to the Clean Air Act provided for a program of monitoring and pollution control in the nation s 156 national parks and wilderness areas. Poor visibility resulting from high particulate concentration has safety effects also. Automobile drivers and airline pilots may find that they are able to see shorter distances and less clearly, increasing the likelihood of accidents involving other vehicles and aircraft. 

Chemical prqperties are also used in the largest field of application for the rare earth elements as catalysts. Most important are the cracking catalysts for the petroleum industry. The rare earth elements are combined into molecular sieves (Y-Zeolite) and serve in fluid bed or fixed bed reactors to increase the yield of gasoline. In addition thereto, there are the combustion catalysts for automobiles and for air pollution control. 

Haagen-Smit, A. J., and M. M. Fox, Photochemical Ozone Formation with Hydrocarbons and Automobile Exhaust, J. Air Pollut. Control Assoc., 4, 105-108, 136 (1954). 

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.)... 

Black FM, High LE, Lang JM. 1980. Composition of automobile evaporative and tailpipe hydrocarbon emissions. J Air Pollut Control Assoc 30 1216-1221. 

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. 

In areas where photochemical air pollution is a serious problem, the olefins and other more reactive hydrocarbons are major concerns rather than just with the total organic emissions. Using factors mainly derived by the Bay Area Air Pollution Control District in San Francisco (5), the total emissions of organic materials have been broken down to give an estimate of the reactive hydrocarbon emissions. About one-third, or about 27 X 10 tons, are considered reactive out of the 88 X 10 total tons of organic materials over half of the estimated reactive emissions result from automobile emissions. 

---