Automobile emission catalysts

Automobile Automobilebumpers Automobile catalysts Automobile emissions Automobile finishes Automobile gasolines Automobiles... 

For the noble metals used in oxidation, the loading is about 0.1 oz per car, with calls for a million ounces per year. The current world production rates of platinum, palladium, and rhodium are 1.9, 1.6, and 0.076 million ounces respectively the current U,S. demand for platinum, palladium, rhodium, and ruthenium are 0.52, 0.72, 0.045, and 0.017 million ounces respectively (72, 73). The supply problem would double if NO reduction requires an equal amount of noble metal. Pollution conscious Japan has adopted a set of automobile emission rules that are the same as the U.S., and Western Europe may follow this creates a demand for new car catalysts approaching the U.S. total. The bulk of world production and potential new mines are in the Soviet Union and South Africa. The importation of these metals, assuming the current price of platinum at 155/oz and palladium at 78/oz, would pose a balance of payment problem. The recovery of platinum contained in spent catalysts delivered to the door of precious metal refiners should be above 95% the value of platinum in spent catalysts is greater than the value of lead in old batteries, and should provide a sufficient incentive for scavengers. 

Catalyst in fuel cells and automobile emission control. 

In the USA, the Clean Air Act of 1970 established air-quality standards for six major pollutants particulate matter, sulfur oxides, carbon monoxide, nitrogen oxides, hydrocarbons, and photochemical oxidants. It also set standards for automobile emissions - the major source of carbon monoxide, hydrocarbons, and nitrogen oxides. An overview of the major standards is given in Tab. 10.2. The levels of, for example, the European Union (1996) are easily achieved with the present catalysts. The more challenging standards, up to those for the ultralow emission vehicle, are within reach, but zero-emission will probably only be attainable for a hydrogen-powered vehicle. 

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. 

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. 

If a process feed contains known catalyst poisons, such as lead compounds in the exhaust of automobile emissions, it may be wise to locate the active species more... 

Zereini, F., Skerstupp, B., Alt, F., Helmers, E., and Urban, H. (1994). Geochemical behaviour of platinum group elements (PGE) in particulate emissions by automobile exhaust catalysts Experimental results and environmental investigations. Sci. Total Environ. 206, 137—146. 

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 world s supply of rhodium is in approximate balance with demand with erratic releases onto the world market from Russia being counterbalanced by national and industrial stockpiles. These fluctuations in availability are reflected in the spot price, which fell from US 64 at the millennium to US 17g by 2001. The current price in 2004 is US 26 g. Of the 2002 world production of 19.0 tonnes and recovered scrap from automobile catalysts of 3.1 tonnes, over 80% was used as rhodium alloy catalysts for automobile emission reduction. The rhodium component is vital in controlling NO emissions and looks set to increase in order to meet higher emission control standards. 

Automobile exhaust catalysts typically contain noble metals such as Pt, Pd and Rh with a ceria promoter supported on alumina. Traditionally, the principal function of the Rh is to control emissions of nitrogen oxides (NO ) by reaction with carbon monoxide, although the increasing use of Pd has been proposed. For example, recent X-ray absorption spectroscopy studies of Holies and Davis show that the average oxidation state of Pd was affected by gaseous environment with an average oxidation slate between 0 and +2 for a stoichiometric mixture of NO and CO. Exposure of Pd particles to NO resulted in the formation of chemisorbed oxygen and/or a surface oxide layer. 

Platinum Catalysts in automobile emissions, ohmic contacts, coatings for high-temperature crucibles. Rhenium Crucibles, high-temperature furnace heaters. 

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

Searles Robert Automobile Emissions Control by Catalyst Belgium... 

Noble metal catalysts are highly active for the oxidation of carbon monoxide and therefore widely used in the control of automobile emissions. Numerous recent studies on noble metal-based three-way catalysts have revealed characteristics of good thermal stability and poison resistance(l). Incorporation of rare earth oxides as an additive in automotive catalysts has improved the dispersion and stability of precious metals present in the catalyst as active components(2). Monolith-supported noble-metal catalysts have also been developed(3). However, the disadvantages of noble metal catalysts such as relative scarcity, high cost and requirement of strict air/fuel ratio in three-way function have prompted attention to be focused on the development of non-noble metal alternatives. 

In the US and Japan automobile exhaust catalysts containing the noble metals platinum, palladium and rhodium are being used for the control of carbon monoxide, hydrocarbons, and nitrogen oxides in order to satisfy regulatory emission control requirements and such catalysts will be introduced in Europe in the near future. 

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

Several catalyst samples of tungsten carbide and W,Mo mixed carbides with different Mo/W atom ratios, have been prepared to test their ability to remove carbon monoxide, nitric oxide and propane from a synthetic exhaust gas simulating automobile emissions. Surface characterization of the catalysts has been performed by X-ray photoelectron spectroscopy (XPS) and selective chemisorption of hydrogen and carbon monoxide. Tungsten carbide exhibits good activity for CO and NO conversion, compared to a standard three-way catalyst based on Pt and Rh. However, this W carbide is ineffective in the oxidation of propane. The Mo,W mixed carbides are markedly different having only a very low activity. 

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

T he successful use of platinum monolithic oxidation catalysts to control automobile emissions over many thousands of miles requires an intimate understanding of the many factors which contribute to catalyst degradation. Contamination of the active catalyst by lead and phosphorus compounds present in fuel and lubricating oil is a major factor in catalyst deterioration. 

Although this report and the resultant hearings on this issue held by the Senate Public Works Committee on November 5 and 6, 1973 did not prevent the use of catalysts on 1975 vehicles, it certainly precipitated a considerable budget increase for the EPA unit at Research Triangle Park (RTP) in North Carolina (34), which had "gone public" with this concern, and resulted in the expenditure of many million of dollars by automobile and catalyst manufacturers and unidentified other taxpayers. Early studies were presented at the February 1974 SAE meeting and at a symposium at RTP in April of 1974. Proponents of catalysts pointed out that alternative calculations based on the use of surrogates (CO, Pb), for which emission levels and roadside concentrations were both known. 

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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