Catalytic converter standards

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. 

Beginning with the 1975 U.S. automobiles, catalytic converters were added to nearly all models to meet the more restrictive emission standards. Since the lead used in gasoline is a poison to the catalyst used in the converter, a scheduled introduction of unleaded gasoline was also required. The U.S. petroleum industry simultaneously introduced unleaded gasoline into the marketplace. 

Besides cleaner fuels, vehicle makers have developed many emission-reducing technologies—both in cleaner combustion and in catalytic converter technologies—to comply with ever stricter tailpipe emission standards. The U.S. EPA stringent standards proposed in 1999 for model year 2004 vehicles will result in new vehicles emitting less than 1 percent of the VOC and NO, emissions of their 1960s counterparts. 

Reduction of exhaust emissions is being tackled in two ways by engineers, including precombustion and postcombustion technology. One of the most effective methods now being researched and adopted includes use of synthetic fuel made from natural gas. This fuel is crystal clear, and just like water, it has no aromatics, contains no sulfur or heavy metals, and when used with a postcombustion device such as a catalytic converter any remaining NO, or other emissions can be drastically reduced. Estimates currently place the cost of this fuel at 1.50 per gallon, with availability in 2004 to meet the next round of stiff EPA exhaust emission standards. 

In the feed pretreatment section oil and water are removed from the recovered or converted CCI2F2. The reactor type will be a multi-tubular fixed bed reactor because of the exothermic reaction (standard heat of reaction -150 kJ/mol). After the reactor the acids are selectively removed and collected as products of the reaction. In the light removal section the CFCs are condensed and the excess hydrogen is separated and recycled. The product CH2F2 is separated from the waste such as other CFCs produced and unconverted CCI2F2. The waste will be catalytically converted or incinerated. A preliminary process design has shown that such a CFC-destruction process would be both technically and economically feasible. 

To meet the new federal emissions standards, General Motors Corporation decided in 1970 to equip its cars with catalytic converters, which lead inactivates. Other carmakers followed suit, and leaded gasoline became one of the few environmentally unsafe products to be forced out of the market place. Get the lead out replaced put a tiger in your tank as the slogan of the environmental 1970s. Ethyl Corporation officials felt betrayed how could General Motors, the father of tetraethyl lead, sell its share of Ethyl for millions of dollars and then arrange for the product s demise ... 

This review has highlighted the key contributions of modern surface science to the understanding of the kinetics and mechanism of nitrogen oxide reduction catalysis. As discussed above, the conversion of NO has been taken as the standard to represent other NOx, and CO has typically been used as the reducing agent in these studies. The bulk of the work has been carried out on rhodium and palladium surfaces, the most common transition metals used in three-way catalytic converters. 

Even though the usual catalytic converter of the exhaust of the standard drive train is omitted, there are also net increases in the chemical industry. The increased demand is for the expensive coating of the electrode-membrane unit (MEA) and the catalysts needed for gas preparation (reformer). 

In all the cases described above, the sulfonating agent, SO3 gas, is usually prepared on site by burning sulphur to S02, followed by subsequent conversion to S03 using a standard V205 catalytic converter. 

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. 

The converter was tested and benchmarked against other catalytic converters. A test without catalyst was also executed (Figure 4.53). Especially the performance of the electrically heated converter is up to six times more efficient than that of a standard converter of a monolithic structure. 

As prescribed by the European Directive 94/12/EEC, the US EPA 1970 Clean Air Act, and other legal provisions, by the year 2000 pre-established emission standards must be complied with for all new cars. Cars registered as from 1993 are Ftted with catalytic converters for treating exhaust gases and thus signibcantly... 

Environmental Protection Agency without any modifications or accessories.32 However, concerns over cancer from Diesel exhaust have made the issue quite complicated in recent years, but those concerns are only for long-term effects. In any event, Diesels have always produced far less than 1%/vol. carbon monoxide, which is still the CO standard for all internal combustion engines. Gasoline engines have only met the same standard after many years of intensive research and the addition of many engine modifications and complex accessories including catalytic converters. 

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