Catalytic converter efficiency

The efficiency of the three-way catalytic converter is also a function of air/fuel ratio. At the stoichiometric air/fiiel ratio of 14.7 kilograms of air per kilogram of fuel, the relative air/fuel ratio known as X equals 1.0. Figure 1 illustrates catalytic converter efficiency for each pollutant as a function of relative air/fuel ratio X (where a positive X indicates a lean mixture and a negative X indicates a rich mixture). The closer the mixture stays to stoichiometric, the more efficient the catalyst at reducing the combined emissions of the three pollutants. 

Degradation of Gasoline Engine Catalytic Converter Efficiency... 

Fuel sulfur and phosphorus have been identified in contributing to problems with catalytic converter efficiency. Fuel sulfur does poison converter catalysts, but not as severely as lead. 

Sulfur and phosphorus can degrade catalytic converter efficiency. 

Another even more significant use of methyl alcohol can be as a fuel in its own right in fuel cells. In recent years, in cooperation with Caltech s Jet Propulsion Laboratory (JPL), we have developed an efficient new type of fuel cell that uses methyl alcohol directly to produce electricity without the need to first catalytically convert it to produce hydrogen. 

M ass Transfer. Exhaust gas catalytic treatment depends on the efficient contact of the exhaust gas and the catalyst. During the initial seconds after start of the engine, hot gases from the exhaust valve of the engine pass through the exhaust manifold and encounter the catalytic converter. Turbulent flow conditions (Reynolds numbers above 2000) exist in response to the exhaust stroke of each cylinder (about 6 to 25 times per second) times the number of cylinders. However, laminar flow conditions are reached a short (- 0.6 cm) distance after entering the cell passages of the honeycomb (5,49—52). 

The performance of the catalytic converter is affected by the conditions of air/fuel control provided by the fuel metering system. A slowly responding fuel metering system can dramatically decrease the conversion efficiency of the converter compared to a fast response multipoint fuel injection system. 

The second method used to reduce exliaust emissions incorporates postcombustion devices in the form of soot and/or ceramic catalytic converters. Some catalysts currently employ zeolite-based hydrocarbon-trapping materials acting as molecular sieves that can adsorb hydrocarbons at low temperatures and release them at high temperatures, when the catalyst operates with higher efficiency. Advances have been made in soot reduction through adoption of soot filters that chemically convert CO and unburned hydrocarbons into harmless CO, and water vapor, while trapping carbon particles in their ceramic honeycomb walls. Both soot filters and diesel catalysts remove more than 80 percent of carbon particulates from the exliatist, and reduce by more than 90 percent emissions of CO and hydrocarbons. 

High levels of sulfur not only form dangerous oxides, but they also tend to poison the catalyst in the catalytic converter. As it flows over the catalyst in the exliaust system, the sulfur decreases conversion efficiency and limits the catalyst s oxygen storage capacity. With the converter working at less than maximum efficiency, the exhaust entering the atmosphere contains increased concentrations, not only of the sulfur oxides but also, of hydrocarbons, nitrogen oxides, carbon monoxides, toxic metals, and particulate matter. 

The strength and interrelation of catalysis, classical promotion and electrochemical promotion is illustrated in Fig. 2.3. The reaction under consideration14 is the reduction of NO by CO in presence of 02. This is a complex reaction system but of great technological importance for the development of efficient catalytic converters able to treat the exhaust gases of lean burn and Diesel engines. 

Air pollution from exhaust emissions NO t and particulate matter from exhaust emissions causing air pollution are -1% at present. By adoption of better combustion control technology, better quality fuels (or even fuel cell-based motor vehicles), and more efficient catalytic converters, researchers aim to mitigate this problem. 

Transportation - production of gasoline and diesel from petroleum, fuel additives for greater efficiency and reduced emissions, catalytic converters, plastics to reduce vehicle weight and improve energy efficiency. 

Recently, it is reported that Xi02 particles with metal deposition on the surface is more active than pure Ti02 for photocatalytic reactions in aqueous solution because the deposited metal provides reduction sites which in turn increase the efficiency of the transport of photogenerated electrons (e ) in the conduction band to the external sjistem, and decrease the recombination with positive hole (h ) in the balance band of Xi02, i.e., less defects acting as the recombination center[l,2,3]. Xhe catalytic converter contains precious metals, mainly platinum less than 1 wt%, partially, Pd, Re, Rh, etc. on cordierite supporter. Xhus, in this study, solutions leached out from wasted catalytic converter of automobile were used for precious metallization source of the catalyst. Xhe XiOa were prepared with two different methods i.e., hydrothermal method and a sol-gel method. Xhe prepared titanium oxide and commercial P-25 catalyst (Deagussa) were metallized with leached solution from wasted catalytic converter or pure H2PtCl6 solution for modification of photocatalysts. Xhey were characterized by UV-DRS, BEX surface area analyzer, and XRD[4]. 

Proceedings of the 4 International Conference on Carbon Dioxide Utilization, Kyoto, Japan, September 7-11, 1997 edited by T. Inui, M.Anpo,K. lzui,S.Yanagida and T.Yam udii Volume 115 Methods for Monitoring and Diagnosing the Efficiency of Catalytic Converters. 

Volume 115 Methods for Monitoring and Diagnosing the Efficiency of Catalytic Converters. 

The control of carbon monoxide emissions is based on the principle that less of the gas is produced when the efficiency of combustion is improved. One device to achieve this objective is the catalytic converter, now required on all motor vehicles sold in the United States. A catalytic converter provides a second stage of combustion in motor vehicles, allowing carbon monoxide and other unburned components of a fuel to be oxidized before release into the atmosphere. (The operation of a catalytic converter is described later in this chapter.)... 

Catalytic converters like the one shown here are highly efficient devices for the conversion of harmful exhaust by-products formed during the combustion of gasoline, diesel oil, and other fuels. (Sheila Terry/Photo Researchers, Inc.)... 

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. 

Because of this type of behavior, a sharp transition at stoichiometry but low sensitivity and temperature effects either rich or lean of this point, the oxygen sensor is most useful in controlling at the stoichiometric point. It is of limited usefulness at other exhaust compositions. However, as shown in Figure 5, this is exactly the point at which a three-way or dual bed catalytic converter is most efficient. Only when the exhaust composition is near the stoichiometric point will both the oxidation of the HC and CO and the reduction of the NO occur satisfactorily. 

For the efficient operation of a catalytic converter placed in a car, it is important to adjust the air-to-fuel ratio... 

The Claus Catalytic Cbnverters. These units represent the heart of any sulfur recovery plant. While the bulk of the sulfur yield may be obtained in the front end reaction furnace the high overall recovery levels demanded by environmental regulations are largely dependent on the efficiency of the Claus catalytic converters. 

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