Catalytic converter for

The development of catalytic converters for combustion of unburned hydrocarbons prohibits a return to lead compounds and henceforth refiners are turning to oxygenated compounds that must be used as a gasoline component therefore, in amounts much greater than those of lead compounds. 

J. Klimstra, Catalytic Converters for Natural Gas Engines—A Measurement and Control Problem, SAE 872165, Society of Automotive Engineers,... 

In tills chapter we consider systems in which a reaction between two gaseous species is carried out in die adsorbed state on die surface of a solid. The products of die reaction will be gaseous, and die solid acts to increase die rate of a reaction which, in die gaseous state only, would be considerably slower, but would normally yield die same products. This effect is known as catalysis and is typified in industty by die role of adsorption in increasing die rate of syndiesis of many organic products, and in die reduction of pollution by die catalytic converter for automobile exliaust. 

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. 

The gas from the sulfur burner (problem 11-4), after reduction of I in a waste-heat boiler, enters a catalytic converter for oxidation of S02 to SO3 in several stages (see Figure 1.4). If the gas enters the converter at 700 K, calculate /so, and the temperature (T/K) of the gas at the end of the first stage, assuming the reaction is adiabatic and equilibrium is attained. Assume P = 1 bar. See Table 11.1 for data. 

Japanese chemists succeeded in obtaining good yields of methane by reaction of H2 with a mixture of carbon monoxide and carbon dioxide, at temperatures as low as 270 °C, by use of a special mixed catalyst containing nickel as the most important metallic constituent. Why is nickel used In the same vein, why is platinum or platinum-rhodium alloy (but not nickel) used in catalytic converters for automobile exhausts (See also Section 17.4.)... 

Catalysts have been used in the chemical industry for hundreds of years and many large-scale industrial processes can only be carried out thanks to the presence of catalysts. However, it is only since the 1970s that catalysis has become familiar to the general public, mainly because of developments in environmental protection, such as the well-known and widely used catalytic converter for automobiles [1]. 

An important requirement of kinetic studies for automotive aftertreatment devices is the capability of performing dynamic reactive experiments. Steady-state tests provide useful information for identification of reaction pathway and stoichiometry, but cannot capture the real operating behavior of catalytic converters for vehicles, which is transient in nature. Indeed, this is so not only because of the continuously changing conditions (temperature, composition, flow rate) of the engine exhausts as extensively addressed in the following sections, the principles of NSRC and SCR applications largely rely on the storage/reaction/release dynamics of NOx and of NH3, respectively. 

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.)... 

Reduction of nitric oxide by carbon monoxide was first reported to occur at low temperature (252-369 K) over gold powder (0.86 m2 g-1) 30 the rate was maximal at 314 K, and nitric oxide inhibited the reaction. This paper also provides an early indication of the activity of gold for the oxidation of carbon monoxide near ambient temperature. Nitric oxide reduction occurs in this way in catalytic converters for the treatment of engine exhaust gases 9... 

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... 

Aluminas are used in various catalytic applications, a-, y-, and -aluminas are all used as support materials, the first one in applications where low surface areas are desired, as in partial oxidation reactions. The latter two, and especially y-alumina, in applications where high surface areas and high thermal and mechanical stability are required. One of the most prominent applications of y-alumina as support is the catalytic converter for pollution control, where an alumina washcoat covers a monolithic support. The washcoat is impregnated with the catalytically active noble metals. Another major application area of high-surface aluminas as support is in the petrochemical industry in hydrotreating plants. Alumina-supported catalysts with Co, Ni, and/or Mo are used for this purpose. Also, all noble metals are available as supported catalysts based on aluminas. Such catalysts are used for hydrogenation reactions or sometimes oxidation reactions. If high... 

Amatayakul, W. and Ramnas, O., Life cycle assessment of a catalytic converter for passenger cars, J. Cleaner Prod., 9, 395-403, 2001. 

Some prominent industrial examples of packed-bed reactors are in ammonia, methanol or vinyl acetate synthesis, and in ethylene, methanol, naphthalene, xylene or SO2 oxidation. In recent years (since the 1975 model year), an important application of packed-bed reactors has been as catalytic converters for pollution control from automotive exhausts. 

L Balling, D Hein, De-NO catalytic converters for vanous types of furnaces and fuels Development, testing, and operation. Proceedings Joint Symposium on Stationary NOj Control, San Francisco, Calif., March 6-9, 1989. 

The standard, when one considers multiphase reactors, has become more complex over the years. Most can be classified as reactions over heterogenous catalysts. The catalytic activity occurs in one phase, the solid phase, while transport of the reactants occurs in a gas or liquid phase, or both. A common example is the catalytic converter for automobile exhaust gas. The key steps for a packed bed reactor are ... 

Reduction of nitric oxide by carbon monoxide is one of the reactions occurring in catalytic converters for the purification of the engine exhaust gases [489] ... 

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