Purification, exhaust gas

H. Christensen, J. Dinesen, H.H. Engell, and K.K. Hansen, Electrochemical Reactor for Exhaust Gas Purification, SAE paper 1999-01-0472, Diesel Exhaust Aftertreatment (SP-1414)225-229 (1999). 

Diesel and gasoline exhaust gas purification has drawn increasing attention. Catalyst materials containing different noble metals, such as Pd, Pt, and Rh,... 

During the last three years, thirty patents have been published describing the use of rare earths in exhaust gas purification. In the event that all automotive catalysts in the USA were to contain 1% rare earth oxide, the market volume would be approximately 100 tons/year. It is probable that where Ce02 is used, the level will be between 1% and 10% in the catalyst. 

Keywords hydroxylamine phosphate, acetone, large scale, exhaust gas purification, flow system, gas-solid reaction, acetone oxime... 

Apart from the quantitative synthesis of 4, this experiment simulated an exhaust gas purification down to zero emission. 

Structured catalysts are also essential in diesel exhaust gas purification. State-of-the-art solutions are marketed by PSA and by Johnson Matthey. The truck market is dominated by diesel engines. In that application, space requirement is a major issue, and intensification is badly needed. Space velocities exceeding 100,000 h 1 arc demanded. Reactive structured filters are the way to go. 

In automobile exhaust gas purification so-called three-way catalysts that are monoliths are the state-of-the-art technology 12,65,134). 

Bioeiltration Ottengraph, S. S. R, Exhaust Gas Purification, in Biotech-nology, vol. 8, Rehn, H. J., and G. Reed, eds., VCH Verlagsgesellschaft, Wein-heim, Germany, 1986 Ottengraph, S. S. R, Biological Elimination of Volatile Xenobiotic Compounds in Biofilters, Bioprocess Eng., 1986, 1 61-69 Smith,... 

Thermal aging, S02 poisoning, and reaction of the active phase with the support are factors that are known to be important in the deactivation of solid catalysts. Noble metals are usually poisoned by lead, whereas base metal oxide catalysts are more susceptible to poisoning by sulfur (88,286-289). Indeed, the deactivation of oxides when used in oxidation or reduction processes and particularly as catalysts for exhaust gas purification has been attributed to a large extent to S02 (14,174,290). In this section, some aspects of the S02 poisoning effect and the nature of the interactions of S02 with perovskite oxides are reviewed. 

The novel class of preceramic paper might offer a versatile and economic approach to process light-weight ceramics with tailored macro- and microscopic porosities for a broad field of applications in transportation (particle filtration, friction sheets in clutches), energy (porous burner, hat exchangers, solar radiation receivers, photovoltaic substrates), and environment (water cleaning, exhaust gas purification, catalytic reactor inserts). 

Both thermal and catalytical exhaust gas purification systems operate at pollutant concentrations >1.5-3 g/Nm autothermally. Since the efficiency of internal heat recovery is 80-90%, no additional energy is required for heating the exhaust gas. Thus both processes are environmentally sound and economical in operation. In Table 10-1 are some working temperatures compared for both processes. Limitations for catalytical processing are the catalyst sensitivity towards poison and overheating. 

Exhaust gas purification, Company booklet, Messer Griesheim GmbH, D-47805 Krefeld, Germany. 

Oxygen sensors for automobiles are utilized for several kinds of the exhaust gas purification system with three-way catalyst and are very important components to control the combustion for the internal combustion engine. 

The oxygen sensors, which are central function systems for the automobile exhaust gas purification system, are only used at the stoichiometric point for the three-way catalyst. In order to improve the fuel economy, it needs the combustion control in the lean burn region. Therefore, the sensor is required to have output controlling at the air/fuel ratio in the lean burn region. 

Guenther J, Konrad B, Krutzsch B, Nolle A, Voigtlaender D, Weibel M, Wenninger G (2002) Exhaust gas purification process and apparatus with internal generation of ammonia for reducing nitrogen oxide. US Patent 6338244 B1 (Jan. 15, 2002)... 

A monolith or parallel passage reactor contains a solid construction with parallel channels, usually with a cross sectional area of a few square mm each. They can be manufactured either by drilling parallel holes in a solid block, or by a ceramic process starting with a pile of layers that look like corrugated cardboard, made of clay, which is then baked. The latter type is used as a carrier for catalysts, and applied where a low gas pressure drop is essential, e.g., in automobile exhaust gas purification. The mass transfer rates in such monoliths can be calculated easily from the equations describing mass (and heat-) transfer in straight tubes, see eqs. (4.24), (4.28) and (4.29). 

Ottengraf SPP (1986) Exhaust gas purification. In Rehm HJ, Reed G (eds) Biotechnology, vol 8. VCH, Weinheim, pp 301-322 Palmer WG, Beaman JR, Walters DM, Creasia DA (1997) Bioavailability of TNT residues in composts of TNT-contaminated soil. J Toxicol Environ Health 51 97-108... 

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