Monolithic catalytic converter

D. W. Wendland and W. R. Matthes, Visualicyation of Automotive Catalytic Converter Internal Flom, SAE 861554,1986 D. W. Wendland, P. L. Sorrell, and J. E. Kreucher, Sources of Monolithic Catalytic Converter Pressure Eoss, SAE 912372, Society of Automotive Engineers, Warrendale, Pa., 1991. 

S. H. Oh and D. L. Van Ostrom, Three Dimensional Modelfor the Analysis of Transient Thermal and Conversional Characteristics of Monolithic Catalytic Converters, SAE 880282, Society of Automotive Engineers, Warrendale, Pa., 1988. 

A lo-cm-diameter 25-cm-long extruded monolith catalytic converter consisting of 2-mm square channels is used to remove pollutants from an automobile. Assuming that there is 1% CO in the exhaust and that the surface reaction rate is infinite with excess O2, calculate the conversion of CO to be expected for the automobile engine described above. 

Figure 1.2.1 Ceramic monolith catalytic converter. Adapted with permission from K. C. laylor. CllfIMTI-X ll. 20 (1990) 551. Copyright 19 -)0. Aniericaii Chemical SiK iety.

K. Zygourakis, Transient operation of monolith catalytic converters A two-dimensional reactor model and the effects of radially nonuniform flow distributions, Chem. Eng. Sci. 44 2075 (1989). 

LC Young and BA Finlayson, Mathematical models of the monolith catalytic converter Part I Development of model and application of orthogonal collocation, AlChE J 22 331 (1976) L C Young and B A Finlayson, Mathematical models of the monolith catalytic converter Part II Application to automobile exhaust, AIChE /. 22 343 (1976). 

S.H. Oh and J.C. Cavendish, Transients of monolithic catalytic converters Response to step changes in feedstream temperature as related to controlling automobile emissions, lEC Prod. Res. Dev. 27 29 (1982). 

A.J.L. Nievergeld, J.H.B.J. Hoebink. and G.B. Marin. The performance of a monolithic catalytic converter of automobile exhaust gas with oscillatory feeding of CO. NO and O A modelling study. Stud. Surf. Sc. Cat. accepted (1995). 

Monolithic catalytic converters continue to receive attention in the literature because of their applications in air pollution control and clean energy production. They differ from packed-bed reactors in their configuration as there are many parallel channels coated with a layer of catalyst. The flow in the channels is typically laminar. Because of its large void fraction, it is expected that the temperature transients will exhibit a significant impact on the performance of the monolith, particularly with respect to thermal stability. 

A fresh and an aged commercial monolithic catalytic converter of the same origin were used for the XRD and CTEM studies. The aged catalyst was derived from an automobile with 60000km mainly under urban conditions. The main characteristics of the examined catalysts were ... 

Schweich D., and Leclerc J.P. Flow, heat and mass transfer in a monolithic catalytic converter. In "Catalysis and Automotive Pollution Control II", A. Cmcq Ed., Studies in surface science and catalysis, Elsevier, p. 437,1991. 

MODELLING THREE-WAY MONOLITHIC CATALYTIC CONVERTER COMPARISON BETWEEN SIMULATION AND EXPERIMENTAL DATA... 

L.C. Young, B.A. Finlayson Mathematical models of the monolith catalytic converter. Parti, development of model and application of the orthogonal collocation, AICliE J., 22, 2, 331-343 (1976). 

D.K.S. Chen, S.H.Oh, E.J. Bisset, D.L. van Ostrom A tliree dimensional model for the analysis of transient thennal and conversion characteristics of monolithic catalytic converters, ... 

THE PERFORMANCE OF A MONOLITHIC CATALYTIC CONVERTER OF AUTOMOBILE EXHAUST GAS WITH OSCILLATORY FEEDING OF CO, NO, AND Oj A MODELLING STUDY... 

Chen D, Bissett E, Oh S, Van Ostrom D (1988) A Three-Dimensional Model for the Analysis of Transient Thermal and Conversion Characteristics of Monolithic Catalytic Converters. 

Nevertheless, secondary measures are mostly still needed to reduce exhaust emissions of cars to meet current emission standard in most countries. These so-called end-of-pipe solutions are based on the catalytic conversion of all HCs, CO and NO (three-way catalyst). The success of the monolithic catalytic converter (which has a lower pressure drop than a fixed bed) is up to now limited to gasoline powered engines. However, in recent years progress has been made in the development of catalytic filters for the cleaning of exhaust gas (e.g., particulate matter) from diesel engines. 

The converter must also preserve the engine efficiency. Presently, monolithic catalytic converters seem to be the most efficient because they operate with a low pressure drop. Depending on the available space under the car, the monolith cross-section can be cylindric, ov or "race-track". The monolith is fitted to the inlet exhaust line by a divergent duct and to the outlet exhaust line by a convergent duct (see Figure 1.2). 

Monolithic catalytic converters are now of wide use on automotives, however their efficiency and their resistance to thermal shocks, poisons, misfiring, etc., must be improved. Beside new catalyst formulations and experimental tests, modeling and understanding of the main physical and chemical processes can help to suggest design improvements. 

Leclerc J.P., D. Schweich, and J. Villermaux (1990) Flow, heat transfer and chemical reaction in race-track monolithic catalytic converters - A theoretical and experimental study , AIChE 1990 spring national meeting, 18-22 mars 1990, Orlando, Floride, USA. 

Oh S.H., and J. Cavendish (1981) Transients of monolithic catalytic converters response to step changes in feedstream temperatures as related to controling automobile emissions , Ind. Eng. Chem. Proc. Des. Devel., 21, 29-37. 

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