Catalytic convertors

The exceptional properties of the alloy are due in no small way to the yttrium component which together with the aluminium forms a stable and firmly bound oxide layer that exhibits excellent resistance to exhaust gas emissions at high temperatures over prolonged periods.( ) At the same time, it provides an ideal surface to receive another coating of metal or metal oxide which, in the context of catalyst applications, is most essential. At the present time most catalytic convertors utilise ceramic substrates which are prone to damage by both mechanical and thermal shock. 

Heinrich, E., Schmidt, G., Kratz, K.L. Determination of platinum-group elements (PGE) from catalytic convertors in soil by means of docimasy and INAA. Fresenius J. Anal. Chem. 354, 883-885 (1996)... 

K.C.Taylor, "Automotive Catalytic Convertors" (Springer, Berlin 1984) and refs.therein... 

It is interesting to compare the mechanism on biographical surfaces, (7.105 with corresponding equation 7.106), which is sucessfully applied in the design of ammonia catalytic convertors with the one recently presented in the textbook on kinetics and catalysis by Chorkendorff and Niemantsverdriet, based on catalytic kinetics over for ideal surfaces... 

The role of transportation sources in the emissions of PAH-POM is not known with accuracy, especially as biologically active POM is concerned. One participating research group cites mobile sources in Scandinavia as contributing 6 to 9% of the total atmospheric PAH, and around 24% in the U.S., although the data base used for the U.S. was not corrected for the use of catalytic convertors. Such estimates should be measured for the local urban environment rather than a national or continental scale which is subject to great variances. 

For some specific processes, the catalyst carrier is shaped as a block with relatively large parallel channels. These are called monoliths or parallel passage catalysts. The channels have diameters of a few millimeters. They are appli particularly in processes where a low pressure drop is essential (e.g., as catalytic convertors for automobile exhausts). 

The primary application for alloy 409 is in the automotive industry as mufflers, catalytic convertors, and tail pipes. It has proven an attractive replacement for carbon steel because it combines economy and good resistance to oxidation and corrosion. 

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