New Developments in Packaging of Ceramic Honeycomb Catalysts 922252

The emissions regulations for the decade of 1990s are not only more stringent but are also required of vehicles other than passenger cars, for example both diesel and gasoline trucks as well as motorcycles. These latter applications involve different operating conditions in terms of space velocities, temperature profiles, and vibrational loads than those typical of passenger cars [1]*. In addition, the performance and durability requirements for these applications call for lower back pressure and longer service life. Furthermore, the space availability and the operating temperature range differ vastly so as to require special packaging designs to meet the durability requirements.

This paper provides new data for ceramic insulating mats, both intumescent and non-intumescent [2,3], and ceramic substrates with thin and thick walls and square and triangular cell geometries [4], which are under development for non-passenger car applications indicated above. In view of either the lower operating temperature, or lower temperature gradient in a truck catalyst than that in a passenger car catalyst, the mechanical durability of catalyst package against engine vibrations, gas pulsations, chassis loads and road shocks becomes more critical than its thermal durability. Accordingly, the packaging design requires greater sophistication in terms of not only the dimensional tolerances but also component properties under operating conditions. Both the fundamentals of packaging design and the recommendations for a durable package are discussed. The design principles are illustrated by two specific applications, one for diesel truck and the other for gasoline truck.