The Single Stone-Monolith Substrate as a Catalytic Unit for Auto Emission Control

Temperature requirements of 1800-2000 F impose a near-ceramic approach to the application catalysts for auto emission control, and the unit structure or monolith substrate is discussed in terms of its specific requirements. Surface modification to include high-surface-area coatings for optimum dispersion of active components is of primary consideration. In addition, progress is reported on some of the approaches to the problem of blending normal catalyst properties for low-temperature activity with the ceramic requirements and high-temperature exposure.

Performance data from laboratory experiments and FTP-CVS evaluation tests are discussed in relation to contact time, material transport, geometric configuration, and aging.

Physical durability, which is influenced by inherent structural properties of the monolith, must be capable of coping with extreme demands created by the continuously changing conditions within the catalytic unit. The status of some of the problems and their implications are reviewed.