Early Observations of Catalyst Poisoning

It is advisable to consider only briefly the deactivation of automotive catalysts by lead, as observed in early attempts of the implementation of catalytic converters on automobiles. These observations are summarized adequately in the earlier reviews (5-5). In particular Table 5 of the review by Yolles and Wise (4) shows that researchers engaged in the development of automotive catalysts before the middle 1960s did not contemplate 

It should be stressed that the early catalyst development was motivated by the 1964 California standards which stipulated, by today s yardstick, a rather mild removal of hydrocarbons to be fulfilled for 12,000 miles of vehicle operation only. This task was met by the use of large beds of catalysts, which were roughly, by an order of magnitude, larger than present-day catalysts. The large beds provided a reserve of activity as the lead deposits successively deactivated zones of the catalyst beginning at the bed inlet. 

Examination of the spent pellets from these early catalyst beds showed already then the deleterious effect of lead on the surface (17,18), the covering of the pellet exterior by impervious lead containing layers (14), the interaction of lead with base metal active components (14), etc., as the causes of activity decrease. 

A companion paper of Su and Weaver (20) presents the results of detailed postmortem examinations of the catalysts, including X-ray 

Already these early results have shown the incompatibility of heavily leaded gasolines with catalysts designed to achieve a rather moderate goal of automotive emission control. The added stringent requirements of the 

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