Effect of SO2 on Catalytic Activity

A closer examination of OSC and the effect of sulfur on OSC suggests that these are actually more complex phenomena. If the role of ceria were simply to store and release oxygen, it should be possible to determine OSC simply by titration with CO and Oj. However, there is strong evidence that simple titration methods do not properly measure OSC. For example, Hepburn, et al. reported that the CO/O2 titration method was unable to differentiate between catalysts which displayed greatly different transient performances on a vehicle. [16]. 

we only show two pulses of O2 (m/e=32) and CO (m/e=28) from a long string of essentially identical, alternating pulses. A complete discussion of this data is given in the original reference however, simple observation indicates that much more CO2 (m/e=44) is formed upon the introduction of CO at 1500 sec on the SO2-poisoned catalyst compared to the unpoisoned catalyst. In this example, approximately 1000 pmol/g of oxygen could be removed from the poisoned catalyst compared to only 700 pmol/g on the unpoisoned catalyst. This increased, reversible oxygen uptake on the S02-poisoned catalyst is due to oxidation and reduction of 

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