Oxygen storage studies

Bunluesin, T., Gorte, R.J., and Graham, G.W. 1998. Studies of the water-gas-shift reaction on ceria-supported Pt, Pd, and Rh Implications for oxygen-storage properties. Appl. Catal. B Environ. 15 107-14. 

For some models adsorption or storage is important. For example, oxygen storage is important in a 3-way catalysis, a catalyst may contain a hydrocarbon storage component for improved low-temperature performance, and ammonia storage is important for ammonia SCR (selective catalytic reduction). Clearly, this sort of behaviour needs to be included in the final model. The nature of the measurements depends on the exact system being studied and will be discussed in more detail later. Suffice to say, from measurements at steady state, the heats of adsorption and coefficients of... 

At first sight, scheme (371) does not agree with the results of our adsorption experiments these experiments showed that activated charcoal does not chemisorb CO at 100°C. It should, however, be taken into consideration that the surface of charcoal subjected to activation or even simply after storage in contact with air is covered with chemisorbed oxygen. The studies of the reactions of carbon with C02 and steam (see Section XX) have demonstrated that oxygen chemisorbed on carbon is indistinguishable from chemisorbed carbon monoxide. So it may be reckoned that activated charcoal is already covered with carbon monoxide before the contact with this gas. 

The aim of oxygen susceptibility studies is to accelerate natural oxidation so that its selectivity is maintained. Here natural means occurring under the normal conditions of storage under catalysis of common impurities . Three specific goals can be identified ... 

The CeO CejOs System The redox properties ofceria and ceria-based materials have been studied in great detail because of their oxygen storage and release capacities, which are highly relevant for their application in modem three-way automotive catalysts [6, 7]. Unfortunately, the temperatures used in these studies are usually far lower than those necessary for thermal reduction in inert atmospheres. Therefore, the applicability of these data must be regarded as limited. Some case studies of ceria-based systems in solarthermal cycles are published in the literature [2,4,14] ... 

Since OSC (Oxygen Storage Capacity) was introduced as a way of determining on quantitative basis the capability of ceria-based supports to release oxygen under reducing conditions, and to uptake it under oxidising conditions (359), numerous studies (35,98,160,180,186,203,249,337,341,354.362-367) have included OSC measurements, as a routine way of characterising the redox properties of these catalytic systems. 

Consequently, a better understanding of the oxygen storage process will derive from a better understanding of both oxygen activation and migration on these samples. To tackle theses questions, the study of isotopic exchange reactions has been developed. 

The main use of CcOj and ceria based compounds is in depollution of noxious species from gaseous stream originating either from stationary or mobile source. The majority of studies deals with the application of ceria as an oxygen storage in TWCs and in the development of novel technologies for the treatment of emissions from diesel and spark ignited internal combustion engines [1,2]. 

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