Oxidation steady state multiplicity during

Steady State Multiplicity During CO Oxidation. Rates were measured for various oxygen-rich feed compositions at a fixed feed flow rate of 100 cmVmin. Regions of multiple steady state reaction rates were determined by maintaining feed composition and flow rate constant and varying the reactor temperature in a programmed manner. 

The catalyst has very low activity during warmup until the catalyst temperature attains -200°C. Since the oxidation reactions are exothermic, the catalyst provides heat, which further heats the catalyst and increases the rate. Therefore, the ACC can exhibit multiple steady states, where the catalyst has essentially no activity until a certain temperature where the catalyst ignites. This is described as lightojf, and a good catalyst system has a low lightoff temperature. Lightoff characteristics are sketched in Figure 7-18. 

We have shown above that dissolution rates of multiple oxides can be related to the abundance and speciation of hydrogen and hydroxyl radicals at different metal centers at the surface. Since dissolution of most complex oxides is nonstoichiometric, the identity of these centers varies as a function of time and experimental conditions. The selective removal of some cations from the solid surface creates a reacted layer that is depleted in those elements that dissolve rapidly (i.e, modifying cations during basalt dissolution or sodium, calcium, and aluminum in the case of feldspars). As steady-state dissolution is controlled by the dismantling of these altered layers, it is critical to know their chemical characteristics and to identify the main mechanisms that control their formation. Two important findings obtained via microbeam techniques will be presented here. 

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