Oxygen pulse

Figure 9. COj (MW=45) and COj (MW=44) response curves for a ethylene -t- oxygen pulse to a continuous acetic acid saturated nitrogen stream after it is passed over the Pd-Au w/KOAc catalyst with different ethylene to oxygen ratios (e.g., 4 to 1).

In the present study the effect of zeolite particle size (micro- vs. nano-particles) and N20 concentrations on ODHP is studied over Fe modified BEA zeolites. The feasibility of periodic reactivation over Fe-BEA catalysts by oxygen pulses for continuous C3H6 production has been also evaluated. 

Effect of Oxygen Pulse on Steam-Reforming Activity... 

The effect of an oxygen pulse on the steam-reforming activity of fresh Pt, Rh, Pt-Rh, and Pt-MoO catalysts was studied both in the... 

EFFECT OF OXYGEN PULSE ON STEAM REFORMING ACTIVITY... 

Fig. 7. The fraction of butadiene and C02 precursosr left adsorbed on a-Fe203 and y-Fe203 as a function of desorption temperature in a butene adsorption experiment. Filled circles are for adsorption-desorption experiments without oxygen, open circles are for those in which the desorption process was interrupted for passage of an oxygen pulse over the catalyst at the indicated temperatures. From Ref. 18, reprinted with permission from Academic Press.

Graham, J.B., R. Dudley, N. Aguilar, and C. Gans (1995). Implications of the late Paleozoic oxygen pulse for physiology and evolution. Nature 375 117-120. 

From the experimental point of view, the OSC is determined by measuring the O2 consumed by the catalyst after reduction under isothermal conditions. This consumption is mostly determined by using the oxygen pulse technique. Re oxidation temperatures ranging from 700 K (354) up to 773 K (359) are typically applied. In accordance with the results reported in Table 4.3, the above quoted range, and even lower temperatures ensure the complete re-oxidation of ceria. The same is true for ceria-containing mixed oxides in which the alio-cation shows a single redox state (Zr", ... 

Table 4.4. Ceria redox state in a series Rh(2.4%yCe02 catalysts roduced al difTerent temperatures. Oxygen consumption data as detetmined by combining Oxygen Pulses at 298 K and TPO-TCD studies. Data taken...

In 1976 Brand et al. [46,64] reported a ratio very near 3 in oxygen pulse experiments with rat liver mitochondria. This result has been supported by data from this laboratory [8,14,47,52,61]. Subsequently, Lehninger et al. [44,65,66] and Azzone et al. [43,56] obtained results that were interpreted to suggest a ratio of 4. 

K.B. Patel, R.L. Willson (1973). Semiquinone free radicals and oxygen. Pulse radiolysis study of one electron transfer equilibria. J. Chem. Soc., Faraday Trans. 1, 69, 814-825. 

Figure 1. Variation of reactant signals in dicyclopentadiene-nitrogen-oxygen pulses at room temperature.

Two basic types of experiments were performed. The first type of experiments are of the multiple-pulse type. In this experiment the catalyst was either first pre-covered with oxygen or carbon monoxide. After this the catalyst was subjected to carbon monoxide pulses or oxygen pulses, respectively. By determining the amount of carbon dioxide produced and the amount of CO or Oj consumed the active surface area of the catalyst can be calculated. 

Figure 6B demonstrated that after the first oxygen pulse three zones with different surface coverages have formed (from left to right) ... 

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