Oxygen adsorption capacity

A comparison between Pt/Ti02 (E) and water treated pure Ti02 (B) indicated that oxygen adsorption capacity of Ti02 increased by 0.93 mol 02/mol Pt upon Pt addition. Although the Pt dispersion of this catalyst is not known, a typical supported Pt catalyst... 

On the contrary, on oxygen-modified metal surfaces where secondary reactions between the adsorbed oxygen and ethylene decomposition products can easily occur, the effect of oxygen on the adsorptive capacity of the... 

The active sites for the oxygen adsorption, which are found on the surface of NiO (250) but not of NiO (200), are to be identified with anionic vacancies because this high heat of adsorption is not caused by the sorption of oxygen on the nickel phase (13). The decrease in the capacity for adsorption of oxygen at 30°C. when the temperature of oxide preparation is increased from 200° to 250°C. is explained by the reduction of surface nickel ions, sites for the adsorption only of oxygen, and the formation of nickel crystallites whose surface atoms may be active towards the adsorption of oxygen at 30°C. Recession of nickel ions below the surface for NiO (250) may also contribute to this decrease. 

We have found that reaction 16.3 can be carried out effectively by some carbides because of their adsorption capacity for oxygen. Reaction 16.3 proceeds rapidly at relatively low temperatures (450-500 K) without CO expulsion into the gas phase. This is important since CO interferes with the NO + 03 reaction. 

It was, in most cases, found that the rate of oxygen adsorption was too fast for measurement at the temperatures of the exchange reactions, and most work was therefore done at temperatures around 120-250°. The saturation coverages at temperatures and pressures typical of the exchange experiments are given in Table I and it is seen that in all cases the coverage is low in terms of the B.E.T. monolayer capacity. 

Fig. 1. Changes in the adsorption activity of ferric oxide after heating in oxygen (curve o) and in nitrogen (curve x). The quantities of ferric oxide required for adsorption of a fixed quantity of the adsorbate are shown on the abscissa. It will be seen that the adsorption capacity of a ferric oxide preparation declines more rapidly if it has been preheated in nitrogen than if it has been heated in oxygen.

Chemical analyses and physical property measurements made on the starting materials and the products of the ammonium fluotitanate reactions are shown in Table 2. The analytical data for the products of the iron ammonium fluoride reaction are shown in Table 3. Following treatment, the various zeolite products contained up to 16.1 wt.% Ti02 in the zeolites treated with ammonium fluotitanate, and up to 16.9 wt.% Fe203 in the zeolites treated with ammonium Iron fluoride. X-ray powder diffraction intensity is decreased in the substituted products, but retention of oxygen and water adsorption capacity indicates that pore volume has been retained. No extraneous peaks due to other crystalline phases were observed in the X-ray powder diffraction patterns of well washed products. 

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