Adsorption isotherm of oxygen on silver

Боресков, Г. К.; Lokhova, I. V.; Хасин, А. В.

doi:10.1007/bf02065452

Cited by 14 publications

(9 citation statements)

References 5 publications

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“…No oxygen adsorption on these modified y-alumina layers was found. This conflicts with the literature [29 ], where oxygen adsorption is found on silver .…”

Section: Interaction : Adsorptioncontrasting

confidence: 99%

Gas and surface diffusion in modified γ-alumina systems

Uhlhorn

Keizer

Burggraaf

1989

Journal of Membrane Science

171

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SummaryThe transport of pure gases through a microporous membrane is described. The alumina-based membrane (pores 2 .5-4 nm) is suitable for Knudsen diffusion separation . To improve the separation factor, interaction with and mobility on the pore wall of one of the gases of a mixture is necessary . To introduce surface diffusion of oxygen and hydrogen, a y-alumina membrane was impregnated with silver . If temperature and atmosphere are controlled carefully, finely dispersed silver up to 17% by weight can be introduced . At higher loads and under oxidizing conditions, particle growth occurs. In adsorption experiments, little oxygen adsorption on the silver-modified y-alumina could be detected . This is due to a decrease in accessible surface area of the silver because of particle growth of silver under oxygen . The mobility of hydrogen on the surface was tested by counterdiffusion experiments, of which the theory is given. Hydrogen shows a considerable mobility on the surface at 293 K . At low pressures the flux ratio of hydrogen to nitrogen improved from 3 .8 to 8.8. Magnesia was introduced into the y-alumina membrane to enhance the adsorption and mobility of CO2. It is known that 30% of the CO 2 transport on non-modified yalumina is surface diffusion . The highest achievable magnesia load was 2 .2% by weight . Introduction of magnesia into the y-alumina surface gives more strong base sites and fewer weak base sites . This results in stronger bonding of C0 2 on the surface, but the amount adsorbed is comparable with the amount of C02 adsorbed on non-modified y-alumina . The contribution of surface diffusion to the total transport decreases with the introduction of magnesia, as is shown by counterdiffusion. The more strongly bonded CO 2 is less mobile, resulting in a smaller surface flux .

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“…No oxygen adsorption on these modified y-alumina layers was found. This conflicts with the literature [29 ], where oxygen adsorption is found on silver .…”

Section: Interaction : Adsorptioncontrasting

confidence: 99%

Gas and surface diffusion in modified γ-alumina systems

Uhlhorn

Keizer

Burggraaf

1989

Journal of Membrane Science

171

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“…Table 1 Reaction of ethylene at 333 K with oxygen preadsorbed on a silver film The latter result makes unlikely the idea that the epoxidation has a higher ethylene reaction molecularity than the deep oxidation of the hydrocarbon, which has been proposed to explain the dependence of the selectivity on the ethylene pressure [5]. The assumption that this dependence results from surface modification by intermediate compounds -products of the adsorption and ethylene oxidation-seems to be more likely, Modification of the silver surface by ethylene transformation products is known to cause an inhibition of the deep oxidation process with an insignificant influence on the partial oxidation rate [9,10]. This results in a selectivity increase.…”

Section: Resultsmentioning

confidence: 98%

Reaction of ethylene with oxygen adsorbed on a silver film. Dependence of the selectivity to ethylene oxide on the ethylene pressure

Хасин

1998

React Kinet Catal Lett

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“…The rate of isotopic exchange has been found to correlate with the catalytic activity for a series of catalysts [531] or even to be the same as the rate of ammonia synthesis [521]. Model calculations show that the coverage by N * is high during NH3 synthesis [396].…”

Section: Isotopic Exchangementioning

confidence: 98%

“…The rate of isotopic exchange measured for the gas phase in the presence of a catalyst is the same as the rate of exchange between the gas and chemisorbed N * [482,521], indicating that the isotopic exchange predominantly proceeds on the surface of the catalyst.…”

Section: Isotopic Exchangementioning

confidence: 99%

“…Evidence for N 2 dissociation as the rate limiting step has been derived from a large number of experimental studies, such as measurements of isotopic exchange rates [356,482,521,526,532,667], measurements of the isotopic exchange between NH3 and N* [507,528,668], measurements of the stochiometric number [664] and measurements ofthe rate of dissolution ofN in bulk Fe from N z and from NH3 [423]. Further evidence has been found by the agreement between the rates of N2 chemisorption and NH3 synthesis [669], the agreement between adsorption rates and surface coverages [508], the agreement between the rate of synthesis for NH3 and the coverage by N* [191], by int~rpretation of reaction orders for NH3 synthesis [670,664] and NH3 decomposition [620], by the value of the activation energy [664] and activation entropy [597,668] for NH3 synthesis, and by the agreement between the calculated density of sites and crystallography [664].…”

Section: N Z Dissociation As the Rate Limiting Stepmentioning

confidence: 99%

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