ChemInform Abstract: THE ROLE OF PLATINUM OXIDE (PTOX) IN THE ISOTHERMAL RATE OSCILLATIONS OF ETHYLENE OXIDATION ON PLATINUM

Vayenas, C.G.; Georgakis, Christos; Michaels, James N.; Tormo, Jordi

doi:10.1002/chin.198121141

Cited by 5 publications

(15 citation statements)

References 1 publication

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“…Increasing flowrate by a factor of three causes a more than 2-fold increase in rate oscillation frequency (Figure 7), again similarly to the case of C 2 H 4 oxidation on Pt [4,12]. This is because the reactor is operated at constant feed composition, thus increasing flowrate causes a decrease in conversion, thus an increase inP O 2 which enhances the rate of catalyst surface reoxidation [4,12] while as can be seen, e.g. in figure 4, the decomposition of surface Rh 2 O 3 is almost instantaneous.…”

Section: Resultssupporting

confidence: 54%

“…increasing P C 2 H 4 =P O 2 ratio causes a decrease in the period, T p , of the oscillation frequency and a decrease in the amplitude. As shown in figure 3 the frequency, 1/ T p , of the oscillations, increases near linearly with the P C 2 H 4 =P O 2 ratio similarly to the case of C 2 H 4 oxidation on Pt [4,12]. Figure 4 shows the effect of temperature on the rate oscillations induced by constant anodic current application at fixed gaseous composition.…”

Section: Resultsmentioning

confidence: 69%

“…It was found that reaction rate oscillations can be induced by positive current and stopped by negative current application [10,11]. The results were interpreted by the electrochemically controlled backspillover of O 2) promoters to the catalyst surface and the concomitant formation and decomposition of surface PtO 2 [10,12,13].…”

Section: Introductionmentioning

confidence: 98%

“…The oscillatory behaviour of the oxidation of ethylene has been extensively investigated on polycrystalline Pt, Rh and Ag catalysts [4,5,[12][13][14][15]. In several cases [4,5,12,13] the technique of solid electrolyte potentiometry (SEP) was used to continuously monitor the activity of oxygen on the catalyst surface during oscillations.…”

Section: Introductionmentioning

confidence: 99%

“…In several cases [4,5,12,13] the technique of solid electrolyte potentiometry (SEP) was used to continuously monitor the activity of oxygen on the catalyst surface during oscillations. In general, the surface oxygen activity and the rate of CO 2 production were found to oscillate simultaneously and in the opposite direction, i.e., a decrease in the activity of surface oxygen always corresponded to an increase in reaction rate.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemically Induced Oscillations of C2H4 Oxidation Over Thin Sputtered Rh Catalyst Films

et al. 2005

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The electrochemically promoted induction of self-sustained catalytic rate and potential oscillations during C 2 H 4 oxidation was studied over sputtered Rh thin (40 nm catalyst films interfaced with ZrO 2 (8 mol% Y 2 O 3 ). The reaction rate oscillates simultaneously with the catalyst potential, and always in the opposite direction. The electrochemically induced oscillatory rate is typically 60 times larger than the open-circuit catalytic rate and 1000 times larger than the electrochemical rate of O 2) supply to the catalyst. The phenomenon is completely reversible and only observed under anodic polarization where the rate oscillates between the values corresponding to metallic Rh and surface Rh 2 O 3 . The oscillations are caused by the electrochemically controlled backspillover of O 2) to the catalyst surface and the concomitant, via repulsive lateral interactions, decomposition of surface rhodium oxide followed by surface reoxidation to Rh 2 O 3 by gaseous O 2 .

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Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrochemically Induced Oscillations of C2H4 Oxidation Over Thin Sputtered Rh Catalyst Films

et al. 2005

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Electrochemical promotion of catalysis controlled by chemical potential difference across a mixed ionic-electronic conducting ceramic membrane – an example of wireless NEMCA

2007

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A La 0.6 Sr 0.4 Co 0.2 F 0.8 O 3 mixed ionic electronic conducting (MIEC) membrane was used in a dual chamber reactor for the promotion of the catalytic activity of a platinum catalyst for ethylene oxidation. By controlling the oxygen chemical potential difference across the membrane, a driving force for oxygen ions to migrate across the membrane and backspillover onto the catalyst surface is established. The reaction is then promoted by the formation of a double layer of oxide anions on the catalyst surface. The electronic conductivity of the membrane material eliminates the need for an external circuit to pump the promoting oxide ion species through the membrane and onto the catalyst surface. This renders this ''wireless'' system simpler and more amenable for large-scale practical application. Preliminary experiments show that the reaction rate of ethylene oxidation can indeed be promoted by almost one order of magnitude upon exposure to an oxygen atmosphere on the sweep side of the membrane reactor, and thus inducing an oxygen chemical potential difference across the membrane, as compared to the rate under an inert sweep gas. Moreover, the rate does not return to its initial unpromoted value upon cessation of the oxygen flow on the sweep side, but remains permanently promoted. A number of comparisons are drawn between the classical electrochemical promotion that utilises an external circuit and the ''wireless'' system that utilises chemical potential differences. In addition a 'surface oxygen capture' model is proposed to explain the permanent promotion of the catalyst activity.

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Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4

Ouariach

Kacimi

Ziyad

2015

Applied Catalysis A: General

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ChemInform Abstract: THE ROLE OF PLATINUM OXIDE (PTOX) IN THE ISOTHERMAL RATE OSCILLATIONS OF ETHYLENE OXIDATION ON PLATINUM

Cited by 5 publications

References 1 publication

Electrochemically Induced Oscillations of C2H4 Oxidation Over Thin Sputtered Rh Catalyst Films

Electrochemically Induced Oscillations of C2H4 Oxidation Over Thin Sputtered Rh Catalyst Films

Electrochemical promotion of catalysis controlled by chemical potential difference across a mixed ionic-electronic conducting ceramic membrane – an example of wireless NEMCA

Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4

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