Forced cycling of catalytic reactors: Number of cycles to reach cycle invariance

Lynch, David T.

doi:10.1002/cjce.5450640625

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…7, the time-average reactor performance with respect to reactants and products over several periods at cycle-invariance, as calculated with Eqs. (18), (19), (20) and (21), are compared to the values obtained at steady-state. These reactor performances correspond to the time-average molar¯ow rates of products and of converted reactants, respectively.…”

Section: Reduction Of N 2 O By Co Under Periodic Conditionsmentioning

confidence: 99%

“…The values at quasi steady-state (QSS), i.e. for an in®nite period [19,20], were calculated as follows: at QSS, the transient period (which lasts less than two hours) can be neglected with respect to the period at steady-state (an in®nite time), so that the time-average molar fractions of the reactants and products correspond to half of their values at steady-state during the half-period under N 2 OCO, since during the halfperiod under CO, the average molar fractions are equal to 0. That the QSS limit is lower than the steady-state ensures that the observed increase in reactor performance is not due to any concentration effect but is actually due to an oxidation state of the catalyst which cannot be achieved under steady-state conditions.…”

Section: Reduction Of N 2 O By Co Under Periodic Conditionsmentioning

confidence: 99%

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Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Randall

Doepper

Renken

1998

Applied Catalysis B: Environmental

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The reduction of NO and N 2 O by CO over a silica-supported iron oxide catalyst was investigated by the transient response method, with different initial oxidation states of the catalyst, i.e. completely reduced (Fe 3 O 4 ), or oxidised (Fe 2 O 3 ). The in¯uence of CO pre-adsorption was also studied. From the material balance on the gas phase species, it was shown that the composition of the catalyst changes during relaxation to steady-state. The degree of reduction of the catalyst at steady-state could thus be estimated. During the transient period, CO was shown to inhibit N 2 O as well as NO reductions by adsorption on reduced sites. The activity of the reduced catalyst was found to be substantially higher as compared to the oxidised catalyst for both reactions. On this basis, it was attempted to keep the catalyst in a reduced state by periodically reducing it with CO. As a result, a signi®cant increase in the performance of the reactor with respect to steady-state operation could be achieved for N 2 O reduction by CO. Finally, the dynamic behaviour of the N 2 O±CO and NO±CO reactions made it possible to evidence reaction steps, the occurrence of which could not be shown during our previous investigations on the separate interactions of the reactants with the catalyst. #

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Section: Reduction Of N 2 O By Co Under Periodic Conditionsmentioning

confidence: 99%

Section: Reduction Of N 2 O By Co Under Periodic Conditionsmentioning

confidence: 99%

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Randall

Doepper

Renken

1998

Applied Catalysis B: Environmental

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“…As can be seen from Figure 4, for the feed containing 1.2% NO and 1.2% CO, the cycle-invariant state is reached after 225 cycles (6.25 h). A partial explanation for the slow convergence to a cycle-invariant state for the feeds with lower reactant concentrations can be found in the study of Lynch (1986) for the CO+02 reaction. However, for the feed containing 0.45% NO and 0.45% CO, the time-average CO conversion remained almost constant at approximately 90% even after 1000 cycles (27.8 h), after which the experiment was stopped.…”

Section: Relaxed-steady-state Operationmentioning

confidence: 99%

Transient and resonant behavior for no reduction by CO over a Pt/Al₂O₃ catalyst during forced composition cycling

Sadhankar

Lynch

1996

Can J Chem Eng

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The reduction of NO by CO over a Pt/AI,O, catalyst has been investigated using the technique of forced concentration cycling in an isothermal recycle reactor at 485 K. Time-average conversions exhibit resonant behavior with increasing frequency. Maximum time-average NO conversion of 78%, compared with the steady-state conversion of 3.8%, was attained during out-of-phase feed concentration cycling. The effect of the phase angle between the NO and CO feed cycles has been examined. Higher conversions are obtained by decreasing the NO phase lead below 180". The convergence to cycle-invariance was slow for high frequency cycling.On a etudie la reduction du NO par le CO sur un catalyseur Pt/AI,O, a l'aide d'une technique de cyclage force de la concentration dans un reacteur de recyclage isotherme a 485 K. Les conversions moyennes dans le temps montrent un comportement de resonance avec I'augmentation de la frequence. Lors du recyclage de la concentration d'alimentation en opposition de phase, on a obtenu une conversion maximale du NO moyennee dans le temps de 78%, comparativement a une conversion de 3,8% en regime permanent. L'effet de I'angle de phase entre les cycles d'alimentation du NO et du CO a ete etudie. On peut ameliorer les conversions en diminuant I'avance de phase du NO en-dessous de 180". La convergence vers f'invariance de cycle est lente pour le cyclage a haute frequence.Keywords: NO reduction by CO, forced oscillations, forced composition cycling.he three-way catalyst currently used in automobile cat-

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Slow convergence to cycle-invariance during forced oscillations of the NO+CO reaction over a Pt catalyst

Sadhankar

Lynch

1996

Chemical Engineering Science

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Forced cycling of catalytic reactors: Number of cycles to reach cycle invariance

Cited by 5 publications

References 8 publications

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Transient and resonant behavior for no reduction by CO over a Pt/Al₂O₃ catalyst during forced composition cycling

Slow convergence to cycle-invariance during forced oscillations of the NO+CO reaction over a Pt catalyst

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Forced cycling of catalytic reactors: Number of cycles to reach cycle invariance

Cited by 5 publications

References 8 publications

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Transient and resonant behavior for no reduction by CO over a Pt/Al2O3 catalyst during forced composition cycling

Slow convergence to cycle-invariance during forced oscillations of the NO+CO reaction over a Pt catalyst

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Transient and resonant behavior for no reduction by CO over a Pt/Al₂O₃ catalyst during forced composition cycling