Catalytic oxidation of carbon monoxide under periodic operation

Abstract

A growing literature demonstrates resonance of the rate of CO oxidation with frequency of composition switching and that a global increase in rate under composition modulation is possible. Differences are found for the various metal catalysts used: CO oxidation is stimulated at frequencies between 0.1 and 1 .O Hz over noble metals, whereas stimulation occurs at frequencies below 0.05 Hz with oxide catalysts. Multiple resonances with an apparent harmonic relationship, "wrong-way " response, or very slow relaxation to reproducible cycles have been observed. These differences suggest mechanisms through which rate improvements arise are not the same for all catalysts.-.~ ~.Des articles de plus en plus nombreux montrent que la vitesse d'oxydation du CO entre en resonance avec la fr&quence du changement de composition et qu'il est possible d'obtenir une augmentation globale de la vitesse en modulant la composition. On a trow6 des differences en fonction des catalyseurs mktalliques utilises: I'oxydation du CO est stimulCe a des frkquences comprises entre 0, I et 1 ,O Hz sur des mktaux nobles, alors que I'on constate une stimulation a des frequences inferieures a 0,OS Hz avec des catalyseurs a base d'oxyde. On a observe des resonances multiples avec une relation harmonique apparente, une reponse (cwrong-way., ou une relaxation trks lente aux cycles reproductiblcs. Ces differences suggkrent que les mecanismes par lesquels ces augmentations de vitesse se produisent. ne sont pas les m&rnes pour tous les catalyseurs.

Transient kinetic model of CO oxidation over a nanostructured Cu0.1Ce0.9O2− catalyst

“…A lot of studies on catalytic oxidation of carbon monoxide under dynamic conditions refer to the reaction proceeding over supported noble metal catalysts [7][8][9][10][11][12][13][14]. The number of studies regarding CO oxidation over oxide catalysts is substantially lower [15,16].…”

Hydrogen separation from mixed gas (H2, N2) using Pd/Al2O3 membrane under forced unsteady state operations

“…The switching time is a key parameter to influence of the regimes of operation, which leads to overall process performances [10,54,60]. The effect of the switching time may differ for each process and operating condition due to different time scale either microprocessing or macroprocessing.…”

Nonlinear predictive control of periodically forced chemical reactors

“…Numerous theoretical and experimental investigations have shown that forced periodic operation of chemical reactors can lead to increased conversion, enhanced yield, reduced parametric sensitivity, reduced hot-spot problems, and stabilized reactor operation in the unstable steady-state region (Bailey, 1977;Cutlip, 1979;Gulari, 1985, 1986;Char et al, 1987a,b;Rigopoulos et al, 1988;Sterman and Ydstie, 1990a,b;Silveston, 1991;Ozgulaen et al, 1992a,b). The control of periodically forced reactors, however, is an important and interesting issue which has not received the attention it deserves.…”