Oscillatory bromate-oxalic acid-Ce-acetone-sulfuric acid reaction, in CSTR

Even when in contact with virtually infinite reservoirs, natural and manmade oscillators typically drift in phase space on a time-scale considerably slower than that of the intrinsic oscillator. A ubiquitous example is the inexorable aging process experienced by all living systems. Typical electrocatalytic reactions under oscillatory conditions oscillate for only a few dozen stable cycles due to slow surface poisoning that ultimately results in destruction of the limit cycle. We report the observation of unprecedented long-lasting temporal oscillations in the electro-oxidation of formic acid on an ordered intermetallic PtSn phase. The introduction of Sn substantially increases the catalytic activity and retards the irreversible surface oxidation, which results in the stabilization of more than 2200 oscillatory cycles in about 40 h; a 30-40-fold stabilization with respect to the behavior of pure Pt surfaces. The dynamics were modeled and numerical simulations point to the surface processes underlying the high stability.

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“…33 Increases in oscillation frequency with flow rate have also been reported for some systems 58. 59…”

Section: Resultsmentioning

confidence: 70%

Long‐Lasting Oscillations in the Electro‐Oxidation of Formic Acid on PtSn Intermetallic Surfaces

et al. 2014

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“…These results suggests that the phase diagram of the system catalyzed by manganese may has a phase diagram similar to the one presented here. For the system catalyzed by cerium, recent results in flow conditions have shown the existence of irregular low-amplitude oscillations that can change to regular high-amplitude oscillations (canard-like behavior) depending on the ratio [Ce(IV)]/[Ce(III)] 62 . More complex patterns are still waiting to be observed experimentally for this system.…”

Section: Resultsmentioning

confidence: 99%

Phase diagram and complex patterns in the modeling of the bromate-oxalic acid-Ce-acetone oscillating reaction

Pereira¹,

Faria²

2007

Quím. Nova

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Recebido em 23/1/06; aceito em 3/7/06; publicado na web em 7/2/07Simulations have been carried out on the bromate -oxalic acid -Ce(IV) -acetone oscillating reaction, under flow conditions, using Field and Boyd's model (J. Phys. Chem. 1985, 89, 3707). Many different complex dynamic behaviors were found, including simple periodic oscillations, complex periodic oscillations, quasiperiodicity and chaos. Some of these complex oscillations can be understood as belonging to a Farey sequence. The many different behaviors were systematized in a phase diagram which shows that some regions of complex patterns were nested with one inside the other. The existence of almost all known dynamic behavior for this system allows the suggestion that it can be used as a model for some very complex phenomena that occur in biological systems.

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“…Observou-se neste estudo que a concentração de acetona tem um impacto capital na dinâmica, implicando basicamente em uma diminuição de amplitude das oscilações com uma diminuição da concentração de acetona. Em um trabalho subseqüente, Pereira e Faria 33 discutiram o papel da acetona no sistema bromato/ácido oxálico/acetona/Ce(IV) em ácido sulfúrico operando em reator agitado de fluxo contínuo ("continuous stirred tank reactor, CSTR"). Além de remover o bromo, os autores discutiram uma eventual participação da acetona na conversão lenta de Ce(IV) em Ce(III), com oscilações regulares presentes apenas a partir de um certo valor crítico da razão [Ce(III)]/[Ce(IV)].…”

Section: +unclassified

Dinâmica complexa no sistema bromato/hipofosfito/acetona/manganês e ferroína

Tokoro¹,

Oliveira²,

Varela³

2007

Quím. Nova

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Recebido em 19/12/06; aceito em 10/4/07; publicado na web em 25/10/07 COMPLEX DYNAMICS IN THE BROMATE/HYPOPHOSPHITE/ACETONE/MANGANESE AND FERROIN SYSTEM. New chemical systems have been recently designed for the study of complex phenomena such as oscillatory dynamics in the temporal domain and spatiotemporal pattern formation. Systems derived from oscillators based on the chemistry of bromate are the most extensively studied, with the celebrated Belousov-Zhabotinsky (BZ) reaction being the most popular example. Problems such as the formation of bubbles (CO 2 ) and solid precipitate in the course of the reaction and the occurrence of simply short-lived oscillations under batch conditions are very common and, in some cases, compromise the use of some of these systems. It is investigated in this paper the dynamic behavior of the bromate/hypophosphite/acetone/dual catalyst system, which has been sugested as an interesting alternative to circumvent those inconvenients. In this work, manganese and ferroin are employed as catalysts and the complete system (BrO 3 -/H 2 PO 2 -/acetone/Mn(II)-ferroin) is studied under batch conditions. Temporal symmetry breaking was studied in a reactor under agitation by means of simultaneous records of the potential changes of platinum and Ag/AgBr electrodes, both measured versus a reversible hydrogen electrode. Additionally, spatio-temporal formation of target patterns and spiral waves were obtained when the oscillating mixture was placed in a quasi two-dimensional reactor.Keywords: oscillations; chemical kinetics; pattern formation. INTRODUÇÃO Propriedades emergentes e sistemas complexosDefine-se formalmente comportamento emergente como "comportamento coletivo de um agregado de subunidades fisicamente similares não observado individualmente por nenhuma sub-unidade" 1 . Em um contexto mais amplo, Korn 2 compilou as principais definições de propriedades emergentes como sendo dadas em termos: da não aditividade das suas partes; de uma novidade, algo simplesmente novo; da não dedutibilidade e, da não preditabilidade. Finalmente, o autor 2 encerra que emergência é a nova associação que conduz a novas e estáveis configurações observáveis. Emergência é a propriedade mais importante dos sistemas complexos. O comportamento de um sistema complexo não pode ser entendido em termos apenas da extrapolação das propriedades dos seus componentes individuais, ou seja, as propriedades que surgem no nível macroscópico não podem ser preditas a partir das propriedades dos componentes microscópicos, como apresentado no artigo clássico More is different 3 .Whitesides e Ismagilov 4 classificaram um sistema complexo como um sistema no qual: sua evolução é muito sensível às condições iniciais ou a pequenas perturbações; o número de componentes independentes interagindo é grande ou, um no qual há vários caminhos através dos quais a evolução do sistema pode proceder. Comportamento complexo expresso na forma de cinética oscilatória e estruturação espacial, por exemplo, é comum em muitos sistemas reacionais mantidos...

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Oscillatory bromate-oxalic acid-Ce-acetone-sulfuric acid reaction, in CSTR

Cited by 13 publications

References 7 publications

Long‐Lasting Oscillations in the Electro‐Oxidation of Formic Acid on PtSn Intermetallic Surfaces

Long‐Lasting Oscillations in the Electro‐Oxidation of Formic Acid on PtSn Intermetallic Surfaces

Phase diagram and complex patterns in the modeling of the bromate-oxalic acid-Ce-acetone oscillating reaction

Dinâmica complexa no sistema bromato/hipofosfito/acetona/manganês e ferroína

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