A temperature nonequilibrium phase transition of the chaotic state in the belousov-zhabotinskii reaction in a closed ideal mixing reactor

The influence of the temperature close to the threshold of generation of a chaotic state in an oscillatory ferroin-catalyzed Belousov-Zhabotinskii chemical reaction was studied in a closed ideal mixing reactor. On the basis of the data obtained it was shown that when the temperature is varied in this chemical system, a nonequilibrium phase transition is observed, in which there is an abrupt change in the reciprocal of the induction period. Under these conditions, close to the temperature of the phase transition the origin of the oscillations is probabilistic.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 3, pp. 147–151, May–June, 1994.     

Bifurcation of irregular oscillatory regimes in the Belousov-Zhabotinskii reaction in a closed reactor

We describe the bifurcation diagram for irregular oscillatory regimes in the Belousov-Zhabotinskii reaction in a closed reactor upon variation of the initial concentrations of ferroin and potassium bromate. We formulate rules for transition from one regime to another.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol, 28, No. 5–6, pp. 474–478, September–December, 1993.     

Thermolysis of hexachlorocyclohexane in a flow-through packed reactor

Thermolysis of hexachlorocyclohexane in a flow-through packed system in an inert gas atmosphere was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1528–1532.Original Russian Text Copyright © 2004 by Kutin, Gubanova, Zorin, Zanozina, Markova, Suprunova, Bykova.     

Spontaneous concentration waves in the belousov-zhabotinskii reaction in viscous solutions

It is shown that the range of values of the parameters of the spontaneous oscillations in the Belousov-Zhabotinskii reaction (bromate + malonic acid + o-phenanthroline complexes of iron(II, III) + sulfuric acid) remains unchanged when viscous solutions are used. Silica gel was used as an inert thickening agent. The absence of any appreciable retardation of the oscillations when the viscosity of the solution is increased shows that the gel employed does not produce any appreciable retardation of the rate of diffusion of low-molecular compounds, which determines the rate of the oscillations.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 493–497, July–August, 1990.The authors are grateful to L. P. Tikhonov for taking part in the discussion of the results.     

Dynamical regimes of a pH-oscillator operated in two mass-coupled flow-through reactors

We present results of experiments focused on emergent and cooperative dynamics in a system of two coupled flow-through stirred reaction cells with diffusion-like mass exchange and a strongly nonlinear chemical reaction between hydrogen peroxide and thiosulphate catalysed by cupric ions in diluted solution of sulphuric acid. Due to complex mechanism, in which a crucial role is played by hydrogen and/or hydroxide ions, dynamics in a single cell entail multiple stationary states, excitability and oscillations conveniently indicated by measuring pH. When coupled, the system shows a plethora of dynamical regimes depending on the coupling strength and flow rate. Under certain conditions both cells display dynamics close to that in the absence of coupling, but majority of the regimes are emergent and cannot be deduced from dynamics of decoupled reactors. The most prominent is a stationary state maintaining highly acidic values of pH in one of the reactors and weakly acidic in the other. When each cell is set to display excitability and the coupled system is externally perturbed, the cells may cooperate and transmit excitations elicited by pulsed perturbations in one cell to the other. Periodic pulses induce firing patterns marked by a various degree of propagated excitations and by being periodic or irregular.     

Influence of low-intensity electromagnetic field on autooscillations of concentration in belousov-zhabotinskii reaction

A study has been made of the influence of an electromagnetic field (EMGF) with a frequency in the 40–60 GHz range and intensity up to 4–8 mW on autowaves of concentration in the reaction of sodium bromate (0.3 M), malonic acid (0.2 M), sulfuric acid (0.45 M), and Ferroin (0.003 M). It has been found that the action of the EMGF leads to decreases in the wavelength by amounts up to 26%. The experimentally measured temperature gradient created by the EMGF in a thin layer of the reaction mixture is no greater than 0.4°K. The value calculated for the solution temperature rise that is required to create the experimentally observed decrease in wavelength is 5–6° K. It is concluded, therefore, that the observed effect cannot be explained solely by thermal action of the EMGF through heating the reaction mixture.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 704–709, November–December, 1989.     

Effect of temperature on bifurcation of self-oscillating modes in the Belousov-Zhabotinskii reaction in a continuous-flow stirred-tank reactor

The effect of the temperature on self-oscillating modes in the Belousov-Zhabotinskii reaction in a continuous-flow stirred-tank reactor (CSTR) at T=288–333 K was investigated. It was found that changing the temperature leads to a cascade of different bifurcations: the steady state changes into sinusoidal oscillations, then chaotic and complex periodic oscillations appear in the system and turn into regular oscillations with a further increase in the temperature. The regular oscillations disappear at T=329 K as a result of a degenerate supercritical Hopf bifurcation.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 31, No. 2, pp. 69–75, March–April, 1995.     

Fully automated flow-through synthesis of secondary sulfonamides in a binary reactor system

A fully automated flow-through process for the production of secondary sulfonamides is presented. Primary sulfonamides were monoalkylated using a two-step "catch and release" protocol to generate library products of high purity. The automated flow synthesis platform incorporates four independent reactor columns and is able to perform automated column regeneration. A 48-member sulfonamide library was prepared as two 24-member sublibraries, affording library compounds in good yields and high purities without the need for further column chromatographic purification.     

effect of initial reagent concentrations on the oscillatory behavior of the BZ reaction in a batch reactor

A detailed investigation on resorcinol as the Belousov–Zhabotinsky (BZ) oscillator in manganese(II) ion catalyzed reaction system with inorganic bromate (oxidant) and acetone (cosubstrate) was carried out in aqueous sulfuric acid medium (1.3 M). The aforesaid reagents were mixed with various concentrations to evolve the effective concentrations at which the reaction system exhibited better oscillations. The various oscillatory parameters such as time period (t_p), induction period (t_in), frequency (v), amplitude (A), and number of oscillations (n) were derived, and the dependence of concentration of the reacting species on these oscillatory parameters was interpreted on the basis of the Field–Koros–Noyes mechanism. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 650–657, 2009     

Immobilization of glucose oxidase on nylon membranes and its application in a flow-through glucose reactor

The immobilization of glucose oxidase on hydrolyzed nylon-6,6 was studied. Various spacers were introduced on the support before the coupling of the enzyme. Best results were obtained when the membrane was covered with denatured bovine serum albumin (BSA) before spacer coupling and immobilization of glucose oxidase (GOD). The influence of various factors (pH, ionic strength, etc.) on the activity of the free and immobilized enzyme was investigated. It was found that the behavior of the fixed glucose oxidase and the free enzyme is very similar. The covalently immobilized enzyme had a lifetime of around 2 months (50% of initial activity).     

Effect of initial substrate concentration of the Belousov-Zhabotinsky reaction on self-oscillation for microgel system

Self-oscillation for the microgel particles ( approximately 200 nm in diameter) was studied by changing initial substrate concentrations (i.e., malonic acid, sodium bromate, and nitric acid) of the Belousov-Zhabotinsky (BZ) reaction that is used for chemical energy for the self-oscillation. The cross-linked microgels are composed of N-isopropylacrylamide and ruthenium tris(2,2'-bipyridine), Ru(bpy) 3, which is a catalyst for the BZ reaction. Comparing with the homogeneous, stirred solution of the bulk solution for the BZ reaction, swelling/deswelling oscillation of the microgels showed longer induction period, different dependence of initial substrate concentrations on oscillation period, and different oscillation rhythm. The change in oscillation for the microgels can be understood by considering the microgel network effect.     

Development of a novel enzyme reactor and application as a chemiluminescence flow-through biosensor

A novel enzyme reactor was prepared using calcium alginate fiber (CAF) and amine-modified nanosized mesoporous silica (AMNMS) as a support. Combination of the adsorption of the enzyme on AMNMS with the cage effect of the polymer greatly increases the catalytic activity and the stability of the immobilized enzyme. It was shown that the lifetime, stability, and catalytic activity of the enzyme reactor were greatly improved by incorporating AMNMS into CAF to efficiently encapsulate the enzyme. Glucose oxidase was chosen as a model enzyme to explore the possibility of using CAF–AMNMS as a matrix for enzyme immobilization in the design of a chemiluminescence (CL) flow-through biosensor. The sensitivity of the flow-through biosensor combined with a novel luminol-diperiodatonickelate CL system was higher than for other reported CL biosensors. The proposed biosensor exhibits short response time, easy operation, long lifetime, high catalytic activity, high sensitivity, and simple assembly.     

Schiff碱配合物模拟酶催化性能的温度效应研究

研究了新型Schiff碱双锰配合物在模拟酶催化亚碘酰苯单加氧化环已烷反应及 被亚碘酰苯氧化破坏反应中的温度效应。结果表明，在模拟酶催化反应体系中同时 存在催化环已烷单加氧反应及催化剂的氧化破坏反应；催化反应速率及氧化破坏反 应速率均随反应温度升高有规律地增大，但氧化破坏反应比催化反应对反应温度更 敏感；催化反应总产率一般随反应温度升高而降低；最适宜的反应温度为25 ℃。     

The effect of glass transition on the self-oscillation regime of tensile drawing of a polymer

The effect of the transition of a polymer into its rubbery state at the glass-transition temperature on the character of the excitation of self-oscillation neck propagation is studied with numerical methods. To describe the rate of plastic yielding near the glass-transition temperature, the Eyring equation is modified by the introduction of the temperature dependence of the parameter related to the free volume. There are three intervals of strain rates. At low strain rates when the yield stress increases with an increase in the strain rate, neck propagation is stable and no oscillations are excited. At high strain rates, when the glass-transition temperature is achieved during stationary neck propagation, the excitation of oscillations shows a mild character and there exists a certain critical length of the samples below which no oscillations are excited. In the intermediate interval of strain rates, the excitation shows a severe character. In this case, the oscillations are excited when, in the transition region, the glass-transition temperature of the polymer is achieved owing to excitations. In strain-rate-sample-length coordinates, the diagram describing the regions of various oscillation behaviors of the samples is constructed.     

Application of a novel co-enzyme reactor in chemiluminescence flow-through biosensor for determination of lactose

A novel enzyme reactor with co-immobilization of β-galactosidase and glucose oxidase in calcium alginate fiber (CAF) and amine modified nanosized mesoporous silica (AMNMS) was prepared which incorporate the adsorption and catalysis of AMNMS with the cage effect of the polymer to increase catalytic activity and stability of immobilized enzyme. The enzyme reactor was applied to prepare a chemiluminescence (CL) flow-through biosensor for determination of lactose combined with a novel luminol-diperiodatonickelate (DPN) CL system we reported. It shows that the CL flow-through biosensor possesses long lifetime, high stability, high catalytic activity and sensitivity. The relative CL intensity was linear with the lactose concentration in the range of 8 × 10⁻⁸-4 × 10⁻⁶ g mL⁻¹ with the detection limit of 2.7 × 10⁻⁸ g mL⁻¹ (3σ). It has been successfully applied to the determination of lactose in milk.     

Stochastic resonance in the oxidation of nadh by atmospheric oxygen in the presence of copper(II) aqua ions in a constant-agitation flow-type reactor

The oxidation of NADH by atmospheric oxygen in the presence of copper(II) aqua ions in a constant-agitation flow-type reactor was investigated. During the experiments the initial concentrations of the reagents ([NADH]₀, [Cu²⁺]₀) and their delivery rate (k₀) were varied. It was established that there are four reaction regimes in the system: steady state (SS); low-amplitude periodic autooscillation (εR); high-amplitude periodic (SR₁) and aperiodic (SR₂) autooscillations. The three-dimensional region of existence for these regimes was constructed in the coordinates [NADH]₀, [Cu²⁺]₀, and k₀. It was shown by statistical analysis that oscillations of the SR₁ and SR₂ types are due to stochastic resonance. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'aaya Khimiya, Vol. 36, No. 2, pp. 95–100, March–April, 2000.     

Propane oxidation on nickel in a self-oscillation mode

The kinetics of the catalytic oxidation of propane with oxygen on nickel in a self-oscillation mode was studied. A comparative analysis of changes in reaction rate oscillations with time in the presence of nickel wire and foil was performed. It was found that the reaction medium influenced the morphology of the catalyst surface. With the use of X-ray photoelectron spectroscopy, it was demonstrated that a NiO layer no less than 100 nm in thickness was formed on the catalyst surface in the course of the reaction of propane oxidation. The mechanism of the appearance of self-oscillations in the test system is discussed.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 269–277.Original Russian Text Copyright © 2005 by Gladky, Kaichev, Bukhtiyarov, Parmon.Deceased.     

Solvent effects on reaction rates in a catalytic slurry reactor

By carrying out static adsorption measurements, it is shown that absolute values of adsorption strength parameters required in an earlier Langmuir type model for liquid phase catalytic hydrogenation in the presence of an adsorbing solvent can be obtained. These can be used to predict the relationship between reaction rate and reactant concentration in the solvent.

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Analysis of the electrolyte diode. Electro-diffusion and chemical reaction within a hydrogel reactor

A reaction–diffusion system describing the electrolyte diode is investigated. This consists of a chemically crosslinked polyvinylalcohol (PVA) hydrogel cylinder in which a pH gradient is provided by having an acid and a base maintained at constant concentrations in reservoirs at each end of the one-dimensional reactor. A potential difference of a given strength is also applied across the gel cylinder. Previous experimental studies of the current–voltage characteristics (CVC) have shown two distinct cases, depending on whether a positive or negative potential difference was applied. The slopes of the linear current–voltage response curve are substantially different in the two cases, that in the 'forward' case being typically several orders of magnitude greater than that in the 'backward' case. Thus the system behaves like a semiconductor diode. The stationary concentration distribution for the different ions is described by a system of reaction–diffusion equations involving migration caused by the electric field. An approximate solution of these equations, using a simplified model, is presented and compared with results obtained by solving the full system numerically. The concentration profiles obtained from the numerical solution confirm the validity of the simplified model.