Tank reactors, continuous flow stirred, oscillations

P. Aroca, Jr., and R. Aroca, Chemical Oscillations A Microcomputer-Controlled Experiment, J. Chem. Ed. 1987,64, 1017 J. Amrehn, P. Resch, and F. W. Schneider, Oscillating Chemiluminescence with Luminol in the Continuous Flow Stirred Tank Reactor, J. Phys. Chem. 1988,92, 3318 D. Avnir, Chemically Induced Pulsations of Interfaces The Mercury Beating Heart, ... 

K.Bar-Eli and R.J.Field, Simulation of the Minimal BrOj Continuous-Flow Stirred Tank Reactor Oscillator on the Basis of a Revised Set of Rate Constants, The Journal of Physical Chemistry, 94, 3660-3663(1990). 

IIIL) Orban, M., De Kepper, P., Epstein, I. R. Systematic Design of Chemical Oscillators, 1982-1 Part 77. An Iodine-free Chlorite-based Oscillator. The Chlorite-Thiosulfate Reaction in a Continuous Flow Stirred Tank Reactor. J. Phys. Chem., 86, 431-433... 

Bar-Eli, K. Field, R. J. Simulation of the minimal bromate(l ) continuous flow stirred tank reactor oscillator on the basis of a revised set of rate constansts. J. Phys. Chem. 1990, 94, 3660-3663. 

The chlorite-iodide reaction has been found by Dateo et al. [79] and later by De Kepper et al. [80] to exhibit complex phenomena such as oscillations and bistability between steady states, when run in a continuous-flow stirred tank reactor (CSTR). The overall stoichiometry of the reaction is... 

Buchholtz, F.G. and Broecher, S., Oscillations of the Bray-Liebhafsky reaction of low flow rates in a continuous flow stirred-tank reactor, J. Phys. Chem. A, 102, 1556-1559, 1988. 

He has also shown that in a continuous-flow stirred tank reactor no bimolecular reaction can show sustained oscillations. 

Another noteworthy achievement is the report of a systematically designed oscillating system, in which two autocatalytic subsystems, arsenite-iodate and chlorite-iodide, were linked in a continuous flow stirred-tank reactor. These two subsystems have been studied independently of each other. The arsenite-iodate subsystem has been thoroughly examined in a CSTR and shown to exhibit bistability under a range of conditions. The oscillations of iodide concentration involved a variation by a factor of more than 10 during each oscillation In an unstirred system, well-defined waves were observed. The chlorite-iodide reaction has also been studied. ... 

The first step in the search procedure is to put into practice the result derived from nonequilibrium thermodynamics that oscillation is a possibility only in a system sufficiently far from equilibrium. In order to maintain a nonequilibrium state we utilize a tool long familiar to chemical engineers and adapted to the study of chemical oscillation by the Bordeaux group (Pacault et al., [15]), the continuous flow stirred tank reactor (cSTR). A schematic diagram of a stirred tank reactor is shown in Figure 1. 

Vanag, V.K., Miguez, D.G., Epstein, I.R. Designing an enzymatic oscillator bistability and feedback controlled oscillations with glucose oxidase in a continuous flow stirred tank reactor. J. Chem. Phys. 125, 194515 (2006)... 

Example 4.8 Chemical reactions and reacting flows The extension of the theory of linear nonequilibrium thermodynamics to nonlinear systems can describe systems far from equilibrium, such as open chemical reactions. Some chemical reactions may include multiple stationary states, periodic and nonperiodic oscillations, chemical waves, and spatial patterns. The determination of entropy of stationary states in a continuously stirred tank reactor may provide insight into the thermodynamics of open nonlinear systems and the optimum operating conditions of multiphase combustion. These conditions may be achieved by minimizing entropy production and the lost available work, which may lead to the maximum net energy output per unit mass of the flow at the reactor exit. 

In Table I the high-vacuum (HV) range means a pressure of 10 to 10 Torr entries designated by Torr mean pressures between 0.1 and 10 Torr flow refers to an unspecified steady-state flow pattern. It is apparent from Table I that there is a great diversity in the different oscillation conditions and catalytic systems. The pressures under which oscillations have been observed vary from 10 Torr for the CO/NO reaction on Pt(lOO) 141, 142) to atmospheric pressure for a large number of systems. The reactors used in these studies include ultrahigh-vacuum (UHV) systems, continuous stirred tank reactors (CSTRs), flow reactors, and reactors designed as infrared (IR) cells, calorimeters, and ellipsometric systems. 

Indeed, PAAc cryogels coupled with a bromate oscillator oscillated between swollen and collapsed states [31]. The reactions of bromate, sulfite, and ferrocyanide ions were conducted in an open continuously stirred tank reactor. Four feed solutions (potassium bromate, sodium sulfite, potassium ferrocyanide, and sulfuric acid) were supplied continuously to the reactor, during which the pH of the reaction solution was monitored as a function of time. The flow rate of the feed solutions is an important parameter in determining the extent of pH oscillations. In Fig. 21, pH versus time plots are shown for four different reduced flow rates k, defined as the flow rate of the feed solutions divided by the reaction volume. It is seen that the pH of the solution oscillates between 6.2-6.9 and 3.2-3.8. The dissociation degree a of a weak electrolyte relates to pH by ... 

Introduction of membranes may, in some cases, lead to more flexibility in the design and study of chemical oscillators. The continuous-stirred tank reactor (CSTR) configuration, which is often used to study chemical oscillators because it maintains reaction and product concentrations away from equilibrium [1, 2], controls the transport of reactants, intermediates, and products by fluid flow, and does not discriminate among species. Membrane selectivity between chemical species can provide a basis for selection of dynamical behaviors that are unavailable with a CSTR. 

The existence of thermoKinetic oscillations is demonstrated most convincingly under well-stirred flowing conditions [1-4] and the deepest insights have been obtained, within the last decade, using continuously-stirred tanK reactors (cstr). But flowing conditions are not a pre-requisite for the existence of thermoKinetic oscillations even if their existence in closed conditions is ephemeral, and there is a very substantial history of the study of oscillatory cool flame phenomena in closed, unstirred vessels [5-0]. 

The exciting issue of steady-state multiplicity has attracted the attention of many researchers. First the focus was on exothermic reactions in continuous stirred tanks, and later on catalyst pellets and dispersed flow reactors as well as on multiplicity originating from complex isothermal kinetics. Nonisothermal catalyst pellets can exhibit steady-state multiplicity for exothermic reactions, as was demonstrated by P.B. Weitz and J.S. Hicks in a classical paper in the Chemical Engineering Science in 1962. The topic of multiplicity and oscillations has been put forward by many researchers such as D. Luss, V. Balakotaiah, V. Hlavacek, M. Marek, M. Kubicek, and R. Schmitz. Bifurcation theory has proved to be very useful in the search for parametric domains where multiple steady states might appear. Moreover, steady-state multiplicity has been confirmed experimentally, one of the classical papers being that of A. Vejtassa and R.A. Schmitz in the AIChE Journal in 1970, where the multiple steady states of a CSTR with an exothermic reaction were elegantly illustrated. 

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