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Continuous stirred reactor oscillations

Rate Oscillations During Propylene Oxide Oxidation on Silver Films in a Continuous Stirred Reactor... [Pg.165]

Studies carried out by Yoshida and coworkers have coupled this phenomena with oscillating chemical reactions (such as the Belousov-Zhabotinsky, BZ, reaction) to create conditions where pseudo non-equilibrium systems which maintain rhythmical oscillations can demonstrated, in both quiescent (4) and continuously stirred reactors (5). The ruthenium complex of the BZ reaction was introduced as a functional group into poly(N-isopropyl acrylamide), which is a temperature-sensitive polymer. The ruthenium group plays it s part in the BZ reaction, and the oxidation state of the catalyst changes the collapse temperature of the gel. The result is, at intermediate temperature, a gel whose shape oscillated (by a factor of 2 in volume) in a BZ reaction, providing an elegant demonstration of oscillation in a polymer gel. This system, however, is limited by the concentration of the catalyst which has to remain relatively small, and hence the volume change is small. [Pg.72]

Other recent contributions to this aspect of the subject include those of Thompson et concerning a numerical technique for analysing particle-size distribution data for latices produced by continuous emulsion polymerization reactors, of Azizyan et alJ on the calculation of the number of steps in the continuous emulsion polymerization of vinyl acetate and chloroprene, of Lukhovitskii and Listratov on continuous emulsion polymerization in an ideal mixing-reactor, and of Brooks et al. on the emulsion polymerization of styrene in a continuous stirred reactor. The results presented in this last paper are particularly interesting in that the polymerization rates were Initially very high, but declined subsequently and did not always attain a steady value, but sometimes oscillated with time. [Pg.71]

Thus it is possible for continuous stirred-tank reactor systems to be stable, or unstable, and also to form continuous oscillations in output, depending upon the system, constant and parameter, values. [Pg.156]

A continuous stirred tank reactor has been reported for the hydrolysis of the triglycerides existing in vegetable oil in the presence of the aqueous phase and for synthesis reactions (Table 5). A microfilter can be used to prevent the immobilized enzyme from leaving the reactor. Kawano et al. [115] investigated the hydrolysis of olive oil in octane with Candida cylindracea lipase in aqueous solution in a Vibro Mixer reactor containing vibration plates connected to the crankshaft of a motor and oscillated with fixed rates. [Pg.581]

The APP technique, recently introduced [50, 51], uses a continuous stirring tank reactor (CSTR) and relies on the sequential perturbation of an oscillating... [Pg.197]

Figure 10 Experimental setup for implementation of CL oscillating reaction-based de terminations. CSTR, continuous stirring tank reactor. (From Ref. 52.)... Figure 10 Experimental setup for implementation of CL oscillating reaction-based de terminations. CSTR, continuous stirring tank reactor. (From Ref. 52.)...
The main features of the copper catalyzed autoxidation of ascorbic acid were summarized in detail in Section III. Recently, Strizhak and coworkers demonstrated that in a continuously stirred tank reactor (CSTR) as well as in a batch reactor, the reaction shows various non-linear phenomena, such as bi-stability, oscillations and stochastic resonance (161). The results from the batch experiments can be suitably illustrated with a two-dimensional parameter diagram shown in Pig. 5. [Pg.449]

M. Perez, R. Font, and M.A. Montava. Regular self-oscillating and chaotic dynamics of a continues stirred tank reactor. Comput. Chem. Eng., 26 889-901, 2002. [Pg.274]

P. Gray and S. K. Scott. Autocatalytic reactions in the isothermal continuous stirred tank reactor Isolas and other forms of multiplicity. Chem. Eng. ScL 38, 29-43 (1983) Autocatalytic reactions in the isothermal continuous stirred tank reactor Oscillations and instabilities in the system A + 2B —> 3B, B —> C. Chem Eng. ScL 34, 1087-1097 (1984). [Pg.82]

The classical problem of multiple solutions and undamped oscillations occurring in a continuous stirred-tank reactor, dealt with in the papers by Aris and Amundson (39), involved a single homogeneous exothermic reaction. Their theoretical analysis was extended in a number of subsequent theoretical papers (40, 41, 42). The present paragraph does not intend to report the theoretical work on multiplicity and oscillatory activity developed from analysis of governing equations, for a detailed review the reader is referred to the excellent text by Schmitz (3). To understand the problem of oscillations and multiplicity in a continuous stirred-tank reactor the necessary and sufficient conditions for existence of these phenomena will be presented. For a detailed development of these conditions the papers by Aris and Amundson (39) and others (40) should be consulted. [Pg.74]

Emulsion polymerization is usually carried out isothermally in batch or continuous stirred-tank reactors. Temperature control is much easier than for bulk or solution polymerization because the small ( 0.5 fim) polymer particles, which are the locus of the reaction, are suspended in a continuous aqueous medium. This complex, multiphase reactor also shows multiple steady states under isothermal conditions. In industrial practice, such a reactor often shows sustained oscillations. Solid-catalyzed olefin polymerization in a slurry batch reactor is a classic example of a slurry reactor where the solid particles change size and characteristics with time during the reaction process. [Pg.143]

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. [Pg.174]

At the start, the cycle begins with a certain amount of Ce+4 ions. The second reaction provides Br- ions, which inhibit the first reaction. This leads to an increase in concentration of Ce+3. After reaching a certain amount of Ce+3, the oxidation reaction starts, since little Ce+4 remains. The system can no longer produce sufficient Br to inhibit the reaction, and Ce+3 decreases rapidly, producing Ce+4 until the cycle is completed. It is possible to maintain indefinite oscillations with constant frequency in a continuous flow stirred reactor into which bromate, malonic acid, and cerium catalyst are being supplied at a uniform rate. [Pg.643]

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. [Pg.54]

The simulations discussed above are focused on the behavior of single catalytic oscillators at fixed reactant pressures. In the full-scale analysis of reactions on nm-supported particles, the reactant pressures should be calculated self-consistently with the reaction kinetics. At present, due to computational limitations, the self-consistent treatment can, however, be done only by using the MF equations (see, e.g., recent simulations [57] of oscillations in CO oxidation in a continuously stirred tank reactor). The MF approach does not, however, make it possible to scrutinize the reaction kinetics on the nm scale. Under such circumstances, the MC and MF treatments are complementary. In particular, the MC results may be employed in order to understand the limits of applicability of the MF approximation. [Pg.76]

The extended model is then used to design a new continuous stirred tank reactor configuration which eliminates the oscillations and which offers substantial improvements in product quality, productivity and operating costs. [Pg.210]

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). [Pg.603]

Control of industrial polymerization reactors is a challenging task because, in general, control engineers lack rigorous polymerization process knowledge, process model, and rapid online or inline sensors to measure polymer properties. Exothermic polymerization processes often exhibit strongly nonlinear dynamic behaviors (e.g., multiple steady states, autonomous oscillations, limit cycles, parametric sensitivity, and thermal runaway), particularly when continuous stirred tank... [Pg.2341]

In an attempt to explain the horatian oscillations due to the B-Z reaction in a well-stirred continuous flow reactor reported by R. A. Schmitz et al., Iwamoto and Seno (1981) proposed a reaction model and a two dimensional mathematical model. [Pg.85]

The nonlinearity of chemical processes received considerable attention in the chemical engineering literature. A large number of articles deal with stand-alone chemical reactors, as for example continuously stirred tank reactor (CSTR), tubular reactor with axial dispersion, and packed-bed reactor. The steady state and dynamic behaviour of these systems includes state multiplicity, isolated solutions, instability, sustained oscillations, and exotic phenomena as strange attractors and chaos. In all cases, the main source of nonlinearity is the positive feedback due to the recycle of heat, coupled with the dependence of the reaction rate versus temperature. [Pg.522]

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. [Pg.124]

Isothermal, Continuous Stirred-Tank Reactor Oscillations and Instabilities in the System A + 2B - 3B B C. [Pg.267]

The key species in the FKN mechanism is BrO, which functions as both oxidant for Ce(III) and reductant for Ce(IV). This species is formed in the reaction between BrOj (bromate) and HBrOj (bromous acid). Neither BrOj nor HBrOz are stable in aqueous media and thus are produced and consumed in the FKN mechanism as intermediate species. A lucid description of the specifics of the oscillating reaction system has been provided by Barkin et al. (1977). A more recent contribution from Bar-Eli (1985) indicates that in a continuously stirred tank reactor (CSTR) only four or five of the total 14 reaction rate constants are required to describe the oscillations. Yoshida and Ushiki (1982) studied the oxidation of Ce(III) by Br03 found an induction period precedes a burst of Ce(IV) production, followed by continued slow generation of Ce(IV). The length of the induction period was highly dependent on the age of the reactant solution. [Pg.376]


See other pages where Continuous stirred reactor oscillations is mentioned: [Pg.27]    [Pg.128]    [Pg.92]    [Pg.74]    [Pg.101]    [Pg.181]    [Pg.237]    [Pg.188]    [Pg.306]    [Pg.308]    [Pg.2]    [Pg.87]    [Pg.5]    [Pg.119]    [Pg.814]    [Pg.209]    [Pg.114]    [Pg.77]    [Pg.82]    [Pg.302]    [Pg.127]    [Pg.64]   
See also in sourсe #XX -- [ Pg.145 , Pg.146 ]




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Stirred continuous

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