Styrene tank reactor

Continuous stirred-tank reactors can behave very differently from batch reactors with regard to the number of particles formed and polymerization rate. These differences are probably most extreme for styrene, a monomer which closely follows Smith-Ewart Case 2 kinetics. Rate and number of particles in a batch reactor follows the relationship expressed by Equation 13. 

IT Duerksen, J.H., "Free Radical Polymerization of Styrene in Continuous Stirred Tank Reactors", Ph.D. Thesis, McMaster University, Hamilton, Ontario (1968). 

Anionic Styrene Polymerization in a Continuous Stirred-Tank Reactor... 

In this work, the characteristic "living" polymer phenomenon was utilized by preparing a seed polymer in a batch reactor. The seed polymer and styrene were then fed to a constant flow stirred tank reactor. This procedure allowed use of the lumped parameter rate expression given by Equations (5) through (8) to describe the polymerization reaction, and eliminated complications involved in describing simultaneous initiation and propagation reactions. 

A. W. De Graff, Continuous Emulsion Polymerization of Styrene in a One Stirred Tank Reactor. Lehigh Univ. Press, Bethlehem, PA, 1970. 

The use of a precision digital density meter as supplied by Mettler Instruments (Anton Paar, Ag.) appeared attractive. Few references on using density measurements to follow polymerization or other reactions appear in the literature. Poehlein and Dougherty (2) mentioned, without elaboration, the occasional use of y-ray density meters to measure conversion for control purposes in continuous emulsion polymerization. Braun and Disselhoff (3) utilized an instrument by Anton Paar, Ag. but only in a very limited fashion. More recently Rentsch and Schultz(4) also utilized an instrument by Anton Paar, Ag. for the continuous density measurement of the cationic polymerization of 1,3,6,9-tetraoxacycloundecane. Ray(5) has used a newer model Paar digital density meter to monitor emulsion polymerization in a continuous stirred tank reactor train. Trathnigg(6, 7) quite recently considered the solution polymerization of styrene in tetrahydrofuran and discusses the effect of mixing on the reliability of the conversion data calculated. Two other references by Russian authors(8,9) are known citing kinetic measurements by the density method but their procedures do not fulfill the above stated requirements. 

While vinyl acetate is normally polymerized in batch or continuous stirred tank reactors, continuous reactors offer the possibility of better heat transfer and more uniform quality. Tubular reactors have been used to produce polystyrene by a mass process (1, 2), and to produce emulsion polymers from styrene and styrene-butadiene (3 -6). The use of mixed emulsifiers to produce mono-disperse latexes has been applied to polyvinyl toluene (5). Dunn and Taylor have proposed that nucleation in seeded vinyl acetate emulsion is prevented by entrapment of oligomeric radicals by the seed particles (6j. Because of the solubility of vinyl acetate in water, Smith -Ewart kinetics (case 2) does not seem to apply, but the kinetic models developed by Ugelstad (7J and Friis (8 ) seem to be more appropriate. 

Emulsion Polymerization in a CSTR. 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 (. 5 Jim) polymer particles, which are the locus of reaction, are suspended in a continuous aqueous medium as shown in Figure 5. This complex, multiphase reactor also shows multiple steady states under isothermal conditions. Gerrens and coworkers at BASF seem to be the first to report these phenomena both computationally and experimentally. Figure 6 (taken from ref. (253)) plots the autocatalytic behavior of the reaction rate for styrene polymerization vs. monomer conversion in the reactor. The intersection... 

Polystyrene can be easily prepared by emulsion or suspension techniques. Harkins (1 ), Smith and Ewart(2) and Garden ( ) have described the mechanisms of emulsTon polymerization in batch reactors, and the results have been extended to a series of continuous stirred tank reactors (CSTR)( o Much information on continuous emulsion reactors Ts documented in the patent literature, with such innovations as use of a seed latex (5), use of pulsatile flow to reduce plugging of the tube ( ), and turbulent flow to reduce plugging (7 ). Feldon (8) discusses the tubular polymerization of SBR rubber wTth laminar flow (at Reynolds numbers of 660). There have been recent studies on continuous stirred tank reactors utilizing Smith-Ewart kinetics in a single CSTR ( ) as well as predictions of particle size distribution (10). Continuous tubular reactors have been examined for non-polymeric reactions (1 1 ) and polymeric reactions (12.1 31 The objective of this study was to develop a model for the continuous emulsion polymerization of styrene in a tubular reactor, and to verify the model with experimental data. 

More recent efforts (primarily at the simulation level) on the optimization of styrene-related systems include Cavalcanti and Pinto [4], suspension reactor for styrene-acrylonitrile, and Hwang et al. [5], thermal copolymerization in a continuously stirred tank reactor (CSTR). 

Tanaka, M., Izumi, T., Application of stirred tank reactor equipped with draft tube to suspension polymerization of styrene, J. Chem. Eng. Jpn. 18 (1985) 345. 

De Graaf and Poehlein (1971) have measured the MWD of styrene in a continuous stirred-tank reactor. A wide range of particle sizes were present, and thus interpretation of the data is hindered by an inadequate knowledge of the size dependence of the various rate parameters. However, the values reported for the average molecular wei ts suggest again a transfer-dominated process this is also consistent with the value ohiained for P which was close to 2, for a variety of conditions. 

Continuous Continuous stirred tank reactor loop reactor, stirred tank reactors, fluidized reactors, tubular reactors Polyvinyl acetate, styrene-butadiene, PVC (E), polystyrene (S), low-density polyethylene (B)... 

Fig. 2 Online state estimation simulations for a continuous stirred tank styrene polymerization reactor with extended Kalman filter.

Hamielec, A. E. and MacGregor, J. F. (1983) Thermal and chemical-initiated copolymerization of styrene/acrylic acid at high temperatures and conversions in a continuous stirred tank reactor, Proc. Internat. Berlin Workshop on Polymer Reaction Engineering, Berlin. 

There are two common types of continuous reactors continuous stirred tank reactors (CSTRs) (53), and plug flow reactors (PFRs). CSTRs are simply large tanks that are ideally well-mixed (such that the emulsion composition is uniform throughout the entire reactor volume) in which the polymerisation takes place. CSTRs are operated at a constant overall conversion. CSTRs are often used in series or trains to build up conversion incrementally. Styrene-butadiene rubber has been produced in this manner. Not all latex particles spend the same amount of time polymerising in a CSTR. Some particles exit sooner than others, producing a distribution of particle residence times, diameters and compositions. 

Pig. 7. Two Continuous stirred tank reactors (CSTR) and a continuous plug flow reactor (CPFR) configuration utilized for continuous mass polymerization of styrene. 

The styrene and acrylonitrile can be copolymerized by free radical methods using a continuous stirred tank reactor (CSTR). The reactivity ratios r,2 and rj, can be taken as 0.04 and 0.41, respectively. Construct a first-order Markov model using the dyad probabilities derived in Section 11.1. 

Temperature and free-radical concentration are important features that vary along the length of the plug-flow tubular reactor model of the polymerization of ethylene/ Stirred-tank reactor models of the anionic polymerization of styrene and of butadiene have been described and tested against experiments. Mathematical modelling of polymerization reactions receives some attention in the book by Froment and Bischoff. ... 

Raw materials like styrene (potentially purified), and processing aid are fed into the reactor(s). The reactor train usually includes continuous stirred tank reactors (CSTR) and/or plug flow reactors (PFR). 

The reactor train usually includes continuous stirred tank reactors (CSTR) and/or plug flow reactors (PFR). The styrene itself acts as the solvent of the reaction. Moreover, up to 10 % of ethylbenzene is added to ensure a better reaction control. The reactors temperatures are between 110 and 180 °C. The pressure is up to 1 MPa in a PFR, whereas reactions in CSTR are carried out under atmospheric or sub-atmospheric pressure. At the end of the reactor train, the styrene monomer conversion reaches 60 - 90 % solid. 

The reaction is carried out continuously in a series of continuously stirred tank reactors (CSTR) under moderate pressure. The latex is then stripped of unreacted monomers. Butadiene is removed in flash tanks, the first at atmospheric pressure and an optional second under vacuum. The latex then passes to steam stripping columns, where styrene is removed. 

Emulsion polymerization is mostly carried out in stirred tank reactors operated semicontinuously. The reason for using semicontinuous operation is that under similar reaction conditions, the polymerization rate is higher than in bulk (see Section ), which makes the thermal control of the reactor difficult even with the relatively low overall viscosity of the reaction medium. Therefore, heat generation rate is controlled by feeding the monomers slowly. In addition, the semicontinuous operation allows better control of polymer characteristics. Continuous stirred tank reactors are used for the production of some high-tonnage emulsion polymers such as styrene-butadiene rubber. 

Continuous stirred tank reactor polymerization reactors can also be subject to oscillatory behavior. A nonisothermal CSTR free radical solution polymerization can exhibit damped oscillatory approach to a steady state, unstable (growing) oscillations upon disturbance, and stable (limit cycle) oscillations in which the system never reaches steady state and never goes unstable, but continues to oscillate with a fixed period and amplitude. However, these phenomena are more commonly observed in emulsion polymerization. High-volume products such as styrene-butadiene rubber (SBR) often are produced by continuous emulsion polymerization. As noted earlier, this is... 

A number of studies endeavored to experimentally determine the values of the desorption rate constant. It is also interesting to note that Lee and Poehlein [46,48,49] modified the approach of Ugelstad et al. [8,9] and applied it to emulsion polymerization carried out in a single continuous stirred tank reactor (CSTR) system. The resultant latex particle size distribution data were then used to determine the value of A des. The k data obtained from other literature are summarized in Table 4.4. Significant variations in the values of k isi for the emulsion polymerizations of styrene at 60 °C are observed. 

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