Semibatch reactor polymerization

Semibatch Model "GASPP". The kinetics for a semibatch reactor are the simpler to model, in spite of the experimental challenges of operating a semibatch gas phase polymerization. Monomer is added continuously as needed to maintain a constant operating pressure, but nothing is removed from the reactor. All catalyst particles have the same age. Equations 3-11 are solved algebraically to supply the variables in equation 5, at the desired operating conditions. The polymerization flux, N, is summed over three-minute intervals from the startup to the desired residence time, t, in hours ... 

For all likely operating conditions, (ie., for t < X), the appropriate values of the concentration and the polymerization rate constant are the values calculated at t = t ( 2). To prove this, the exit age distribution function for a backmix reactor was used to weight the functions for Cg and kj and the product was integrated over all exit ages (6). It is enlightening at this point to compare equation 18 with one that describes the yield attainable in a typical laboratory semibatch reactor at comparable conditions. ... 

The yield that can be attained by a semibatch process is generally higher because the semibatch run starts from scratch, with maximum values of both variables Cg (o) = Cg and k] (o) = k . However, the yield from a continuous run in which t equals the batch time is governed by the product of Cg (t) and kj (t), so > and k (t) = k °. Because neither of these conditions is likely to be fulfilled completely, a continuous polymerization in a backmix reactor will probably always fail to attain the Y attainable by a semibatch reactor at the same t. However, several backmix reactors in series will approach the behavior of a plug flow continuous reactor, which is equivalent to a semibatch reactor. 

This section is divided into three parts. The first is a comparison between the experimental data reported by Wisseroth (].)for semibatch polymerization and the calculations of the kinetic model GASPP. The comparisons are largely graphical, with data shown as point symbols and model calculations as solid curves. The second part is a comparison between some semibatch reactor results and the calculations of the continuous model C0NGAS. Finally, the third part discusses the effects of certain important process variables on catalyst yields and production rates, based on the models. 

Semibatch operation safety, 21 843 Semibatch polymer colloid process, 20 376 Semibatch polymerization of vinyl acetate, 25 608 Semibatch reactors, 21 332 Semibright nickel, 9 820 Semibulk containers, 18 5-6 Semibullvalene... 

Semibatch reactors are commonly used for small-volume chemical production. This reactor type is frequently used for biological reactions and for polymerization. In the batch reactor. 

Figure 7. Degree of polymerization with reaction time in a controlled semibatch reactor. Key ---, WADP -------,...

Liotta, V. Sudol, E.D. El-Aasser, M.S. Georgakis, C. On-line monitoring, modeling, and model validation of semibatch emulsion polymerization in an automated reactor control facility. J. Polym. Sci. Pt. A Polym. Chem. 1998, 36 (10), 1553-1571. 

Mitra et al. (1998) employed NSGA (Srinivas and Deb, 1994) to optimize the operation of an industrial nylon 6 semibatch reactor. The two objectives considered in this study were the minimization of the total reaction time and the concentration of the undesirable cyclic dimer in the polymer produced. The problem involves two equality constraints one to ensure a desired degree of polymerization in the product and the other, to ensure a desired value of the monomer conversion. The former was handled using a penalty function approach whereas the latter was used as a stopping criterion for the integration of the model equations. The decision variables were the vapor release rate history from the semibatch reactor and the jacket fluid temperature. It is important to note that the former variable is a function of time. Therefore, to encode it properly as a sequence of variables, the continuous rate history was discretized into several equally-spaced time points, with the first of these selected randomly between the two (original) bounds, and the rest selected randomly over smaller bounds around the previous generated value (so as... 

You are asked to design a semibatch reactor to be used in the production of specialized polymers (ethylene glycol-ethylene oxide co-polymers). The semi-batch operation is used to improve the molecular-weight distribution. Reactant B (EG) and a fixed amount of homogeneous catalyst are charged initially into the reactor (the proportion is 6.75 moles of catalyst per 1000 moles of Reactant B). Reactant A (EO) is injected at a constant rate during the operation. The polymerization reactions are represented by the following liquid-phase chemical reactions ... 

Types of Reactor Processes Batch Reactors Semibatch Reactors Continuous Reactors Emulsion Polymerization Kinetics Other Preparation Methods... 

The change in polymer composition as a result of monomer drift gives a macroscopic composition distribution. It can be eliminated by polymerizing at the azeotrope, by polymerizing to low conversion, by continuously adding the more reactive monomer in a semibatch reactor, or by polymerizing in a CSTR, the last method... 

In Equations 6.70-6.74, is the propagation rate coefficient for the addition of monomer j to a growing polymer radical ending in monomer i, (pi is the mole fraction of radicals ending in monomer i, [P ] is the total concentration of radicals in the reactor, P is the time-varying feed rate of monomer i to the semibatch reactor, V is the reactor volume, MW is the molecular weight of monomer i, is the rate of polymerization of monomer i, and and are the densities of monomer i and the polymer, respectively. 

Tip 13 (related to Tip 12) Copolymerization, copolymer composition, composition drift, azeotropy, semibatch reactor, and copolymer composition control. Most batch copolymerizations exhibit considerable drift in monomer composition because of different reactivities (reactivity ratios) of the two monomers (same ideas apply to ter-polymerizations and multicomponent cases). This leads to copolymers with broad chemical composition distribution. The magnirnde of the composition drift can be appreciated by the vertical distance between two items on the plot of the instantaneous copolymer composition (ICC) or Mayo-Lewis (model) equation item 1, the ICC curve (ICC or mole fraction of Mj incorporated in the copolymer chains, F, vs mole fraction of unreacted Mi,/j) and item 2, the 45° line in the plot of versus/j. 

Semibatch solution polymerization is a well-established method for producing acrylic resins. In the semibatch solution process, solvent is commonly charged to the reactor and heated to the desired reaction temperature, typically 100-140 °C. Monomer, initiator, and other ingredients are slowly fed to the reactor over a period of 4-6 h to achieve a desired solids content (typically up to 70% by weight solids). During polymerization, the solvent may be refluxed to help remove the heat of polymerization [40]. At the end of the polymerization, a hold time and post charge of initiator solution are common to techniques designed to reduce... 

Semibatch and continuous stirred-tank reactors (CSTRs) are much more commonly found in polyolefin production. Semibatch reactors are the standard choice for laboratory-scale polymerizations, while CSTRs dominate industrial production, as will be seen in Section 2.5. The equations derived above are easily translated into semibatch and CSTR operation mode by simply adding terms for the inflow and outflow streams in the reactor. For instance, consider Equation 2.49 for the zeroth moment of dead chains. The molar flow rate [mol s ] leaving the reactor is given by... 

Seth, V. Gupta, S.K. (1995) Free radical polymerizations associated with the Trommsdorff effect under semibatch reactor conditions an improvement model. Journal of Polymer Engineering, 15(3-4), 283-323. 

Polymerization of reactants is a common occurrence in many reactions. Although this is also a parallel scheme, it will be noticed that high concentrations of A combined with low concentrations of B will favor the desired product R. Thus, a semibatch reactor (SBR) would be the preferred candidate since the above condition is met in this reactor. We will see the design equations and principles of operation of SBRs later in this chapter. On the other hand, the common BR, PFR, and MFR would all give lower selectivities because they all allow the second reaction to proceed without hindrance. 

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