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Polymerization batch /plug-flow

Polymerization Reaction Polymerization Process Batch Plug Flow CSTR... [Pg.719]

Polymerization reactions. Polymers are characterized by the distribution of molecular w eight about the mean as well as by the mean itself. The breadth of this distribution depends on whether a batch or plug-flow reactor is used on the one hand or a continuous well-mixed reactor on the other. The breadth has an important influence on the mechanical and other properties of the polymer, and this is an important factor in the choice of reactor. [Pg.33]

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. [Pg.206]

Graessley and his co-workers have made calculations of the effects of branching in batch polymerizations, with particular reference to vinyl acetate polymerization, and have considered the influence of reactor type on the breadth of the MWD (89, 91, 95, 96). Use was made of the Bamford and Tompa (93) method of moments to obtain the ratio MJMn, and in some cases the MWD by the Laguerre function procedure. It was found (89,91) that narrower distributions are produced in batch (or the equivalent plug-flow) systems than in continuous systems with mixing, a result referrable to the wide distribution of residence times in the latter. [Pg.30]

A number of innovative polymerization reactors using loop reactors, plug-flow and static mixer reactors, and continuous stirred-tank reactors have been reported. For example, Wilkinson and Geddes (15) describe a 50-liter reactor that has the same capacity as a 5000-gallon batch reactor. Extruders, thin-film evaporators, and other devices designed to provide intense mixing for viscous or unstable materials have also been used as reactors. [Pg.494]

The polymerization time in continuous processes depends on the time the reactants spend in the reactor. The contents of a batch reactor will all have the same residence time, since they are introduced and removed from the vessel at the same times. The continuous flow tubular reactor has the next narrowest residence time distribution, if flow in the reactor is truly plug-like (i.e., not laminar). These two reactors are best adapted for achieving high conversions, while a CSTR cannot provide high conversion, by definition of its operation. The residence time distribution of the CSTR contents is broader than those of the former types. A cascade of CSTR s will approach the behavior of a plug flow continuous reactor. [Pg.371]

Olefin polymerization in batch reactors is not common. Laboratory-scale high-throughput reactors are perhaps one of the few examples of such reactors applied to olefin polymerization. Some olefin polymerization tubular reactors can also be treated as batch reactors, where a polymerization-time to reactor-length transformation can be made and directly applied to the equations derived above if the tubular reactor has plug-flow residence time. [Pg.68]

Performing polymerization reactions in perfectly mixed flow reactors leads to quite different results from those obtained in batch or plug flow reactors, as discussed in 1951 already by Denbigh [1951]. The key point concerns the relative lifetimes of the active propagating polymer species. If this is long relative to the mean holding time of the fluid in the reactor, the rules in Section... [Pg.468]

In the case of free radical polymerization (figure 13.2) the dispersion index D at low degrees of conversion appears to be 1.5. In a batch or plug flow reactor D increases as the degree of conversion goes up. The reason is that the propagationrinitiation ratio decreases as the monomer is consumed. For a segregated CSTR the effect is enhanced by the residence time distribution. For a well mixed CSTR D remains constant and low. This is explained by the fact that all polymer molecules are made under identical conditions. [Pg.295]


See other pages where Polymerization batch /plug-flow is mentioned: [Pg.717]    [Pg.294]    [Pg.34]    [Pg.233]    [Pg.338]    [Pg.93]    [Pg.329]    [Pg.233]    [Pg.141]    [Pg.434]    [Pg.18]    [Pg.20]    [Pg.22]    [Pg.23]    [Pg.34]    [Pg.36]    [Pg.114]    [Pg.115]    [Pg.147]    [Pg.52]    [Pg.2108]    [Pg.2110]    [Pg.2094]    [Pg.2096]    [Pg.274]    [Pg.437]    [Pg.177]    [Pg.283]    [Pg.308]    [Pg.138]    [Pg.164]    [Pg.317]    [Pg.167]    [Pg.3770]    [Pg.23]    [Pg.469]    [Pg.235]    [Pg.517]    [Pg.346]    [Pg.355]   
See also in sourсe #XX -- [ Pg.111 ]




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