5- batch conversion

For batch reactors, account has to be taken of the time required to achieve a given conversion. Batch cycle time is addressed later. 

The existence of an azeotropic composition has some practical significance. By conducting a polymerization with the monomer feed ratio equal to the azeotropic composition, a high conversion batch copolymer can be prepared that has no compositional heterogeneity caused by drift in copolymer composition with conversion. Thus, the complex incremental addition protocols that arc otherwise required to achieve this end, are unnecessary. Composition equations and conditions for azeotropic compositions in ternary and quaternary eopolymerizations have also been defined.211,21... 

Although low conversion reactors can be used for PS and HIPS, high conversion batch reactors are generally limited to PS because of difficulties with HIPS. In particular, the HIPS cake from a polypress is difficult to grind and, because of poor temperature control, is inferior in toughness. 

High Conversion Batch Mass Reactors. Because of the very high viscosities at high conversion, these reactors are unagitated. Temperature control therefore depends upon conduction through the polymer to extended heat transfer surfaces. Most common are the cooled plates of the plate and frame... 

Example 13.6 The following data were obtained using low-conversion batch experiments on the bulk (solvent-free), free-radical copol)mierization of styrene (X) and acrylonitrile (Y). Determine the copolymer reactivity ratios for this pol5Tnerization. 

Room temperature conversions—Batch Swern usually 2005/[66]... 

The modeling of ECR systems involves, as that of any other reaction system, the development of a suitable reaction model for subsequent use in reactor modeling. The reaction model for an ECR is an expression for the dependence of current density on reaction parameters such as reactant concentration, electrode potential, rate constants, pH, temperature, etc. The reactor model relates the reactor parameters to performance criteria. The objective is to evolve suitable expressions for the computation of the electrode area required for a desired conversion, batch time, etc. We devote the next section to developing reaction models for simple electrochemical systems and proceed to reactor modeling in the following section. 

Incompatible and ideal copolymerizations behave very differently in high-conversion batch polymerizations. This is illustrated in Figure 12.4 for the AN-VA and AN-MA monomer pairs discussed above. In the AN-VA system, the AN is consumed more rapidly than the VA. Therefore, the unreacted monomer mixture becomes richer in VA as conversion increases. This results in a drift in copolymer composition with conversion. The AN-MA system, in contrast, shows little or no drift, and consequently a more uniform copolymer... 

Conversion Batch Semicontinuous Continuous (steady state)... 

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