Choice of reactor configuration

The effects of various reactor configurations on the properties of the polymer (MWD, CCD, etc.) have been reviewed for each of the three main schemes of polymerization kinetics. Reactor selection based on polymerization kinetics as well as practical considerations will now be discussed. Since polymers are products by process , it is not surprising that very specific conclusions can 

Reactor Monomer linkage Termination No termination Polymer linkage 

Batch or PFR Wider than Flory Poisson Flory 

Homogeneous CSTR Flory Flory Wider than Flory 

Segregated CSTR Wider than Between Between 

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Of these, fixed-bed adiabatic reactors are the cheapest in terms of capital cost. Tubular reactors are more expensive than fixed-bed adiabatic reactors, with the highest capital costs associated with moving and fluidized beds. The choice of reactor configuration for reactions involving a solid supported catalyst is often dominated by the deactivation characteristics of the catalyst. 

Catalyst degradation can be a dominant issue in the choice of reactor configuration, depending on the rate of deactivation. Slow deactivation can be dealt with by... 

The choice of reactor configuration and conditions can also be based on the optimization of a superstructure. Combinations of complexities can be included in the optimization. An added advantage of the approach is that it also allows novel configurations to be identified, as well as standard configurations. 

The choice of reactor configuration depends on the properties of the reaction system. For example, bioconversions for which the homogeneous catalyst distribution is particularly important are optimally performed in a reactor with the biocatalyst compartmentalized by the membrane in the reaction vessel. The membrane is used to retain large components, such as the enzyme and the substrate while allowing small molecules (e.g., the reaction product) to pass through. For more labile molecules, immobilization may increase the thermal, pH and storage stability of biocatalysts. 

Choice of reactor configuration aerated STR bubble reactors jet loop or air lift fluidized... 

Using the Phases to Guide in the Choice of Reactor Configuration... 

For carrying out multiphase reactions (gas-solid, gas-liquid, gas-liquid-solid, liquid-liquid, gas-liquid-solid, liquid-liquid-solid,...), the number of reactor configurations that are possible is extremely large. There is therefore a need to give careful consideration to the choice of the ideal reactor configuration that meets fully with all the process musts and, to the maximum possible extent, the process wants. The process musts could be ... 

Polyolefins are produced in practically all types of reactor configurations -autoclaves, tubular reactors, loop reactors, fiuidized-bed reactors - making them a prime choice for polymer reaction engineering studies. Polymerization may take place in either gas or liquid phases. For liquid-phase reactors, the monomers can be either liquid (as in the case of propylene and higher a-olefins) or dissolved in an inert diluent. Industrial catalysts for olefin polymerization are mainly heterogeneous, but some processes also use soluble catalysts. There are many different types of catalysts for olefin polymerization and they can be used to synthesize polymer chains with very different microstructures and properties. 

The design of a polymerization reactor begins with the selection of the type of reactor (batch, semibatch or continuous) and then proceeds to the sizing and details of the reactor configuration. Only then can the details of operation and control be addressed. To this end, we will begin with a discussion of the basic types of reactors. Ultimately, it will be clear that the choice of reactor type is determined not only by practical considerations such as scale of production and propensity for fouling, but also by the specific polymerization kinetics. More complete discussions of reactor types and their residence time distributions may be found in references [1,2],... 

Another important challenge is to enhance the reliability of the design and scale up of multi-phase reactors, such as fluidized bed reactors and bubble-colunms. The design uncertainty caused by the complex flow in these reactors has often led to the choice of a reactor configuration that is more reliable but less efficient. An example is Mobil use a packed-bed reactor for the methanol to gasoline process in New Zealand, even though a... 

The current work indicates that sulfided platinum catalysts are, in general, more active and selective than Pt, Pd, or sulfided Pd catalysts for reductive alkylation of primary amines with ketones. The choice of the catalyst preparation parameters, especially the support, plays a major role in determining the performance of the catalyst. Diamines, especially of lower molecular weight, tend to react with ketones even at room temperature to form heterocycles such as imidazolidine, diazepanes, and pyrimidines. Hence, a continuous reactor configuration that minimizes the contact between the amine and the ketone, along with a highly active catalyst is desired to obtain the dialkylated product. In general, sulfided Pt appears to be more suited for the reductive alkylation of ethylenediamine while unsulfided Pd or Pt may also be used if 1,3-diaminopropane is the amine. 

The performance of most catalysts deteriorates with time3-5. The rate at which the deterioration takes place is not only an important factor in the choice of catalyst and reactor conditions but also the reactor configuration. 

The remainder of this text attempts to establish a rational framework within which many of these questions can be attacked. We will see that there is often considerable freedom of choice available in terms of the type of reactor and reaction conditions that will accomplish a given task. The development of an optimum processing scheme or even of an optimum reactor configuration and mode of operation requires a number of complex calculations that often involve iterative numerical calculations. Consequently machine computation is used extensively in industrial situations to simplify the optimization task. Nonetheless, we have deliberately chosen to present the concepts used in reactor design calculations in a framework that insofar as possible permits analytical solutions in order to divorce the basic concepts from the mass of detail associated with machine computation. 

Stainless steel is the material of choice for process chemistry. Consequently, stainless steel microreactors have been developed that include complete reactor process plants and modular systems. Reactor configurations have been tailored from a set of micromixers, heat exchangers, and tube reactors. The dimensions of these reactor systems are generally larger than those of glass and silicon reactors. These meso-scale reactors are primarily of interest for pilot-plant and fine-chemical applications, but are rather large for synthetic laboratories interested in reaction screening. The commercially available CYTOS Lab system (CPC 2007), offers reactor sizes with an internal volume of 1.1 ml and 0.1 ml, and modular microreactor systems (internal reactor volumes 0.5 ml to... 

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