Single-component reaction

Fig. 10.29 Comparison between the experimental data on the reactive extrusion product of n-butyl methacrylate in a counterrotating, fully intermeshing extruder, (a, h) The dependence of conversion and M,x on throughput (c, d) the dependence of conversion and M on die pressure. (+, O) experimental point, (— ) model prediction. [Reprinted hy permission from K. J. Gadzenveld et al., The Modeling of Counterrotating TSEs as Reactors for Single-component Reactions, Chem. Eng. ScL, 49, 1639 (1994).]...

Single-component reactions can occur throughout the bulk of the material. At the start of the reaction only one single component, monomer or prepolymer, is present or the components used are well miscible and premixed. For this group of reactions the temperature of the mixture plays an important role, as well as macro-mixing over the length of the extruder, which is related to the residence time distribution. Both parameters determine the progress of the reaction. 

The effects of catalyst on the product distribution for selected plastic/residue doublecomponent systems are shown in Table 14.2. The results show that the presence of residue increased the overall conversion in the double-component coprocessing reactions compared to the single-component reactions except in the case of polystyrene [14]. 

The degree of polymerization (M ) can also be expressed in terms of the conversion (Q. Considering again a single-component reaction, consisting of reactants with two functional groups, the number of chain molecules (including monomers) ([/) equals half the amount of end... 

The reaction diagram for a single component reaction, as shown in Fig. 7.2 has two adjustable parameters, the amount of initiator and therefore the radical concentration and the temperature, all other parameters depend on changes in these two primary variables (2). Due to the deeomposition kinetics, the radical concentration depends of course also on the temperature of the reacting mixture. In reactive extrusion this temperature is affected by the wall temperature and the heat transfer coefficient but also by the reaction velocity, which, in turn, is influenced by the radical concentration and the temperature. The reaction velocity, together with the residence time determines the conversion, which has its effect on the viscosity of the reacting mixture. The viscosity is also affected by the average... 

With a single-component reaction, only one material is present and micromixing and diffusion do not play a role. To determine the scale-up... 

For thermal similarity the reasoning is similar to that given for single component reactions. This implies that also for multieomponent reaetions thermal similarity can be reached if DalV is large but that no consistency can be obtained if this number is small. 

Recent significant advance in the area of the transition metal-mediated aromatic ring construction reactions enables the construction of substituted benzenoid aromatic rings with efficient and convenient manners [1], These aromatic ring constrnction reactions provide promising new routes to the complex benzenoid aromatic compounds. In this chapter, I snmmarize the intermolecular multicomponent reactions and the intramolecnlar single-component reactions, which are able to construct benzenoid aromatic rings. 

As the intermolecular multicomponent reactions, three-component cycloaddition reactions (21.2 [2+2-1-2] cycloaddition and 21.3 [3+2+1] cycloaddition) and two-component cycloaddition reactions (21.4 [4+2] cycloaddition) are described. As the intramolecnlar single-component reactions, cycloaromatization reactions (21.5 intramolecular hydroarylation of alkynes and cychzation via transition metal vinybdenes) are described. Aromatic ring constrnction reactions involving aryne reactions (Chapter 12), rearrangement reactions (Chapters 16 and 18), metathesis reactions (Chapter 17), and coupling reactions (Chapters 19 and 20) are described in these different chapters. 

In this chapter, single-component reactions are discussed. To model the extruder as a reactor for this kind of reaction, a complex interaction of reaction and extruder parameters has to be unraveled [7,8]. As an example of a single-component reaction the polymerization of n-butylmethacrylate is studied and analyzed. 

The bulk polymerization of n-butylmethacrylate is a free-radical addition polymerization. With this type of single-component reaction, polymer chains are formed in a relatively short time and are subsequently excluded from... 

Fig. 4 The steady-state reactive extrusion diagram for single-component reactions.

The performance of single-component polymerizations in a twin screw extruder is dependent on several extruder parameters. Each parameter has its specific influence on the conversion of the reaction and the average molar mass of the polymer formed. To understand the influence of the parameters, a theoretical analysis of the reactive extrusion process was developed in the form of a reactive extrusion interaction diagram. The conclusions which can be drawn from the theoretical and the experimental investigations of a single-component reaction (the polymerization of butylmethacrylate) in a twin screw extruder are as follows ... 

To be able to model the extruder completely for single>component reactions extended investigations on the kinetics of the reaction, the influence of the barrel wall temperature and different initiators have to be carried out. 

Ganzeveld, K. J. and Janssen, L. P. B. M., The modelling of counter-rotating twin screw extruders as reactors for single-component reactions, Chem. Eng. Sci. 49 1639 (1994). 

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