Reactivity modelling

Finally, let us return to the question of the practical importance of thermal diffusion and thermal transpiration in modeling reactive catalyst... 

Within the predictive capabilities of the models, reactivity is given by bThe larger r- the more reactive the molecule (or ion or radical). Note that the tenriinal carbon atoms in buta-1,3-diene are predicted by Iltiekcl theoiy to be slightly more reactive than the carbon atoms in ethylene. Qualitative eoirelation with experience is seen fur sume alkenes and free radicals in Fig. 7-3,... 

Table 7.1 Terminal Model Reactivity Ratios for Some Common Monomer Pairs9...

Thus, the terminal model allows the copolymer composition for a given monomer feed to be predicted from just two parameters the reactivity ratios rAB and rBA- Some values of terminal model reactivity ratios for common monomer pairs are given in Table 7.1. Values for other monomers can be found in data... 

The Chemistry of Radical Polymerization Table 7.5. Implicit Penultimate Model Reactivity Ratios... 

It is also possible to process copolymer composition data to obtain reactivity ratios for higher order models (e.g. penultimate model or complex participation, etc.). However, composition data have low power in model discrimination (Sections 7.3.1.2 and 7.3.1.3). There has been much published on the subject of the design of experiments for reactivity ratio determination and model discrimination.49 "8 136 137 Attention must be paid to the information that is required the optimal design for obtaining terminal model reactivity ratios may not be ideal for model discrimination.49... 

Terminal model reactivity ratios may be estimated from the initial monomer feed composition and the dyad concentrations in low conversion polymers using the following relationships (eqs. 45, 46). 

Similarly, penultimate model reactivity ratios can be estimated from initial monomer feed composition and triad concentrations using eqs. 50-53. 

Harwood112 proposed that the solvent need not directly affect monomer reactivity, rather it may influence the way the polymer chain is solvated. Evidence for the proposal was the finding for certain copolymerizations, while the terminal model reactivity ratios appear solvent dependent, copolymers of the same overall composition had the same monomer sequence distribution. This was explained in... 

The apparent terminal model reactivity ratios are then r => aK and c =rR, K It follows that rABVBf = rABrBA - const. The bootstrap effect does not require the terminal model and other models (penultimate, complex participation) in combination with the bootstrap effect have been explored.103,1 4215 Variants on the theory have also appeared where the local monomer concentration is a function of the monomer feed composition.11[Pg.431]

Publish comprehensive guidance on model reactive hazard management systems. At a minimum, ensure that these guidelines cover ... 

Taylor R, Krishna R. Modeling reactive distillation. Chem Eng Sci 2000 55 5183-5229. 

In this example of model reactive polymer processing of two immiscible blend components, as with Example 11.1, we have three characteristic process times tD,, and the time to increase the interfacial area, all affecting the RME results. This example of stacked miscible layers is appealing because of the simple and direct connection between the interfacial layer and the stress required to stretch the multilayer sample. In Example 11.1 the initially segregated samples do create with time at 270°C an interfacial layer around each PET particulate, but the torsional dynamic steady deformation torques can not be simply related to the thickness of the interfacial layer, <5/. However, the initially segregated morphology of the powder samples of Example 11.1 are more representative of real particulate blend reaction systems. 

B3LYP/6-31++G(d,p) and solvation models Reactivity toward lithiation 2004T10899... 

The techniques just described have been extensively used in modeling reactive flow problems at NRL. Efficient solution of the coupled ordinary differential equations associated with these problems has enabled us to perform a wide variety of calculations on H2 °2 anC Ha/Oo mixtures which have greatly extended our understanding of tne combustion and detonation behavior of these systems. In addition numerous atmospheric problems have been studied. Details on these investigations are provided in references (7) and (9). 

Lichtner P. C. (1998) Modelling reactive flow and transport in natural systems. Proceedings of the Rome Seminar on Environmental Geochemistry, 5-72. 

Understanding chemical reactivity of zeolites is in fact the primary focus of interest of most zeolite studies. Modeling reactivity has formed the subject of many reviews that describe both the computational techniques and specific results in detail (see, e.g.. Refs. 4, 6, 58). 

---