Conversion degrees

TREYBiG AND ANTHONY Atiionic Styrene Polymerization TABLE IV. EXPERIMENTAL MONOMER CONVERSIONS DEGREES OF POLYMERIZATION FOR CFSTR RUNS 1 313 AND -15... 

In most cases the conversion degrees and the yields in aldehydes are good (86-95%) and the regioselectivity goes from 1.2 1 to 31.1 1, depending on the ligand used. 

The kinetics of the CTMAB thermal decomposition has been studied by the non-parametric kinetics (NPK) method [6-8], The kinetic analysis has been performed separately for process I and process II in the appropriate a regions. The NPK method for the analysis of non-isothermal TG data is based on the usual assumption that the reaction rate can be expressed as a product of two independent functions,/ and h(T), where f(a) accounts for the kinetic model while the temperature-dependent function, h(T), is usually the Arrhenius equation h(T) = k = A exp(-Ea / RT). The reaction rates, da/dt, measured from several experiments at different heating rates, can be expressed as a three-dimensional surface determined by the temperature and the conversion degree. This is a model-free method since it yields the temperature dependence of the reaction rate without having to make any prior assumptions about the kinetic model. 

Figure 2. Experimental reaction rates vs. the conversion degree for the CTMAB decomposition in SBA-3 at different heating rates (from bottom to top 3, 6, 9, 12 and...

The methane and the carbon dioxide selectivities as well as the selectivities concerning the product fractions C2 to C3 and C4+ with the respective conversion degrees and a-values at 513 K are shown in Table 2.5. 

The influence of the increasing conversion degree along the catalyst bed on the effectiveness factor is illustrated in Table 12.3. The calculations were carried out for three different CO conversions X = 5, 40, and 80%. 

FIGURE 12.3 Concentration profiles of CO, H2, and H20 in a wax-filled pore (Lpore = 6.7510-4 m -> dparticlecyl = Lpom-4 = 2.710-3 m) at different CO conversion degrees X = 5% (left), 40% (middle), and 80% (right) modeled with Presto Kinetics. 

When having a look at variable conversion degrees, the different gas phase concentrations affect the liquid phase concentrations via the solubility equilibrium, as shown in Table 12.3. 

For a better understanding of the obtained effectiveness factors in Table 12.2, the results of the simulation at different conversion degrees (concentrations of CO, H2, and H20 in a cylindrical catalyst pore) are depicted in Figure 12.3. 

The data derived from modeling at different conversion degrees (X = 5, 40, and 80%) were also compared to the results obtained from the calculation of the classical Thiele modulus. The calculated (by the Thiele modulus) and modeled (by Presto Kinetics) effectiveness factors showed comparable values. Hence, the usage of simulation software is not required to get a first impression of the diffusion limitations in a Fischer-Tropsch catalyst pore. Nevertheless, modeling represents a valuable tool to better understand conditions within a catalyst pore. 

These findings suggest that a prerequisite for the successful continuous operation of bioreactors for azo-dye conversion is the thorough control of carbon loading the azo-dye conversion degree drops to vanishing levels if carbon depletion occurs. 

Continuous Stirred Tank Reactor (CSTR). The conversion degree of the azo-dye, the reaction volume (V) and the volumetric flow rate (Q) of the dye-bearing stream are related to each other through the material balance referred to the dye and extended to the reactor volume. Assuming an unstructured model for the biophase, the material balance yields... 

The Structural Treatment of Limiting Conversion Degree for Solid-State Imidization... 

From the equation (1) p decrease at Df reduction follows, as always Djmacromolecular coil inner regions and results to the fuller chemical transformations, i.e., to conversion degree Q increase. Besides, it is known [4], that at macromolecular coil formation by irreversible aggregation mechanisms in its central part... 

Proceeding from the said above, it s possible to define the limiting conversion degree Qiim by the following identity [8] ... 

Further parameters (3 can be made estimated according to the equation (3) and compared with the limited conversion degree Q, obtained experimentally [1], Such comparison for PAA imidization process without filler and in the presence of 2 phr Na -montmorillonite at... 

Figure 1. The kinetic curves conversion degree time (Q-t) for reesterification reaction without catalyst (1) and in TBT presence (2).

In case of reaction course in the Euclidean spaces the value D is equal to the dimension of this space d and for fractal spaces D is accepted equal to spectral dimension ds [6], By plotting p i=( 1 -O) (where O is conversion degree) as a function of t in log-log coordinates the value D from the slope of these plots can be determined. It was found, that the mentioned plots fall apart on two linear parts at t<100 min with small slope and at PT00 min the slope essentially increases. In this case the value ds varies within the limits 0,069-3,06. Since the considered reactions are proceed in Euclidean space, that is pointed by a linearity of kinetic curves Q-t, this means, that the reesterefication reaction proceeds in specific medium with Euclidean dimension d, but with connectivity degree, characterized by spectral dimension ds, typical for fractal spaces [5],... 

Figure 1. The dependence of conversion degree Q at t= 60 and 300 min on active time f for reesterification reaction without mica (1) and in presence NMM (2), SMM (3), AMM (4).

The aldose (11.1 mmol) was dissolved in water to a final concentration of 0.5 m and subjected to oxidation by addition of glucose oxidase (200 mg, 400 U) and a large excess of catalase (1 mL, 25 kU). The mixture was vigorously stirred under air and the pH was kept constant at 7.5 by means of a pH-stat adding continuously 1 m NaOH. The conversion degree was directly calculated considering the volume of added 1 m NaOH, since 1 mol of NaOH neutralizes 1 mol of aldonic acid formed. 

As expected, the overall reaction rate increases with increasing catalyst volume rate. The effect can be explained in terms of the dependency of the mass transport coefficient ll on the Re munber (Eq. 12). Due to the increase of the volume hold-up of the aqueous phase, the residence time of the organic phase decreases, so that the observed conversion degrees do not change within the limits of the investigated regime. 

On one-electron reduction followed by one-electron oxidation, cis isomers of 2- and 4-nitrostilbenes turn into the neutral nitrostilbene molecules, but in the trans forms. On oxidation of the naked anion-radicals, the neutral trans forms are the only products (cis trans conversion degrees were 100%). In the case of the coordination complexes, the trans isomers are formed only up to 40% (Todres 1992). Scheme 3.45 describes these transformations. 

Figure 11.17 compares the substrate conversion degrees obtained in a PFR and... 

Sucrose (1 M concentration) is hydrolyzed with a conversion degree of 98% by invertase immobihzed in a porous support with a bead size of 3 mm in a continous operation with a flow rate of 5 l.min ... 

A lipase from Rhizomucor miehei is immobilized onto a porous polyamide support with a bead diameter of 0.3 mm and used for the hydrolysis of 100 mM caprylin at pH 7.0 and 30°C, in a continous plug flow reactor. Calculate the amount of immobilized lipase needed to achieve a conversion degree of 97% with an inlet flow rate of 1 l.min ... 

An important quantity that can be deduced from the reaction profile is the rate of the cross-linking polymerization (Rp), i.e., the number of double bonds polymerized or of cross-links formed per second. Rp values were determined from the maximum slope of the kinetic curves (usually reached for conversion degrees between 20 and 40%). Table I summarizes the Rp values for the two photoresists tested under various conditions, namely conventional UV and continuous or pulsed laser irradiation at different light intensities. According to these kinetic data, Rp increases almost as fast as the light-intensity the ratio Io/Rp which is directly related to the product of the light-intensity and the required exposure time was found to vary only in the range 10-8 to... 

Fig. 21. Molecular weight distribution obtained by the turbidimetric method, as a function of the degree of conversion. Degree of conversion (mole/1) a —1.5 b —3.0 c —5.2 d —9.5 (74)...

---