Conversion-time diagram

Carefully determined conversion-time diagrams, in-situ spectroscopic studies and, if possible, kinetic time laws belong to the fundamentals of catalysis research and are prerequisites for a mechanistic understanding [8]. 

The hydrolysis of ds-2-NHTs-cyclopentane nitrile ( )-2a over a prolonged reaction time was investigated to check whether it could be extended over the amide stage to formation of acid 2c, a derivative of cispentacin. The conversion-time diagram of ( )-2a is depicted in Figure 15.3, suggesting that the acid 2c could be accumulated in an amount of 34% after 206 h [34]. 

Figure 15.7 Conversion-time diagram of cis-NHTs-cyclopentane carbonitrile ((+)-13a) hydrolysis by NIT-106.

The conversion-time diagram of ( )-13a to 13c in Figure 15.7 shows that the kinetic resolution of this substrate proceeds nearly quantitatively within 2 h. 

Fig. 1. Conversion-time diagram (radical-initiated graft polymerization) G-graft, H-homopolymerization.

Fig. 2. Conversion-time diagram (anionic graft reaction).

Figure 2.14. A three-dimensional conversion-time-temperature (aTT) diagram. Reprinted from Figure 7 (Osinski, 1993). Copyright (1993), with permission from Elsevier.

The conversion vs. time diagram (Figure 1) illustrates the dependence of the reaction rate on the chain length of the alkene. The reaction proceeds according to first-order kinetics, i.e., the consumption rate of the substrate alkene is proportional to the concentration of the substrate. 

Figure / Acetone cracking. Conversion versus space-time diagram at 750°C (from Froment, era/. [5.6]).

The curing kinetics of system EPS-l/DDM was studied by a method of reverse gas chromatography (RGC) [29]. The basic parameter received from processing of the experimental data, was the constant of reaction rate k determined for an interval of conversion degrees a = 0.1-0.7 of the kinetical curve degree of conversion-time (a-t). For the determination of k the standard procedure was used the dependences, a, on the reaction time t, as lg[a/(l-a)]=/ (t) which have appeared linear were made. Then the value k (see Equation (10.4)) was determined from a slope of these linear diagrams. Ketones (metyl ethyl ketone, 1,4-dioxane, cyclohexanone) were chosen as the standard substances for the determination of retention time with argon as the gas-carrier. 

STA Diagram Conversion Time versus Temperature (Isoconversion, Conversion Level 70 %)... 

If one wishes to attain high conversion at constant composition, the more reactive monomer must be added in a programmed manner. The procedure is as follows from the copolymerization diagram (or from the reactivity ratios) one obtains the monomer composition that will lead, at low conversion, to the desired copolymer composition. A conversion/time curve is drawn up for this system and the composition of the copolymer determined from time to time. From this, one can find how much of the more reactive monomer is to be added at given times during the polymerization in order to maintain an approximately constant composition (see Example 3.39). Special computer software has already been developed for this. 

As an aid in the precise definition of integral and differential reactors, Fig. 4.13 shows a conversion versus time diagram, and the transfer of these data to a continuous tubular reactor (Moser and Lafferty, 1976). 

In the previous section, conversion-time data indicate that for the FRRPP of styrene in ether, practical asymptotic values of 15 or 40% conversion were achieved for starting monomer compositions of 10 or 14.3 wt% (Figs. 2.3.5 and 2.3.8). From the phase envelopes shown in Fig. 2.3.1, these data correspond to overall polymer compositions in the reactor to be up to 2 or 4 wt% only. It should also be noted that number-average PS molecular weights were only up to 6,000 Da (Fig. 2.3.6) or 3,000 Da (Fig. 2.3.9), while thermodynamic data in Fig. 2.3.1 went down to PS molecular weight of only 25,000 Da. This means that the polymer may not have entered the polymer-rich regions in the phase diagram if it is required to cross the IPPC or spinodal, from a nonreactive standpoint. Indeed, reactor fluids have been shown to exhibit viscosities close to that of the solvent than a polymer solution at these conditions of FRRPP of styrene in ether. If the polymer macromolecules... 

Fig. 6 illustrates the value of direct information on reaction rate. After catalyst addition there is at first a marked increase of reaction rate at constant temperature, where one would e q>ect a first order decrease. This is due to a considerable increase in polarity of the reaction mixture as a consequence of conversion. The heat flow record demonstrates this fact more evidently than a classical conversion versus time diagram. ... 

Conversion of creep data into creep moduius versus time diagrams... 

Pressure/vacuum, 435, 466 Vacuum systems, 343 Absolute pressure conversions, 363 Air inleakage, 366 Calculations, 366-375 Dissolved gases release, 368 Estimated air inleakage, table, 366 Evacuation time, 371 Maximum air leakage, chart, 367 Specific air inleakage rates, 368 Temperature approach, 375 Classifications, 343 Diagrams, 380 Pressure drop, 353 Pressure levels, 343, 352 Pressure terminology, 348 Pump down example, 381 Pump down time, 380 Thermal efficiency, 384 Valve codes, 26... 

The most important data during main drying is the temperature at the moving sublimation front which cannot be measured by Ths or RTDs. In 1958, Neumann and Oetjen 11.651 showed that the barometric temperature measurement (BTM) measures exactly this data. In Fig. 1.77 this is schematically shown if the drying chamber is separated from the condenser by a valve for a short time the pressure in the chamber rises to the saturation vapor pressure (ps) corresponding to the temperature of the sublimation front. ps can be converted into the ice temperature by the water vapor- temperature diagram (e. g. 0.3 mbar = -30 °C). Data for accurate conversion are given in Table 1.11 the temperatures between -100 and -1 °C. 

The second large-scale process was the batch mass suspension process. Monsanto did the pioneer work on this (41). In this process, prepolymerization is carried out in bulk and main polymerization in suspension the latter is taken to conversions of over 99%. In contrast to the continuous mass process, peroxide starters are used in order to achieve a high conversion at tolerable reaction times. Figure 3 shows a basic flow diagram of such a plant. A detailed discussion of advantages and disadvantages of the two processes can be found in R. Bishop s monograph published in 1971 (42), and it is continued in a paper by Simon and Chappelear in 1979 (43). It was a decisive factor for the economic success of impact polystyrene that these processes had been completely developed and mastered in theory and practice. 

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