Conversion range

The catalysts most often described in the literature (209—211,252) are sodium or potassium hydroxide, methoxide, or ethoxide. The reported ratio of alkali metal hydroxides or metal alcoholates to that of poly(vinyl acetate) needed for conversion ranges from 0.2 to 4.0 wt % (211). Acid catalysts ate normally strong mineral acids such as sulfuric or hydrochloric acid (252—254). Acid-cataly2ed hydrolysis is much slower than that of the alkaline-cataly2ed hydrolysis, a fact that has limited the commercial use of these catalysts. 

Typically NO conversion ranges from 80 to 95% and there are corresponding decreases in CO and hydrocarbon concentrations. Potential problems associated with NSCR appHcations include catalyst poisoning by oil additives, such as phosphoms and 2inc, and inadequate control systems (37). 

The viscosity of the organic phase increases during the reaction, notably in the 70-100% conversion range. 

Striking support of this contention is found in recent data of Castro (16) shown in Figure 14. In this experiment, the polymerization (60-156) has been carried out in a cone-and-plate viscometer (Rheometrics Mechanical Spectrometer) and viscosity of the reaction medium monitored continuously as a function of reaction time. As can be seen, the viscosity appears to become infinite at a reaction time corresponding to about 60% conversion. This suggests network formation, but the chemistry precludes non-linear polymerization. Also observed in the same conversion range is very striking transition of the reaction medium from clear to opaque. 

The proportion by weight of the former will, of course, equal ktr[S]/ ktr[S]+2kt[M ]. These remarks apply only to increments of polymer for wide conversion ranges, the broadening effects due to changes in p and in this ratio must be considered. 

GP 2] [R 3a] A nearly constant selectivity of up of about 60% at conversions ranging from 20 to 70% was determined for sputtered silver on anodically oxidized (porous) aluminum alloy (AlMg3) with two different ethylene loads (4 or 20 vol.-% ethylene, 80 or 96 vol.-% oxygen 0.3 MPa 230 °C) [44]. The highest yield... 

OS 30] ]R 30] [P 22] The synthesis of nine C-C bonded products was made from four carbamates and five silyl enol ethers [66, 67]. Conversions ranged from 49 to 69% the corresponding selectivities ranged from 67 to 100%. Similar performance was achieved when serially processing the same reactions (see Serial combinatorial synthesis). 

OS 41a] ]R 19] ]P 30] Ten different substrates (C4-C8 alcohols) were reacted with rhodium(I)-tris(fn-sulfophenyl)phosphane [110]. The variance in conversions (ranging from about 1-62%) determined was explained by differences in the solubility of the alcohols in the aqueous catalytic layer and by their different intrinsic activities. Chain length and steric/electronic effects of the different alcohols affected their reactivity in a well-known pattern (Figure 4.63). The results obtained correspond to the conversions achieved in a well-mixed traditional batch reactor (40 cm ). They further agreed with data from mono-phasic processing. 

GL 1] [R 1] [P la] Using acetonitrile as solvent, the conversions ranged from 14 to 50% at selectivities of33-57% [38] (see also [3]). This corresponds to yields of 5-20%. The highest yield was found for a liquid volume flow of 11.6 ml h using a 1.1 mol toluene concentration at -20 °C. The fluorine/toluene molar ratio was 0.925. 

Figure 1A shows the conversion-ee dependencies in the enantioselective hydrogenation of 2,3-butanedione (BD). As shown that the introduction of quinuclidine (Q), as an AT A, significantly increased the ee values in the whole conversion range. Upon Q addition, first order rate constant k3 increased from 0.0102 to 0.0158 while k2 remained almost unchanged (0.0008 and 0.0005, respectively). After 4 hours reaction time, measurable amount of butanediols was found. The yields of butanediols were as follows in the absence of quinuclidine R,R=2.0%, S,S=1.7%, R,S=5.4%, in its presence R,R=2.3% S,S=1.2% R,S=3.7%. Figure IB shows the ee-conversion dependencies... 

Some examples are illustrative of the use of the use of HCBs for metabolite synthesis. Table 9.4 shows the reaction of various HCBs for the production of metabolites. Reactions are typically complete within 4 h. In the examples shown, conversions range from 70 to 100% in... 

Fig. 5 shows the time dependence of the solid-state ion exchange process. The process has pseudo first order kinetics in the investigated conversion range for both (i) the distribution and crystallinity loss of the CdCl2 salt and (ii) the formation of new Cd,H-Y phase. The rate constant obtained for the decay of... 

To elucidate the cause of the microwave-induced enhancement of the rate of this reaction in more detail the transformation of 2-t-butylphenol was performed at low temperatures (up to -176 °C). At temperatures below zero the reaction did not proceed under conventional conditions. When the reaction was performed under micro-wave conditions in this low temperature region, however, product formation was always detected (conversion ranged from 0.5 to 31.4%). It was assumed that the catalyst was superheated or selectively heated by microwaves to a temperature calculated to be more than 105-115 °C above the low bulk temperature. Limited heat transfer in the solidified reaction mixture caused superheating of the catalyst particles and this was responsible for initiation of the reaction even at very low temperatures. If superheating of the catalyst was eliminated by the use of a nonpolar solvent, no reaction products were detected at temperatures below zero (see also Sect. 10.3.3). 

The selective diene hydrogenation of monoterpenes such as myrcene, which contain both isolated monoene and diene moieties, forms a particular challenge [84]. The catalyst [RhH(CO)(PPh3)3] (60) has been reported to perform remarkably well for such hydrogenation reactions, and the diene moiety was shown to be selectively reduced to the monoene, while the isolated double bond remained unaffected under the reaction conditions used (Scheme 14.20). The rates of reaction expressed as average TOF (determined at ca. 80% conversion) ranged from ca. 640 (in benzene, 20 atm H2 at 100 °C) to 7600 mol mol 1 h 1 (in cyclohexane, 20 atm H2 at 80 °C). The hydrogenation in benzene solution resulted in... 

Using THERMPLOT, vary F to establish a single steady state at the low temperature, low conversion range. With the same parameters, obtain the steady states values of CA and TR using THERM. Enter these values as CAset and TRset in THERMFF. Using sliders vary the values of Fmin, Tjmin and Tjmax. 

The product is readily analyzed by vapor phase chromatography. Since the only impurity is o-xylene (conversions range from 80% to 100%), the percentage of reduction product was... 

The production of CDs via enzymatic reaction with starch has been recently reviewed (i 7). CGTase is an extracellular protein and is usually isolated as a crude mixture from the medium. This crude protein is used directly for industrial fermentations. The basic process involves standard enz3miatic fermentation, with careful attention to reaction temperature. All three CDs and some Unear oligosaccharides are normally produced. Yields are highly dependent on the source of starch substrate. Potato starch is normally used or an extract of potato starch is often added to other starches 18-19), The potato starch component(s) responsible for stimulating CD formation have not been determined. Low starch concentrations (5%-10%) are normally used industrially. Published yields are in the 50% - 80% conversion range. 

Fig. 10. Fractional conversion versus Damkohler number for half,-, first- and second-order reactions taking place in a single ideal CSTR. Shaded areas represent possible conversion ranges lying between perfectly micromixed flow (M) and completely segregated flow (S). Data taken from reference 32. A = R —...

The failure to fit the data over the complete conversion range from 0 to 100% to a third-order plot has sometimes been ascribed to failure of the assumption of equal functional group reactivity, but this is an invalid conclusion. The nonlinearities are not inherent characteristics of the polymerization reaction. Similar nonlinearities have been observed for nonpolymerization esterification reactions such as esterifications of lauryl alcohol with lauric or adipic acid and diethylene glycol with caproic acid [Flory, 1939 Fradet and Marechal, 1982b]. 

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