Yield fractional

Modem catalysts produce a much higher percentage of isotactic polypropylene than ia the past, eliminating the need for a cosdy extraction step to remove an atactic fraction. Yields ate high enough (>10,000 g polymer/g catalyst) so that a catalyst removal (de-ashing) step is no longer requited. 

Y is fractional yield of retained species, and and Vj are the volume of process fluid at the beginning and end of a batch run, respectively. This equation is vahd only when R, retention, is constant. 

The drermodynamic data for CuaS-FeS (Krivsky and Schuhmann, 1957) show that drese sulphides mix to form approximately ideal ionic liquids. These are molten salts in which the heat of mixing is essentially zero, and die entropy of mixing is related to the ionic fractions of die cations and anions. In the present case die ionic fractions yield values for the activities of the two sulphides... 

The following details establish reactor performance, considers the overall fractional yield, and predicts the concentration profiles with time of complex reactions in batch systems using the Runge-Kutta numerical method of analysis. 

The quaternary fraction of pot curare, after the removal of some neoprotocuridine, was separated into a portion salted out by sodium bicarbonate, and a portion not so precipitated. The latter was fractionated on a plan described in the original, the most active product obtained being an amorphous iodide with a paralysing dose of 1- 5 mg. per kilo frog. This iodide was phenolic, gave the Millon reaction, but no strychnine-like reaction with bichromate and sulphuric acid. No crystalline product could be isolated, but on complete methylation certain of the fractions yielded crystalline methiodides as follows —... 

Early investigations indicated the presence of an alkaloid in G. fremontii and G. racemosa. Six species were examined recently by Oneto, who found no alkaloid in G. jiavescens, amorphous bases in G. fremontii and G. buxifolia, and alkaloids yielding crystalline hydrochlorides in G. elliptica, G. wrightii and G. veatchii. The bark of the last-mentioned species was worked up for total alkaloids, which on fractionation yielded two crystalline bases. 

The above procedure is applied to 2-heptene (9.8 g, 0.1 mole), 11.5 g (0.066 mole) of NBS, and 0.1 g of benzoyl peroxide in 50 ml of carbon tetrachloride. The mixture is refluxed with stirring for 2 hours. Final fractionation yields 50-65% of 4-bromo-2-heptene, bp 70-71732 mm. 

A correlation index is a useful criterion for indicating the crude class or type. The following relationship between the mid-hoiling point in Kelvin degrees (°K) and the specific gravity of a crude oil or a fraction yields the correlation index (Bureau of Mines Correlation index). 

The crude product is dissolved in benzene-hexane (1 1) and applied to a column containing 125 g. of silicic acid (Note 10). Elution with the same solvent gives traces (less than 5 mg. each) of the two fast-moving components in fractions 2 and 4 (125-ml. fractions) and chromatographically pure cholane-24-aI in fractions 5-8 (Note 11). Evaporation of the pooled fractions yields 870 mg. (84%) of the pure crystalline aldehyde, m.p. 102-104°. Recrystallization from 5 ml. of acetone raises the melting point to 103-104° (Note 12). 

A — 78 rC solution of (Z)-2-butenyl(diisopinocampheyl)borane (theoretically 25 mmol prepared from ( + )-a-pinenc as described in Section 1.3.3.3.3.1.1.1.) is treated with 2.0 mL (35 mmol) of acetaldehyde (added dropwise). The mixture is stirred for 3 h at — 78CC and is then treated with 18.3 mL (55 mmol) of 3 N sodium hydroxide and 7.5 mL of 30% hydrogen peroxide solution. This mixture is refluxed for 1 h. The organic phase is separated, washed with water and NaCl and dried over MgS04. The filtrate is carefully fractionated yield 75% d.r. (syn/anti) >99 1 (GC) bp Torr 90% ee. 

Removal of solvent from the extracts leaves a residue that is purified by dry-column chromatography.2 The residue is dissolved in 40 ml. of acetone in a 300-ml., round-bottomed flask, 30 g. of silica gel (Note 8) is added, and the acetone is removed with a rotary evaporator. The resulting solid mixture is placed on top of 360 g. of dry silica gel (Note 8) packed in flexible nylon tubing (Note 9), and the column is developed with 420 ml. of 10 1 (vjv) benzene-acetone. Approximately 150 ml. of solvent drips from the bottom of the column toward the end of development, and this eluent is collected in 25-ml. fractions and checked for product by thin layer chromatography (Note 10). The column itself is then cut into 2-cm. sections, the silica gel in each section is eluted with three 25-ml. portions of ethyl acetate, and the eluent from each section is analyzed by thin-layer chromatography (Note 10). Combination of all the product-containing fractions yields 1.2-1.5g. (40-47%) of the benzylated compound as an oil, n 1.6083 (Notes 11 and 12). 

Phospholipase A activity was subsequently demonstrated to be present in venom, and it too required Ca (25). DEAE-cellulose fractionation yielded four proteins, two of which were phospholipase A and hemolytic, and two of which had neither phospholipase A nor hemolytic activities. Either of the latter two proteins enhanced to various degrees the hemolytic activity of either of the two phospholipases. The findings suggest considerable analogy with synergistic mechanisms underlying the hemolytic action of the venoms of a number of snakes. 

The feasibility of reusing the phase transfer catalyst via the reuse of the third liquid phase in a tri-liquid catalytic system has been investigated in our laboratory [6,7]. In the present study, the catalyst-rich liquid phase was repeatedly used for four times and the changes in the conversion of RBr and the fractional yield of ROAc were observed. 

Again it is important that both the particular reactant and product, concerned, should be stated, when defining a fractional yield. 

Another definition of fractional yield is based on the reaction rates... 

The reactions are assumed to take place under isothermal conditions at 130°C at 10 bar. The liquid feed of BA is 0.0133 kmol-s 1 and the gaseous feed of chlorine is 0.1 kmol-s-1. The objective is to maximize the fractional yield of a-monochlorobutanoic acid with respect to butanoic acid. Specialized software is required to perform the calculations, in this case, using simulated annealing. 

Example 14.1 Consider again the chlorination reaction in Example 7.3. This was examined as a continuous process. Now assume it is carried out in batch or semibatch mode. The same reactor model will be used as in Example 7.3. The liquid feed of butanoic acid is 13.3 kmol. The butanoic acid and chlorine addition rates and the temperature profile need to be optimized simultaneously through the batch, and the batch time optimized. The reaction takes place isobarically at 10 bar. The upper and lower temperature bounds are 50°C and 150°C respectively. Assume the reactor vessel to be perfectly mixed and assume that the batch operation can be modeled as a series of mixed-flow reactors. The objective is to maximize the fractional yield of a-monochlorobutanoic acid with respect to butanoic acid. Specialized software is required to perform the calculations, in this case using simulated annealing3. 

The optimization is now constrained to be at a fixed (optimized) chlorine addition rate, but the temperature profile optimized. Profile optimization is used for the temperature, as discussed in Chapter 3. The batch cycle time required is 1.42 h. The resulting fractional yield of MBA from BA now reaches 92.7%. 

Table 14.1 Fractional yields of MBA from BA under different reactors and operating modes.

In Fig. 2 the following is depicted the hydrogenation products of Yubari coal at a reaction temperature of 400°C were fractionated by the procedure shown in Fig. 1, and the changes of these fraction yields by reaction time are shown. Inasmuch as the presence of Py-2 is scarce in coal, the observed results were obtained in the decreasing period, thus it may readily be surmised that Py-2 must be produced in the initial stages of the reaction. Here we consider oil-1 as the final product, and it may be noted that all fractions other than oil-1, show an initial... 

Thus the fractional yields of the different products are independent of time and of the orders of the reaction. If the increments in the products can be determined (in many cases R0 and S0 will be zero), then it is possible to evaluate the ratio kjk2. Moreover, for this case,... 

In order to determine the product distribution quantitatively, it is necessary to combine material balance and reaction rate expressions for a given reactor type and contacting pattern. On the other hand, if the reactor size is desired, alternative design equations reflecting the material balances must be employed. For these purposes it is appropriate to work in terms of the fractional yield. This is the ratio of the amount of a product formed to the amount of reactant consumed. The instantaneous fractional yield of a product V (denoted by the symbol y) is defined... 

The equations derived earlier for the effluent concentrations in the PFR and CSTR cases may be substituted into equation 9.2.1 to obtain numerical values of the fractional yield of the intermediate V as a function of the fraction of... 

Comparison of the fractional yields of V in mixed and plug flow reactors for the consecutive first-order reactions. A A- V W. (Adapted from Chemical Reaction Engineering, Second Edition, by O. Levenspiel. Copyright 1972. Reprinted by permission of John Wiley and Sons, Inc.)... 

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