Boiling point distillation for

Figure 1. True boiling point distillations for Illinois H-coal, Wyodak H-coal, and SRC-II syncrudes...

Figure 1. Simulated true boiling point distillations for SRC-II, Illinois H-coal, and Wyodak H-coal whole process products...

Determination of boiling points. Distillation method (Fig. II, 12, 1) for carbon tetrachloride (25 nil. distillation flask and small water condenser), and SiwoloboflF s method (Fig. II, 12, 2) for carbon tetrachloride, aniline and nitrobenzene. Calibration curve for thermometer. Determination of b.p. of unknown liquid. 

In order to obtain boiling point corrections for distillation under reduced pressure the following expressions are used ... 

The purity of benzene marketed for most laboratory purposes is usually greater than 95.5% with the principal impurities being toluene and other hydrocarbons with boiling points similar to that of benzene. Methods used to assess the quality of benzene include determination of density, boiling point, distillation characteristics, and specific gravity. Benzene of high purity samples is conveniendy measured by freezing point, as outlined in ASTM ID 1016. 

Figure 7.10 Boiling-point diagram for a binary solution, illustrating two theoretical plates of an idealized fractional distillation process that progressively enriches the distillate in the low-boiling component A (see text).

Another boiling point is 179-181°/10 mm. The boiling points reported for ethyl benzalmalonate vary widely. The temperature observed depends on the degree of superheating and the rapidity of distillation. 

When complex multicomponent mixtures are distilled, particularly those associated with oil refining, it is difficult to characterize them in terms of their components. Instead, they are characterized in terms of their boiling range, which gives some indication of the quantities of the components present. The true boiling point distillation (TBP) is probably the most useful, in which the percent distilled is recorded as a function of the boiling temperature of the mixture. For the TPB distillation, a 5 1 reflux ratio is often used with 15 theoretical stages in a laboratory characterization column (see Section III). 

Fig. 6.6 First-order HC rate constant as a function of boiling-point fraction for NiW/zeolite Y and NiW/ASA catalysts with a Middle-East flashed distillate feedstock (72)...

Figure 3. Simulated distillation boiling point curves for virgin bitumen, mal-tenes, and asphaltenes...

Evaporation and Distillation. Steam is used to supply heat to most evaporation (qv) and distillation (qv) processes, such as in sugar-juice processing and alcohol distillation. In evaporation, pure solvent is removed and a low volatility solute is concentrated. Distillation transfers lower boiling components from the Hquid to the vapor phase. The vapors are then condensed to recover the desired components. In steam distillation, the steam is admitted into direct contact with the solution to be evaporated and the flow of steam to the condenser is used to transport distillates of low volatility. In evaporation of concentrated solutions, there maybe substantial boiling point elevation. For example, the boiling point of an 80% NaOH solution at atmospheric pressure is 226°C. 

Figure 14-12 A boiling point diagram for a solution of two volatile liquids, A and B. The lower curve represents the boihng point of a liquid mixture with the indicated composition. The upper curve represents the composition of the vapor in equilibrium with the boiling liquid mixmre at the indicated temperature. Pure liquid A boUs at a lower temperamre than pure hquid B hence, A is the more volatile liquid in this illustration. Suppose we begin with an ideal equimolar mixmre = Xg = 0.5) of liquids A and B. The point P represents the temperature at which this solution boils, Tj. The vapor that is present at this equilibrium is indicated by point Q (X = 0.8). Condensation of that vapor at temperature Ti gives a liquid of the same composition (point E). At this point we have described one step of simple distillation. The boiling liquid at point if is in equilibrium with the vapor of composition indicated by point S (X > 0.95), and so on.

Each curve in Fig. 6 is analogous to a population distribution curve for the molecules in the crude feed and products. Each could also be represented as weight or volume distribution. The curves are constructed from the amoimts of material with atmospheric boiling points in, for example, three-degree boiling range intervals in the precision distillation or gas chromatographic analyses. 

For Cd, laminar flow clean benches or clean rooms were recommended to avoid contamination. Acids used should be further purified by sub-boiling point distillation. If all precautions to reduce blanks are not followed too high results will be observed. 

Suppose that the boiling-point diagrams for two different total pressures are as shown in Fig. 6-4. Such an azeotrope may be separated by use of two columns as shown in Fig. 6-5. The feed (XA = 0.3) is introduced to the second column at the higher pressure P2. The bottom product contains a relatively pure component B and the top product consists of the minimum-boiling azeotrope XD A = 0.8 and X D b = 0.2. The distillate is fed to the first column which is operated at the total pressure of PThis column produces a bottom product which is relatively pure in A. The top product is essentially the azeotropic composition at Pt (XD a = 0.6 and X t) B — 0A), and thus it is added to the feed to the second column. 

If the feed is in the two-phase region, the two phases may be separated and fed to each of two columns. Suppose that the boiling-point diagram for a mixture of components A and B is as shown in Fig. 6-8. The feed is introduced to the separator shown in Fig. 6-9 which operates at the temperature Tsep. Phase I is then fed to column 1 and phase II to column 2. The bottom products of columns 1 and 2 are relatively pure B and Ay respectively. The distillate compositions are approximately those of the azeotrope, and consequently the distillates are fed to the separator. 

Figure 6-4 Boiling-point diagrams for a minimum-boiling homogeneous azeotrope which is sensitive to a change in the total pressure. (M. Van Winkle, Distillation, 1967, by courtesy McGraw-Hill Book Company.)...

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