Distillation versus

Takeoka GR, Flath RA, Guntert M, et al. 1988. Nectarine volatiles Vacuum steam distillation versus headspace sampling. J Agric Food Chem 36 553-560. 

Separate naphtha and middle distillate versus whole oil initial hydrotreating. 

The above development raises conceptually the problem of steam distillation versus reboiled stripping. The first has the advantage of simpler equipment, but the disadvantage of contamination. With the second the situation is reversed. The choice depends largely on local conditions. 

Entrainer-Based Reactive Distillation Versus Conventional Reactive Distillation For The Synthesis Of Fatty Acid Esters... 

Fig. S.11. Mole fraction of product A2 in distillate versus stage DamkShler number at different number of stages N for process configuration in Fig. 5.3...

There are many important industrial applications of azeotropic separations, which employ a variety of methods. In this book we discuss several of these chemical systems and demonstrate the application of alternative methods of separation. The methods presented include pressure-swing distillation, azeotropic distillation with a light entrainer, extractive distillation with a heavy entrainer (solvent), and pervaporation. The chemical systems used in the numerical case studies included ethanol-water tetrahydrofuran (THF)-water, isopropanol-water, acetone-methanol, isopentane-methanol, n-butanol-water, acetone-chloroform, and acetic acid-water. Economic and dynamic comparisons between alternative methods are presented for some of the chemical systems, for example azeotropic distillation versus extractive distillation for the isopropanol-water system. 

The feed split is simply the amount of feed that leaves as distillate versus the amount that leaves as bottoms. The other variable, fractionation, is the amount of separation that occurs per stage. The overall column fractionation depends on the number of stages, the energy input, and the difficulty of separation. A typical control scheme for this column is shown in Figure 8.3. 

Vacuum Distillation Versus Direct Solvent Extraction... 

Fig. 18.4-2. Distillation versus pervaporation. The vapor-liquid equilibrium is given by the dotted line and the pervaporation into vacuum is given by the solid line. The data are for ethanol-water using a polyvinyl alcohol membrane. Note there is no azeotrope for pervaporation.

Boiling points versus composition diagram for a near-ideal solution, showing the progress of a distillation. 

Fig. 7. Extractive distillation column profiles for the acetone—methanol—water separation (40). (a) Liquid composition versus theoretical tray location where...

FIG. 13-75 Number of theoretical stages versus solvent-to-feed ratio for extractive distillation, a) Close-boiling vinyl acetate-etbyl acetate system with phenol solvent, (h) A2eotropic acetone-methanol system with water solvent. 

A plot of the distillate composition, y versus percent distilled (from Step 7) will show the value of the instantaneous vapor composition. 

The Hausbrand vapor-pressure diagram [127, 128] in Figure 8-40 is a useful approach for the steam distillation calculation. This particular diagram was prepared for six organic compounds and the corresponding water vapor pressure as (it - ps) for three system pressures of 760, 300, and 70 mm Hg versus temperature,... 

In most of today s FCC operations, the desired reactions take place in the riser. In recent years, a number of refiners have modified the FCC unit to eliminate, or severely reduce, post-riser cracking. Quick separation of catalyst from the hydrocarbon vapors at the end of the riser is extremely important in increasing the yield of the desired product. The post-riser reactions produce more gas and coke versus less gasoline and distillate. Presently, there are a number of commercially proven riser disengaging systems offered by the FCC licenser designed to minimize the post-riser cracking of the hydrocarbon vapors. 

Table 41.3 shows a performance comparison of Pt/Pd TUD-1 with a commercial Pt/Pd catalyst (26). The feedstock is a typical straight run gasoil ( SRGO ), a distillate precursor to diesel fuel. Under identical test conditions, the TUD-1 catalyst achieved 75% aromatics saturation versus 50% for the same volume of commercial catalyst. This superior result is particularly interesting because the TUD-1 catalyst had a much lower density than the commercial material, so that less catalyst by weight was required in the reactor. 

Figure 9.14 A plot of di/bi versus ij tends to follow a straight line when plotted on logarithmic axes. (From Smith R and Jobson M, 2000, Distillation, Encyclopedia of Separation Science, Academic Press reproduced by permission).

A method described by Florence and Farrer [584] separated tin from its associated lead by distillation from an aqueous sulfuric acid medium into which the vapour from boiling 50% hydrobromic acid is passed. The distillate provides an ideal supporting electrolyte for the determination of tin (II) (produced by reduction with hydrazinium hydroxide) by anodic stripping at a rotating vitreous-carbon electrode in the presence of codeposited mercury [585,586]. The tin is deposited at -0.70 V versus the SCE for 5 minutes, and then stripped at -0.50 V during a sweep from -0.70 V to -0.45 V at 5 V per minute. Tin in seawater is coprecipitated on ferric hydroxide, and the precipitate is then dissolved in the aqueous sulfuric acid, and subjected to the above procedure. The average content for Pacific coastal waters was found to be 0.58 xg/l. 

The potential for the condensation and fractional distillation of air on the outside of equipment containing cryogenic liquids with boiling points less than that of 02 must be considered. For example, because N2 boils at a lower temperature than 02 (-196 versus -183°C), air can condense on the outside of liquid N2-bearing piping. The liquid that drops off of the piping will be enriched in 02 and can pose an enhanced fire or explosion risk in the vicinity of the equipment. 

Electrochemical equipment and cells used for these investigations have also been described previously. (8.9 ) Polycrystalline Ag (Johnson Matthey, 99.9%) was mechanically polished with alumina (Buehler) to a mirror finish and sonicated in triply distilled H20 before each run. All potentials were measured and are reported versus a saturated calomel reference electrode (SCE). 

Azeotropic and extractive distillation Distillation processes Extractive distillation(s) argon, 13 460 for aroma isolation, 11 519 atmospheric, 13 646 batch versus continuous, 3 780 of coal-tar naphthalene, 17 78-79 corrosion, 3 779-780 of crude oil, 12 401-402 13 593 debottlenecking, 13 521 in fatty acid neutralization, 22 740 favorable vapor-liquid equilibria, 3 778 feed composition, 3 778 general separation heuristics for, 22 316-317... 

Continuous binary distillation is illustrated by the simulation example CON-STILL. Here the dynamic simulation example is seen as a valuable adjunct to steady state design calculations, since with MADONNA the most important column design parameters (total column plate number, feed plate location and reflux ratio) come under the direct control of the simulator as facilitated by the use of sliders. Provided that sufficient simulation time is allowed for the column conditions to reach steady state, the resultant steady state profiles of composition versus plate number are easily obtained. In this way, the effects of changes in reflux ratio or choice of the optimum plate location on the resultant steady state profiles become almost immediately apparent. 

Figure 8. Calcium values in vertebrate bone and soft tissue samples versus 6 Ca in dietary source (Skulan and DePaolo 1999). Bone values are systematically about 1.3%o lower than source values. Soft tissue values are more variable. All of the values are hypothesized to reflect the balance between Ca dietary intake and exchange with bone calcium (Fig. 9). The soft tissue values are variable largely because the residence time of Ca in the tissues is short. The high value of the egg white reflects Rayleigh-type distillation the egg white loses light Ca to the shell as the shell forms. The small amount of Ca left in the egg white is highly fractionated. The low 6 Ca value of the seal muscle is interpreted as a sign of distress the seal may have had a dietary Ca deficiency for several days or longer before it died, and hence was deriving most of its Ca from bone dissolution.

The evaporation rate can be derived either (1) by a plot of time versus weight using a solvent having a known evaporation rate for comparison or (2) from the distillation profile (ASTM D86 IP 123). Although the results obtained on the naphtha provide a useful guide, it is, wherever possible, better to carry out a performance test on the final product when assessing enviromnental effects. 

Takamatsu et al. studied the diffusion of water into the acid as well as mono-, di-, and trivalent salt forms of 1155 and 1200 EW samples."pj e gravimetric uptakes of membranes immersed in distilled liquid water versus time were determined. Three approximate diffusion formulas were applied to the data, and all yielded essentially the same result. The log D versus 1/7 plots, over the range 20—81 °C, yielded activation energies of 4.9 and 13.0 kcal/mol for the acid and K+ forms, respectively. Diffusion coefficients of various mineral cations that permeated from aqueous electrolytes were considerably smaller than that of water. Also, log Z7was seen to be proportional to the quantity q a, where q is the charge of the cation and a is the center-to-center distance between the cation and fixed anion in a contact ion pair. 

The half-life of acrolein in unsterilized supply water samples from an irrigation area was 29 h versus 43 h in thymol-treated water. A half-life of 43 h was also reported for acrolein in buffered distilled water at identical pH. These data suggest that biotransformation occurred in these aquatic systems. At higher aqueous concentrations (6.0 to 50.5 mg/L), the marked decrease in pH suggests that carboxylic acids were formed as end products (Bowmer and Higgins, 1976). 

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