Dysidiolide


Asphalt. This is a distillatioa residuum that can also be produced by propane deasphalting (Fig. 7) (33) and thereafter modified to meet specifications. For example, asphalt (qv) can be made softer by blending hard asphalt with the extract obtained ia the solveat treatmeat of lubricatiag oils. Oa the other hand, soft asphalts can be converted iato harder asphalts by oxidation (air blowiag).  [c.212]

NTU (Number of Transfer Units) The NTU required for a given separation is closely related to the number of theoretical stages or plates required to cariy out the same separation in a stagewise or plate-type apparatus. For equimolal counterdiffusion, such as in a binary distillatiou, the number of overall gas-phase transfer units Nqg required for changing the composition of the vapor stream from yi to yo is  [c.603]

Sometimes, alternative single- or multiple-stage vapor-liquid separation operations, of the types shown in Fig. 13-7, may be more suitable than distillatiou for the specified task.  [c.1244]

For some binary systems, one of the components is more volatile over only a part of the composition range. Two systems of this type, ethyl acetate-ethanol and chloroform-acetone, are shown in Figs. 13-10 to 13-12. Figure 13-10 shows that for two binary systems chloroform is less volatile than acetone below a concentration of 66 mole percent chloroform and that ethyl acetate is less volatile than ethanol below a concentration of 53 mole percent ethyl acetate. Above these concentrations, volatility is reversed. Such mixtures are known as azeotropic mixtures, and the composition in which the reversal occurs, which is the composition in which vapor and liquid compositions are equal, is the azeotropic composition, or azeotrope. The azeotropic liquid may be homogeneous or heterogeneous (two immiscible liquid phases). Many of the binary mixtures of Table 13-1 form homogeneous azeotropes. Non-azeotrope-forming mixtures such as benzene and toluene in Figs. 13-8 and 13-9 can be separated by simple distillation into two essentially pure products. By contrast, simple distillation of azeotropic mixtures will at best yield the azeotrope and one essentially pure species. The distillate and bottoms products obtained depend upon the feed composition and whether a minimum-boiling azeotrope is formed as with the ethyl acetate-ethanol mixture in Fig. 13-11 or a maximum-boiling azeotrope is formed as with the chloroform-acetone mixture in Fig. 13-12. For example, if a mixture of 30 mole percent chloroform and 70 mole percent acetone is fed to a simple distillatiou column, such as that shown in Fig. 13-1, operating at 101.3 kPa (1 atm), the distillate could approach pure acetone and the bottoms could approach the azeotrope.  [c.1248]

Batch distillation, which is the process of separating a specific quantity (the charge) of a liquid mixture into products, is used extensively in the laboratory and in small production units that may have to serve for many mixtures. When there are N components in the feed, one batch column will suffice where N — 1 simple continuous-distillatiou columns would be required.  [c.1334]

For more complex equipment, the columns might contain measurements for internal distillatiou, batch-reactor intermediate conditions, or tubular-reactor between-bed conditions. Some of these  [c.2559]

Steam Distillatioo. A compact and efficient apparatus is shown in Fig, 43. The liquid to be steam-distilled is placed in the tube A and water is placed in the outer flask B. On heating B, steam passes into the inner tube A through the inlet tube C, and steam-volatile compounds are rapidly distilled and collected in the receiver placed at the end of the condenser D.  [c.66]

Charging the steam-distillatiOD apparatus After steaming-out, and  [c.494]

This provides an excellent exercise in distillutiuii under diminished- pressure.  [c.694]

The techniques of analytical chemistry have been appHed ia the fragrance iadustry for as loag as they have beea available. lagredieats have loag beea characterized by wet chemical methods, color tests, distillatioa, and bulk analytical methods such as density and refractive iadex. These were as limited ia value for fragrance materials as for other areas of organic chemistry. The rise of more specific iastmmentation duting the middle of the twentieth century brought great changes ia the ability to test and standardize materials. Gas—Hquid chromatography (glc) is particularly appHcable to analysis of fragrances and fragrance materials. Refinements ia the iastmmeatatioa of glc, especially capillary columns, have made welcome additions to quality-control laboratories. Nevertheless, odor quality caimot be ensured by even the best analytical techniques available ia the 1990s. The fragrance iadustry therefore rehes oa both odor evaluatioa and analytical methods for control of ingredient and product quality.  [c.83]

Acid-catalyzed glycosidic hydrolysis of polysaccharides is much more rapid than alkaline hydrolysis. Sulfite pulpiag at low pH must be carried out at a relatively low (135°C) temperature to avoid excessive polysaccharide depolymerization. The carbohydrate yield is higher ia sulfite pulpiag, eg, 46% for a bleached softwood pulp compared with ca 44% for bleached kraft, because there is no peeling. The reduciag-end functions of polysaccharide chains are oxidized to aldonic acid end units by bisulfite. However, a low hemiceUulose pulp suitable for produciag cellulose derivaties, eg, rayon (see Fibers, cellulose esters) or cellulose acetate (see Cellulose esters), can be made by a two-stage cooking phase such as the Sivola process. The Sivola process is acidic ia the first stage, which reduces the average degree of polymerization (DP) of the hemiceUuloses, but alkaline ia the second stage, which dissolves and removes the hemiceUulose. A more important stabilization mechanism ia sulfite pulpiag is deacetylatioa of the softwood galactoglucomaiman, ia which the dissolved hemiceUulose teads to crystallize or be redeposited oa the ceUulose microfibrils if the acetate substitueats are removed. This may be promoted if a mildly alkaline first stage is foUowed by a more acidic stage, as ia the Stora process.  [c.272]

Heuristics are reliable, weU-estabfished rules for reduciag the number of potential alternative sequences with minimum effort, and often lead to near-optimal separation system designs. Most of the heuristics for distillation sequenciag were originally formulated from parametric studies. A number of Heuristics have beea suggested, some of which coatradict each other (5—8). Heuristic methods have also beea exteaded to sequeaciag aoasharp distillatioa separatioas and to combiaations of distillation, mixing, and stream bypass operations (9—11).  [c.444]

Materials and Scaling Issues. Two aspects of the basically simple desalination process require special attention. One is the high corrosivity of seawater, especially pronounced ia the higher temperature distillatioa processes, which requires the use of corrosioa-resistant, and therefore expensive, materials. Typical materials ia use are copper—nickel alloys, stainless steel, titanium, and, at lower temperatures, fiber-reiaforced polymers and special concrete compositions (39). It is noteworthy that ia quest of a lower initial cost, the use of iaadequate materials of coastmctioa ia many locatioas combiaed with poor operatioa by virtually uatraiaed hands led to rapid deterioration and failure of plants long before their estimated design life. Adequate experience suggests by now how to avoid such failures. The other aspect is scale formation (40,41), discussed ia more detail below.  [c.241]

Coumaria has also beea purified by vacuum azeotropic distillatioa with polyhydroxy alcohols such as triethyleae glycol (65). Puriftcatioa by zoae melting techniques has been described ia several pubHcatioas (66—68).  [c.321]

Residue Curve Maps and Distdlatiou Region Diagrams. 13-56  [c.1240]

FIG. 13-24 Distillatiou coliimu with cue feed, a total coudeuser, aud a partial rehoiler.  [c.1262]

Multistage distillatiou under continuous, steady-state operating conditions is widely used in practice to separate a variety of mixtures. Table 13-7, taken from the study of Mix, Dweck, Weinberg, and Armstrong [Am. Inst. Chem. Eng. J. Symp. Ser 76, 192, 10 (1980)] lists key components for 27 industri distiUatiou processes. The design of multiequilibrium-stage columns can be accomplished by graphical techniques when the feed mixture contains only two components. The x-y diagram  [c.1264]

Although much progress has been made in identifying the chemical species present in petroleum, it is generally sufficient for purposes of design and analysis of plant operation of distillation to cTiarac terize petroleum and petroleum frac tions by gravity, laboratoiy-distillatiou curves, component analysis of light ends, and hydrocarbon-type analysis of middle and heavy ends. From such data, as discussed in the Technical Data Book—Petroleum Refining [American Petroleum Institute (API), Washington], five different average boiling points and an index of paraffinicity can be determined these are then used to predict the physical properties of complex mixtures by a number of well-accepted correlations, whose use will be explained in detail and illustrated with examples. Many other characterizing properties or attributes such as sulfur content, pour point, water and sediment content, salt content, metals content, Reid vapor pressure, Saybolt Universal viscosity, aniline point, octane number, freezing point, cloud point, smoke point, diesel index, refractive index, cetane index, neutralization number, wax content, carbon content, and penetration are generally measured for a crude oil or certain of its fractious according to well-specified ASTM tests. But these attributes are of much less interest here even though feedstocks and products may be required to meet certain specified values of the attributes.  [c.1324]

Results of a typical ASTM distillatiou test for an automotive gasoline are given in Table 13-26, in which temperatures have already been corrected to a pressure of 101.3 kPa (760 torr). It is generally assumed that percent loss corresponds to volatile uoucoudeusables that are distilled off at the beginning of the test. In that case, the percent recovered values in Tame 13-26 do not correspond to percent evaporated values, which are of greater scientific value. Therefore, it is common to adjust the reported temperatures according to a fiuear interpolation procedure given in the ASTM test method to obtain corrected temperatures in terms of percent evaporated at the standard intervals as included in Table 13-26. In the example, the corrections are not large because the loss is only 1.5 volume percent.  [c.1324]

As discussed by Nelson (op. cit.), virtually no frac tionation occurs in an ASTM distillatiou. Thus, components in the mixture do distill one by one in the order of their boiling points but as mixtures of successively higher boihug points. The IBP, EP, and intermediate points have little theoretical significance, and, in fact, components boiling below the IBP and above the EP are present in the sample. Never-  [c.1324]

Other Operating Methods A useful control method for difficult industrial or laboratory distiUations is cycling operation. The most common form of cycling control is operating the column at total reflux until equihbrium is established, taking off the complete distillate for a short period of time, and then returning to total reflux. An alternative scheme is to interrupt vapor flow to the column periodically by the use of a solenoid-operated butterfly valve in the vapor hue from the pot. In both cases, equations necessary to describe the system are very complex, as shown by Schrodt et al. [Chem. Eng. Sci., 22, 759 (1967)]. The most reliable method for establishing the cycle relationships is by experimental trial on an operating column. Several investigators have also proposed that batch distillatiou can be programmed to attain time optimization by proper variation of the refuix ratio. A comprehensive discussion is presented by Coward [Chem. Eng. Sci., 22, 503 (1967)].  [c.1337]

Effect of Column Holdup When the holdup of liquid on the trays and in the condenser is not neghgible compared with the holdup in the pot, the distillate composition at constant-reflux ratio changes with time at a different rate than when the column holdup is negligible because of two separate effects. First, with an appreci le cohimn holdup, composition of the charge to the pot will be higher in the light component than the pot composition at the start of the distillatiou the reason for this is that before product takeoff begins, column holdup must be supplied, and its average composition is higher than that of the charge Hquid from which it is supphed. Thus, when overhead takeoff begins, the pot composition is lower than it would be if there were no column holdup and separation is more difficult. The second effect of column holdup is to slow the rate of exchange of the components the holdup exerts an inertia effect, which prevents compositions from changing as rapidly as they would otherwise, and the degree of separation is usu ly improved. As both these effec ts occur at me same time and change in importance during the course of distillatiou, it is difficult, without rigorous calculations, to predict whether the overall effect of holdup will be favorable or detrimental it is equally difficult to estimate the magnitude of the holdup effect.  [c.1337]

Consider the simple batch- or multicomponent-distillatiou operation in Fig. 13-105. The still consists of a pot or reboiler, a column with N theoretical trays or equivalent packing, and a condenser with an accompanying reflux drum. The mixture to be distilled is charged to the reboiler, to which heat is then supphed. Vapor leaving the top tray is totally condensed and drained into the reflux drum. Initially, no distillate is withdrawn from the system, but instead a total-reflux condition is established at a fixed overhead vapor rate. Then, starting at time t = 0, distillate is removed at a constant molal rate and sent to a receiver that is not shown in Fig. 13-105. Simultaneously, a fixed refliix ratio is estabhshed such that the overhead vapor rate is not changed from that at total reflux. Alternatively, heat input to the reboiler can be maintained constant and distillate rate allowed to vaiy accordingly. The equations of Distefano for a batch distillatiou operated in this manner are as follows (after minor rearrangement), where i,j refers to the ith of C components in the mixture and the/th of N theoretical plates.  [c.1338]

Vacuum distillatiou is used to remove the residue from the distillate product. Additional heavy oil may be recovered from the vacuum bottoms by employing Exxon s Flexicoldng process.  [c.2373]

If the default file previously was defined, selection 1 is skipped and the file is read in using selection 2. Selection 3 defines a segment with a title, the number of segment replications. iv]v of material, internal pressure, diameter, the ASME critical wall thickness, and the segment length. Selection 4 computes the pipe failure probabilities, selection 5 plots the results, selection 6 prints the results, and 7 saves the definitions to a disk. The program has edit capability if changes are needed in an approximately correct setup, or a data file may be prepared and edited with an ASCII text editor. Both output and input files may be labeled for storage and retrieval or optionally the dctault name may be accepted.  [c.452]

Cefroxadine (33) possesses an activity spectrum rather similar to that of cephalexin and so can be placed generally in the first generation of cephalosporins. Structurally, it has a side chain at C-7 identical with that of cephradine (D-absolute stereochemistry) so its oral efficacy is predictable. The side chain at C-3 of cephalosporins is significant not only for potency but also controls many pharmacokinetic features of these drugs. In the case of cefroxadine, an unprecedented (in these pages) enol methyl ether moiety is found. Of the various syntheses, cefroxadine can be made starting with the phenacetyl amide of 7-aminocephalosporanic acid (25). This is deacetylat-  [c.182]


See pages that mention the term Dysidiolide : [c.1904]    [c.397]    [c.504]    [c.320]    [c.65]    [c.321]    [c.382]    [c.1240]    [c.1240]    [c.1240]    [c.1240]    [c.1240]    [c.1240]    [c.1240]    [c.1240]    [c.1248]    [c.1323]    [c.1324]    [c.1338]    [c.91]    [c.487]    [c.170]    [c.3]    [c.6]    [c.56]   
13 Chemistry in the Marine Environment (2000) -- [ c.77 ]