Methanol binary azeotropes with

Isoprene [78-79-5] (2-methyl-1,3-butadiene) is a colorless, volatile Hquid that is soluble in most hydrocarbons but is practically insoluble in water. Isoprene forms binary azeotropes with water, methanol, methylamine, acetonitrile, methyl formate, bromoethane, ethyl alcohol, methyl sulfide, acetone, propylene oxide, ethyl formate, isopropyl nitrate, methyla1 (dimethoxymethane), ethyl ether, and / -pentane. Ternary azeotropes form with water—acetone, water—acetonitrile, and methyl formate—ethyl bromide (8). Typical properties of isoprene are Hsted in Table 1. 

The quantity of hexane necessary to entrain water, methanol, ethanol, acetone, and acetaldehyde dimethyl acetal to the top was estimated as the sum of the hexane quantities required to form the binary azeotropes with the quantities of water, methanol, ethanol, acetone, and acetaldehyde dimethyl acetal in the mixture. 

Properties Colorless liquid etherlike odor. Fp -88.68C, bp 63.2-65.6C, d 0.913 (20/4C), refr index 1.4320 (20C), flash p -22F (-30C). Insoluble in water 0.3 g/100 g water. Miscible with most organic solvents. Forms a binary azeotrope with methanol, a ternary azeotrope with methanol-water. 

Liquid with pungent odor. bp7 81.4. tig 1.4086. dj 0.8636 dj5 0 8407. Easily soluble in water, methanol, ethanol, ether, acetone, glacial acetic acid. Slightly sol in hydrocarbons. Forms a binary azeotrope with water, bp 75 (12% water), uv spectrum and electric moments Rogers, J. Am. Chem. Soc. 69, 2544 (1947). Polymerizes on standing, LDm in mioe and rats 35 mg/kg, C.A. 72, 124809b 0970). 

Water is the most common azeotropic component In the bible of azeotropic information, the reference given in Ref. 3, Appendix 2, there are 64 pages devoted to lists of binary azeotropes with water Each page has approximately 50 entries of different azeotropes with water as one component. For comparison, there are 30, 35, 10, and 13 pages for methanol, ethanol, n-propanol, and isopropanol, respectively... 

Schematic DRD shown in Fig. 13-59 are particularly useful in determining the imphcations of possibly unknown ternary saddle azeotropes by postulating position 7 at interior positions in the temperature profile. It should also be noted that some combinations of binary azeotropes require the existence of a ternaiy saddle azeotrope. As an example, consider the system acetone (56.4°C), chloroform (61.2°C), and methanol (64.7°C). Methanol forms minimum-boiling azeotropes with both acetone (54.6°C) and chloroform (53.5°C), and acetone-chloroform forms a maximum-boiling azeotrope (64.5°C). Experimentally there are no data for maximum or minimum-boiling ternaiy azeotropes. The temperature profile for this system is 461325, which from Table 13-16 is consistent with DRD 040 and DRD 042. However, Table 13-16 also indicates that the pure component and binary azeotrope data are consistent with three temperature profiles involving a ternaiy saddle azeotrope, namely 4671325, 4617325, and 4613725. All three of these temperature profiles correspond to DRD 107. Experimental residue cui ve trajectories for the acetone-...

As seen in Table 1, the boiling temperature of the possible entrainers is either lower or higher than that of the original components. All candidates form a binary heterogeneous azeotrope with -hexane. Methanol and acetonitrile... 

Nitromethane shows the simplest residue curve map with one unstable curved separatrix dividing the triangle in two basic distillation regions. Methanol and acetonitrile give rise two binary azeotropic mixtures and three distillation regions that are bounded by two unstable curved separatrices. Water shows the most complicated residue curve maps, due to the presence of a ternary azeotrope and a miscibility gap with both the n-hexane and the ethyl acetate component. In all four cases, the heteroazeotrope (binary or ternary) has the lowest boiling temperature of the system. As it can be seen in Table 3, all entrainers except water provide the n-hexane-rich phase Zw as distillate product with a purity better than 0.91. Water is not a desirable entrainer because of the existence of ternary azeotrope whose n-hexane-rich phase has a water purity much lower (0.70). Considering in Table 3 the split... 

Figure 3.10 shows typical RCM for nonideal mixtures involving azeotropes. For the mixture ace tone/heptane /benzene (plot a) there is only one distillation field. The problem seems similar to a zeotropic system, except for the fact that the minimum boiler is a binary azeotrope and not a pure component. With the mixture acetone/chloroform/toluene (plot b) there is one distillation boundary linking the high-boiler with the low-boiler azeotrope. Consequently, there are two distillation regions. Similar behavior shows the plot c, with two azeotropes. The mixture acetone/chloroform/methanol (plotd) has four azeotropes (3 binaries and 1 ternary) displaying a behavior with four distillation regions. 

The binary azeotrope between acetone and methanol is the point with the lowest temperature on the map, and all profiles originate from this point. 

As an example, the separation of a butene/methanol/MTBE system is investigated. Methyl tertiary-butyl ether (MTBE) is the desired product, and hence needs to be efficiently recovered from a reactor output. Difficulty arises when separating such a mixture with conventional distillation processes, because of the binary azeotropes that exist between methanol and MTBE, as well as between methanol and butene. The driving force for separation in membrane processes differs from that in distillation, thus a membrane process will not exhibit the same azeotropic behavior. Thus, the limitations on distillation processes can be overcome by using a membrane unit. 

The conventional processes for the manufacture of MTBE uses a catalytic reactor with a slight excess of methanol (methanol/isobutylene = 1.05 to 2). The products correspond to the near-equilibrium conversion of 90-95 %. The reaction mixture is separated using distillation, but this is complicated by the formation of the binary azeotropes methanol-MTBE and isobutylene-methanol. The unreacted isobutylene is difficult to separate from other volatile C4 products. In the RD process. 

The ternary system of methyl acetate, methanol, and water illustrates the occurrence of a distillation boundary. Figures 1.27 and 1.28 give the binary azeotropes of the system at 20psia using NRTL physical properties. Figure 1.29 shows the ternary diagram with a distillation boundary. 

B. Explore. These components are in the Aspen Plus data bank and residue curves were generated with Aspen Plus using NRTL fFigure 11-111 (obviously, other process simulators could be used). Since there is one minimum boiling binary azeotrope between methanol (light component) and toluene (heavy) component without a distillation boundary, this residue curve map is similar to Figure 8-lla. We expect that the flowchart in either Figure 11-lQa or 11-1 Oh will do the separation. 

C. Plan. The fresh feed point is plotted in Figure 11-11. Since the methyl butyrate concentration in the fresh feed is low, this point is close to the binary toluene-methanol line. If we don t recycle intermediate (methyl butyrate) we may have a problem with the binary azeotrope. Thus, for a feasible design, it is safer to start with recycle of intermediate. 

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