Methyl acetate columns

Today the main process application for bubble cap trays is in reactive distillation columns or in chemical absorption columns in either case, it may be necessary to control very carefully the residence time of the liquid to complete a reaction step. For example, bubble-cap trays are used for the methyl acetate column described earlier and published by Agreda et al. An abridged version of the Bolles treatment of bubble-cap tray design is given in the fifth edition of Perry s handbook." ... 

If it is desired to purify an inferior product, 1 litre of it is refiuxed for 6 hours with 85 ml. of acetic anhydride and then distilled through a fractionating column the liquid passing over at 56-57° is collected. The distillate is shaken with 20 g. of anhydrous potassium carbonate for 10 minutes, filtered and redistilled. The resulting methyl acetate has a purity of 99- 9 %. 

Ethyl acetate. Use 58 g. (73-5 ml.) of absolute ethyl alcohol, 225 g. of glacial acetic acid and 3 g. of concentrated sulphuric acid. Reflux for 6-12 hours. Work up as for n-propyl acetate. B.p. 76- 77°. Yield 32 g. Much ethyl acetate is lost in the washing process. A better yield may be obtained, and most of the excess of acetic acid may be recovered, by distilhng the reaction mixture through an efficient fractionating column and proceeding as for methyl acetate. 

Ethyl n-butyrate. Use a mixture of 88 g. (92 ml.) of n-butyric acid, 23 g. (29 ml.) of ethanol and 9 g. (5 ml.) of concentrated sulphuric acid. Reflux for 14 hours. Pour into excess of water, wash several times with water, followed by saturated sodium bicarbonate solution until all the acid is removed, and finally with water. Dry with anhydrous magnesium sulphate, and distU. The ethyl n-but3rrate passes over at 119 5-120-5°, Yield 40 g. An improved yield can be obtained by distilhng the reaction mixture through an efficient fractionating column until the temperature rises to 125°, and purifying the crude ester as detailed above under methyl acetate. 

Methyl acetate Acetic acid Glacial acetic Ethyl acetate column finishing column acid storage recovery coiumn... 

Recovery of dilute acetic acid is achieved by esterification with methanol using a sulfonated resin (Dowex 50w) in a packed distillation column (54). Pure methyl acetate is obtained. This reaction is second order in acetic acid, 2ero order in methanol, and partially diffusion controlled. 

Ion exchange resin heads used as column packing Hydrolysis of methyl acetate t lichigami, J. Chem. Eng. Jap., 23,. 354 (1990)... 

FIG. 13-79 Integrated reactive-extractive distillation column for the production of methyl acetate. 

Reactive distillation is a technique for combining a number of process operations in a single device. One company has developed a reactive distillation process for the manufacture of methyl acetate that reduces the number of distillation columns from eight to three, also eliminating an extraction column and a separate reactor (Agreda et al., 1990 Doherty and Buzad, 1992 Siirola, 1995). Inventory is reduced... 

Purification of luciferin (Rudie etal., 1976). The luciferin fractions from the DEAE-cellulose chromatography of luciferase were combined and concentrated in a freeze-dryer. The concentrated solution was saturated with ammonium sulfate, and extracted with methyl acetate. The methyl acetate layer was dried with anhydrous sodium sulfate, concentrated to a small volume, then applied on a column of silica gel (2 x 18 cm). The luciferin adsorbed on the column was eluted with methyl acetate. Peak fractions of luciferin were combined, flash evaporated, and the residue was extracted with methanol. The methanol extract was concentrated (1 ml), then chromatographed on a column of SephadexLH-20 (2 x 80 cm) usingmethanol asthe solvent. The luciferin fractions eluted were combined and flash evaporated. The residue was... 

Eastman uses acetic anhydride primarily for esterification of cellulose, producing acetic acid as a byproduct. This acetic acid is used to convert the methanol into methyl acetate in a reactor-distillation column in which acetic acid and methanol flow countercurrently. 

The novel approach finally taken was to conduct the reaction and purification steps in a reactor-distillation column in which methyl acetate could be made with no additional purification steps and with no unconverted reactant streams. Since the reaction is reversible and equilibrium-limited, high conversion of one reactant can be achieved only with a large excess of the other. However, if the reacting mixture is allowed to flash, the conversion is increased by removal of the methyl acetate from the liquid phase. With the reactants flowing countercurrently in a sequence of... 

The conventional process consists of a reactor followed by eight distillation columns, one liquid-liquid extractor and a decantor. The reactive distillation process consists of one column that produces high-purity methyl acetate that does not require additional purification and there is no need to recover unconverted reactant. The reactive distillation process costs one fifth of the conventional process and consumes only one fifth of the energy. 

An aqueous solution of 0.02 M methyl acetate at 25 C was passed through a column of trioctyl phosphate ( on a cellulose base) which acted as an acid catalytst. The reaction is... 

Figure 6 shows the TPR spectra of adsorbed CO on nickel. The CO was desorbed mostly as the molecular form, whereas the amounts of desorbed carbon dioxide and methane were quite small. Thus, most of the CO adsorbed on nickel is in an undissociated state, and the extent of its adsorption is fairly weak, as the desorption is completed below 200 C. In contrast, the adsorption of methyl acetate on nickel is stronger than those of other reactants or products, as evaluated from the retention time in the nickel-activated carbon column shown in Table III. This fact suggests that most of the nickel is covered by methyl acetate and reaction products, and the coverage of adsorbed CO is quite low under the reaction conditions when the partial pressure of CO is close to that of methyl acetate. The carbonylation is therefore accelerated by increasing the CO/AcOMe ratio which increases the coverage of CO adsorbed competitively with methyl acetate. 

Porous silica is most widely used as adsorbent, but bonded phase materials with polar groups or crosslinked acrylonitrile39> have also been tested. Silica requires painstaking control of activity. In the separation of poly(styrene-co-methyl methacrylate) samples with dichloroethane—chloroform mixtures, clearer results were obtained with a silica column previously rinsed with methanol40. Continuously decreasing activity of silica columns was observed in the elution of poly(styrene-co-methyl acrylate) with CCU-methyl acetate mixtures38). 

Figure 8 shows the 259 nm UV record from the gradient elution of the mixture of three samples containing 46.6, 57.3, or 77.9 wt % methyl-acrylate units. This was the first report on copolymer separation by HPLC 38). The chromatogram was obtained on a silica column (600 x 7.5 mm, d0 = 5 nm dP = 15 pm) with a CCU/methyl acetate gradient (7-35 % in 35 min). In spite of the decaying activity of the column the composition distribution of the 57.3% sample could be evaluated. 

Fig. 8. Copolymer separation. Gradient elution of the mixture of three poly(styrene-c -methyl acrylate) samples on a silica column (600 x 7.5 mm do = 5nm dp= 15 pm). Gradient tetrachloro-methane/methyl acetate (7-35% B in 35 min) flow rate 1 ml/min. The figures at the peaks indicate the composition of the respective copolymer in mol % methyl acrylate. Molar mass values 46.6 — 261 kg/mol 57.3 — 276 77.9 — 302. (From Ref. 381 with permission)...

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